J/ApJ/862/94 Multiwavelength obs. of GRB 161219B (Laskar+, 2018)
First ALMA light curve constrains refreshed reverse shocks and jet magnetization
in GRB 161219B.
Laskar T., Alexander K.D., Berger E., Guidorzi C., Margutti R., Fong W.-F.,
Kilpatrick C.D., Milne P., Drout M.R., Mundell C.G., Kobayashi S.,
Lunnan R., Barniol Duran R., Menten K.M., Ioka K., Williams P.K.G.
<Astrophys. J., 862, 94 (2018)>
=2018ApJ...862...94L 2018ApJ...862...94L
ADC_Keywords: GRB; Photometry, UBVRI; Photometry, millimetric/submm;
Radio continuum; Ultraviolet
Keywords: gamma-ray burst: general ; gamma-ray burst: individual (GRB 161219B)
Abstract:
We present detailed multiwavelength observations of GRB 161219B at
z=0.1475, spanning the radio to X-ray regimes, and the first Atacama
Large Millimeter/submillimeter Array (ALMA) light curve of a
γ-ray burst (GRB) afterglow. The centimeter- and millimeter-band
observations before 8.5 days require emission in excess of that
produced by the afterglow forward shock (FS). These data are
consistent with radiation from a refreshed reverse shock (RS) produced
by the injection of energy into the FS, signatures of which are also
present in the X-ray and optical light curves. We infer a constant-
density circumburst environment with an extremely low density,
n0∼3x10-4cm-3, and show that this is a characteristic of all
strong RS detections to date. The Karl G. Lansky Very Large Array
(VLA) observations exhibit unexpected rapid variability on roughly
minute timescales, indicative of strong interstellar scintillation.
The X-ray, ALMA, and VLA observations together constrain the jet break
time, tjet∼32 days, yielding a wide jet opening angle of
θjet∼13°, implying beaming-corrected γ-ray and
kinetic energies of E_γ∼4.9x1048erg and EK∼1.3x1050erg,
respectively. Comparing the RS and FS emission, we show that the
ejecta are only weakly magnetized, with relative magnetization,
RB∼1, compared to the FS. These direct, multifrequency measurements
of a refreshed RS spanning the optical to radio bands highlight the
impact of radio and millimeter data in probing the production and
nature of GRB jets.
Description:
GRB 161219B was discovered by the Swift Burst Alert Telescope (BAT) on
2016 December 19 at 18:48:39 UT. The burst duration is
T90=6.94±0.79s.
The optical afterglow was discovered by the Swift UV/Optical Telescope
(UVOT) in observations beginning 112s after the BAT trigger
(Marshall & D'Ai 2016GCN.20306....1M 2016GCN.20306....1M).
Spectroscopic observations 36h after the burst with the X-shooter
instrument on the European Southern Observatory (ESO) 8.2m Very Large
Telescope (VLT) provided a redshift of z=0.1475 (2016GCN.20321....1T 2016GCN.20321....1T).
The Swift X-ray Telescope (XRT) began observing GRB 161219B 108s after
the BAT trigger. The X-ray afterglow was localized to
RAJ2000=06:06:51.37, DEJ2000=-26:47:29.7, with an uncertainty radius
of 1.4" (90% containment). XRT continued observing the afterglow for
123 days in photon counting mode.
We began observing GRB 161219B with two 1m telescopes in Sutherland
(South Africa), which are operated by the Las Cumbres Observatory
Global Network (LCOGT), on 2016 December 19, 20:43 UT, at 1.9h since
the GRB, in Sloan Digital Sky Survey (SDSS) r' and i' filters.
Observations with 1 and 2m LCOGT telescopes (formerly Faulkes
Telescopes North and South) both in Hawaii and in Siding Springs
(Australia) proceeded on a daily basis for 4 days, followed by a
regularly increasing spacing until 2017 January 14 (25 days post-GRB).
Additional optical observations with the 2m Liverpool Telescope (LT)
in the same filters culminated on January 23 (35 days post-GRB).
We obtained uBVgri imaging of GRB 161219B from 2016 December 22 to
2017 March 21 using the Direct CCD Camera on the Swope 1.0m telescope
at Las Campanas Observatory in Chile.
We observed GRB 161219B with the Low Resolution Imaging Spectrometer
on the 10m Keck I telescope on 2017 March 29 in UBgRIz bands.
We obtained seven epochs of near-IR observations in the JHK bands with
the Wide-field Camera (WFCAM) mounted on the United Kingdom Infrared
Telescope (UKIRT) spanning ∼2.5 to ∼270d.
We present the results of our optical and near-IR (NIR) photometry,
together with a compilation of all other optical observations reported
in GCN circulars in Table 3.
We obtained ALMA observations of the afterglow at 1.3 days after the
burst through program 2016.1.00819.T (PI: Laskar) in Band 3, with two
4GHz-wide basebands centered at 91.5 and 103.5GHz, respectively.
We observed the afterglow using the Karl G. Jansky Very Large Array
(VLA) starting 0.5 days after the burst through program 15A-235
(PI: Berger). We detected and tracked the flux density of the
afterglow from 1.2 to 37GHz over nine epochs until ∼159d after the
burst.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
06 06 51.37 -26 47 29.7 GRB 161219B = GRB 161219B
----------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 35 187 Swift UVOT observations of GRB 161219B
table3.dat 117 472 Optical and Near-IR observations of GRB 161219B
table4.dat 19 10 GRB 161219B: log of ALMA observations
table5.dat 37 88 GRB 161219B: log of VLA observations
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See also:
B/swift : Swift Master Catalog (HEASARC, 2004-)
B/eso : ESO Science Archive Catalog (ESO, 1991-2019)
J/A+A/474/793 : INTEGRAL observations of GRB 070311 (Guidorzi+, 2007)
J/ApJ/686/1209 : Optical properties of GRB afterglows (Melandri+, 2008)
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-wave. obs. (Laskar+, 2015)
J/ApJ/833/88 : GRB 160509A VLA monitoring campain results (Laskar+, 2016)
J/ApJ/858/65 : A VLA study of high-z GRBs. I. GRB140311A (Laskar+, 2018)
http://www.swift.ac.uk/xrt_positions/727541/ : Swift-XRT position of GRB161219B
http://www.swift.ac.uk/xrt_spectra/727541/ : Swift-XRT spectra of GRB161219B
http://www.swift.ac.uk/xrt_curves/727541/ : Swift-XRT LCs of GRB161219B
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 E9.3 d Time [0.002/122.6] Mid-time of observation since
discovery: 2016 December 19 18:48:39 UT
11- 13 A3 --- Band Swift/UVOT band
15- 23 E9.3 mJy Flux [0.002/0.9] Flux density in Band
25- 33 E9.3 mJy e_Flux [0.0003/0.2] Uncertainty in Flux
35 I1 --- Det [0/1] Detection code (1=Yes or 0=No)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 E9.3 d Time [0.0005/277] Mid-time of observation since
discovery: 2016 December 19 18:48:39 UT
11- 27 A17 --- Obs Observatory and instrument identifiers
29- 34 A6 --- Filter Filter used (1)
36- 43 E8.2 Hz Freq [1.3e+14/8.4e+14] Frequency of Filter
45- 53 E9.3 mJy Flux [0.004/1.4] Flux density in Filter (2)
55- 63 E9.3 mJy e_Flux [2.3e-05/0.5] Uncertainty in Flux (3)
65 I1 --- Det [0/1] Detection code (1=Yes or 0=No)
67-117 A51 --- Ref Observation reference
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Note (1): CR is clear filter calibrated to the R band.
Note (2): Not corrected for Galactic extinction.
Note (3): An uncertainty of 0.2 AB mag is assumed where not provided.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 F5.2 d Time Mid-time of observation since
discovery: 2016 December 19 18:48:39 UT
7-11 F5.1 GHz Freq [91.5/103.5] Frequency
13-16 I4 uJy S [51/1332] Flux density
18-19 I2 uJy e_S [14/43] S uncertainty
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 E9.3 d Time [0.5/159.1] Mid-time of observation since
discovery: 2016 December 19 18:48:39 UT
11- 15 F5.2 GHz Freq [1.2/33.5] Frequency
17- 25 E9.3 uJy Flux [56.6/3505] Flux density at Freq
27- 35 E9.3 uJy e_Flux [8.6/150] Uncertainty in Flux
37 I1 --- Det [1] Detection code (1=Yes or 0=No)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 23-Jul-2019