GRB 050124

C. Markwardt (GSFC/UMD), S. Barthelmy, L. Barbier (GSFC), 
J. Cummings (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), K. McLean (LANL), 
T. McMahon (Langston U.), D. Palmer (LANL), A. Parsons (GSFC), 
G. Sato (ISAS), P. Schady (MSSL), T. Sakamoto (GSFC), 
M. Suzuki (Saitama), J. Tueller (GSFC)
on behalf of the Swift-BAT team:

At 11:30:03 UT, the Swift Burst Alert Telescope (BAT) triggered and
located on-board GRB050124.  The spacecraft did not autonomously slew
to the burst because automatic operations were disabled for weekend
operations.  The spacecraft will be repointed via a Target of
Opportunity command.

The BAT on-board calculated location is RA,Dec 192.879, +13.026
(J2000) with an uncertainty of 6 arcmin (radius, 3-sigma, including a
systematic uncertainty).  This is a high significance burst.  The
structure of the burst is double-peaked with a duration of ~4 seconds.

J. Cummings (GSFC), S. Barthelmy, L. Barbier (GSFC), A. Breeveld (MSSL),
J. Cannizzo (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), 
D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), 
K. McLean (LANL), T. McMahon (Langston U.), D. Palmer (LANL), 
A. Parsons (GSFC), G. Sato (ISAS), P. Schady (MSSL), T. Sakamoto (GSFC), 
A. Smale (NASA HQ), M. Suzuki (Saitama), J. Tueller (GSFC)


This is a followup report on Swift/BAT GRB050124 (GCN Circ. 2972
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 , Markwardt
et al.) The ground-calculated BAT location is RA, Dec 192.884, 13.024 degrees 
(J2000). At 43 degrees from the BAT boresight, we expect the uncertainty 
to be primarily systematic due to currently uncalibrated image distortion 
(Swift/BAT image calibration activities are still in progress). The 
systematic uncertainty is approximately 3 arcmin (radius). 

Further analysis yields a fluence of (2.1 +- 0.2) x 10^-6 ergs/cm2 and a
1-second peak flux of (6.8 +- 0.4) ph/cm2/s in the 15-350 keV band. The  
power-law photon index is 1.48 in the 20 - 150 keV band.

T90 is 4.1 seconds and T50 is 2.1 seconds. The burst had 2 peaks, the first
2 seconds long with a rise in 0.1 seconds from a baseline that was slightly 
elevated for about 1.4 seconds, and the second about 1 second long. There is
a low-significance (3.6 sigma image) hint of a 1-second precursor at -16
seconds from the trigger.

C. Pagani (OAB), J. Kennea, D. N. Burrows, J. E. Hill, J. A. Nousek (PSU), G.
Chincarini, G. Tagliaferri, A. Moretti, P. Romano, S. Campana (OAB), M. Goad,
K. Page, A. Wells, J. Osborne, A. Beardmore (U. Leicester), M. Chester (PSU),
S. Barthelmy, N. Gehrels, N. White (GSFC), P. Schady (MSSL), M. Tripicco
(GSFC), L. Cominsky (Sonoma State U.),
P. Giommi (ASDC) on behalf of the Swift XRT team.

The Swift X-Ray Telescope (XRT) was pointed at GRB050124 ( GCN 2972
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 , Markwardt
et al.; GCN 2973
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 , Cummings et al.) on 2005/01/24 at 14:34 UT.  The spacecraft
did not autonomously slew to the burst since automated slewing was not enabled
at the time the burst occurred.  The observation was performed as a Target of
Opportunity beginning about 3 hours after the burst.  The first XRT exposure
was at 14:35:16 UT.  The observation continued until 15:17:12 UT.  The XRT was
in Auto State and the ToO was performed as if it were an automated burst
observation.  XRT attempted to determine a prompt centroid but found
insufficient counts.  It took one frame in Piled-up Photodiode mode, one in
Low-rate Photodiode mode, and then settled into Windowed Timing mode (1-D
position resolution, 2 ms timing) for the bulk of the observation (1100
frames), with about 220 frames in Photon-Counting mode (2-D position
resolution, 2.5s timing).

We processed the data on the ground and detect a bright X-ray source in this
field.  The X-ray centroid has an approximate location of:
RA(J2000) = 12:51:31.1
Dec(J2000) = 13:02:34.3.

This position is not corrected for stellar aberration, and we estimate an
uncertainty of about 30 arcseconds as a result.  A more accurate position will
be available once the data are processed by the XRT pipeline software.

Checks against SIMBAD and the HEASARC master X-ray catalog yielded no known
source at this position on the sky.   The XRT position is about 70 arcseconds
from the refined BAT positions (GCN 2973
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 ).

We have a total of about 600 counts from this object in the first observation
set.  The spectrum appears consistent with a power-law, but detailed fitting
awaits the pipeline-processed data.  Additional automated observations are in
progress when the afterglow field is observable by Swift.

[GCN OPS NOTE (24Jan05): In the first line, the "GRB010124" was changed to "GRB050124"
as per author's request.]

J. P. Osborne, K. Page, M. Goad (UL), A. Beardmore, A. F. Abbey, A. A. 
Wells (U. Leicester), S. Campana, A. Moretti, C. Pagani,  P. Romano, G. 
Tagliaferri, G. Chincarini (OAB), L. Angelini, F. Marshall, N. Gehrels 
(NASA/GSFC), J. E. Hill, J. Kennea, D. N. Burrows, J. A. Nousek, P. Roming, 
P. Meszaros (PSU), G. Cusumano, V. Mangano (IFSFC), P. Schady (MSSL), and 
S. Piranomonte (ASDC) report on behalf of the Swift XRT team:

We have obtained a refined XRT position, using the ground-based pipeline 
processing software, including stellar aberration correction.  The refined 
position for the X-ray afterglow is: RA(J2000) = 12:51:30.4, Dec(J2000) = 
+13:02:39.0.  We estimate a remaining uncertainty of about 8 arcseconds, 
including a systematic error of about 5 arcseconds due to residual 
alignment offsets that have not been fully calibrated yet.

We now have data from 3 orbits.  Data were collected between 14:35:15 and 
15:17:12 UT, between 16:11:35 and 16:53:41 UT, and between 17:48:02 and 
18:30:03.  The point source is clearly fading, with average observed count 
rates 0.20 cps, 0.14 cps, and 0.09 cps in the three observations.

A preliminary spectral fit to data from the first orbit gives a spectral 
power law photon index of  1.3 +/- 0.1, assuming Galactic absorption (2E20 
cm^-2).  The average estimated unabsorbed 1-5 keV flux is then about 6E-12 
erg cm^-2 s^-1 at about 3.5 hours post-burst.

GRB 050124 : Lulin R-band follow-up observation

Z.Y. Lin, K.Y. Huang, W.H. Ip (NCU), Y. Urata, T. Tamagawa (RIKEN),
Y. Qiu (BAO), Y.Q. Lou(THCA) on behalf of the East Asian collaboration
report:

"We have observed the error range of GRB 050124 reported by Markwardt
et al.(GCN 2972
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 ) using Lulin 1-m telescope at Taiwan. The R band
dithering observations started from 4.37 to 5.17 hours after the
burst. No obvious source was found at the bright X-ray source
position (Pagani et al. GCN 2974
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 ). There are no new source brighter
than 20 magnitude during our observations."

This message may be cited.

S.Maeno,E.Sonoda,Y.Matsuo,M.Yamauchi
(University of Miyazaki)


"We have observed the field covering the error box of
GRB 050124 (GCN 2972
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 ;Swift-BAT Trigger time is 11:30:03 UT) 
with the unfiltered CCD camera on the 30-cm telescope
at University of Miyazaki.
The observation was started 17:41:25 UT on Jan.24.
Observed field of view is 43 arcmin centerd on 
R.A.=12h 50m 28s
Dec= 13d 07' 30"
After co-adding a set of 2 images of 30 sec exposures,
we have compared with the USNO A2.0 catalog. Preliminary analysis
shows there is no new source brighter than 17.0 mag.

E. Berger (Carnegie Observatories) and S.R. Kulkarni (Caltech) report on
behalf of a larger collaboration:

"We imaged the 8-arcsec XRT error circle (GCN 2975
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 ) of GRB 050124 (GCN
2972
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 ) with NIRC on the Keck I telescope on January 25.504 UT (24.6 hours
after the burst).  A total of 9 min were obtained in the Ks band.  We find
two sources within the XRT error circle, which we designate C1 and C2.      
Object C1 is point-like and is located at (J2000):
        RA = 12:51:30.7
        DEC= 13:02:42  
Object C2, 8.4" to the southwest, appears extended.  Further observations
are planned to check for variability.  A finding chart is available at:
	http://www.ociw.edu/~eberger/grb050124_finder.ps

This message may be cited.

Y. Yatsu and N. Kawai (Tokyo Tech) report on behalf of MITSUME
collaboration, 

"We observed the field of GRB050124 (GCN 2972
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 , Markwardt et al.) with
the 50 cm Mitsume Telescope at Akeno, Japan in I band starting at 3.8
hours after the trigger.

We detected no new objects with following upper limits, as estimated by
comparison with the USNO A2.0 catalog.  

Start Time    stacked frames     upper limit

15:17:17 UT   30 sec x 100       I > 18.0   
16:11:07 UT   30 sec x 100       I > 18.5
17:04:18 UT   30 sec x 98        I > 18.8

The observing condition was not optimum due to the full moon and the
low elevation angle, but it improved with the increase of the target
elevation."

B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS
consortium, report:
 
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 050124
(GCN 2972
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 , Markwardt et al.) beginning ~20.2 hours post-burst
(2005-01-25 07:42:48 UT).  Total summed exposure times amounted
to 180s in BRIYJK and 120s in H and V.  Preliminary visual comparison
of the optical images to the SDSS and the IR images to
2MASS frames does not reveal any new sources brighter than our
detection limits (listed below).
 
The following approximate upper limits on detection were estimated
by comparison with the USNO B1.0 and 2MASS catalogs:
 
         B > 20.1
         R > 20.6
         I > 20.4
         J > 18.3
         K > 16.9

S. Hunsberger (PSU), A. Breeveld (MSSL), P. Roming (PSU), K. Mason, P. Schady
(MSSL), M. Ivanushkina (PSU), K. McGowan, T. Poole (MSSL), C. Gronwall (PSU),
M. De Pasquale, A. Blustin (MSSL), P. Brown (PSU), S. Rosen, C. James (MSSL),
P. Boyd, S. T. Holland, M. Still, W. Landsman (GSFC), P. Smith, B. Hancock
(MSSL), S. Koch (PSU), M. Carter, H. Huckle (MSSL), P. Broos (PSU), T. Kennedy
(MSSL), S. Barthelmy (GSFC), D. Burrows, J. Nousek, M. Chester (PSU), N.
Gehrels (GSFC), K. Hurley (UCB), G. Chincarini (OAB) on behalf of the Swift
UVOT team.

The Swift Ultra-Violet/Optical Telescope (UVOT) began observations of GRB050124
(GCN 2972
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 ) on January 24, 2005, at 14:34:56 UT.  The spacecraft did not
autonomously slew to the burst since automated slewing was not enabled.  The
observation was performed as a Target of Opportunity beginning about 3 hours
after the burst.  Based on comparisons to the USNO-B1.0 Catalogue, we detect no
source down to a magnitude of 17.4 in the V-filter for a 100 second UVOT Finding
Chart exposure.  We caution that the instrument is not yet fully
calibrated and that this magnitude limit is an estimate.

E. Berger (Carnegie Observatories) and S.R. Kulkarni (Caltech) report on
behalf of a larger collaboration:

"We re-observed the 8-arcsec XRT error circle (GCN 2975
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 ) of GRB 050124
(GCN2972
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 ) with Keck/NIRC on January 26.47 UT.  A total of 18 min were
obtained in the Ks band.  We find that object C1 in our previous Keck/NIRC
image (GCN 2978
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 ) has faded by about 0.5 mag, while object C2 remained
constant in flux.  We therefore conclude that C1 is the afterglow of GRB
050124."

This message may be cited.

J. P. U. Fynbo, B. L. Jensen (NBI), B. Thomsen (U. Aarhus), J. Hjorth (NBI),
E. �rndahl, H. Hyv�nen (U. Turku) and M. I. Andersen (AIP) report:

"We imaged the 8-arcsec Swift/XRT error circle (GCN 2975
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 ) of GRB 050124
(GCN 2972
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 ) in the K band with NOT/NOTCam on January 25.11 UT. Object C1, 
suggested to be the NIR afterglow of GRB 050124 (GCN 2978
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 , 2983
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 ), was
considerably brighter in the NOTCam image at t+15h than in the Keck/NIRSpec 
image at t+24h (GCN 2978
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 ). This confirms the transient nature of the source
and strengthens the afterglow candidacy."

A. M. Soderberg (Caltech) and D. A. Frail (NRAO) report on behalf of a
larger collaboration:

"On 2005 January 29.41 UT we carried out follow-up observations with the
VLA centered on the NIR afterglow candidate reported by Berger et
al. (GCN #2978
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 ) for GRB 050124 (GCN #2972
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 ).  At a frequency of
8.46 GHz no emission was detected above a 2-sigma level of 99 microJy."

GRB 050124 : Kiso Optical limit

A. Tomita (Wakayama Univ.), S. Nishiura (Tokyo Gakugei Univ.)
Y. Urata (RIKEN), K-Y. Huang (NCU) on behalf of EAFON report;

"We have imaged entire error region of GRB 060124 (Holland et al. #
4570) using Kiso 1.05 m Schmidt telescope from 25 min after the burst.
Comparison with DSS II image, there is no new object down to R=20.4
magnitude (S/N=3). "

This message may be cited.

L.J. Pellizza (CEA Saclay, France & IAFE, Argentina), P.-A.
Duc (CEA Saclay, France), E. Le Floc'h (Steward Obs., USA),
& I.F. Mirabel (ESO), on behalf of the MISTICI
collaboration.

We imaged the field of GRB 050124 (Markwardt et al. 2005,
GCN 2972
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 ) on April 29, 2005 and May 10, 2005. R (10 x 308
seconds) and Ks (42 x 60 seconds) frames were obtained
respectively with FORS1 and ISAAC at VLT. In the combined
R image we detect a single object within the revised XRT
error circle (Moretti et al. 2006, A&A, 448, L9), down to
our limiting magnitude R_lim ~ 26. No object is detected
in our combined Ks image down to a limiting magnitude
Ks_lim ~ 21. The position of the possible host galaxy is
RA(J2000) = 12:51:30.45, DEC(J2000) = +13:02:43.0 (0.2
arcsec error). Its magnitude is R = 23.9 (uncertainty
~0.5 mag). Astrometry was performed using USNO B1.0 stars,
while photometry was calibrated against 2MASS and USNO
B1.0 (second epoch) magnitudes.