J/ApJ/892/97 GRB 190114C light curves (Jordana-Mitjans+, 2020)
Lowly polarized light from a highly magnetized jet of GRB 190114C.
Jordana-Mitjans N., Mundell C.G., Kobayashi S., Smith R.J., Guidorzi C.,
Steele I., Shrestha M., Gomboc A., Marongiu M., Martone R., Lipunov V.,
Gorbovskoy E.S., Buckley D.A.H., Rebolo R., Budnev N.M.
<Astrophys. J. 892, 97 (2020)>
=2020ApJ...892...97J 2020ApJ...892...97J (SIMBAD/NED BibCode)
ADC_Keywords: Gamma rays ; GRB ; Photometry ; Optical
Keywords: high energy astrophysics - gamma-ray bursts - magnetic fields -
polarimetry - shocks - jets - photometric systems
Abstract:
We report multicolor optical imaging and polarimetry observations of
the afterglow of the first TeV-detected gamma-ray burst (GRB), GRB
190114C, using the RINGO3 and MASTER II polarimeters. Observations
begin 31s after the onset of the GRB and continue until ∼7000s
postburst. The light curves reveal a chromatic break at ∼400-500s,
with initial temporal decay α=1.669±0.013 flattening to
α∼1 postbreak, which we model as a combination of reverse and
forward shock components with magnetization parameter RB∼70. The
observed polarization degree decreases from 7.7%±1.1% to 2%-4%
52-109s postburst and remains steady at this level for the subsequent
∼2000s at a constant position angle. Broadband spectral energy
distribution modeling of the afterglow confirms that GRB 190114C is
highly obscured (Av,HG=1.49±0.12mag;
NH,HG=(9.0±0.03)x1022cm-2). We interpret the measured
afterglow polarization as intrinsically low and dominated by dust
-in contrast to the P>10% measured previously for other GRB reverse
shocks-with a small contribution from polarized prompt photons in
the first minute. We test whether first- and higher-order inverse
Compton scattering in a magnetized reverse shock can explain the low
optical polarization and subteraelectronvolt emission but conclude
that neither is explained in the reverse shock inverse Compton model.
Instead, the unexpectedly low intrinsic polarization degree in GRB
190114C can be explained if large-scale jet magnetic fields are
distorted on timescales prior to reverse shock emission.
Description:
We report the early-time optical observations of the afterglow of the
first TeV- detected gamma-ray burst (GRB), GRB 190114C, using the
MASTER Global Robotic Net (with the Very Wide-Field camera and MASTER
II) and the Liverpool Telescope (with the RINGO3 imager-polarimeter
and the Optical Wide Field Camera). GRB 190114C was triggered by the
Swift Burst Alert Telescope on 2019 January 14 at T0=20:57:03 UT with
coordinates RA(J2000)=03:38:1.63, Dec(J2000)=-26:56:48.1 (Gropp et al.,
2019GCN.23688....1G 2019GCN.23688....1G). The spectroscopic redshift of GRB 190114C is
0.4245±0.0005 (Castro-Tirado et al.,2019GCN.23708....1C 2019GCN.23708....1C).
The follow-up observations began 31s after Swift trigger and
continued until ∼7000 s post-burst. The multiwavelength light curves
reveal a chromatic break at ∼400-500s; the initial temporal decay
is of 1.669±0.013 and flattens to ∼1 after the break.
The tabulated data belongs to the electronic version of Table 1 from
the journal publication. This table includes the bandpass name with
the instrument used, the mean observing time after Swift trigger, the
length of the observing window, the magnitudes and the flux density.
The MASTER Global Robotic Net detected the GRB 190114C afterglow
during the first 31-48s after Swift trigger with the Very Wide-Field
(VWF) camera in a white band --- this data is labelled as
rMASTERVWFSAAO and rMASTERVWFIAC in the table. The 0.4-m MASTER II
observations started 46s post-burst in a white band and lasted until
∼2300s post-burst --- this data is labelled as rMASTERIISAAO and
rMASTERIIIAC. Two MASTER sites observed GRB 190114C at the same
time: the South African Astronomical Observatory (SAAO) and the
Instituto de Astrofisica de Canarias (IAC). rMASTERVWFSAAO,
rMASTERVWFIAC, rMASTERIISAAO, rMASTERIIIAC white-band
observations are standardized in an r-equivalent band.
The observations from the 2-m Liverpool Telescope started 201s after
the burst with RINGO3 instrument and with the BV,R,I bands
simultaneously --- this data is labelled as BV_RINGO3, R_RINGO3,
I_RINGO3 in the table. Observations continued until ∼7000s
post-burst. BV_RINGO3, R_RINGO3, I_RINGO3 magnitudes and flux density
are standardized in RINGO3 photometric system. The BV,R,I RINGO3
bandpasses have the following mean photonic wavelengths: 5385Å,
7030Å, 8245Å, respectively, and have a spectral coverage of
2232Å, 1130Å, 835Å, respectively (quoting the
full-widths-at-half-maximum). The Optical Wide Field Camera (IO:O)
also observed GRB 190114C with the r filter at ∼2200s post-burst ---
this data is labelled as r_IOO.
The tabulated data includes the bandpass name with the instrument
used, the mean observing time corrected by T0 (the Swift trigger
time), the length of the observing window and the GRB magnitudes and
flux density with their uncertainties. The magnitudes and the flux
density are corrected by atmospheric and Galactic extinction
(reddening of E(B-V)=0.0124±0.0005, Schlegel et al.
1998ApJ...500..525S 1998ApJ...500..525S) but not for the host galactic extinction
(E(B-V)=0.51±0.04).
Objects:
-------------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------------
03 38 01.63 -26 56 48.1 GRB 190114 C = GRB 190114 C
-------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 57 1137 GRB 190114C LT Observations with RINGO3 BV/R/I,
IO:O r Bands, and MASTER VWF/MASTER II
Observations in an r-equivalent Band
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Band Bandpass name and instrument (1)
18- 23 F6.1 s tmid Mean observing time after Swift trigger
25- 29 F5.1 s texp/2 Half of the length of the observing window
31- 35 F5.2 mag mag Magnitudes in Band (2)
37- 40 F4.2 mag e_mag Photometric uncertainty of the magnitude
42- 49 E8.2 Jy Flux Flux density in Band (2)
51- 57 E7.1 Jy e_Flux Photometric uncertainty of the flux density
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Note (1): Bands as follows:
BV_RINGO3 = RINGO3 BV band, 2-m Liverpool Telescope
I_RINGO3 = RINGO3 I band, 2-m Liverpool Telescope
R_RINGO3 = RINGO3 R band, 2-m Liverpool Telescope
r_IOO = Optical Wide Field Camera r band, 2-m Liverpool Telescope
rMASTERIIIAC = IAC MASTERII r band, 0.4-m MASTER II
rMASTERIISAAO = SAAO MASTERII r band, 0.4-m MASTER II
rMASTERVWFIAC = IAC MASTERVWF r band, Very Wide-Field (VWF) camera
rMASTERVWFSAAO = SAAO MASTERVWF r band, Very Wide-Field (VWF) camera
Note (2): Magnitudes and flux density values are corrected for atmospheric and
Galactic extinction (reddening of E(B-V)=0.0124±0.0005, Schlegel et al.
1998ApJ...500..525S 1998ApJ...500..525S), but not by the host galaxy extinction
(E(B-V)=0.51±0.04).
rMASTERVWFSAAO, rMASTERVWFIAC, rMASTERIISAAO, rMASTERIIIAC
observations are white-band and standardized in an r-equivalent band.
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Acknowledgements:
Nuria Jordana-Mitjans, N.Jordana(at)bath.ac.uk
(End) Patricia Vannier [CDS] 10-Apr-2020