J/ApJ/904/166 X-Ray, optical & radio obs. of GRB 160625B (Cunningham+, 2020)
GRB 160625B: Evidence for a Gaussian-shaped Jet.
Cunningham V., Cenko S.B., Ryan G., Vogel S.N., Corsi A., Cucchiara A.,
Fruchter A.S., Horesh A., Kangas T., Kocevski D., Perley D.A., Racusin J.
<Astrophys. J., 904, 166 (2020)>
=2020ApJ...904..166C 2020ApJ...904..166C
ADC_Keywords: GRB; Optical; Radio sources; X-ray sources
Keywords: Gamma-ray bursts ; Relativistic jets
Abstract:
We present multiwavelength modeling of the afterglow from the long
γ-ray burst (GRB)160625B using Markov Chain Monte Carlo
techniques of the afterglowpy Python package. GRB160625B is an
extremely bright burst with a rich set of observations spanning from
radio to γ-ray frequencies. These observations range from
∼0.1days to >1000days, 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 (2.7σ-5.3σ)
over the traditional top-hat model. Our estimate for the opening angle
of the burst ranges from 1.26 to 3.90, 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 ∼1053erg. 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.
Description:
The Neil Gehrels Swift Observatory began observing Gamma-Ray Burst
(GRB) 160625B 2.5 hours after the initial Gamma-ray Burst Monitor
(GBM) trigger. The X-ray Telescope (XRT) on board Swift observed
GRB160625B for 47 days.In addition to the XRT data we include the
late-time Chandra observations taken by K20 at 69.8 and 144days after
the burst.
We utilized several optical instruments to observe the GRB; the 2m
Faulkes Telescope North (FTN) operated by Las Cumbres Observatory
(LCO), the 2m Liverpool Telescope (LT) at Roque de los Muchachos
Observatory (ORM), and the Low Dispersion Survey Spectrograph 3
(LDSS3) at Magellan, ranging from 0.56 to 37days post-trigger.
We also observed the GRB with the Reionization And Transients InfraRed
camera (RATIR) beginning 8hr after the trigger until it faded beyond
detection at ∼50 days and also reported u-band observations taken with
the Ultraviolet/Optical Telescope (UVOT) on board Swift. Late-time
Hubble Space Telescope (HST) observations were reported by K20 71.5
and 140.2 days post-trigger.
We consolidate previous Karl G. Jansky VLA observations (Program IDs
15A-235 and S81171, PIs: Berger and Cenko, respectively) from 1.37 to
209 days after the burst for the most complete sample of radio data.
We obtained additional late-time observations of GRB160625B taken at
6GHz (C band) on 2020 February 4 15:14:24 (1319 days post-burst;
Program ID SC1031, PI: Cenko) for an on-source integration time of
1.8hr.
Objects:
----------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------
20 34 23.55 +06 55 09.5 GRB 160625B = GRB 160625B
----------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 42 96 X-ray data
table2.dat 66 284 Optical data
table3.dat 47 81 Radio data
--------------------------------------------------------------------------------
See also:
J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)
J/ApJ/781/37 : Multi-band photometry of GRB 130427A (Perley+, 2014)
J/ApJ/814/1 : GRB 120326A, 100418A & 100901A multi-wave obs. (Laskar+, 2015)
J/ApJ/818/18 : Jet angles & gamma-ray energetic estimations (Goldstein+, 2016)
J/ApJ/833/88 : GRB 160509A VLA monitoring campain results (Laskar+, 2016)
J/ApJ/829/7 : 3rd Swift/BAT GRB catalog (past ∼11yrs) (BAT3) (Lien+, 2016)
J/ApJ/859/134 : VLA study of high-redshift GRBs. II. GRB140304A (Laskar+, 2018)
J/ApJ/884/121 : Radio to UV observations of GRB 181201A (Laskar+, 2019)
J/ApJ/893/46 : The fourth Fermi-GBM GRB catalog: 10 years (von Kienlin+, 2020)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.3 d Time [0.11/145] Time since GBM trigger in days (1)
9 I1 keV Energy [5] Energy of observations
11- 18 F8.3 nJy Flux [0.13/5934] Flux density
20- 27 F8.3 nJy e_Flux [0.03/1268] Error in FluxDensity
29- 42 A14 --- Inst Instrument name; Chandra or Swift
--------------------------------------------------------------------------------
Note (1): Times are in reference to the first GBM trigger
(Jun 25 2016 22:40:16.28 UTC).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.3 d Time [0.11/141] Time since GBM trigger in days (1)
9- 13 A5 --- Filt Bandpass filter
15- 19 F5.2 --- ABmag [0/26.6] Apparent AB magnitude
21- 25 F5.2 --- e_ABmag [0.01/25] Error in ABmag
27- 31 F5.3 10+14Hz Freq [1.83/8.66] Frequency of observations
33- 39 F7.3 uJy Flux [0/598] Flux density; corrected for extinction
41- 47 F7.4 uJy e_Flux [0.006/46] Error in FluxDensity (2)
49 I1 --- Signi [0/1] Significance of upper limit detections (2)
51- 66 A16 --- Inst Instrument name
--------------------------------------------------------------------------------
Note (1): Times are in reference to the first GBM trigger
(Jun 25 2016 22:40:16.28 UTC).
Note (2): If an observation is an upper limit, rather than a detection, the
value in the 'Significance' column denotes the significance of the
detection, e.g. 0=detection, 1=1sigma upper limit. When the
value is >0 the 'e_FluxDensity' column is the upper limit itself.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.3 d Time [1.35/1319] Time since GBM trigger in days (1)
10- 14 F5.2 GHz Freq [1.45/39] Frequency of observations in GHz
16- 19 I4 uJy Flux [0/1310] Flux density
21- 26 F6.2 uJy e_Flux [2.46/270] Error in FluxDensity (2)
28 I1 --- Signi [0/1] Significance of upper limit detections (2)
30- 33 A4 --- Inst Instrument name
35- 47 A13 --- Ref Reference to original publication source (3)
--------------------------------------------------------------------------------
Note (1): Times are in reference to the first GBM trigger
(Jun 25 2016 22:40:16.28 UTC).
Note (2): If an observation is an upper limit, rather than a detection, the
value in the 'Significance' column denotes the significance of the
detection, e.g. 0=detection, 1=1 sigma upper limit. When the
value is >0 the 'e_FluxDensity' column is the upper limit itself.
Note (3): References as follows:
Alexander2017 = Alexander+, 2017ApJ...848...69A 2017ApJ...848...69A
Kangas2020 = Kangas+, 2020ApJ...894...43K 2020ApJ...894...43K
Troja2017 = Troja+, 2017Natur.547..425T 2017Natur.547..425T
This_Work = This work
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 18-Mar-2022