J/ApJ/833/88 GRB 160509A VLA monitoring campaign results (Laskar+, 2016)
A reverse shock in GRB 160509A.
Laskar T., Alexander K.D., Berger E., Fong W.-F., Margutti R., Shivvers I.,
Williams P.K.G., Kopac D., Kobayashi S., Mundell C., Gomboc A., Zheng W.,
Menten K.M., Graham M.L., Filippenko A.V.
<Astrophys. J., 833, 88-88 (2016)>
=2016ApJ...833...88L 2016ApJ...833...88L (SIMBAD/NED BibCode)
ADC_Keywords: Gamma rays ; Radio continuum
Keywords: gamma-ray burst: general; gamma-ray burst: individual: GRB 160509A
Abstract:
We present the second multi-frequency radio detection of a reverse
shock in a γ-ray burst. By combining our extensive radio
observations of the Fermi-Large Area Telescope γ-ray burst
160509A at z=1.17 up to 20 days after the burst with Swift X-ray
observations and ground-based optical and near-infrared data, we show
that the afterglow emission comprises distinct reverse shock and
forward shock contributions: the reverse shock emission dominates in
the radio band at ≲10 days, while the forward shock emission
dominates in the X-ray, optical, and near-infrared bands. Through
multi-wavelength modeling, we determine a circumburst density of
n0∼10-3cm-3, supporting our previous suggestion that a
low-density circumburst environment is conducive to the production of
long-lasting reverse shock radiation in the radio band. We infer the
presence of a large excess X-ray absorption column,
NH∼1.5x1022cm-2, and a high rest-frame optical extinction,
AV∼3.4mag. We identify a jet break in the X-ray light curve at
tjet∼6days, and thus derive a jet opening angle of
θjet∼4°, yielding a beaming-corrected kinetic energy and
radiated γ-ray energy of EK∼4x1050erg and
Eγ∼1.3x1051erg (1-104keV, rest frame), respectively.
Consistency arguments connecting the forward shocks and reverse shocks
suggest a deceleration time of tdec∼460s∼T90, a Lorentz factor of
Γ(tdec)∼330, and a reverse-shock-to-forward-shock fractional
magnetic energy density ratio of
RB=εB,RS/εB,FS∼8. Our study highlights the power
of rapid-response radio observations in the study of the properties
and dynamics of γ-ray burst ejecta.
Description:
GRB 160509A was discovered by the Fermi LAT on 2016 May 09 at
08:59:04.36 UTC (Longo+ 2016GCN..19403...1L).
We observed the afterglow with the VLA starting at 0.36 days. We
tracked the flux density of the afterglow over multiple epochs
spanning 1.2-33.5GHz, using 3C48, 3C286, and 3C147 as flux and
bandpass calibrators, and J2005+7752 as the gain calibrator.
Our VLA observations spanning 0.36-20 days after the burst clearly
reveal the presence of multiple spectral components in the radio
afterglow.
Objects:
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RA (ICRS) DE Designation(s)
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20 47 00.9 +76 06 30 GRB 160509A = GRB 160509A
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 37 81 GRB 160509A: Log of VLA observations
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See also:
J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 F7.4 d Delt [0.3/20] Time since discovery Δt (1)
9- 14 F6.3 GHz Freq [1.2/37] Frequency of the observation
16- 21 F6.1 uJy Flux [43/2411] Flux density at Freq
23- 27 F5.1 uJy e_Flux [11/315] Uncertainty in Flux
29 I1 --- Det [0/1]? Detection code for Flux (2)
31- 37 A7 --- Setup VLA receiver band used
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Note (1): 2016 May 09 at 08:59:04.36 UTC.
Note (2): Code as follows:
1 = Detection;
0 = 3σ upper limit.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Apr-2017