J/ApJ/859/134 A VLA study of high-redshift GRBs. II. GRB140304A (Laskar+, 2018)
A VLA study of high-redshift GRBs.
II. The complex radio afterglow of GRB 140304A: shell collisions and
two reverse shocks.
Laskar T., Berger E., Margutti R., Zauderer B.A., Williams P.K.G.,
Fong W.-F., Sari R., Alexander K.D., Kamble A.
<Astrophys. J., 859, 134-134 (2018)>
=2018ApJ...859..134L 2018ApJ...859..134L (SIMBAD/NED BibCode)
ADC_Keywords: GRB; Optical; Radio continuum
Keywords: gamma-ray burst: general; gamma-ray burst: individual: GRB 140304A
Abstract:
We present detailed multifrequency, multiepoch radio observations of
GRB 140304A at z=5.283 from 1 to 86GHz and from 0.45 to 89days. The
radio and millimeter data exhibit unusual multiple spectral
components, which cannot be simply explained by standard forward and
reverse shock scenarios. Through detailed multiwavelength analysis
spanning radio to X-rays, we constrain the forward shock parameters to
Ek,iso∼4.9x1054erg, A*∼2.6x10-2, εe∼2.5x10-2,
εB∼5.9x10-2, p∼2.6, and θjet∼1.1°, yielding a
beaming-corrected γ-ray and kinetic energy,
Eγ∼2.3x1049erg and EK∼9.5x1050erg, respectively. We
model the excess radio emission as due to a combination of a late-time
reverse shock (RS) launched by a shell collision, which also produces
a rebrightening in the X-rays at ∼0.26days, and either a standard RS
or diffractive interstellar scintillation (ISS). Under the standard RS
interpretation, we invoke consistency arguments between the forward
and reverse shocks to derive a deceleration time, tdec∼100s, the
ejecta Lorentz factor, Γ(tdec)∼300, and a low RS
magnetization, RB∼0.6. Our observations highlight both the power of
radio observations in capturing RS emission and thus constraining the
properties of GRB ejecta and central engines and the challenge
presented by ISS in conclusively identifying RS emission in GRB radio
afterglows.
Description:
GRB 140304A was discovered by the Niel Gehrels Swift Observatory Burst
Alert Telescope (BAT) on 2014 March 4 at 13:22:31 UT.
The Swift X-ray Telescope (XRT) began observing the field at 75.2s
after the BAT trigger, leading to the detection of an X-ray afterglow.
XRT continued observing the afterglow for 5.3 days in photon counting
mode, with the last detection at 3.0 days.
The Swift UV/Optical Telescope (UVOT) observed GRB 140304A beginning
138s after the burst (Marshall & Evans 2014GCN.15920....1M 2014GCN.15920....1M). We
analyzed the UVOT data using HEASOFT (v. 6.16) and corresponding
calibration files, and we list our derived upper limits in Table 2. We
compiled all observations reported in GCN circulars and present the
compilation in Table 3.
We observed GRB 140304A with the Combined Array for Research in
Millimeter Astronomy (CARMA) beginning on 2014 March 04.02 UT
(0.54days after the burst) in continuum wideband mode with 8GHz
bandwidth (16 windows, 487.5MHz each) at a mean frequency of 85.5GHz.
Following an initial detection (Zauderer+ 2014GCN.15931....1Z 2014GCN.15931....1Z), we
obtained two additional epochs.
We observed the afterglow using the VLA starting 0.45 days after the
burst. We detected and tracked the flux density of the afterglow from
1.2 to 33.5 GHz over seven epochs until 89 days after the burst, when
it faded beyond detection at all frequencies.
We summarize our millimeter-band and VLA observations in Table 4.
Objects:
-------------------------------------------------------------
RA (ICRS) DE Designation(s)
-------------------------------------------------------------
02 02 33.90 +33 28 27.9 GRB 140304A = Fermi bn140304557
-------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 23 46 Swift UVOT observations of GRB 140304A
table3.dat 136 21 Optical observations of GRB 140304A
table4.dat 43 67 GRB 140304A: log of radio observations
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See also:
J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)
J/A+A/560/A70 : GRB 100621A unusual afterglow (Greiner+, 2013)
J/A+A/562/A29 : GRB 100814A GROND and UVOT light curves (Nardini+, 2014)
J/ApJ/781/37 : Multi-band photometry of GRB 130427A (Perley+, 2014)
J/ApJ/814/1 : GRB 120326A, 100418A, 100901A multi-lambda obs. (Laskar+, 2015)
J/ApJ/858/65 : VLA study of high-redshift GRBs. I. GRB140311A (Laskar+, 2018)
http://www.swift.ac.uk/xrt_positions/00590206/ : Swift-XRT enhanced position
for GRB 140304A
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 E8.2 d DeltaT [0.003/6.7] Days since discovery
on 2014 March 4 at 13:22:31 UT
10- 14 A5 --- Filt Swift/UVOT filter used
16- 23 E8.2 mJy Flux [9.5/409] The 3σ flux density upper limit
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 E9.3 d DeltaT [0.0009/1.6] Time since discovery
on 2014 March 4 at 13:22:31 UT
11- 15 A5 --- Tel Observatory identifier ("HJT", "ICATE" or
"NOT")
17- 22 A6 --- Inst Instrument identifier ("RATIR", "MASTER" or
"ALFOSC")
24- 25 A2 --- Filt Filter used (1)
27- 34 E8.2 Hz Freq [1.8e+14/4.6e+14] Midpoint frequency of Filt
36- 44 E9.2 mJy Flux [0.002/0.8] Flux density in Filter (2)
46- 54 E9.3 mJy e_Flux [0.0008/0.2] Uncertainty in Flux (2)
56 I1 --- Det? Detection?; 1=Yes
58-136 A79 --- Ref GCN reference
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Note (1): CR indicates clear filter calibrated to R-band.
Note (2): An uncertainty of 0.2 AB mag is assumed where not provided. All
upper limits are 3σ. The data have not been corrected for
Galactic extinction.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 E9.3 d DeltaT [0.4/89.1] Days since discovery
on 2014 March 4 at 13:22:31 UT
11- 15 A5 --- Tel Facility identifier ("VLA" or "CARMA")
17- 21 F5.2 GHz Freq [1.4/85.5] Frequency of the radio observation
23- 31 E9.3 mJy Flux [0.02/1.2] Flux density at Freq
33- 41 E9.3 mJy e_Flux [0.01/0.4] Uncertainty in Flux
43 I1 --- Det? Detection?; 1=Yes
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-Jun-2019