GRB 140808A
GCN Circular 16725
Subject
GRB 140808A/iPTF14eag: AMI 15 GHz detection
Date
2014-08-20T09:16:00Z (11 years ago)
From
Gemma Anderson at U of Oxford <gemma.anderson@astro.ox.ac.uk>
G. E. Anderson, T. D. Staley, R. P. Fender (University of Oxford),
M. M. Kasliwal (Carnegie), A. Horesh (Caltech)
We observed the position of iPTF14eag (Singer et al., GCN 16668),
which is the optical afterglow of the Fermi GBM detected GRB 140808A
(Zhang, GCN 16669), at 15 GHz with the Arcminute Microkelvin Imager
(AMI-LA). The observations started on 2014 August 18.61 to 18.78 UT,
corresponding to 10.6 days post-burst. We have detected the radio
counterpart (Corsi et al., GCN 16694) with a preliminary flux of
0.30 +/- 0.06 mJy.
An earlier observation conducted on 2014 August 12.61 to 12.78 UT,
corresponding to 4.6 days post-burst, yielded a marginal 3.8 sigma
detection of 0.15 +/- 0.04 mJy.
Further AMI monitoring is planned. We thank the AMI staff for scheduling
these observations.
These observations were made as part of the 4 PI SKY project.
GCN Circular 16715
Subject
Radio upper limit on the GRB 140808A with the GMRT
Date
2014-08-19T08:37:16Z (11 years ago)
From
Poonam Chandra at TIFR <poonam@ncra.tifr.res.in>
Poonam Chandra (NCRA-TIFR) and A. J. Nayana (NCRA-TIFR) report on behalf
of a larger collaboration:
We carried out the Giant Metrewave Radio Telescope (GMRT) observations of
GRB 1400808A in the 1390 MHz band on 2014 August 18.66 UT.
We do not detect the radio afterglow of the GRB at the optical position
(Singer et al. GCN 16668). The 3-sigma upper limit at the GRB position
is 160 uJy and the map resolution is "4.03x1.89".
We thank GMRT staff for making these observations possible.
GCN Circular 16694
Subject
GRB 140808A / PTFeag: VLA K-band observations
Date
2014-08-16T21:12:47Z (11 years ago)
From
Alessandra Corsi at Texas Tech U <alessandra.corsi@ttu.edu>
A. Corsi (Texas Tech) and A. Horesh (Weizmann Inst.) report on behalf of a larger collaboration:
We imaged the position of PTF14eag (the optical afterglow candidate of
GRB 140808A; Singer et al., GCN 16668) with the Karl G. Jansky Very
Large Array (VLA) in K-band, starting at about 2.1 days after the Fermi
trigger 429152043 / 140808038 (Zhang, GCN 16669). A provisional
reduction shows a source consistent with the location of PTF14eag.
At this time, we estimate a preliminary flux of about 130 uJy at 22 GHz.
The image rms is about 19 uJy.
Further observations are planned.
GCN Circular 16684
Subject
GRB 140808A / iPTF14eag optical follow-up at HCT
Date
2014-08-12T06:27:45Z (11 years ago)
From
Varun Bhalerao at IUCAA <varunb@iucaa.ernet.in>
D. K. Sahu (IIA), V. Bhalerao (IUCAA), G. C. Anupama (IIA) report:
We imaged iPTF14eag, the optical counterpart of GRB 140808A (Singer et al., GCN Circ. 16668; Zhang, GCN Circ. 16669), with the 2m. Himalayan Chandra Telescope (HCT) ��� of the Indian Astronomical Observatory, Hanle, India. We obtained a total exposure of ���2700 sec in Bessell's R band, in the time range from UT 2014-08-08 15:37 to 16:38. The source was clearly detected with R = 20.6 +- 0.1. Combined with iPTF R band photometry (Singer et al., GCN Circ 16668), the decay fits a power law with slope -0.99 +- 0.02.
���We thank the iPTF team for alerting us about this burst.���
GCN Circular 16682
Subject
GRB 140808A: Confirmation of the Swift-XRT afterglow
Date
2014-08-11T16:07:54Z (11 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
K.L. Page (U. Leicester) and S.B. Cenko (NASA/GSFC) report on behalf of
the Swift-XRT team:
In GCN Circ. 16670, Page et al. reported the detection of an X-ray source
coincident with the iPTF optical source suggested to be the afterglow of
Fermi GRB 140808A (Singer et al., GCN Circ. 16668; Zhang, GCN Circ.
16669).
Starting 224 ks after the Fermi trigger, a second epoch of XRT data was
collected. The X-ray source is now no longer detected, having faded below
a 3-sigma upper limit of 2.46 x 10^-3 count s^-1 (0.3-10 keV). We
therefore confirm that this is the X-ray afterglow of GRB 140808A.
This circular is an official product of the Swift-XRT team.
GCN Circular 16673
Subject
Konus-Wind observation of GRB 140808A
Date
2014-08-09T14:54:50Z (11 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:
A long-duration GRB 140808A
(Fermi-GBM detection: Zhang, GCN Circ. 16669)
triggered Konus-Wind at T0=3239.264 s UT (00:53:59.264).
The burst light curve shows two emission episodes, the first,
reported in GCN 16669, from ~T0-1.9 s to ~T0+3.6 s,
and the second, from ~T0+303 s to ~T0+336 s.
The second episode is also seen in the INTEGRAL (SPI-ACS) data but
it can't be unambiguously attributed to the GRB by the triangulation,
so far. The total duration of the burst is ~338 s.
The emission is seen up to ~5 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB140808_T03239/
As observed by Konus-Wind, the first episode
had a fluence of 3.12(-0.30,+0.33)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+0.312 s,
of 1.6(-0.4,+0.4)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the first episode
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.95 (-0.26,+0.29)
and Ep = 127 (-18,+25) keV (chi2 = 91/78 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.6
(chi2 = 90/77 dof)
The second episode had a fluence of 4.2(-1.2,+4.0)x10^-6 erg/cm2,
in the 20 keV - 10 MeV energy range.
The time-averaged spectrum of this episode
(measured from T0+303.36 to T0+336.128 s)
is best fit in the 20 keV - 5 MeV range
by the power law with exponential cutoff model
with alpha = -1.22 (-0.37,+0.48)
and Ep = 376 (-158,+1558) keV (chi2 = 82/88 dof).
Assuming the second episode is related to the GRB the total fluence
is 7.3(-1.2,+4.0)x10^-6 erg/cm2. From the redshift z=3.29
(Gorosabel et al., GCN Circ. 16671)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~1.7x10^53 erg,
the peak luminosity L_iso is ~3.8x10^52 erg/s.
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 16672
Subject
GRB 140808A: Swift/UVOT Upper Limits
Date
2014-08-09T10:06:12Z (11 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (IAA-CSIC/UCL-MSSL) and S. B. Cenko (GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 140808A
42 ks after the GBM trigger (Zhang et al., GCN Circ. 16669).
No optical afterglow consistent with the candidate optical position
(iPTF14eag; Singer et al. GCN Circ. 16668) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 41951 47112 835 >22.3
v 42055 47902 857 >20.7
u 41848 51959 1212 >21.2
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 16671
Subject
GRB 140808A: Redshift from the 10.4m GTC telescope
Date
2014-08-08T23:46:38Z (11 years ago)
From
Javier Gorosabel at IAA-CSIC <jgu@iaa.es>
J. Gorosabel (IAA-CSIC/UPV-EHU), A. de Ugarte Postigo (IAA-CSIC/DARK-NBI),
C. Thoene (IAA-CSIC), D. Perley (Caltech), A. Garcia Rodriguez (GTC),
report on behalf of a larger collaboration:
We observed the optical candidate iPTF14eag of the Fermi GRB140808A
(Singer et al. GCN 16668; Zhang, GCN 16669; Page et al. GCN 16670) with
the 10.4m GTC (+OSIRIS). Spectroscopic observations were carried out at
21:43:48--22:29:36 UT (20.8-21.9 hours post burst).
Three 900s spectra were obtained with the R1000B grism, covering the range
between 3630 and 7500 A, at a resolution of ~1000. A preliminary reduction
based on archival calibration lamps, reveals a strong DLA and several
absorption metallic lines (CII, SiIV, SiII, CIV, AlII) consistent with a
common redshift of z=3.29, which we identify as the redshift of the GRB.
GCN Circular 16670
Subject
GRB 140808A: Swift-XRT observations
Date
2014-08-08T18:47:37Z (11 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
K.L. Page, P.A. Evans (U. Leicester) and S.B. Cenko (GSFC) report on
behalf of the Swift-XRT team:
We have analysed 3.0 ks of XRT data for the GBM-detected burst: GRB
140808A (Zhang, GCN Circ. 16669), from 41.9 ks to 52.0 ks after the GBM
trigger. The data are entirely in Photon Counting (PC) mode. An X-ray
source is detected within the XRT field of view. Using 1513 s of PC
mode data and 1 UVOT images, we find an enhanced XRT position (using
the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1
catalogue): RA, Dec = 221.22196, +49.21463 which is equivalent to:
RA (J2000): 14h 44m 53.27s
Dec(J2000): +49d 12' 52.7"
with an uncertainty of 3.3 arcsec (radius, 90% confidence). This
position is 1.6 arcsec from the iPTF position (Singer et al., GCN CIrc.
16668). The source has a mean count rate of 1.5e-02 ct/sec; we cannot
determine at the present time whether it is fading. We note that this
count rate is just below the ROSAT All Sky Survey detection limit, so
this source would not have been listed in the RASS. However, given the
transient nature of the iPTF optical candidate, it seems likely this is
a new X-ray source.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00020403.
This circular is an official product of the Swift-XRT team.
GCN Circular 16669
Subject
GRB 140808A: Fermi GBM detection
Date
2014-08-08T16:33:39Z (11 years ago)
From
Binbin Zhang at UAH <binbin.zhang@uah.edu>
Bin-Bin Zhang (UAH) reports on behalf of the Fermi GBM Team:
"At 00:54:00.62 UT on 08 August 2014, the Fermi Gamma-Ray Burst��
Monitor triggered and located GRB 140808A (trigger 429152043/140808038)
for which a possible counterpart was detected by iPTF14eag��
(Singer et al. 2014, GCN 16668). The GBM on-ground location,��
using the Fermi GBM trigger data, is consistent with the��
iPTF14eag location.
The angle from the Fermi LAT boresight is 63 degrees.
The GBM light curve one main episode which consists of several��
overlapping peaks, with a total duration of about 4.7 s (50-300keV).��
The time-averaged spectrum from T0+0 s to T0+5.0 s is well fit by��
a Band function parameterized as alpha=-0.4+/-0.1, beta=-2.9+/-0.3,��
Ep=115.2+/-7.7 keV.
The event fluence (10-1000 keV) in this time interval is
(3.2 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+0.5 s in the 10-1000 keV band is 9.3 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 16668
Subject
GRB 140808A: optical afterglow candidate iPTF14eag
Date
2014-08-08T09:40:43Z (11 years ago)
From
Leo Singer at CIT/PTF <lsinger@caltech.edu>
L. P. Singer (Caltech), M. M. Kasliwal (Carnegie Observatories/Princeton),
V. B. Bhalerao (IUCAA), S. B. Cenko (NASA/GSFC), D. A. Perley (Caltech),
and J. Johansson (Stockholm University) report on behalf of the
intermediate Palomar Transient Factory (iPTF) collaboration:
Fermi GBM triggered on GRB 140808A (Fermi trigger 429152043 /
140808038) at 2014-08-08 00:54:00.62. At 04:08:50 (3.25 hours after
the burst), we began our search for optical counterparts using the
Palomar 48-inch Oschin telescope (P48). We began searching 13 fields
spanning 95 deg2, covering most of the 1-sigma statiscal+systematic
region of the final Fermi GBM localization. We estimate a 69% chance
that these fields contain the true location of the source.
Sifting through candidate variable sources using image subtraction
and standard iPTF vetting procedures, we detected several optical
transients:
iPTF14eag, at the coordinates:
RA(J2000) = 14h 44m 53.33s (221.222219 deg)
Dec(J2000) = +49d 12' 51.1" (+49.214207 deg)
This source was detected at R = 18.91 +/- 0.06 mag at 3.35 hours
after the burst, and faded to R = 19.29 +/- 0.10 by 4.91 hours.
Relative to the time of the burst, this decay fits a power law
with index alpha = -0.9 +/- 0.3.
There were no previous iPTF detections at this position through 2014
May 28, and there are no coincident sources in SDSS.
iPTF14eai, at the coordinates:
RA(J2000) = 14h 17m 29.91s (214.374606 deg)
Dec(J2000) = +47d 07' 30.1" (+47.125041 deg)
This candidate was detected at R = 19.37 +/- 0.11 mag at 3.27 hours
after the burst, and was possibly fading. It is coincident with the
r = 18.43 galaxy SDSS J141729.93+470729.7. Because the galaxy is not
resolved in our P48 images, we caution that the transient's magnitude
derived from image subtraction is tentative.
iPTF14eac, at the coordinates:
RA(J2000) = 14h 25m 07.98s (216.283253 deg)
Dec(J2000) = +50d 32' 04.1" (+50.534476 deg)
This source was detected at R = 18.30 +/- 0.06 at 3.44 hours after
the burst. There was an earlier possible R = 20.16 +/- 0.21 mag
detection from coadded P48 images on 2014 June 09. It is located in a
spiral arm of PGC2375699.
Given the rapid fading of iPTF14eag and the lack of a host or
quiescent counterpart, we propose it as an optical afterglow
candidate. We have requested Swift TOO observations. We encourage
spectroscopic and photometric follow-up to confirm the nature of the
source.
The diagram
http://www.its.caltech.edu/~lsinger/iptf/Fermi429152043.pdf shows the
locations of our candidates and the 13 P48 fields in relation to the
Fermi GBM 1- and 2-sigma statistical+systematic contours.