31. |
- Tartaglia, Leonardo, et al.
(författare)
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SN 2018ijp : the explosion of a stripped-envelope star within a dense H-rich shell?
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 650
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we discuss the outcomes of the follow-up campaign of SN 2018ijp, discovered as part of the Zwicky Transient Facility survey for optical transients. Its first spectrum shows similarities to broad-lined Type Ic supernovae around maximum light, whereas later spectra display strong signatures of interaction between rapidly expanding ejecta and a dense H-rich circumstellar medium, coinciding with a second peak in the photometric evolution of the transient. This evolution, along with the results of modeling of the first light-curve peak, suggests a scenario where a stripped star exploded within a dense circumstellar medium. The two main phases in the evolution of the transient could be interpreted as a first phase dominated by radioactive decays, and a later interaction-dominated phase where the ejecta collide with a pre-existing shell. We therefore discuss SN 2018jp within the context of a massive star depleted of its outer layers exploding within a dense H-rich circumstellar medium.
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32. |
- Tartaglia, Leonardo, et al.
(författare)
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The Early Discovery of SN 2017ahn : Signatures of Persistent Interaction in a Fast-declining Type II Supernova
- 2021
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 907:1
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Tidskriftsartikel (refereegranskat)abstract
- We present high-cadence, comprehensive data on the nearby (D 33 Mpc) Type II supernova (SN II) 2017ahn, discovered within about one day of the explosion, from the very early phases after explosion to the nebular phase. The observables of SN 2017ahn show a significant evolution over the 470 days of our follow-up campaign, first showing prominent, narrow Balmer lines and other high-ionization features purely in emission (i.e., flash spectroscopy features), which progressively fade and lead to a spectroscopic evolution similar to that of more canonical SNe II. Over the same period, the decline of the light curves in all bands is fast, resembling the photometric evolution of linearly declining H-rich core-collapse SNe. The modeling of the light curves and early flash spectra suggests that a complex circumstellar medium surrounds the progenitor star at the time of explosion, with a first dense shell produced during the very late stages of its evolution that is swept up by the rapidly expanding ejecta within the first ~6 days of the SN evolution, while signatures of interaction are observed also at later phases. Hydrodynamical models support the scenario in which linearly declining SNe II are predicted to arise from massive yellow super- or hypergiants depleted of most of their hydrogen layers.
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33. |
- Tartaglia, Leonardo, et al.
(författare)
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The long-lived Type IIn SN 2015da : Infrared echoes and strong interaction within an extended massive shell star star star
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 635
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we report the results of the first similar to four years of spectroscopic and photometric monitoring of the Type IIn supernova SN 2015da (also known as PSN J13522411+3941286, or iPTF16tu). The supernova exploded in the nearby spiral galaxy NGC 5337 in a relatively highly extinguished environment. The transient showed prominent narrow Balmer lines in emission at all times and a slow rise to maximum in all bands. In addition, early observations performed by amateur astronomers give a very well-constrained explosion epoch. The observables are consistent with continuous interaction between the supernova ejecta and a dense and extended H-rich circumstellar medium. The presence of such an extended and dense medium is difficult to reconcile with standard stellar evolution models, since the metallicity at the position of SN 2015da seems to be slightly subsolar. Interaction is likely the mechanism powering the light curve, as confirmed by the analysis of the pseudo bolometric light curve, which gives a total radiated energy greater than or similar to 10(51) erg. Modeling the light curve in the context of a supernova shock breakout through a dense circumstellar medium allowed us to infer the mass of the prexisting gas to be similar or equal to 8 M-circle dot, with an extreme mass-loss rate for the progenitor star similar or equal to 0.6 M-circle dot yr(-1), suggesting that most of the circumstellar gas was produced during multiple eruptive events. Near- and mid-infrared observations reveal a fluxexcess in these domains, similar to those observed in SN 2010jl and other interacting transients, likely due to preexisting radiatively heated dust surrounding the supernova. By modeling the infrared excess, we infer a mass greater than or similar to 0.4 x 10(-3) M-circle dot for the dust.
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34. |
- Yan, Lin, et al.
(författare)
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Helium-rich Superluminous Supernovae from the Zwicky Transient Facility
- 2020
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 902:1
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Tidskriftsartikel (refereegranskat)abstract
- Helium is expected to be present in the massive ejecta of some hydrogen-poor superluminous supernovae (SLSN-I). However, until now only one event has been identified with He features in its photospheric spectra (PTF10hgi). We present the discovery of a new He-rich SLSN-I, ZTF19aawfbtg (SN2019hge), atz = 0.0866. This event has more than 10 optical spectra at phases from -41 to +103 days relative to the peak, most of which match well with that of PTF10hgi. Confirmation comes from a near-IR spectrum taken at +34 days, revealing Heifeatures with P-Cygni profiles at 1.083 and 2.058 mu m. Using the optical spectra of PTF10hgi and SN2019hge as templates, we examined 70 other SLSNe-I discovered by Zwicky Transient Facility in the first two years of operation and found five additional SLSNe-I with distinct He-features. The excitation of Heiatoms in normal core-collapse supernovae requires nonthermal radiation, as proposed by previous studies. These He-rich events cannot be explained by the traditional(56)Ni mixing model because of their blue spectra, high peak luminosities, and long rise timescales. Magnetar models offer a possible solution since pulsar winds naturally generate high-energy particles, potential sources of nonthermal excitation. An alternative model is the interaction between the ejecta and dense H-poor circumstellar material, which may be supported by observed undulations in the light curves. These six SLSNe-Ib have relatively low-peak luminosities (rest frameM(g) = -20.06 0.16).
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35. |
- Yang, Sheng, et al.
(författare)
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Optical Follow-up of Gravitational-wave Events during the Second Advanced LIGO/VIRGO Observing Run with the DLT40 Survey
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 875:1
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Tidskriftsartikel (refereegranskat)abstract
- We describe the gravitational-wave (GW) follow-up strategy and subsequent results of the Distance Less Than 40 Mpc survey (DLT40) during the second science run (O2) of the Laser Interferometer Gravitational-wave Observatory and Virgo collaboration (LVC). Depending on the information provided in the GW alert together with the localization map sent by the LVC, DLT40 would respond promptly to image the corresponding galaxies selected by our ranking algorithm in order to search for possible electromagnetic (EM) counterparts in real time. During the LVC O2 run, DLT40 followed 10 GW triggers, observing between similar to 20 and 100 galaxies within the GW localization area of each event. From this campaign, we identified two real transient sources within the GW localizations with an appropriate on-source time-one was an unrelated SN Ia (SN 2017cbv), and the other was the optical kilonova, AT 2017fgo/SSS17a/DLT17ck, associated with the binary neutron star (BNS) coalescence GW170817 (a.k.a gamma-ray burst GRB 170817A). We conclude with a discussion of the DLT40 survey's plans for the upcoming LVC O3 run, which include expanding our galaxy search fields out to D approximate to 65 Mpc to match the LVC's planned three-detector sensitivity for BNS mergers.
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36. |
- Zhang, Kaicheng, et al.
(författare)
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SN 2014J in M82 : new insights on the spectral diversity of Type Ia supernovae
- 2018
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 481:1, s. 878-893
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Tidskriftsartikel (refereegranskat)abstract
- We present extensive spectroscopic observations for one of the closest Type Ia supernovae (SNe Ia), SN 2014J discovered in M82, ranging from 10.4 d before to 473.2 d after B-band maximum light. The diffuse interstellar band features detected in a high-resolution spectrum allow an estimate of line-of-sight extinction as A(v) similar to 1.9 +/- 0.6 mag. Spectroscopically, SN 2014J can be put into the high-velocity (HV) subgroup in Wang's classification with a velocity of Si II lambda 6355 at maximum light of upsilon(0) = 1.22 +/- 0.01 x 10(4) km s(-1) but has a low velocity gradient (LVG, following Benetti's classification) of (v) over bar = 41 +/- 2 km s(-1) d(-1), which is inconsistent with the trend that HV SNe Ia generally have larger velocity gradients. We find that the HV SNe Ia with LVGs tend to have relatively stronger Si III (at similar to 4400 angstrom) absorptions in early spectra, larger ratios of S II lambda 5468 to S II lambda 5640, and weaker Si II 5972 absorptions compared to their counterparts with similar velocities but high velocity gradients. This shows that the HV+ LVG subgroup of SNe Ia may have intrinsically higher photospheric temperature, which indicates that their progenitors may experience more complete burning in the explosions relative to the typical HV SNe Ia.
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37. |
- Zhang, Tianmeng, et al.
(författare)
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Observations of a Fast-expanding and UV-bright Type Ia Supernova SN 2013gs
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 872:1
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present extensive optical and ultraviolet (UV) observations of the type Ia supernova (SN Ia) 2013gs discovered during the Tsinghua-NAOC Transient Survey. The photometric observations in the optical show that the light curves of SN 2013gs are similar to those of normal SNe Ia, with an absolute peak magnitude of M-B = -19.25 +/- 0.15 mag and a post-maximum decline rate Delta m(15)(B) = 1.00 +/- 0.05 mag. Gehrels Swift Ultr-Violet/Optical Telescope observations indicate that SN 2013gs shows unusually strong UV emission (especially in the uvw1 band) at around the maximum light (M-uvw1 similar to -18.9 mag). The SN is characterized by relatively weak Fe II III absorptions at similar to 5000 angstrom in the early spectra and a larger expansion velocity (v(Si) similar to 13,000 km s(-1) around the maximum light) than the normal-velocity SNe Ia. We discuss the relation between the uvw1 - v color and some observables, including Si II velocity, line strength of Si II lambda 6355 and Fe II/III lines, and Delta m(15)(B). Compared to other fast-expanding SNe Ia, SN 2013gs exhibits Si and Fe absorption lines with similar strength and bluer uvw1 - v color. We briefly discussed the origin of the observed UV dispersion of SNe Ia.
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38. |
- Glasbey, JC, et al.
(författare)
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- 2021
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swepub:Mat__t
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