| 1. |
- Bravo, L, et al.
(författare)
-
- 2021
-
swepub:Mat__t
|
|
| 2. |
- Tabiri, S, et al.
(författare)
-
- 2021
-
swepub:Mat__t
|
|
| 3. |
- Cunningham, Virginia, et al.
(författare)
-
GRB 160625B : Evidence for a Gaussian-shaped Jet
- 2020
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 904:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present multiwavelength modeling of the afterglow from the long gamma-ray burst (GRB) 160625B using Markov Chain Monte Carlo techniques of the afterglowpy Python package. GRB 160625B is an extremely bright burst with a rich set of observations spanning from radio to gamma-ray frequencies. These observations range from similar to 0.1 days to >1000 days, thus making this event extremely well suited to such modeling. In this work we compare top-hat and Gaussian jet structure types in order to find best-fit values for the GRB jet collimation angle, viewing angle, and other physical parameters. We find that a Gaussian-shaped jet is preferred (2.7 sigma-5.3 sigma) over the traditional top-hat model. Our estimate for the opening angle of the burst ranges from 126 to 390, depending on jet-shape model. We also discuss the implications that assumptions on jet shape, viewing angle, and particularly the participation a fraction of electrons have on the final estimation of GRB intrinsic energy release and the resulting energy budget of the relativistic outflow. Most notably, allowing the participation fraction to vary results in an estimated total relativistic energy of similar to 10(53) erg. This is two orders of magnitude higher than when the total fraction is assumed to be unity; thus, this parameter has strong relevance for placing constraints on long GRB central engines, details of the circumburst media, and host environment.
|
|
| 4. |
- Yang, Sheng, et al.
(författare)
-
Is supernova SN 2020faa an iPTF14hls look-alike?
- 2021
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 646
-
Tidskriftsartikel (refereegranskat)abstract
- Context. We present observations of ZTF20aatqesi (SN 2020faa). This Type II supernova (SN) displays a luminous light curve (LC) that started to rebrighten from an initial decline. We investigate this in relation to the famous SN iPTF14hls, which received a great deal of attention and multiple interpretations in the literature, but whose nature and source of energy still remain unknown.Aims. We demonstrate the great similarity between SN 2020faa and iPTF14hls during the first 6 months, and use this comparison to forecast the evolution of SN 2020faa and to reflect on the less well observed early evolution of iPTF14hls.Methods. We present and analyse our observational data, consisting mainly of optical LCs from the Zwicky Transient Facility in the gri bands and of a sequence of optical spectra. We construct colour curves and a bolometric lc, and we compare ejecta-velocity and black-body radius evolutions for the two supernovae (SNe) and for more typical Type II SNe.Results. The LCs show a great similarity with those of iPTF14hls over the first 6 months in luminosity, timescale, and colour. In addition, the spectral evolution of SN 2020faa is that of a Type II SN, although it probes earlier epochs than those available for iPTF14hls.Conclusions. The similar LC behaviour is suggestive of SN 2020faa being a new iPTF14hls. We present these observations now to advocate follow-up observations, since most of the more striking evolution of SN iPTF14hls came later, with LC undulations and a spectacular longevity. On the other hand, for SN 2020faa we have better constraints on the explosion epoch than we had for iPTF14hls, and we have been able to spectroscopically monitor it from earlier phases than was done for the more famous sibling.
|
|
