GRB 070126
GCN Circular 6027
Subject
GRB 070126?: Swift detection of a possible burst
Date
2007-01-26T03:04:26Z (18 years ago)
From
Loredana Vetere at PSU <vetere@astro.psu.edu>
L. Vetere (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC),
S. T. Holland (CRESST/GSFC/USRA), S. Immler (GSFC/USRA),
C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), J. L. Racusin (PSU), J. L. Racusin (PSU),
M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester) and
E. Troja (INAF-IASFPA) report on behalf of the Swift Team:
At 02:33:26 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a possible source (trigger=257741). Swift slewed immediately
to the location.
The BAT on-board calculated location is
RA, Dec 33.460, -73.523 which is
RA(J2000) = 02h 13m 50s
Dec(J2000) = -73d 31' 23"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows no significant variation,
which is not uncommon for image triggers. We will have to wait for ground
analysis to determine if this is a real source.
The XRT began observing the field at 02:35:21 UT, 116 seconds after the
BAT trigger. XRT centroided on a cosmic ray and no source is visible in
the field of view up to an exposure time of 203s.
The UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 123 seconds after the BAT trigger. The
quickly available image does not cover any portion of the BAT error
circle.
GCN Circular 6037
Subject
Possible GRB 070126: Swift/UVOT Upper Limit
Date
2007-01-26T17:22:58Z (18 years ago)
From
Stefan Immler at NASA/GSFC <immler@milkyway.gsfc.nasa.gov>
S. Immler (NASA/USRA) and L. Vetere (PSU) report on the behalf of the
Swift UVOT team:
The Swift/UVOT began observing the field of the possible burst GRB 070126
123 seconds after the BAT trigger (Vetere et al., GCN 6027). No optical
afterglow candidate is detected in the BAT error circle within the first
100 s
White exposure or in a coadded 590 s image, down to a limiting magnitude
of 21.0 (3-sigma). The other UVOT filters only cover a small fraction
(around 25%) of the BAT error circle.
No correction has been made for the expected extinction corresponding to
E(B-V) = 0.05 mag (Schlegel et al. 1998).
GCN Circular 6040
Subject
GRB 070126, Swift-BAT refined analysis of a very faint burst
Date
2007-01-26T20:25:16Z (18 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
E. Fenimore (LANL), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), L. Vetere (PSU)
on behalf of the Swift-BAT team:
Using the data set from T-240 to T+500 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 070126 (trigger #257741)
(Veter, et al., GCN Circ. 6027). The BAT ground-calculated position
is RA, Dec = 33.579, -73.532 deg which is
RA(J2000) = 2h 14m 18.9s
Dec(J2000) = -73d 31' 54"
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 99%.
The mask-weighted lightcurve shows a broad, weak, and soft bump from
T_zero to ~T+60 sec. T90 (15-350 keV) is 51 +- 5 sec (estimated error
including systematics).
The time-averaged spectrum from T+1.0 to T+56.0 is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.9 +- 0.5. The fluence in the 15-150 keV band is 1.6 +- 0.6 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+10.00 sec in the 15-150 keV
band is 0.2 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90%
confidence level. The flux of this burst is at the lower limit of the
BAT sensitivity.
GCN Circular 6045
Subject
GRB070126: Swift-XRT possible detection of an afterglow
Date
2007-01-28T10:26:47Z (18 years ago)
From
Loredana Vetere at PSU <vetere@astro.psu.edu>
L. Vetere, J. Racusin (PSU) reports on behalf of Swift XRT Team:
We analysed the first 28ks of XRT data of the faint burst GRB 070126
(Vetere et al., GCN 6027). We do find in the BAT error circle (Fenimore
et al., GCN 6040) a detection of a faint uncatalogued X-ray source at
the following coordinates:
RA(J2000) = 2h 14m 09.78s
Dec(J2000) = -73d 32' 06.7"
with an estimated uncertainty of 4.4 arcseconds (90% containment).
This position lies 0.7 arcmin from the BAT refined position reported
by Fenimore et al. (GCN 6040).
The PSF corrected count rate is (7.1 +/- 2.3)e-4 cts/s. No other point
source is detected above the 3 sigma upper limit of 1.0e-3 cts/s inside
BAT error circle.
Due to the small number of counts, we are unable to determine whether
the source is decaying at this time. Observations are continuing and
further analysis regarding the fading nature of this source will be
issued as the data become available.
This circular is an official product of the Swift XRT Team.
GCN Circular 6046
Subject
GRB 070126: VLT observations
Date
2007-01-28T12:00:08Z (18 years ago)
From
Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center <malesani@astro.ku.dk>
D. Malesani (Dark/NBI), P.M. Vreeswijk (ESO), P. Jakobsson (Herfordshire),
J.P.U. Fynbo (Dark/NBI), report on behalf of a larger collaboration:
We observed the field of the faint GRB 070126 (Vetere et al., GCN 6027)
with the ESO VLT + FORS2 on 2006 Jan 26.17 UT (1.52 hr after the GRB).
Short exposures (~1 min) were acquired in BVRIz. Inside the XRT error
circle (Vetere \& Racusin, GCN 6045) we detect a single, extended source,
which is present in the USNO-B1 catalog and in the DSS images, at the
coordinates (0.5" error):
RA(J2000) = 02:14:10.03
Dec(J2000) = -73:32:05.7
Given the lack of evidence for variability of the X-ray source, the
possible association of this galaxy with the GRB or the X-ray source is at
present unclear.
Our images cover ~80% of the refined BAT error circle (Fenimore et al.,
GCN 6040). No new sources brighter than the DSS limits (R~20.5) are seen
across the whole observed region.
We acknowledge excellent support from the ESO staff at Paranal, in
particular Hugues Sana, Thomas Rivinius, Leonardo Vanzi and Dominique
Naef.
GCN Circular 6052
Subject
GRB 070126: Swift/UVOT refined analysis
Date
2007-01-29T17:37:37Z (18 years ago)
From
Stefan Immler at NASA/GSFC <immler@milkyway.gsfc.nasa.gov>
S. Immler (NASA/USRA) and L. Vetere (PSU) report on the behalf
of the Swift UVOT team:
An extended source is found at the position reported by Malesani
et al. (GCN 6046) in UVOT images of GRB 070126, consistent with
the position of the XRT source (Vetere & Racusin, GCN 6045). The
source is also present in DSS images and could be the host galaxy of
the faint burst.
The table below gives the measured UVOT magnitudes. The position
of the burst is outside the UVOT field-of-view for all other filters.
Filter T_start T_end Exposure Mag Error
WHITE 123 6146 590 21.8 0.4
UVW1 3900 40895 3592 21.0 0.3
UVM2 5128 40337 3333 21.5 0.3
UVW2 4719 6214 2588 >20.4 (3-sigma UL)
T_start and T_end are the start and stop times of the summed
exposures in seconds from the trigger. No correction has been
made for the expected extinction corresponding to E(B-V) =
0.05 mag (Schlegel et al. 1998).
GCN Circular 6068
Subject
GRB070126: Swift-XRT Observation
Date
2007-02-02T00:06:37Z (18 years ago)
From
Loredana Vetere at PSU <vetere@astro.psu.edu>
L. Vetere, J. Racusin, D.N. Burrows, C. Pagani (PSU) report on behalf
of Swift XRT Team:
We have re-observed the field of GRB 070126 (Vetere et al., GCN 6027)
from 2007-01-30 00:49:07.62 (~340ks after BAT trigger) to 2007-02-01
14:10:17.0 for a total exposure of ~27.2ks.
The possible afterglow candidate that we reported in GCN 6045 is still
present and shows a slightly increased count rate (1.4 +/- 0.3)E-03 cts/sec
compared to (0.76 +/- 0.23) E-03 cts/sec obtained with the first 28ks of
observation. We thus conclude that the object reported is not the X-ray
afterglow of GRB 070126.
No other point sources are detected above the 3 sigma upper limit of
1.0e-3 cts/s inside BAT error circle.
This circular is an official product of the Swift XRT Team.