| 1. |
- Schulze, S., et al.
(författare)
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GRB 120422A/SN 2012bz : Bridging the gap between low- and high-luminosity gamma-ray bursts
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 566
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Tidskriftsartikel (refereegranskat)abstract
- Context. At low redshift, a handful of gamma-ray bursts (GRBs) have been discovered with luminosities that are substantially lower (L-iso less than or similar to 10(48.5) erg s(-1)) than the average of more distant ones (L-iso greater than or similar to 10(49.5) erg s(-1)). It has been suggested that the properties of several low-luminosity (low-L) GRBs are due to shock break-out, as opposed to the emission from ultrarelativistic jets. This has led to much debate about how the populations are connected. Aims. The burst at redshift z = 0.283 from 2012 April 22 is one of the very few examples of intermediate-L GRBs with a gamma-ray luminosity of L-iso similar to 10(49.6-49.9) erg s(-1) that have been detected up to now. With the robust detection of its accompanying supernova SN 2012bz, it has the potential to answer important questions on the origin of low-and high-L GRBs and the GRB-SN connection. Methods. We carried out a spectroscopy campaign using medium-and low-resolution spectrographs with 6-10-m class telescopes, which covered a time span of 37.3 days, and a multi-wavelength imaging campaign, which ranged from radio to X-ray energies over a duration of similar to 270 days. Furthermore, we used a tuneable filter that is centred at H alpha to map star-formation in the host and the surrounding galaxies. We used these data to extract and model the properties of different radiation components and fitted the spectral energy distribution to extract the properties of the host galaxy. Results. Modelling the light curve and spectral energy distribution from the radio to the X-rays revealed that the blast wave expanded with an initial Lorentz factor of Gamma(0) similar to 50, which is a low value in comparison to high-L GRBs, and that the afterglow had an exceptionally low peak luminosity density of less than or similar to 2 x 10(30) erg s(-1) Hz(-1) in the sub-mm. Because of the weak afterglow component, we were able to recover the signature of a shock break-out in an event that was not a genuine low-L GRB for the first time. At 1.4 hr after the burst, the stellar envelope had a blackbody temperature of k(B)T similar to 16 eV and a radius of similar to 7 x 10(13) cm (both in the observer frame). The accompanying SN 2012bz reached a peak luminosity of M-V = -19.7 mag, which is 0.3 mag more luminous than SN 1998bw. The synthesised nickel mass of 0.58 M-circle dot, ejecta mass of 5.87 M-circle dot, and kinetic energy of 4.10x10(52) erg were among the highest for GRB-SNe, which makes it the most luminous spectroscopically confirmed SN to date. Nebular emission lines at the GRB location were visible, which extend from the galaxy nucleus to the explosion site. The host and the explosion site had close-to-solar metallicity. The burst occurred in an isolated star-forming region with an SFR that is 1/10 of that in the galaxy's nucleus. Conclusions. While the prompt gamma-ray emission points to a high-L GRB, the weak afterglow and the low Gamma(0) were very atypical for such a burst. Moreover, the detection of the shock break-out signature is a new quality for high-L GRBs. So far, shock break-outs were exclusively detected for low-L GRBs, while GRB 120422A had an intermediate L-iso of similar to 10(49.6-49.9) erg s(-1). Therefore, we conclude that GRB 120422A was a transition object between low-and high-L GRBs, which supports the failed-jet model that connects low-L GRBs that are driven by shock break-outs and high-L GRBs that are powered by ultra-relativistic jets.
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| 2. |
- Maguire, K., et al.
(författare)
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A statistical analysis of circumstellar material in Type Ia supernovae
- 2013
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 436:1, s. 222-240
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Tidskriftsartikel (refereegranskat)abstract
- A key tracer of the elusive progenitor systems of Type Ia supernovae (SNe Ia) is the detection of narrow blueshifted time-varying Na I D absorption lines, interpreted as evidence of circumstellar material surrounding the progenitor system. The origin of this material is controversial, but the simplest explanation is that it results from previous mass-loss in a system containing a white dwarf and a non-degenerate companion star. We present new single-epoch intermediate-resolution spectra of 17 low-redshift SNe Ia taken with XShooter on the European Southern Observatory Very Large Telescope. Combining this sample with events from the literature, we confirm an excess (similar to 20 per cent) of SNe Ia displaying blueshifted narrow Na I D absorption features compared to redshifted Na I D features. The host galaxies of SNe Ia displaying blueshifted absorption profiles are skewed towards later-type galaxies, compared to SNe Ia that show no Na I D absorption and SNe Ia displaying blueshifted narrow Na I D absorption features have broader light curves. The strength of the Na I D absorption is stronger in SNe Ia displaying blueshifted Na I D absorption features than those without blueshifted features, and the strength of the blueshifted Na I D is correlated with the B - V colour of the SN at maximum light. This strongly suggests the absorbing material is local to the SN. In the context of the progenitor systems of SNe Ia, we discuss the significance of these findings and other recent observational evidence on the nature of SN Ia progenitors. We present a summary that suggests that there are at least two distinct populations of normal, cosmologically useful SNe Ia.
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| 3. |
- Malesani, D., et al.
(författare)
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Early Spectroscopic Identification of SN 2008D
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 692:2, s. L84-L87
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Prentice, S. J., et al.
(författare)
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Investigating the properties of stripped-envelope supernovae; what are the implications for their progenitors?
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 485:2, s. 1559-1578
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Tidskriftsartikel (refereegranskat)abstract
- We present observations and analysis of 18 stripped-envelope supernovae observed during 2013-2018. This sample consists of five H/He-rich SNe, sixH-poor/He-rich SNe, three narrow lined SNe Ic, and four broad lined SNe Ic. The peak luminosity and characteristic time-scales of the bolometric light curves are calculated, and the light curves modelled to derive Ni-56 and ejecta masses (M-Ni and M-cj). Additionally, the temperature evolution and spectral line velocity curves of each SN are examined. Analysis of the [O I] line in the nebular phase of eight SNe suggests their progenitors had initial masses < 20 M-circle dot. The bolometric light curve properties are examined in combination with those of other SE events from the literature. The resulting data set gives the M-ej distribution for 80 SE-SNe, the largest such sample in the literature to date, and shows that SNe Ib have the lowest median M-ej, followed by narrow-lined SNe Ic, H/He-rich SNe, broad-lined SNe Ic, and finally gamma-ray burst SNe. SNe Ic-6/7 show the largest spread of M-ej ranging from similar to 1.2-11 M-circle dot, considerably greater than any other subtype. For all SE-SNe = 2.8 +/- 1.5 M-circle dot which further strengthens the evidence that SE-SNe arise from low-mass progenitors which are typically <5 M-circle dot at the time of explosion, again suggesting M-ZAMS < 25 M-circle dot. The low and lack of clear bimodality in the distribution implies < 30 M-circle dot progenitors and that envelope stripping via binary interaction is the dominant evolutionary pathway of these SNe.
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| 5. |
- Gutiérrez, C. P., et al.
(författare)
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SN 2017ivv : two years of evolution of a transitional Type II supernova
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 499:1, s. 974-992
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Tidskriftsartikel (refereegranskat)abstract
- We present the photometric and spectroscopic evolution of the Type II supernova (SN II) SN 2017ivv (also known as ASASSN-17qp). Located in an extremely faint galaxy (M-r =-10.3 mag), SN 2017ivv shows an unprecedented evolution during the 2 yr of observations. At early times, the light curve shows a fast rise (similar to 6-8 d) to a peak of M-g(max) = -17.84 mag, followed by a very rapid decline of 7.94 +/- 0.48 mag per 100 d in the V band. The extensive photometric coverage at late phases shows that the radioactive tail has two slopes, one steeper than that expected from the decay of Co-56 (between 100 and 350 d), and another slower (after 450 d), probably produced by an additional energy source. From the bolometric light curve, we estimated that the amount of ejected 5(6)Ni is similar to 0.059 +/- 0.003M(circle dot). The nebular spectra of SN 2017ivv show a remarkable transformation that allows the evolution to be split into three phases: (1) H alpha strong phase (<200 d); (2) H alpha weak phase (between 200 and 350 d); and (3) H alpha broad phase (>500 d). We find that the nebular analysis favours a binary progenitor and an asymmetric explosion. Finally, comparing the nebular spectra of SN 2017ivv to models suggests a progenitor with a zero-age main-sequence mass of 15-17M(circle dot).
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| 6. |
- Inserra, C., et al.
(författare)
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OGLE-2013-SN-079 : A LONELY SUPERNOVA CONSISTENT WITH A HELIUM SHELL DETONATION
- 2015
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 799:1
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Tidskriftsartikel (refereegranskat)abstract
- We present observational data for a peculiar supernova discovered by the OGLE-IV survey and followed by the Public ESO Spectroscopic Survey for Transient Objects. The inferred redshift of z = 0.07 implies an absolute magnitude in the rest-frame I-band of M-1 similar to -17.6 mag. This places it in the luminosity range between normal Type Ia SNe and novae. Optical and near infrared spectroscopy reveal mostly Ti and Ca lines, and an unusually red color arising from strong depression of flux at rest wavelengths <5000 angstrom. To date, this is the only reported SN showing Ti-dominated spectra. The data are broadly consistent with existing models for the pure detonation of a helium shell around a low-mass CO white dwarf and double-detonation models that include a secondary detonation of a CO core following a primary detonation in an overlying helium shell.
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| 7. |
- Smartt, S. J., et al.
(författare)
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PESSTO : survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 579
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Tidskriftsartikel (refereegranskat)abstract
- Context. The Public European Southern Observatory Spectroscopic Survey of Transient Objects (PESSTO) began as a public spectroscopic survey in April 2012. PESSTO classifies transients from publicly available sources and wide-field surveys, and selects science targets for detailed spectroscopic and photometric follow-up. PESSTO runs for nine months of the year, January - April and August - December inclusive, and typically has allocations of 10 nights per month. Aims. We describe the data reduction strategy and data products that are publicly available through the ESO archive as the Spectroscopic Survey data release 1 (SSDR1). Methods. PESSTO uses the New Technology Telescope with the instruments EFOSC2 and SOFI to provide optical and NIR spectroscopy and imaging. We target supernovae and optical transients brighter than 20.5(m) for classification. Science targets are selected for follow-up based on the PESSTO science goal of extending knowledge of the extremes of the supernova population. We use standard EFOSC2 set-ups providing spectra with resolutions of 13-18 angstrom between 3345-9995 angstrom. A subset of the brighter science targets are selected for SOFI spectroscopy with the blue and red grisms (0.935-2.53 mu m and resolutions 23-33 angstrom) and imaging with broadband JHK(s) filters. Results. This first data release (SSDR1) contains flux calibrated spectra from the first year (April 2012-2013). A total of 221 confirmed supernovae were classified, and we released calibrated optical spectra and classifications publicly within 24 h of the data being taken (via WISeREP). The data in SSDR1 replace those released spectra. They have more reliable and quantifiable flux calibrations, correction for telluric absorption, and are made available in standard ESO Phase 3 formats. We estimate the absolute accuracy of the flux calibrations for EFOSC2 across the whole survey in SSDR1 to be typically similar to 15%, although a number of spectra will have less reliable absolute flux calibration because of weather and slit losses. Acquisition images for each spectrum are available which, in principle, can allow the user to refine the absolute flux calibration. The standard NIR reduction process does not produce high accuracy absolute spectrophotometry but synthetic photometry with accompanying JHK(s) imaging can improve this. Whenever possible, reduced SOFI images are provided to allow this. Conclusions. Future data releases will focus on improving the automated flux calibration of the data products. The rapid turnaround between discovery and classification and access to reliable pipeline processed data products has allowed early science papers in the first few months of the survey.
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| 8. |
- Starling, R. L. C., et al.
(författare)
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Discovery of the nearby long, soft GRB 100316D with an associated supernova
- 2011
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 411:4, s. 2792-2803
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Tidskriftsartikel (refereegranskat)abstract
- We report the Swift discovery of the nearby long, soft gamma-ray burst GRB 100316D, and the subsequent unveiling of its low-redshift host galaxy and associated supernova. We derive the redshift of the event to be z = 0.0591 +/- 0.0001 and provide accurate astrometry for the gamma-ray burst (GRB) supernova (SN). We study the extremely unusual prompt emission with time-resolved gamma-ray to X-ray spectroscopy and find that the spectrum is best modelled with a thermal component in addition to a synchrotron emission component with a low peak energy. The X-ray light curve has a remarkably shallow decay out to at least 800 s. The host is a bright, blue galaxy with a highly disturbed morphology and we use Gemini-South, Very Large Telescope and Hubble Space Telescope observations to measure some of the basic host galaxy properties. We compare and contrast the X-ray emission and host galaxy of GRB 100316D to a subsample of GRB-SNe. GRB 100316D is unlike the majority of GRB-SNe in its X-ray evolution, but resembles rather GRB 060218, and we find that these two events have remarkably similar high energy prompt emission properties. Comparison of the host galaxies of GRB-SNe demonstrates, however, that there is a great diversity in the environments in which GRB-SNe can be found. GRB 100316D is an important addition to the currently sparse sample of spectroscopically confirmed GRB-SNe, from which a better understanding of long GRB progenitors and the GRB-SN connection can be gleaned.
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| 9. |
- De Cia, Annalisa, et al.
(författare)
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Light Curves of Hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 860:2
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the light-curve properties of a sample of 26 spectroscopically confirmed hydrogen- poor superluminous supernovae (SLSNe-I) in the Palomar Transient Factory survey. These events are brighter than SNe Ib/c and SNe Ic-BL, on average, by about 4 and 2. mag, respectively. The peak absolute magnitudes of SLSNe-I in rest-frame g band span -22 less than or similar to M-g less than or similar to -20 mag, and these peaks are not powered by radioactive Ni-56, unless strong asymmetries are at play. The rise timescales are longer for SLSNe than for normal SNe Ib/c, by roughly 10 days, for events with similar decay times. Thus, SLSNe-I can be considered as a separate population based on photometric properties. After peak, SLSNe-I decay with a wide range of slopes, with no obvious gap between rapidly declining and slowly declining events. The latter events show more irregularities (bumps) in the light curves at all times. At late times, the SLSN-I light curves slow down and cluster around the 56Co radioactive decay rate. Powering the late-time light curves with radioactive decay would require between 1 and 10M(circle dot) of Ni masses. Alternatively, a simple magnetar model can reasonably fit the majority of SLSNe-I light curves, with four exceptions, and can mimic the radioactive decay of 56Co, up to similar to 400 days from explosion. The resulting spin values do not correlate with the host-galaxy metallicities. Finally, the analysis of our sample cannot strengthen the case for using SLSNe-I for cosmology.
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| 10. |
- Nicholl, M., et al.
(författare)
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On the diversity of superluminous supernovae : ejected mass as the dominant factor
- 2015
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 452:4, s. 3869-3893
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Tidskriftsartikel (refereegranskat)abstract
- We assemble a sample of 24 hydrogen-poor superluminous supernovae (SLSNe). Parameterizing the light-curve shape through rise and decline time-scales shows that the two are highly correlated. Magnetar-powered models can reproduce the correlation, with the diversity in rise and decline rates driven by the diffusion time-scale. Circumstellar interaction models can exhibit a similar rise-decline relation, but only for a narrow range of densities, which may be problematic for these models. We find that SLSNe are approximately 3.5 mag brighter and have light curves three times broader than SNe Ibc, but that the intrinsic shapes are similar. There are a number of SLSNe with particularly broad light curves, possibly indicating two progenitor channels, but statistical tests do not cleanly separate two populations. The general spectral evolution is also presented. Velocities measured from Fe II are similar for SLSNe and SNe Ibc, suggesting that diffusion time differences are dominated by mass or opacity. Flat velocity evolution in most SLSNe suggests a dense shell of ejecta. If opacities in SLSNe are similar to other SNe Ibc, the average ejected mass is higher by a factor 2-3. Assuming. = 0.1 cm(2) g(-1), we estimate a mean (median) SLSN ejecta mass of 10 M-circle dot (6 M-circle dot), with a range of 3-30 M-circle dot. Doubling the assumed opacity brings the masses closer to normal SNe Ibc, but with a high-mass tail. The most probable mechanism for generating SLSNe seems to be the core collapse of a very massive hydrogen-poor star, forming a millisecond magnetar.
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