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1.
  • Brennan, S. J., et al. (author)
  • Photometric and spectroscopic evolution of the interacting transient AT 2016jbu(Gaia16cfr)
  • 2022
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 513:4, s. 5642-5665
  • Journal article (peer-reviewed)abstract
    • We present the results from a high-cadence, multiwavelength observation campaign of AT 2016jbu (aka Gaia16cfr), an interacting transient. This data set complements the current literature by adding higher cadence as well as extended coverage of the light-curve evolution and late-time spectroscopic evolution. Photometric coverage reveals that AT 2016jbu underwent significant photometric variability followed by two luminous events, the latter of which reached an absolute magnitude of MV ∼ −18.5 mag. This is similar to the transient SN 2009ip whose nature is still debated. Spectra are dominated by narrow emission lines and show a blue continuum during the peak of the second event. AT 2016jbu shows signatures of a complex, non-homogeneous circumstellar material (CSM). We see slowly evolving asymmetric hydrogen line profiles, with velocities of 500 km s−1 seen in narrow emission features from a slow-moving CSM, and up to 10 000 km s−1 seen in broad absorption from some high-velocity material. Late-time spectra (∼+1 yr) show a lack of forbidden emission lines expected from a core-collapse supernova and are dominated by strong emission from H, He I, and Ca II. Strong asymmetric emission features, a bumpy light curve, and continually evolving spectra suggest an inhibit nebular phase. We compare the evolution of H α among SN 2009ip-like transients and find possible evidence for orientation angle effects. The light-curve evolution of AT 2016jbu suggests similar, but not identical, circumstellar environments to other SN 2009ip-like transients.
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2.
  • Brennan, S. J., et al. (author)
  • Progenitor, environment, and modelling of the interacting transient AT 2016jbu (Gaia16cfr)
  • 2022
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 513:4, s. 5666-5685
  • Journal article (peer-reviewed)abstract
    • We present the bolometric light curve, identification and analysis of the progenitor candidate, and preliminary modelling of AT 2016jbu (Gaia16cfr). We find a progenitor consistent with a ∼ 22–25 M⊙ yellow hypergiant surrounded by a dusty circumstellar shell, in agreement with what has been previously reported. We see evidence for significant photometric variability in the progenitor, as well as strong Hα emission consistent with pre-existing circumstellar material. The age of the environment, as well as the resolved stellar population surrounding AT 2016jbu, supports a progenitor age of >10 Myr, consistent with a progenitor mass of ∼22 M⊙. A joint analysis of the velocity evolution of AT 2016jbu and the photospheric radius inferred from the bolometric light curve shows the transient is consistent with two successive outbursts/explosions. The first outburst ejected material with velocity ∼650 km s−1, while the second, more energetic event ejected material at ∼4500 km s−1. Whether the latter is the core collapse of the progenitor remains uncertain. We place a limit on the ejected 56Ni mass of <0.016 M⊙. Using the Binary Population And Spectral Synthesis (BPASS) code, we explore a wide range of possible progenitor systems and find that the majority of these are in binaries, some of which are undergoing mass transfer or common-envelope evolution immediately prior to explosion. Finally, we use the SuperNova Explosion Code (SNEC) to demonstrate that the low-energy explosions within some of these binary systems, together with sufficient circumstellar material, can reproduce the overall morphology of the light curve of AT 2016jbu.
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3.
  • Anderson, J. P., et al. (author)
  • A nearby super-luminous supernova with a long pre-maximum plateau and strong C (II) features
  • 2018
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 620
  • Journal article (peer-reviewed)abstract
    • Context. Super-luminous supernovae (SLSNe) are rare events defined as being significantly more luminous than normal terminal stellar explosions. The source of the additional power needed to achieve such luminosities is still unclear. Discoveries in the local Universe (i.e. z < 0.1) are scarce, but afford dense multi-wavelength observations. Additional low-redshift objects are therefore extremely valuable.Aims. We present early-time observations of the type I SLSN ASASSN-18km/SN 2018bsz. These data are used to characterise the event and compare to literature SLSNe and spectral models. Host galaxy properties are also analysed.Methods. Optical and near-IR photometry and spectroscopy were analysed. Early-time ATLAS photometry was used to constrain the rising light curve. We identified a number of spectral features in optical-wavelength spectra and track their time evolution. Finally, we used archival host galaxy photometry together with H( II )region spectra to constrain the host environment.Results. ASASSN-18km/SN 2018bsz is found to be a type I SLSN in a galaxy at a redshift of 0.0267 (111 Mpc), making it the lowest-redshift event discovered to date. Strong C- II lines are identified in the spectra. Spectral models produced by exploding a Wolf-Rayet progenitor and injecting a magnetar power source are shown to be qualitatively similar to ASASSN-18km/SN 2018bsz, contrary to most SLSNe-I that display weak or non-existent C (II) lines. ASASSN-18km/SN 2018bsz displays along, slowly rising, red plateau of >26 days, before a steeper, faster rise to maximum. The host has an absolute magnitude of -19.8 mag (r), a mass of M-* = 1.5(-0.33)(+0.08) x 10(9) M-circle dot, and a star formation rate of =0.50(-0.19)(+2.22) M-circle dot yr(-1). A nearby H (II) region has an oxygen abundance (O3N2) of 8.31 +/- 0.01 dex.
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4.
  • Hsiao, E. Y., et al. (author)
  • Strong near-infrared carbon in the Type Ia supernova iPTF13ebh
  • 2015
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 578
  • Journal article (peer-reviewed)abstract
    • We present near-infrared (NIR) time-series spectroscopy, as well as complementary ultraviolet (UV), optical, and NIR data, of the Type Ia supernova (SN Ia) iPTF13ebh, which was discovered within two days from the estimated time of explosion. The first NIR spectrum was taken merely 2 : 3 days after explosion and may be the earliest NIR spectrum yet obtained of a SN Ia. The most striking features in the spectrum are several NIR C I lines, and the C I lambda 1.0693 mu m line is the strongest ever observed in a SN Ia. Interestingly, no strong optical C II counterparts were found, even though the optical spectroscopic time series began early and is densely cadenced. Except at the very early epochs, within a few days from the time of explosion, we show that the strong NIR C I compared to the weaker optical C II appears to be general in SNe Ia. iPTF13ebh is a fast decliner with Delta m(15)(B) = 1.79 +/- 0.01, and its absolute magnitude obeys the linear part of the width-luminosity relation. It is therefore categorized as a transitional event, on the fast-declining end of normal SNe Ia as opposed to subluminous/91bg-like objects. iPTF13ebh shows NIR spectroscopic properties that are distinct from both the normal and subluminous/91bg-like classes, bridging the observed characteristics of the two classes. These NIR observations suggest that composition and density of the inner core are similar to that of 91bg-like events, and that it has a deep-reaching carbon burning layer that is not observed in more slowly declining SNe Ia. There is also a substantial difference between the explosion times inferred from the early-time light curve and the velocity evolution of the Si II lambda 0.6355 mu m line, implying a long dark phase of similar to 4 days.
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5.
  • Hsiao, E. Y., et al. (author)
  • Carnegie Supernova Project-II : The Near-infrared Spectroscopy Program
  • 2019
  • In: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 131:995
  • Journal article (peer-reviewed)abstract
    • Shifting the focus of Type Ia supernova (SN Ia) cosmology to the near infrared (NIR) is a promising way to significantly reduce the systematic errors, as the strategy minimizes our reliance on the empirical width-luminosity relation and uncertain dust laws. Observations in the NIR are also crucial for our understanding of the origins and evolution of these events, further improving their cosmological utility. Any future experiments in the rest-frame NIR will require knowledge of the SN Ia NIR spectroscopic diversity, which is currently based on a small sample of observed spectra. Along with the accompanying paper, Phillips et al., we introduce the Carnegie Supernova Project-II (CSP-II), to follow-up nearby SNe Ia in both the optical and the NIR. In particular, this paper focuses on the CSP-II NIR spectroscopy program, describing the survey strategy, instrumental setups, data reduction, sample characteristics, and future analyses on the data set. In collaboration with the Harvard-Smithsonian Center for Astrophysics (CfA) Supernova Group, we obtained 661 NIR spectra of 157 SNe Ia. Within this sample, 451 NIR spectra of 90 SNe Ia have corresponding CSP-II follow-up light curves. Such a sample will allow detailed studies of the NIR spectroscopic properties of SNe Ia, providing a different perspective on the properties of the unburned material; the radioactive and stable nickel produced; progenitor magnetic fields; and searches for possible signatures of companion stars.
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6.
  • Tartaglia, L., et al. (author)
  • The Early Detection and Follow-up of the Highly Obscured Type II Supernova 2016ija/DLT16am
  • 2018
  • In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 853:1
  • Journal article (peer-reviewed)abstract
    • We present our analysis of the Type II supernova DLT16am (SN 2016ija). The object was discovered during the ongoing D < 40 Mpc (DLT40) one-day cadence supernova search at r similar to 20.1 mag in the edge-on nearby (D = 20.0 +/- 4.0 Mpc) galaxy NGC 1532. The subsequent prompt and high-cadenced spectroscopic and photometric follow-up revealed a highly extinguished transient, with E(B - V) = 1.95 +/- 0.15 mag, consistent with a standard extinction law with R-V = 3.1 and a bright (M-V = -18.48 +/- 0.77 mag) absolute peak magnitude. A comparison of the photometric features with those of large samples of SNe II reveals a fast rise for the derived luminosity and a relatively short plateau phase, with a slope of S-50V = 0.84 +/- 0.04 mag/50 days, consistent with the photometric properties typical of those of fast-declining SNe II. Despite the large uncertainties on the distance and the extinction in the direction of DLT16am, the measured photospheric expansion velocity and the derived absolute V-band magnitude at similar to 50 days after the explosion match the existing luminosity-velocity relation for SNe II.
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7.
  • Andrews, Jennifer E., et al. (author)
  • SN 2017gmr : An Energetic Type II-P Supernova with Asymmetries
  • 2019
  • In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 885:1
  • Journal article (peer-reviewed)abstract
    • We present high-cadence UV, optical, and near-infrared data on the luminous Type II-P supernova SN;2017gmr from hours after discovery through the first 180 days. SN;2017gmr does not show signs of narrow, high-ionization emission lines in the early optical spectra, yet the optical light-curve evolution suggests that an extra energy source from circumstellar medium (CSM) interaction must be present for at least 2 days after explosion. Modeling of the early light curve indicates a ?500 R progenitor radius, consistent with a rather compact red supergiant, and late-time luminosities indicate that up to 0.130;;0.026 M of Ni-56 are present, if the light curve is solely powered by radioactive decay, although the Ni-56 mass may be lower if CSM interaction contributes to the post-plateau luminosity. Prominent multipeaked emission lines of H? and [O i] emerge after day 154, as a result of either an asymmetric explosion or asymmetries in the CSM. The lack of narrow lines within the first 2 days of explosion in the likely presence of CSM interaction may be an example of close, dense, asymmetric CSM that is quickly enveloped by the spherical supernova ejecta.
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8.
  • Margutti, R., et al. (author)
  • A PANCHROMATIC VIEW OF THE RESTLESS SN 2009ip REVEALS THE EXPLOSIVE EJECTION OF A MASSIVE STAR ENVELOPE
  • 2014
  • In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 780:1
  • Journal article (peer-reviewed)abstract
    • The double explosion of SN 2009ip in 2012 raises questions about our understanding of the late stages of massive star evolution. Here we present a comprehensive study of SN 2009ip during its remarkable rebrightenings. High-cadence photometric and spectroscopic observations from the GeV to the radio band obtained from a variety of ground-based and space facilities (including the Very Large Array, Swift, Fermi, Hubble Space Telescope, and XMM) constrain SN 2009ip to be a low energy (E similar to 1050 erg for an ejecta mass similar to 0.5 M-circle dot) and asymmetric explosion in a complex medium shaped by multiple eruptions of the restless progenitor star. Most of the energy is radiated as a result of the shock breaking out through a dense shell of material located at similar to 5 x 10(14) cm with M similar to 0.1 M-circle dot, ejected by the precursor outburst similar to 40 days before the major explosion. We interpret the NIR excess of emission as signature of material located further out, the origin of which has to be connected with documented mass-loss episodes in the previous years. Our modeling predicts bright neutrino emission associated with the shock break-out if the cosmic-ray energy is comparable to the radiated energy. We connect this phenomenology with the explosive ejection of the outer layers of the massive progenitor star, which later interacted with material deposited in the surroundings by previous eruptions. Future observations will reveal if the massive luminous progenitor star survived. Irrespective of whether the explosion was terminal, SN 2009ip brought to light the existence of new channels for sustained episodic mass loss, the physical origin of which has yet to be identified.
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9.
  • Galbany, L., et al. (author)
  • Evidence for a Chandrasekhar-mass explosion in the Ca-strong 1991bg-like type la supernova 2016hnk
  • 2019
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 630
  • Journal article (peer-reviewed)abstract
    • Aims. We present a comprehensive dataset of optical and near-infrared photometry and spectroscopy of type Ia supernova (SN) 2016hnk, combined with integral field spectroscopy (IFS) of its host galaxy, MCG -01-06-070, and nearby environment. Our goal with this complete dataset is to understand the nature of this peculiar object.Methods. Properties of the SN local environment are characterized by means of single stellar population synthesis applied to IFS observations taken two years after the SN exploded. We performed detailed analyses of SN photometric data by studying its peculiar light and color curves. SN 2016hnk spectra were compared to other 1991bg-like SNe Ia, 2002es-like SNe Ia, and Ca-rich transients. In addition, we used abundance stratification modeling to identify the various spectral features in the early phase spectral sequence and also compared the dataset to a modified non-LTE model previously produced for the sublumnious SN 1999by.Results. SN 2016hnk is consistent with being a subluminous (M-B = -16.7 mag, S-BV =0.43 +/- 0.03), highly reddened object. The IFS of its host galaxy reveals both a significant amount of dust at the SN location, residual star formation, and a high proportion of old stellar populations in the local environment compared to other locations in the galaxy, which favors an old progenitor for SN 2016hnk. Inspection of a nebular spectrum obtained one year after maximum contains two narrow emission lines attributed to the forbidden [Ca II] lambda lambda 7291,7324 doublet with a Doppler shift of 700 km s(-1). Based on various observational diagnostics, we argue that the progenitor of SN 2016hnk was likely a near Chandrasekhar-mass (M-Ch) carbon-oxygen white dwarf that produced 0.108 M-circle dot of Ni-56. Our modeling suggests that the narrow [Ca II] features observed in the nebular spectrum are associated with Ca-48 from electron capture during the explosion, which is expected to occur only in white dwarfs that explode near or at the M-Ch limit.
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10.
  • Pastorello, A., et al. (author)
  • Massive stars exploding in a He-rich circumstellar medium - IV. Transitional Type Ibn supernovae
  • 2015
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 449:2, s. 1921-1940
  • Journal article (peer-reviewed)abstract
    • We present ultraviolet, optical and near-infrared data of the Type Ibn supernovae (SNe) 2010al and 2011hw. SN 2010al reaches an absolute magnitude at peak of M-R = -18.86 +/- 0.21. Its early light curve shows similarities with normal SNe Ib, with a rise to maximum slower than most SNe Ibn. The spectra are dominated by a blue continuum at early stages, with narrow P-Cygni He I lines indicating the presence of a slow-moving, He-rich circumstellar medium. At later epochs, the spectra well match those of the prototypical SN Ibn 2006jc, although the broader lines suggest that a significant amount of He was still present in the stellar envelope at the time of the explosion. SN 2011hw is somewhat different. It was discovered after the first maximum, but the light curve shows a double peak. The absolute magnitude at discovery is similar to that of the second peak (M-R = -18.59 +/- 0.25), and slightly fainter than the average of SNe Ibn. Though the spectra of SN 2011hw are similar to those of SN 2006jc, coronal lines and narrow Balmer lines are clearly detected. This indicates substantial interaction of the SN ejecta with He-rich, but not H-free, circumstellar material. The spectra of SN 2011hw suggest that it is a transitional SN Ibn/IIn event similar to SN 2005la. While for SN 2010al the spectrophotometric evolution favours a H-deprived Wolf-Rayet progenitor (of WN-type), we agree with the conclusion of Smith et al. that the precursor of SN 2011hw was likely in transition from a luminous blue variable to an early Wolf-Rayet (Ofpe/WN9) stage.
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11.
  • Davis, S., et al. (author)
  • SN 2013ai : A Link between Hydrogen-rich and Hydrogen-poor Core-collapse Supernovae
  • 2021
  • In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 909:2
  • Journal article (peer-reviewed)abstract
    • We present a study of the optical and near-infrared (NIR) spectra of SN 2013ai along with its light curves. These data range from discovery until 380 days after explosion. SN 2013ai is a fast declining Type II supernova (SN II) with an unusually long rise time, 18.9 2.7 days in the V-band, and a bright V-band peak absolute magnitude of -18.7 0.06 mag. The spectra are dominated by hydrogen features in the optical and NIR. The spectral features of SN 2013ai are unique in their expansion velocities, which, when compared to large samples of SNe II, are more than 1,000 km s(-1) faster at 50 days past explosion. In addition, the long rise time of the light curve more closely resembles SNe IIb rather than SNe II. If SN 2013ai is coeval with a nearby compact cluster, we infer a progenitor zero-age main-sequence mass of similar to 17 M. After performing light-curve modeling, we find that SN 2013ai could be the result of the explosion of a star with little hydrogen mass, a large amount of synthesized Ni-56, 0.3-0.4 M, and an explosion energy of 2.5-3.0 x 10(51) erg. The density structure and expansion velocities of SN 2013ai are similar to those of the prototypical SN IIb, SN 1993J. However, SN 2013ai shows no strong helium features in the optical, likely due to the presence of a dense core that prevents the majority of gamma-rays from escaping to excite helium. Our analysis suggests that SN 2013ai could be a link between SNe II and stripped-envelope SNe.
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12.
  • Foley, Ryan J., et al. (author)
  • Extensive HST ultraviolet spectra and multiwavelength observations of SN 2014J in M82 indicate reddening and circumstellar scattering by typical dust
  • 2014
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 443:4, s. 2887-2906
  • Journal article (peer-reviewed)abstract
    • SN 2014J in M82 is the closest detected Type Ia supernova (SN Ia) in at least 28 yr and perhaps in 410 yr. Despite its small distance of 3.3 Mpc, SN 2014J is surprisingly faint, peaking at V = 10.6 mag, and assuming a typical SN Ia luminosity, we infer an observed visual extinction of A(V) = 2.0 +/- 0.1 mag. But this picture, with R-V = 1.6 +/- 0.2, is too simple to account for all observations. We combine 10 epochs (spanning a month) of HST/Space Telescope Imaging Spectrograph (STIS) ultraviolet through near-infrared spectroscopy with HST/Wide Field Camera 3 (WFC3), Katzman Automatic Imaging Telescope, and FanCam photometry from the optical to the infrared and nine epochs of high-resolution TRES (Tillinghast Reflection Echelle Spectrograph) spectroscopy to investigate the sources of extinction and reddening for SN 2014J. We argue that the wide range of observed properties for SN 2014J is caused by a combination of dust reddening, likely originating in the interstellar medium of M82, and scattering off circumstellar material. For this model, roughly half of the extinction is caused by reddening from typical dust (E(B - V) = 0.45 mag and R-V = 2.6) and roughly half by scattering off Large Magellanic Cloud-like dust in the circumstellar environment of SN 2014J.
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13.
  • Levesque, E. M., et al. (author)
  • THE HIGH-METALLICITY EXPLOSION ENVIRONMENT OF THE RELATIVISTIC SUPERNOVA 2009bb
  • 2010
  • In: The Astrophysical Journal Letters. - 2041-8205. ; 709:1, s. l26-L31
  • Journal article (peer-reviewed)abstract
    • We investigate the environment of the nearby (d approximate to 40 Mpc) broad-lined Type Ic supernova (SN) 2009bb. This event was observed to produce a relativistic outflow likely powered by a central accreting compact object. While such a phenomenon was previously observed only in long-duration gamma-ray bursts (LGRBs), no LGRB was detected in association with SN 2009bb. Using an optical spectrum of the SN 2009bb explosion site, we determine a variety of interstellar medium properties for the host environment, including metallicity, young stellar population age, and star formation rate. We compare the SN explosion site properties to observations of LGRB and broad-lined SN Ic host environments on optical emission line ratio diagnostic diagrams. Based on these analyses, we find that the SN 2009bb explosion site has a metallicity between 1.7 Z(circle dot) and 3.5 Z(circle dot), in agreement with other broad-lined SN Ic host environments and at odds with the low-redshift LGRB host environments and recently proposed maximum metallicity limits for relativistic explosions. We consider the implications of these findings and the impact that SN 2009bb's unusual explosive properties and environment have on our understanding of the key physical ingredient that enables some SNe to produce a relativistic outflow.
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14.
  • Malesani, D., et al. (author)
  • Early Spectroscopic Identification of SN 2008D
  • 2009
  • In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 692:2, s. L84-L87
  • Journal article (peer-reviewed)abstract
    • SN 2008D was discovered while following up an unusually bright X-ray transient (XT) in the nearby spiral galaxy NGC 2770. We present early optical spectra ( obtained 1.75 days after the XT) which allowed the first identification of the object as a supernova ( SN) at redshift z = 0.007. These spectra were acquired during the initial declining phase of the light curve, likely produced in the stellar envelope cooling after shock breakout, and rarely observed. They exhibit a rather flat spectral energy distribution with broad undulations, and a strong, W-shaped feature with minima at 3980 and 4190 angstrom ( rest frame). We also present extensive spectroscopy and photometry of the SN during the subsequent photospheric phase. Unlike SNe associated with gamma-ray bursts, SN 2008D displayed prominent He features and is therefore of Type Ib.
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15.
  • Marion, G. H., et al. (author)
  • Early Observations and Analysis of the Type Ia SN 2014J in M82
  • 2015
  • In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 798:1, s. 39-
  • Journal article (peer-reviewed)abstract
    • We present optical and near infrared (NIR) observations of the nearby Type Ia SN 2014J. Seventeen optical and 23 NIR spectra were obtained from 10 days before (–10d) to 10 days after (+10d) the time of maximum B-band brightness. The relative strengths of absorption features and their patterns of development can be compared at one day intervals throughout most of this period. Carbon is not detected in the optical spectra, but we identify C I λ1.0693 in the NIR spectra. Mg II lines with high oscillator strengths have higher initial velocities than other Mg II lines. We show that the velocity differences can be explained by differences in optical depths due to oscillator strengths. The spectra of SN 2014J show that it is a normal SN Ia, but many parameters are near the boundaries between normal and high-velocity subclasses. The velocities for O I, Mg II, Si II, S II, Ca II, and Fe II suggest that SN 2014J has a layered structure with little or no mixing. That result is consistent with the delayed detonation explosion models. We also report photometric observations, obtained from –10d to +29d, in the UBVRIJH and Ksbands. The template fitting package SNooPy is used to interpret the light curves and to derive photometric parameters. UsingRV = 1.46, which is consistent with previous studies, SNooPy finds that AV = 1.80 for E(B – V)host = 1.23 ± 0.06 mag. The maximum B-band brightness of –19.19 ± 0.10 mag was reached on February 1.74 UT ± 0.13 days and the supernova has a decline parameter, Δm 15, of 1.12 ± 0.02 mag.
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16.
  • Pastorello, A., et al. (author)
  • Forbidden hugs in pandemic times II. The luminous red nova variety AT 2020hat and AT 2020kog
  • 2021
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 647
  • Journal article (peer-reviewed)abstract
    • We present the results of our monitoring campaigns of the luminous red novae (LRNe) AT 2020hat in NGC 5068 and AT 2020kog in NGC 6106. The two objects were imaged (and detected) before their discovery by routine survey operations. They show a general trend of slow luminosity rise, lasting at least a few months. The subsequent major LRN outbursts were extensively followed in photometry and spectroscopy. The light curves present an initial short-duration peak, followed by a redder plateau phase. AT 2020kog is a moderately luminous event peaking at similar to 7 x 10(40) erg s(-1), while AT 2020hat is almost one order of magnitude fainter than AT 2020kog, although it is still more luminous than V838 Mon. In analogy with other LRNe, the spectra of AT 2020kog change significantly with time. They resemble those of type TM supernovae at early phases, then they become similar to those of K-type stars during the plateau, and to M-type stars at very late phases. In contrast, AT 2020hat already shows a redder continuum at early epochs, and its spectrum shows the late appearance of molecular bands. A moderate-resolution spectrum of AT 2020hat taken at +37 d after maximum shows a forest of narrow P Cygni lines of metals with velocities of 180 km s(-1), along with an Ha emission with a full-width at half-maximum velocity of 250 km s(-1). For AT 2020hat, a robust constraint on its quiescent progenitor is provided by archival images of the Hubble Space Telescope. The progenitor is clearly detected as a mid-K type star, with an absolute magnitude of M-F606W = -3.33 +/- 0.09 mag and a colour of F606W - F814W = 1.14 +/- 0.05 mag, which are inconsistent with the expectations from a massive star that could later produce a core-collapse supernova. Although quite peculiar, the two objects nicely match the progenitor versus light curve absolute magnitude correlations discussed in the literature.
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17.
  • Scalzo, R. A., et al. (author)
  • Early ultraviolet emission in the Type Ia supernova LSQ12gdj : No evidence for ongoing shock interaction
  • 2014
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 445:1, s. 30-48
  • Journal article (peer-reviewed)abstract
    • We present photospheric-phase observations of LSQ12gdj, a slowly declining, UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has extinction-corrected absolute magnitude M-B = -19.8, and pre-maximum spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN 2007if. We use ultraviolet photometry from Swift, ground-based optical photometry, and corrections from a near-infrared photometric template to construct the bolometric (1600-23 800 angstrom) light curve out to 45 d past B-band maximum light. We estimate that LSQ12gdj produced 0.96 +/- 0.07 M-circle dot of Ni-56, with an ejected mass near or slightly above the Chandrasekhar mass. As much as 27 per cent of the flux at the earliest observed phases, and 17 per cent at maximum light, is emitted bluewards of 3300 angstrom. The absence of excess luminosity at late times, the cutoff of the spectral energy distribution bluewards of 3000 angstrom and the absence of narrow line emission and strong Na I D absorption all argue against a significant contribution from ongoing shock interaction. However, similar to 10 per cent of LSQ12gdj's luminosity near maximum light could be produced by the release of trapped radiation, including kinetic energy thermalized during a brief interaction with a compact, hydrogen-poor envelope (radius < 10(13) cm) shortly after explosion; such an envelope arises generically in double-degenerate merger scenarios.
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18.
  • Soderberg, A. M., et al. (author)
  • A relativistic type Ibc supernova without a detected gamma-ray burst
  • 2010
  • In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 463:7280, s. 513-515
  • Journal article (peer-reviewed)abstract
    • Long duration gamma-ray bursts (GRBs) mark(1) the explosive death of some massive stars and are a rare sub-class of type Ibc supernovae. They are distinguished by the production of an energetic and collimated relativistic outflow powered(2) by a central engine (an accreting black hole or neutron star). Observationally, this outflow is manifested(3) in the pulse of gamma-rays and a long-lived radio afterglow. Until now, central-engine driven supernovae have been discovered exclusively through their gamma-ray emission, yet it is expected(4) that a larger population goes undetected because of limited satellite sensitivity or beaming of the collimated emission away from our line of sight. In this framework, the recovery of undetected GRBs may be possible through radio searches(5,6) for type Ibc supernovae with relativistic outflows. Here we report the discovery of luminous radio emission from the seemingly ordinary type Ibc SN 2009bb, which requires a substantial relativistic outflow powered by a central engine. A comparison with our radio survey of type Ibc supernovae reveals that the fraction harbouring central engines is low, about one per cent, measured independently from, but consistent with, the inferred(7) rate of nearby GRBs. Independently, a second mildly relativistic supernova has been reported(8).
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19.
  • Soderberg, A. M., et al. (author)
  • Discovery of a Relativistic Supernova Without a Gamma-ray Trigger
  • 2009
  • Other publication (pop. science, debate, etc.)abstract
    • Type Ibc supernovae (SNe Ibc) mark the gravitational collapse of some massive stars (M > 20 Msun) propelling several solar masses of material to typical velocities of ~10,000 km/s. The closely-related but exceedingly rare class of long-duration gamma-ray bursts (GRBs) produce, in addition, a relativistic outflow powered by a central engine (accreting black hole or neutron star) and have been found exclusively through their gamma-ray signal. Here we report the discovery of luminous radio emission from the seemingly ordinary Type Ibc SN 2009bb which outshines that of all other SNe Ibc observed on a comparable timescale. These observations require a substantial mildly-relativistic outflow and indicate that the explosion was powered by a central engine, thus representing the first such event discovered without the aid of a gamma-ray trigger. A comparison with our extensive radio survey of SNe Ibc reveals that the fraction of such events is low (roughly 1 percent), measured independently from, and yet consistent with, the inferred rate of nearby GRBs. This discovery marks the observational realization that long-wavelength surveys will soon rival gamma-ray satellites in pinpointing nearby engine-driven explosions.
  •  
20.
  • Stritzinger, M. D., et al. (author)
  • The carbon-rich type Ic supernova 2016adj in the iconic dust lane of Centaurus A : Potential signatures of an interaction with circumstellar hydrogen
  • 2024
  • In: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 686
  • Journal article (peer-reviewed)abstract
    • We present a comprehensive data set of supernova (SN) 2016adj located within the central dust lane of Centaurus A. SN 2016adj is significantly reddened and after correcting the peak apparent B-band magnitude (mB = 17.48 ± 0.05) for Milky Way reddening and our inferred host-galaxy reddening parameters (i.e., RVhost = 5.7±0.7 and AVhost = 6.3 ± 0.2 mag), we estimated it reached a peak absolute magnitude of MB ∼ −18. A detailed inspection of the optical and near-infrared (NIR) spectroscopic time series reveals a carbon-rich SN Ic and not a SN Ib/IIb as previously suggested in the literature. The NIR spectra show prevalent carbon-monoxide formation occurring already by +41 days past B-band maximum, which is ≈11 days earlier than previously reported in the literature for this object. Interestingly, around two months past maximum, the NIR spectrum of SN 2016adj begins to exhibit H features, with a +97 days medium resolution spectrum revealing both Paschen and Bracket lines with absorption minima of ∼2000 km s−1, full-width-half-maximum emission velocities of ∼1000 km s−1, and emission line ratios consistent with a dense emission region. We speculate that these attributes are due to a circumstellar interaction (CSI) between the rapidly expanding SN ejecta and a H-rich shell of material that formed during the pre-SN phase. A bolometric light curve was constructed and a semi-analytical model fit suggests the SN synthesized 0.5 M⊙ of 56Ni and ejected 4.7 M⊙ of material, though these values should be approached with caution given the large uncertainties associated with the adopted reddening parameters and known light echo emission. Finally, inspection of the Hubble Space Telescope archival data yielded no progenitor detection.
  •  
21.
  • Takats, K., et al. (author)
  • SN 2009N : linking normal and subluminous Type II-P SNe
  • 2014
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 438:1, s. 368-387
  • Journal article (peer-reviewed)abstract
    • We present ultraviolet, optical, near-infrared photometry and spectroscopy of SN 2009N in NGC 4487. This object is a Type II-P supernova with spectra resembling those of subluminous II-P supernovae, while its bolometric luminosity is similar to that of the intermediate-luminosity SN 2008in. We created SYNOW models of the plateau phase spectra for line identification and to measure the expansion velocity. In the near-infrared spectra we find signs indicating possible weak interaction between the supernova ejecta and the pre-existing circumstellar material. These signs are also present in the previously unpublished near-infrared spectra of SN 2008in. The distance to SN 2009N is determined via the expanding photosphere method and the standard candle method as D = 21.6 +/- 1.1 Mpc. The produced nickel-mass is estimated to be similar to 0.020 +/- 0.004 M-circle dot. We infer the physical properties of the progenitor at the explosion through hydrodynamical modelling of the observables. We find the values ofthe total energy as similar to 0.48 x 10(51) erg, the ejected mass as similar to 11.5 M-circle dot, and the initial radius as similar to 287 R-circle dot.
  •  
22.
  • Anderson, P., et al. (author)
  • The lowest-metallicity type II supernova from the highest-mass red supergiant progenitor
  • 2018
  • In: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 2:7, s. 574-579
  • Journal article (peer-reviewed)abstract
    • Red supergiants have been confirmed as the progenitor stars of the majority of hydrogen-rich type II supernovae(1). However, while such stars are observed with masses > 25 M-circle dot (ref. (2)), detections of > 18 M-circle dot progenitors remain elusive(1). Red supergiants are also expected to form at all metallicities, but discoveries of explosions from low-metallicity progenitors are scarce. Here, we report observations of the type II supernova, SN 2015bs, for which we infer a progenitor metallicity of <= 0.1 Z(circle dot) from comparison to photospheric-phase spectral models(3), and a zero-age main-sequence mass of 17-25 M-circle dot through comparison to nebular-phase spectral models(4,5). SN 2015bs displays a normal 'plateau' light-curve morphology, and typical spectral properties, implying a red supergiant progenitor. This is the first example of such a high-mass progenitor for a 'normal' type II supernova, suggesting a link between high-mass red supergiant explosions and low-metallicity progenitors.
  •  
23.
  • Cai, Y.-Z., et al. (author)
  • Intermediate-luminosity red transients : Spectrophotometric properties and connection to electron-capture supernova explosions
  • 2021
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 654
  • Journal article (peer-reviewed)abstract
    • We present the spectroscopic and photometric study of five intermediate-luminosity red transients (ILRTs), namely AT 2010dn, AT 2012jc, AT 2013la, AT 2013lb, and AT 2018aes. They share common observational properties and belong to a family of objects similar to the prototypical ILRT SN 2008S. These events have a rise time that is less than 15 days and absolute peak magnitudes of between −11.5 and −14.5 mag. Their pseudo-bolometric light curves peak in the range 0.5–9.0 × 1040 erg s−1 and their total radiated energies are on the order of (0.3–3) × 1047 erg. After maximum brightness, the light curves show a monotonic decline or a plateau, resembling those of faint supernovae IIL or IIP, respectively. At late phases, the light curves flatten, roughly following the slope of the 56Co decay. If the late-time power source is indeed radioactive decay, these transients produce 56Ni masses on the order of 10−4 to 10−3 M⊙. The spectral energy distribution of our ILRT sample, extending from the optical to the mid-infrared (MIR) domain, reveals a clear IR excess soon after explosion and non-negligible MIR emission at very late phases. The spectra show prominent H lines in emission with a typical velocity of a few hundred km s−1, along with Ca II features. In particular, the [Ca II] λ7291,7324 doublet is visible at all times, which is a characteristic feature for this family of transients. The identified progenitor of SN 2008S, which is luminous in archival Spitzer MIR images, suggests an intermediate-mass precursor star embedded in a dusty cocoon. We propose the explosion of a super-asymptotic giant branch star forming an electron-capture supernova as a plausible explanation for these events.
  •  
24.
  • Holmbo, S., et al. (author)
  • Discovery and progenitor constraints on the Type Ia supernova 2013gy
  • 2019
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 627
  • Journal article (peer-reviewed)abstract
    • We present an early-phase g-band light curve and visual-wavelength spectra of the normal Type Ia supernova (SN) 2013gy. The light curve is constructed by determining the appropriate S-corrections to transform KAIT natural-system B- and V-band photometry and Carnegie Supernova Project natural-system g-band photometry to the Pan-STARRS1 g-band natural photometric system. A Markov chain Monte Carlo calculation provides a best-fit single power-law function to the first ten epochs of photometry described by an exponent of 2.16(-0.06)(+0.06) and a time of first light of MJD 56629.4(-0.1)(+0.1), which is 1.93(-0.13)(+0.12) days (i.e., <48 h) before the discovery date (2013 December 4.84 UT) and -19.10(-0.13)(+0.12) days before the time of B- band maximum (MJD 56648.5 +/- 0.1). The estimate of the time of first light is consistent with the explosion time inferred from the evolution of the Si II lambda 6355 Doppler velocity. Furthermore, discovery photometry and previous nondetection limits enable us to constrain the companion radius down to R-c <= 4 R-circle dot. In addition to our early-time constraints, we used a deep +235 day nebular-phase spectrum from Magellan/IMACS to place a stripped H-mass limit of <0.018 M-circle dot. Combined, these limits effectively rule out H-rich nondegenerate companions.
  •  
25.
  • Pan, Y. -C, et al. (author)
  • 500 days of SN 2013dy : spectra and photometry from the ultraviolet to the infrared
  • 2015
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 452:4, s. 4307-4325
  • Journal article (peer-reviewed)abstract
    • SN 2013dy is a Type Ia supernova (SN Ia) for which we have compiled an extraordinary data set spanning from 0.1 to similar to 500 d after explosion. We present 10 epochs of ultraviolet (UV) through near-infrared (NIR) spectra with Hubble Space Telescope/Space Telescope Imaging Spectrograph, 47 epochs of optical spectra (15 of them having high resolution), and more than 500 photometric observations in the BVrRiIZYJH bands. SN 2013dy has a broad and slowly declining light curve (Delta m(15)(B)= 0.92 mag), shallow Si II lambda 6355 absorption, and a low velocity gradient. We detect strong C II in our earliest spectra, probing unburned progenitor material in the outermost layers of the SN ejecta, but this feature fades within a few days. The UV continuum of SN 2013dy, which is strongly affected by the metal abundance of the progenitor star, suggests that SN 2013dy had a relatively high-metallicity progenitor. Examining one of the largest single set of high-resolution spectra for an SN Ia, we find no evidence of variable absorption from circumstellar material. Combining our UV spectra, NIR photometry, and high-cadence optical photometry, we construct a bolometric light curve, showing that SN 2013dy had a maximum luminosity of 10.0(-3.8)(+4.8) x 10(42) erg s(-1). We compare the synthetic light curves and spectra of several models to SN 2013dy, finding that SN 2013dy is in good agreement with a solar-metallicity W7 model.
  •  
26.
  • Shappee, B. J., et al. (author)
  • THE YOUNG AND BRIGHT TYPE IA SUPERNOVA ASASSN-141p : DISCOVERY, EARLY-TIME OBSERVATIONS, FIRST-LIGHT TIME, DISTANCE TO NGC 4666, AND PROGENITOR CONSTRAINTS
  • 2016
  • In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 826:2
  • Journal article (peer-reviewed)abstract
    • On 2014 December 9.61, the All-sky Automated Survey for SuperNovae (ASAS-SN or Assassin) discovered ASASSN-141p just similar to 2 days after first light using a global array of 14 cm diameter telescopes. ASASSN-141p went on to become a bright supernova (V = 11.94 mag), second only to SN 2014J for the year. We present prediscovery photometry (with a detection less than a day after first light) and ultraviolet through near-infrared photometric and spectroscopic data covering the rise and fall of ASASSN-141p for more than 100 days. We find that ASASSN-141p had a broad light curve (Delta m(15) (B) = 0.80 +/- 0.05), a B-band maximum at 2457015.82 +/- 0.03, a rise time of 16.941(-0.10)(+0.11) days, and moderate host-galaxy extinction (E (B - V)host = 0.33 +/- 0.06). Using ASASSN-141p, we derive a distance modulus for NGC 4666 of mu = 30.8 +/- 0.2, corresponding to a distance of 14.7 +/- 1.5 Mpc. However, adding ASASSN-141p to the calibrating sample of Type Ia supernovae still requires an independent distance to the host galaxy. Finally, using our early-time photometric and spectroscopic observations, we rule out red giant secondaries and, assuming a favorable viewing angle and explosion time, any nondegenerate companion larger than 0.34 RG(circle dot).
  •  
27.
  • Stritzinger, M. D., et al. (author)
  • The Carnegie Supernova Project II : Observations of the luminous red nova AT 2014ej
  • 2020
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 639
  • Journal article (peer-reviewed)abstract
    • We present optical and near-infrared broadband photometry and optical spectra of AT 2014ej from the Carnegie Supernova Project-II. These observations are complemented with data from the CHilean Automatic Supernova sEarch, the Public ESO Spectroscopic Survey of Transient Objects, and from the Backyard Observatory Supernova Search. Observational signatures of AT 2014ej reveal that it is similar to other members of the gap-transient subclass known as luminous red novae (LRNe), including the ubiquitous double-hump light curve and spectral properties similar to that of LRN SN 2017jfs. A medium-dispersion visual-wavelength spectrum of AT 2014ej taken with the Magellan Clay telescope exhibits a P Cygni H alpha feature characterized by a blue velocity at zero intensity of approximate to 110 km s(-1) and a P Cygni minimum velocity of approximate to 70 km s(-1). We attribute this to emission from a circumstellar wind. Inspection of pre-outbust Hubble Space Telescope images yields no conclusive progenitor detection. In comparison with a sample of LRNe from the literature, AT 2014ej lies at the brighter end of the luminosity distribution. Comparison of the ultra-violet, optical, infrared light curves of well-observed LRNe to common-envelope evolution models from the literature indicates that the models underpredict the luminosity of the comparison sample at all phases and also produce inconsistent timescales of the secondary peak. Future efforts to model LRNe should expand upon the current parameter space we explore here and therefore may consider more massive systems and a wider range of dynamical timescales.
  •  
28.
  • Teodoro, M., et al. (author)
  • He II lambda 4686 IN eta CARINAE : COLLAPSE OF THE WIND-WIND COLLISION REGION DURING PERIASTRON PASSAGE
  • 2012
  • In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 746:1, s. 73-
  • Journal article (peer-reviewed)abstract
    • The periodic spectroscopic events in eta Carinae are now well established and occur near the periastron passage of two massive stars in a very eccentric orbit. Several mechanisms have been proposed to explain the variations of different spectral features, such as an eclipse by the wind-wind collision (WWC) boundary, a shell ejection from the primary star or accretion of its wind onto the secondary. All of them have problems explaining all the observed phenomena. To better understand the nature of the cyclic events, we performed a dense monitoring of eta Carinae with five Southern telescopes during the 2009 low-excitation event, resulting in a set of data of unprecedented quality and sampling. The intrinsic luminosity of the He II lambda 4686 emission line (L similar to 310 L-circle dot) just before periastron reveals the presence of a very luminous transient source of extreme UV radiation emitted in the WWC region. Clumps in the primary's wind probably explain the flare-like behavior of both the X-ray and He II lambda 4686 light curves. After a short-lived minimum, He II lambda 4686 emission rises again to a new maximum, when X-rays are still absent or very weak. We interpret this as a collapse of the WWC onto the surface of the secondary star, switching off the hard X-ray source and diminishing the WWC shock cone. The recovery from this state is controlled by the momentum balance between the secondary's wind and the clumps in the primary's wind.
  •  
29.
  • DerKacy, J. M., et al. (author)
  • SN 2021fxy : mid-ultraviolet flux suppression is a common feature of Type Ia supernovae
  • 2023
  • In: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 522:3, s. 3481-3505
  • Journal article (peer-reviewed)abstract
    • We present ultraviolet (UV) to near-infrared (NIR) observations and analysis of the nearby Type Ia supernova SN 2021fxy. Our observations include UV photometry from Swift/UVOT, UV spectroscopy from HST/STIS, and high-cadence optical photometry with the Swope 1-m telescope capturing intranight rises during the early light curve. Early B - V colours show SN 2021fxy is the first 'shallow-silicon' (SS) SN Ia to follow a red-to-blue evolution, compared to other SS objects which show blue colours from the earliest observations. Comparisons to other spectroscopically normal SNe Ia with HST UV spectra reveal SN 2021fxy is one of several SNe Ia with flux suppression in the mid-UV. These SNe also show blueshifted mid-UV spectral features and strong high-velocity Ca ii features. One possible origin of this mid-UV suppression is the increased effective opacity in the UV due to increased line blanketing from high velocity material, but differences in the explosion mechanism cannot be ruled out. Among SNe Ia with mid-UV suppression, SNe 2021fxy and 2017erp show substantial similarities in their optical properties despite belonging to different Branch subgroups, and UV flux differences of the same order as those found between SNe 2011fe and 2011by. Differential comparisons to multiple sets of synthetic SN Ia UV spectra reveal this UV flux difference likely originates from a luminosity difference between SNe 2021fxy and 2017erp, and not differing progenitor metallicities as suggested for SNe 2011by and 2011fe. These comparisons illustrate the complicated nature of UV spectral formation, and the need for more UV spectra to determine the physical source of SNe Ia UV diversity.
  •  
30.
  • Lampeitl, H., et al. (author)
  • First-year Sloan Digital Sky Survey-II supernova results : consistency and constraints with other intermediate-redshift data sets
  • 2010
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 401:4, s. 2331-2342
  • Journal article (peer-reviewed)abstract
    • We present an analysis of the luminosity distances of Type Ia Supernovae (SNe) from the Sloan Digital Sky Survey-II (SDSS-II) SN Survey in conjunction with other intermediate-redshift (z < 0.4) cosmological measurements including redshift-space distortions from the Two-Degree Field Galaxy Redshift Survey (2dFGRS), the integrated Sachs–Wolfe (ISW) effect seen by the SDSS and the latest baryon acoustic oscillation (BAO) distance scale from both the SDSS and 2dFGRS. We have analysed the SDSS-II SN data alone using a variety of ‘model-independent’ methods and find evidence for an accelerating Universe at a >97 per cent level from this single data set. We find good agreement between the SN and BAO distance measurements, both consistent with a Λ-dominated cold dark matter cosmology, as demonstrated through an analysis of the distance duality relationship between the luminosity (dL) and angular diameter (dA) distance measures. We then use these data to estimate w within this restricted redshift range (z < 0.4). Our most stringent result comes from the combination of all our intermediate-redshift data (SDSS-II SNe, BAO, ISW and redshift-space distortions), giving w=−0.81+0.16−0.18 (stat) ± 0.15 (sys) and ΩM= 0.22+0.09−0.08 assuming a flat universe. This value of w and associated errors only change slightly if curvature is allowed to vary, consistent with constraints from the cosmic microwave background. We also consider more limited combinations of the geometrical (SN, BAO) and dynamical (ISW, redshift-space distortions) probes. 
  •  
31.
  • Leloudas, G., et al. (author)
  • The normal Type Ia SN 2003hv out to very late phases
  • 2009
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 505:1, s. 265-279
  • Journal article (peer-reviewed)abstract
    • Aims: We study a thermonuclear supernova (SN), emphasizing very late phases. Methods: An extensive dataset for SN 2003hv that covers the flux evolution from maximum light to day +786 is presented. This includes 82 epochs of optical imaging, 24 epochs of near-infrared (NIR) imaging, and 10 epochs of optical spectroscopy. These data are combined with published nebular-phase IR spectra, and the observations are compared to model light curves and synthetic nebular spectra. Results: SN 2003hv is a normal Type Ia supernova (SN Ia) with photometric and spectroscopic properties consistent with its rarely observed B-band decline-rate parameter, Δ m15(B) = 1.61 ± 0.02. The blueshift of the most isolated [Fe ii] lines in the nebular-phase optical spectrum appears consistent with those observed in the IR at similar epochs. At late times there is a prevalent color evolution from the optical toward the NIR bands. We present the latest-ever detection of a SN Ia in the NIR in Hubble Space Telescope images. The study of the ultraviolet/optical/infrared (UVOIR) light curve reveals that a substantial fraction of the flux is “missing” at late times. Between 300 and 700 days past maximum brightness, the UVOIR light curve declines linearly following the decay of radioactive 56Co, assuming full and instantaneous positron trapping. At 700 days we detect a possible slowdown of the decline in optical-bands, mainly in the V-band. Conclusions: The data are incompatible with a dramatic infrared catastrophe (IRC). However, the idea that an IRC occurred in the densest regions before 350 days can explain the missing flux from the UVOIR wavelengths and the flat-topped profiles in the NIR. We argue that such a scenario is possible if the ejecta are clumpy. The observations suggest that positrons are most likely trapped in the ejecta. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO Programmes 073.D-0294(AB), 074.D-0259(BC) and 075.D-0116(AB)), Cerro Tololo Inter-American Observatory, Lick Observatory, Las Campanas Observatory, Siding Spring Observatory, and the Hubble Space Telescope. Tables 3, 4, and Appendix A are only available in electronic form at http://www.aanda.org
  •  
32.
  • Pastorello, A., et al. (author)
  • Supernovae 2016bdu and 2005gl, and their link with SN 2009ip-like transients : another piece of the puzzle
  • 2018
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 474:1, s. 197-218
  • Journal article (peer-reviewed)abstract
    • Supernova (SN) 2016bdu is an unusual transient resembling SN 2009ip. SN 2009ip-like events are characterized by a long-lasting phase of erratic variability that ends with two luminous outbursts a few weeks apart. The second outburst is significantly more luminous (about 3 mag) than the first. In the case of SN 2016bdu, the first outburst (Event A) reached an absolute magnitude M-r approximate to -15.3 mag, while the second one (Event B) occurred over one month later and reached M-r approximate to -18 mag. By inspecting archival data, a faint source at the position of SN 2016bdu is several times in the past few years. We interpret these detections as signatures of a phase of erratic variability, similar to that experienced by SN 2009ip between 2008 and mid-2012, and resembling the currently observed variability of the luminous blue variable SN 2000ch in NGC 3432. Spectroscopic monitoring of SN 2016bdu during the second peak initially shows features typical of an SN IIn. One month after the Event B maximum, the spectra develop broad Balmer lines with P Cygni profiles and broad metal features. At these late phases, the spectra resemble those of a typical Type II SN. All members of this SN 2009ip-like group are remarkably similar to the Type IIn SN 2005gl. For this object, the claim of a terminal SN explosion is supported by the disappearance of the progenitor star. While the similarity with SN 2005gl supports a genuine SN explosion scenario for SN 2009ip-like events, the unequivocal detection of nucleosynthesized elements in their nebular spectra is still missing.
  •  
33.
  • Reynolds, T. M., et al. (author)
  • SN 2016gsd : an unusually luminous and linear Type II supernova with high velocities
  • 2020
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 493:2, s. 1761-1781
  • Journal article (peer-reviewed)abstract
    • We present observations of the unusually luminous Type II supernova (SN) 2016gsd. With a peak absolute magnitude of V = -19.95 +/- 0.08, this object is one of the brightest Type II SNe, and lies in the gap of magnitudes between the majority of Type II SNe and the superluminous SNe. Its light curve shows little evidence of the expected drop from the optically thick phase to the radioactively powered tail. The velocities derived from the absorption in( )H alpha are also unusually high with the blue edge tracing the fastest moving gas initially at 20 000 km s(-1), and then declining approximately linearly to 15000 km s(-1) over similar to 100 d. The dwarf host galaxy of the SN indicates a low-metallicity progenitor which may also contribute to the weakness of the metal lines in its spectra. We examine SN 2016gsd with reference to similarly luminous, linear Type II SNe such as SNe 1979C and 1998S, and discuss the interpretation of its observational characteristics. We compare the observations with a model produced by the JEKYLL code and find that a massive star with a depleted and inflated hydrogen envelope struggles to reproduce the high luminosity and extreme linearity of SN 2016gsd. Instead, we suggest that the influence of interaction between the SN ejecta and circumstellar material can explain the majority of the observed properties of the SN. The high velocities and strong H alpha absorption present throughout the evolution of the SN may imply a circumstellar medium configured in an asymmetric geometry.
  •  
34.
  • Takats, K., et al. (author)
  • SN 2009ib : a Type II-P supernova with an unusually long plateau
  • 2015
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 450:3, s. 3137-3154
  • Journal article (peer-reviewed)abstract
    • We present optical and near-infrared photometry and spectroscopy of SN 2009ib, a Type II-P supernova in NGC 1559. This object has moderate brightness, similar to those of the intermediate-luminosity SNe 2008in and 2009N. Its plateau phase is unusually long, lasting for about 130 d after explosion. The spectra are similar to those of the subluminous SN 2002gd, with moderate expansion velocities. We estimate the Ni-56 mass produced as 0.046 +/- A 0.015 M-aS (TM). We determine the distance to SN 2009ib using both the expanding photosphere method (EPM) and the standard candle method. We also apply EPM to SN 1986L, a Type II-P SN that exploded in the same galaxy. Combining the results of different methods, we conclude the distance to NGC 1559 as D = 19.8 +/- A 3.0 Mpc. We examine archival, pre-explosion images of the field taken with the Hubble Space Telescope, and find a faint source at the position of the SN, which has a yellow colour [(V - I)(0) = 0.85 mag]. Assuming it is a single star, we estimate its initial mass as M-ZAMS = 20 M-aS (TM). We also examine the possibility, that instead of the yellow source the progenitor of SN 2009ib is a red supergiant star too faint to be detected. In this case, we estimate the upper limit for the initial zero-age main sequence (ZAMS) mass of the progenitor to be similar to 14-17 M-aS (TM). In addition, we infer the physical properties of the progenitor at the explosion via hydrodynamical modelling of the observables, and estimate the total energy as similar to 0.55 x 10(51) erg, the pre-explosion radius as similar to 400 R-aS (TM), and the ejected envelope mass as similar to 15 M-aS (TM), which implies that the mass of the progenitor before explosion was similar to 16.5-17 M-aS (TM).
  •  
35.
  • Tartaglia, L., et al. (author)
  • The Progenitor and Early Evolution of the Type IIb SN 2016gkg
  • 2017
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 836:1
  • Journal article (peer-reviewed)abstract
    • We report initial observations and analysis on the Type IIb SN 2016gkg in the nearby galaxy NGC 613. SN. 2016gkg exhibited a clear double-peaked light curve during its early evolution, as evidenced by our intensive photometric follow-up campaign. SN. 2016gkg shows strong similarities with other Type IIb SNe, in particular, with respect to the He I. emission features observed in both the optical and near-infrared. SN. 2016gkg evolved faster than the prototypical Type. IIb SN. 1993J, with a decline similar to that of SN. 2011dh after the first peak. The analysis of archival Hubble Space Telescope images indicate a pre-explosion source at SN. 2016gkg's position, suggesting a progenitor star with a similar to mid-F spectral type and initial mass 15-20 M-circle dot, depending on the distance modulus adopted for NGC. 613. Modeling the temperature evolution within 5 days of explosion, we obtain a progenitor radius of similar to 48-124 R-circle dot, smaller than that obtained from the analysis of the pre-explosion images (240-320 R-circle dot).
  •  
36.
  • Cai, Y-Z., et al. (author)
  • AT 2017be-a new member of the class of intermediate-luminosity red transients
  • 2018
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 480:3, s. 3424-3445
  • Journal article (peer-reviewed)abstract
    • We report the results of our spectrophotometric monitoring campaign for AT 2017be in NGC 2537. Its light curve reveals a fast rise to an optical maximum, followed by a plateau lasting about 30 d, and finally a fast decline. Its absolute peak magnitude (M-r similar or equal to -12 mag) is fainter than that of core-collapse supernovae, and is consistent with those of supernova impostors and other intermediate-luminosity optical transients. The quasi-bolometric light-curve peaks at similar to 2 x 10(40) erg s(-1), and the late-time photometry allows us to constrain an ejected Ni-56 mass of similar to 8 x 10(-4)M(circle dot). The spectra of AT 2017 be show minor evolution over the observational period, a relatively blue continuum showing at early phases, which becomes redder with time. A prominent H alpha emission line always dominates over other Balmer lines. Weak Fe II features, Can H&K, and the Ca II NIR triplet are also visible, while P-Cygni absorption troughs are found in a high-resolution spectrum. In addition, the [Ca II] lambda lambda 7291, 7324 doublet is visible in all spectra. This feature is typical of intermediate-luminosity red transients (ILRTs), similar to SN 2008S. The relatively shallow archival Spitzer data are not particularly constraining. On the other hand, a non-detection in deeper near-infrared HST images disfavours a massive Luminous Blue Variable eruption as the origin for AT 2017be. As has been suggested for other ILRTs, we propose that AT 2017be is a candidate for a weak electron-capture supernova explosion of a superasymptotic giant branch star, still embedded in a thick dusty envelope.
  •  
37.
  • Kangas, T., et al. (author)
  • Gaia16apd-a link between fast and slowly declining type I superluminous supernovae
  • 2017
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 469:1, s. 1246-1258
  • Journal article (peer-reviewed)abstract
    • We present ultraviolet (UV), optical and infrared photometry and optical spectroscopy of the type Ic superluminous supernova (SLSN) Gaia16apd (= SN 2016eay), covering its evolution from 26 d before the g-band peak to 234.1 d after the peak. Gaia16apd was followed as a part of the NOT Unbiased Transient Survey (NUTS). It is one of the closest SLSNe known (z = 0.102 +/- 0.001), with detailed optical and UV observations covering the peak. Gaia16apd is a spectroscopically typical type Ic SLSN, exhibiting the characteristic blue early spectra with O II absorption, and reaches a peak M-g = -21.8 +/- 0.1 mag. However, photometrically it exhibits an evolution intermediate between the fast and slowly declining type Ic SLSNe, with an early evolution closer to the fast-declining events. Together with LSQ12dlf, another SLSN with similar properties, it demonstrates a possible continuum between fast and slowly declining events. It is unusually UV-bright even for an SLSN, reaching a non-K-corrected M-uvm2 similar or equal to -23.3 mag, the only other type Ic SLSN with similar UV brightness being SN 2010gx. Assuming that Gaia16apd was powered by magnetar spin-down, we derive a period of P = 1.9 +/- 0.2 ms and a magnetic field of B = 1.9 +/- 0.2 x 10(14) G for the magnetar. The estimated ejecta mass is between 8 and 16 M circle dot, and the kinetic energy between 1.3 and 2.5 x 10(52) erg, depending on opacity and assuming that the entire ejecta is swept up into a thin shell. Despite the early photometric differences, the spectra at late times are similar to slowly declining type Ic SLSNe, implying that the two subclasses originate from similar progenitors.
  •  
38.
  • Krisciunas, Kevin, et al. (author)
  • THE MOST SLOWLY DECLINING TYPE Ia SUPERNOVA 2001ay
  • 2011
  • In: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 142:3, s. 74-
  • Journal article (peer-reviewed)abstract
    • We present optical and near-infrared photometry, as well as ground-based optical spectra and Hubble Space Telescope ultraviolet spectra, of the Type Ia supernova (SN) 2001ay. At maximum light the Si II and Mg II lines indicated expansion velocities of 14,000 km s-(1), while Si III and S II showed velocities of 9000 km s(-1). There is also evidence for some unburned carbon at 12,000 km s(-1). SN 2001ay exhibited a decline-rate parameter of Delta m(15)(B) = 0.68 +/- 0.05 mag; this and the B-band photometry at t greater than or similar to + 25 day past maximum make it the most slowly declining Type Ia SN yet discovered. Three of the four super-Chandrasekhar-mass candidates have decline rates almost as slow as this. After correction for Galactic and host-galaxy extinction, SN 2001ay had M(B) = -19.19 and M(V) = -19.17 mag at maximum light; thus, it was not overluminous in optical bands. In near-infrared bands it was overluminous only at the 2 sigma level at most. For a rise time of 18 days (explosion to bolometric maximum) the implied (56)Ni yield was (0.58 +/- 0.15)/alpha M(circle dot), with alpha = L(max)/E(Ni) probably in the range 1.0-1.2. The (56)Ni yield is comparable to that of many Type Ia SNe. The normal (56)Ni yield and the typical peak optical brightness suggest that the very broad optical light curve is explained by the trapping of gamma rays in the inner regions.
  •  
39.
  • Stritzinger, M. D., et al. (author)
  • Optical and near-IR observations of the faint and fast 2008ha-like supernova 2010ae
  • 2014
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 561, s. A146-
  • Journal article (peer-reviewed)abstract
    • A comprehensive set of optical and near-infrared (NIR) photometry and spectroscopy is presented for the faint and fast 2008ha-like supernova (SN) 2010ae. Contingent on the adopted value of host extinction, SN 2010ae reached a peak brightness of -13.8 > M-V > -15.3 mag, while modeling of the UVOIR light curve suggests it produced 0.003-0.007 M-circle dot of Ni-56, ejected 0.30-0.60 M-circle dot of material, and had an explosion energy of 0.04-0.30 x 10(51) erg. The values of these explosion parameters are similar to the peculiar SN 2008ha -for which we also present previously unpublished early phase optical and NIR light curves - and places these two transients at the faint end of the 2002cx-like SN population. Detailed inspection of the post-maximum NIR spectroscopic sequence indicates the presence of a multitude of spectral features, which are identified through SYNAPPS modeling to be mainly attributed to Co II. Comparison with a collection of published and unpublished NIR spectra of other 2002cx-like SNe, reveals that a Co II footprint is ubiquitous to this subclass of transients, providing a link to Type Ia SNe. A visual-wavelength spectrum of SN 2010ae obtained at +252 days past maximum shows a striking resemblance to a similar epoch spectrum of SN 2002cx. However, subtle differences in the strength and ratio of calcium emission features, as well as diversity among similar epoch spectra of other 2002cx-like SNe indicates a range of physical conditions of the ejecta, highlighting the heterogeneous nature of this peculiar class of transients.
  •  
40.
  • Stritzinger, M. D., et al. (author)
  • The Carnegie Supernova Project I : Photometry data release of low-redshift stripped-envelope supernovae
  • 2018
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 609
  • Journal article (peer-reviewed)abstract
    • The first phase of the Carnegie Supernova Project (CSP-I) was a dedicated supernova follow-up program based at the Las Campanas Observatory that collected science data of young, low-redshift supernovae between 2004 and 2009. Presented in this paper is the CSP-I photometric data release of low-redshift stripped-envelope core-collapse supernovae. The data consist of optical (uBgVri) photometry of 34 objects, with a subset of 26 having near-infrared (YJH) photometry. Twenty objects have optical pre-maximum coverage with a subset of 12 beginning at least five days prior to the epoch of B-band maximum brightness. In the near-infrared, 17 objects have pre-maximum observations with a subset of 14 beginning at least five days prior to the epoch of J-band maximum brightness. Analysis of this photometric data release is presented in companion papers focusing on techniques to estimate host-galaxy extinction and the light-curve and progenitor star properties of the sample. The analysis of an accompanying visual-wavelength spectroscopy sample of similar to 150 spectra will be the subject of a future paper.
  •  
41.
  • Taddia, Francesco, et al. (author)
  • Supernova 2008J : early time observations of a heavily reddened SN 2002ic-like transient
  • 2012
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 545, s. L7-
  • Journal article (peer-reviewed)abstract
    • Aims: We provide additional observational evidence that some Type Ia supernovae (SNe Ia) show signatures of circumstellar interaction (CSI) with hydrogen-rich material. Methods: Early phase optical and near-infrared (NIR) light curves and spectroscopy of SN 2008J obtained by the Carnegie Supernova Project are studied and compared to those of SNe 2002ic and 2005gj. Our NIR spectrum is the first obtained for a 2002ic-like object extending up to 2.2 μm. A published high-resolution spectrum is used to provide insight on the circumstellar material (CSM). Results: SN 2008J is found to be affected by AV ~ 1.9 mag of extinction and to closely resemble SN 2002ic. Spectral and color comparison to SNe 2002ic and 2005gj suggests RV < 3.1. Spectral decomposition reveals the underlying SN emission matches a 1991T-like event and, since SN 2008J is as luminous as SN 2005gj (Vmax = -20.3 mag), we conclude that their CSI emissions are similarly robust. The high-resolution spectrum reveals narrow emission lines produced from un-shocked gas characterized by a wind velocity of ~50 km s-1. We conclude that SN 2008J best matches an explosion of a SN Ia that interacts with its CSM. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (ESO Programme 080.A-0516).Figure 4 and Tables 1-6 are available in electronic form at http://www.aanda.org
  •  
42.
  • Östman, Linda, et al. (author)
  • NTT and NOT spectroscopy of SDSS-II supernovae
  • 2011
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 526, s. A28-
  • Journal article (peer-reviewed)abstract
    • Context. The Sloan Digital Sky Survey II (SDSS-II) Supernova Survey, conducted between 2005 and 2007, was designed to detect a large number of type Ia supernovae around z ~ 0.2, the redshift "gap" between low-z and high-z supernova searches. The survey has provided multi-band (ugriz) photometric lightcurves for variable targets, and supernova candidates were scheduled for spectroscopic observations, primarily to provide supernova classification and accurate redshifts. We present supernova spectra obtained in 2006 and 2007 using the New Technology Telescope (NTT) and the Nordic Optical Telescope (NOT). Aims: We provide an atlas of supernova spectra in the range z = 0.03-0.32 that complements the well-sampled lightcurves from SDSS-II in the forthcoming three-year SDSS supernova cosmology analysis. The sample can, for example, be used for spectral studies of type Ia supernovae, which are critical for understanding potential systematic effects when supernovae are used to determine cosmological distances. Methods: The spectra were reduced in a uniform manner, and special care was taken in estimating the uncertainties for the different processing steps. Host-galaxy light was subtracted when possible and the supernova type fitted using the SuperNova IDentification code (SNID). We also present comparisons between spectral and photometric dating using SALT lightcurve fits to the photometry from SDSS-II, as well as the global distribution of our sample in terms of the lightcurve parameters: stretch and colour. Results: We report new spectroscopic data from 141 type Ia supernovae, mainly between -9 and +15 days from lightcurve maximum, including a few cases of multi-epoch observations. This homogeneous, host-galaxy subtracted, type Ia supernova spectroscopic sample is among the largest such data sets and unique in its redshift interval. The sample includes two potential SN 1991T-like supernovae (SN 2006on and SN 2007ni) and one potential SN 2002cx-like supernova (SN 2007ie). In addition, the new compilation includes spectra from 23 confirmed type II and 8 type Ib/c supernovae.
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43.
  • Ashall, C., et al. (author)
  • Carnegie Supernova Project-II : Using Near-infrared Spectroscopy to Determine the Location of the Outer Ni-56 in Type Ia Supernovae
  • 2019
  • In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 875:2
  • Journal article (peer-reviewed)abstract
    • We present the H-band wavelength region of 37 postmaximum light near-infrared spectra of three normal, nine transitional, and four subluminous type. Ia supernovae (SNe Ia), extending from +5. days to +20. days relative to the epoch of B-band maximum. We introduce a new observable, the blue-edge velocity, v(edge), of the prominent Fe/Co/Ni-peak H-band emission feature, which is quantitatively measured. The v(edge) parameter is found to decrease over subtype ranging from around -14,000 km s(-1) for normal SNe Ia, to -10,000 km s(-1) for transitional SNe. Ia, down to -5000 km s(-1) for the subluminous SNe. Ia. Furthermore, inspection of the +10 +/- 3 days spectra indicates that v(edge) is correlated with the color-stretch parameter, s(BV), and hence with peak luminosity. These results follow the previous findings that brighter SNe. Ia tend to have Ni-56 located at higher velocities as compared to subluminous objects. As v(edge) is a model-independent parameter, we propose it can be used in combination with traditional observational diagnostics to provide a new avenue to robustly distinguish between leading SNe. Ia explosion models.
  •  
44.
  • Fox, Ori D., et al. (author)
  • The slow demise of the long-lived SN 2005ip
  • 2020
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 498:1, s. 517-531
  • Journal article (peer-reviewed)abstract
    • The Type IIn supernova (SN IIn) 2005ip is one of the most well-studied and long-lasting examples of an SN interacting with its circumstellar environment. The optical light curve plateaued at a nearly constant level for more than five years, suggesting ongoing shock interaction with an extended and clumpy circumstellar medium (CSM). Here, we present continued observations of the SN from ∼1000 to 5000 d post-explosion at all wavelengths, including X-ray, ultraviolet, near-infrared (NIR), and mid-infrared. The UV spectra probe the pre-explosion mass loss and show evidence for CNO processing. From the bolometric light curve, we find that the total radiated energy is in excess of 1050 erg, the progenitor star’s pre-explosion mass-loss rate was ≳1×10−2M⊙ yr−1⁠, and the total mass lost shortly before explosion was ≳1M⊙⁠, though the mass lost could have been considerably larger depending on the efficiency for the conversion of kinetic energy to radiation. The ultraviolet through NIR spectrum is characterized by two high-density components, one with narrow high-ionization lines, and one with broader low-ionization H i, He i, [O i], Mg ii, and Fe ii lines. The rich Fe ii spectrum is strongly affected by Lyα fluorescence, consistent with spectral modelling. Both the Balmer and He i lines indicate a decreasing CSM density during the late interaction period. We find similarities to SN 1988Z, which shows a comparable change in spectrum at around the same time during its very slow decline. These results suggest that, at long last, the shock interaction in SN 2005ip may finally be on the decline.
  •  
45.
  • Gall, C., et al. (author)
  • Two transitional type Ia supernovae located in the Fornax cluster member NGC 1404 : SN 2007on and SN 2011iv
  • 2018
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 611
  • Journal article (peer-reviewed)abstract
    • We present an analysis of ultraviolet (UV) to near-infrared observations of the fast-declining Type Ia supernovae (SNe Ia) 2007on and 2011iv, hosted by the Fornax cluster member NGC 1404. The B-band light curves of SN 2007on and SN 2011iv are characterised by Delta m(15)(B) decline-rate values of 1.96 mag and 1.77 mag, respectively. Although they have similar decline rates, their peak B-and H-band magnitudes di ff er by similar to 0.60 mag and similar to 0.35 mag, respectively. After correcting for the luminosity vs. decline rate and the luminosity vs. colour relations, the peak B-band and H-band light curves provide distances that di ff er by similar to 14% and similar to 9%, respectively. These findings serve as a cautionary tale for the use of transitional SNe Ia located in early-type hosts in the quest to measure cosmological parameters. Interestingly, even though SN 2011iv is brighter and bluer at early times, by three weeks past maximum and extending over several months, its B - V colour is 0.12 mag redder than that of SN 2007on. To reconcile this unusual behaviour, we turn to guidance from a suite of spherical one-dimensional Chandrasekhar-mass delayed-detonation explosion models. In this context, Ni-56 production depends on both the so-called transition density and the central density of the progenitor white dwarf. To first order, the transition density drives the luminosity-width relation, while the central density is an important second-order parameter. Within this context, the di ff erences in the B - V colour evolution along the Lira regime suggest that the progenitor of SN 2011iv had a higher central density than SN 2007on.
  •  
46.
  • Leloudas, G., et al. (author)
  • SN 2006oz : rise of a super-luminous supernova observed by the SDSS-II SN Survey
  • 2012
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 541, s. A129-
  • Journal article (peer-reviewed)abstract
    • Context. A new class of super-luminous transients has recently been identified. These objects reach absolute luminosities of M-u < -21, lack hydrogen in their spectra, and are exclusively discovered by non-targeted surveys because they are associated with very faint galaxies. Aims. We aim to contribute to a better understanding of these objects by studying SN 2006oz, a newly-recognized member of this class. Methods. We present multi-color light curves of SN 2006oz from the SDSS-II SN Survey that cover its rise time, as well as an optical spectrum that shows that the explosion occurred at z similar to 0.376. We fitted black-body functions to estimate the temperature and radius evolution of the photosphere and used the parametrized code SYNOW to model the spectrum. We constructed a bolometric light curve and compared it with explosion models. In addition, we conducted a deep search for the host galaxy with the 10 m GTC telescope. Results. The very early light curves show a dip in the g-and r-bands and a possible initial cooling phase in the u-band before rising to maximum light. The bolometric light curve shows a precursor plateau with a duration of 6-10 days in the rest-frame. A lower limit of M-u < -21.5 can be placed on the absolute peak luminosity of the SN, while the rise time is constrained to be at least 29 days. During our observations, the emitting sphere doubled its radius to similar to 2 x 10(15) cm, while the temperature remained hot at similar to 15 000 K. As for other similar SNe, the spectrum is best modeled with elements including O II and Mg II, while we tentatively suggest that Fe III might be present. The host galaxy is detected in gri with 25.74 +/- 0.19, 24.43 +/- 0.06, and 24.14 +/- 0.12, respectively. It is a faint dwarf galaxy with M-g = -16.9. Conclusions. We suggest that the precursor plateau might be related to a recombination wave in a circumstellar medium (CSM) and discuss whether this is a common property of all similar explosions. The subsequent rise can be equally well described by input from a magnetar or by ejecta-CSM interaction, but the models are not well constrained owing to the lack of post-maximum observations, and CSM interaction has difficulties accounting for the precursor plateau self-consistently. Radioactive decay is less likely to be the mechanism that powers the luminosity. The host is a moderately young and star-forming, but not a starburst, galaxy.
  •  
47.
  • Oates, S. R., et al. (author)
  • Multiwavelength observations of the Type IIb supernova 2009mg
  • 2012
  • In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 424:2, s. 1297-1306
  • Journal article (peer-reviewed)abstract
    • We present Swift Ultra-Violet Optical Telescope and X-Ray Telescope (XRT) observations, and visual wavelength spectroscopy of the Type IIb supernova (SN) 2009mg, discovered in the Sb galaxy ESO 121-G26. The observational properties of SN 2009mg are compared to the prototype Type IIb SNe 1993J and 2008ax, with which we find many similarities. However, minor differences are discernible including SN 2009mg not exhibiting an initial fast decline or u-band upturn as observed in the comparison objects, and its rise to maximum is somewhat slower leading to slightly broader light curves. The late-time temporal index of SN 2009mg, determined from 40 d post-explosion, is consistent with the decay rate of SN 1993J, but inconsistent with the decay of 56Co. This suggests leakage of ?-rays out of the ejecta and a stellar mass on the small side of the mass distribution. Our XRT non-detection provides an upper limit on the mass-loss rate of the progenitor of . Modelling of the SN light curve indicates a kinetic energy of , an ejecta mass of and a 56Ni mass of 0.10 +/- 0.01 M?.
  •  
48.
  • Pastorello, A., et al. (author)
  • SN 2009E : a faint clone of SN 1987A
  • 2012
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 537
  • Journal article (peer-reviewed)abstract
    • Context. 1987A-like events form a rare sub-group of hydrogen-rich core-collapse supernovae that are thought to originate from the explosion of blue supergiant stars. Although SN 1987A is the best known supernova, very few objects of this group have been discovered and, hence, studied. Aims. In this paper we investigate the properties of SN 2009E, which exploded in a relatively nearby spiral galaxy (NGC 4141) and that is probably the faintest 1987A-like supernova discovered so far. We also attempt to characterize this subgroup of core-collapse supernovae with the help of the literature and present new data for a few additional objects. Methods. The lack of early-time observations from professional telescopes is compensated by frequent follow-up observations performed by a number of amateur astronomers. This allows us to reconstruct a well-sampled light curve for SN 2009E. Spectroscopic observations which started about 2 months after the supernova explosion, highlight significant differences between SN 2009E and the prototypical SN 1987A. Modelling the data of SN 2009E allows us to constrain the explosion parameters and the properties of the progenitor star, and compare the inferred estimates with those available for the similar SNe 1987A and 1998A. Results. The light curve of SN 2009E is less luminous than that of SN 1987A and the other members of this class, and the maximum light curve peak is reached at a slightly later epoch than in SN 1987A. Late-time photometric observations suggest that SN 2009E ejected about 0.04 M-circle dot of Ni-56, which is the smallest Ni-56 mass in our sample of 1987A-like events. Modelling the observations with a radiation hydrodynamics code, we infer for SN 2009E a kinetic plus thermal energy of about 0.6 foe, an initial radius of similar to 7x10(12) cm and an ejected mass of similar to 19 M-circle dot. The photospheric spectra show a number of narrow (v approximate to 1800 km s(-1)) metal lines, with unusually strong Ba II lines. The nebular spectrum displays narrow emission lines of H, Na I, [Ca II] and [O I], with the [O I] feature being relatively strong compared to the [Ca II] doublet. The overall spectroscopic evolution is reminiscent of that of the faint Ni-56-poor type II-plateau supernovae. This suggests that SN 2009E belongs to the low-luminosity, low Ni-56 mass, low-energy tail in the distribution of the 1987A-like objects in the same manner as SN 1997D and similar events represent the faint tail in the distribution of physical properties for normal type II-plateau supernovae.
  •  
49.
  • Stritzinger, M. D., et al. (author)
  • Comprehensive observations of the bright and energetic Type lax SN 2012Z : Interpretation as a Chandrasekhar mass white dwarf explosion
  • 2015
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 573
  • Journal article (peer-reviewed)abstract
    • We present ultraviolet through near-infrared (NIR) broadband photometry, and visual-wavelength and NIR spectroscopy of the Type lax supernova (SN) 2012Z. The data set consists of both early- and late-time observations, including the first late phase NIR spectrum obtained for a spectroscopically classified SN lax. Simple model calculations of its bolometric light curve suggest SN 2012Z produced similar to 0.3 M-circle dot of Ni-56, ejected about a Chandrasekhar mass of material, and had an explosion energy of similar to 10(51) erg, making it one of the brightest (M-B = -18.3 mag) and most energetic SN Iax yet observed. The late phase (+269d) NIR spectrum of SN 2012Z is found to broadly resemble similar epoch spectra of normal SNe Ia; however, like other SNe Iax, corresponding visual-wavelength spectra differ substantially from all supernova types. Constraints from the distribution of intermediate mass elements, e.g., silicon and magnesium, indicate that the outer ejecta did not experience significant mixing during or after burning, and the late phase NIR line profiles suggests most of the Ni-56 is produced during high density burning. The various observational properties of SN 2012Z are found to be consistent with the theoretical expectations of a Chandrasekhar mass white dwarf progenitor that experiences a pulsational delayed detonation, which produced several tenths of a solar mass of Ni-56 during the deflagration burning phase and little (or no) Ni-56 during the detonation phase. Within this scenario only a moderate amount of Rayleigh-Taylor mixing occurs both during the deflagration and fallback phase of the pulsation, and the layered structure of the intermediate mass elements is a product of the subsequent denotation phase. The fact that the SNe lax population does not follow a tight brightness-decline relation similar to SNe Ia can then be understood in the framework of variable amounts of mixing during pulsational rebound and variable amounts of Ni-56 production during the early subsonic phase of expansion.
  •  
50.
  • Stritzinger, M. D., et al. (author)
  • The Carnegie Supernova Project I : Methods to estimate host-galaxy reddening of stripped-envelope supernovae
  • 2018
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 609
  • Journal article (peer-reviewed)abstract
    • We aim to improve upon contemporary methods to estimate host-galaxy reddening of stripped-envelope (SE) supernovae (SNe). To this end the Carnegie Supernova Project (CSP-I) SE SN photometry data release, consisting of nearly three dozen objects, is used to identify a minimally reddened sub-sample for each traditionally defined spectroscopic sub-type (i.e., SNe IIb, SNe Ib, SNe Ic). Inspection of the optical and near-infrared (NIR) colors and color evolution of the minimally reddened sub-samples reveals a high degree of homogeneity, particularly between 0 d to +20 d relative to B-band maximum. This motivated the construction of intrinsic color-curve templates, which when compared to the colors of reddened SE SNe, yields an entire suite of optical and NIR color excess measurements. Comparison of optical/optical vs. optical/NIR color excess measurements indicates the majority of the CSP-I SE SNe suffer relatively low amounts of reddening (i.e., E(B - V)(host) < 0.20 mag) and we find evidence for different R-host(V) values among di ff erent SE SN. Fitting the color excess measurements of the seven most reddened (i. e., E(B - V)(host) > 0.20 mag) objects with the Fitzpatrick (1999, PASP, 111, 63) reddening law model provides robust estimates of the host visual-extinction A(host)(V) and R-host(V). In the case of the SE SNe with relatively low amounts of reddening, a preferred value of R-host(V) is adopted for each sub-type, resulting in estimates of A(V)(host) through Fitzpatrick (1999) reddening law model fits to the observed color excess measurements. Our analysis suggests SE SNe reside in galaxies characterized by a range of dust properties. We also find evidence that SNe Ic are more likely to occur in regions characterized by larger A(V)(host) values compared to SNe IIb/Ib and they also tend to suffer more extinction. The later finding is consistent with work in the literature suggesting SNe Ic tend to occur in regions of on-going star formation.
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