GRB 100212A

D. Grupe (PSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), S. Campana (INAF-OAB),
V. D'Elia (ASDC), P. A. Evans (U Leicester), J. M. Gelbord (PSU),
C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC),
E. A. Hoversten (PSU), J. A. Kennea (PSU),
O. M. Littlejohns (U Leicester), V. Mangano (INAF-IASFPA),
J. Mao (INAF-OAB), R. Margutti (Univ Bicocca&OAB),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
M. Perri (ASDC), P. Romano (INAF-IASFPA),
B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU),
R. L. C. Starling (U Leicester), G. Tagliaferri (INAF-OAB),
T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the
Swift Team:

At 14:07:22 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100212A (trigger=412081).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 356.462, +49.497 which is 
   RA(J2000) = 23h 45m 51s
   Dec(J2000) = +49d 29' 50"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 2 sec.  The peak count rate
was ~5500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 14:08:19.8 UT, 57.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 356.41805, 49.49497 which
is equivalent to:
   RA(J2000)  = 23h 45m 40.33s
   Dec(J2000) = +49d 29' 41.9"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 103 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (1.3e+21
cm^-2, Kalberla et al. 2005), with an excess column of 2.5
(+1.73/-1.52) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 1.39e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
280 seconds after the BAT trigger. No credible afterglow candidate has been
found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the
XRT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The
8'x8' region for the list of sources generated on-board covers 100% of the XRT
error circle. The list of sources is typically complete to about 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.18. 

Burst Advocate for this burst is D. Grupe (grupe AT astro.psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

D. Malesani, G. Leloudas, J. P. U. Fynbo (DARK/NBI), D. Xu (WIS and 
DARK/NBI), P. Jakobsson (Univ. Iceland), A. Somero, S. Katajainen 
(Tuorla Obs.), T. Pursimo (NOT), report on behalf of a larger collaboration:

We observed the field of GRB 100212A (Grupe et al., GCN 10401
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 ) with the 
NOT equipped with ALFOSC. Observations started on Feb 12.841 UT (6.05 hr 
after the GRB), in the R band.

Close to the refined XRT error circle (as reported in the SPER web page 
http://www.swift.ac.uk/sper/index.php at 21:30 UT), we detect a source 
which is not visible in the DSS. Its coordinates are (J2000):

RA = 23:45:40.23
Dec = +49:29:40.7

The object is 2.5" away from the centre of the XRT position, currently 
reported to have a 2.2" error radius.

The R-band magnitude of the source is R = 20.3 assuming R = 17.3 for the 
USNO star at RA = 23:45:42.93, Dec = +49:30:29.3. The source looks 
pointlike under a seeing of 1" and is clearly brighter than other 
closeby objects visible in the DSS.

We suggest this object to be the afterglow of GRB 100212A.

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 699 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 100212A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 356.41830, +49.49432 which is equivalent
to:

RA (J2000): 23h 45m 40.39s
Dec (J2000): +49d 29' 39.6"

with an uncertainty of 2.0 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.

T. N. Ukwatta (GWU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
D. Grupe (PSU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC)
(i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 100212A (trigger #412081)
(Grupe, et al., GCN Circ. 10401
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 ).  The BAT ground-calculated position is
RA, Dec = 356.445, 49.492 deg, which is 
   RA(J2000)  =  23h 45m 46.9s 
   Dec(J2000) = +49d 29' 30.5" 
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 86%.
 
The mask-weighted light curve shows multiple peaks.  The main peak starts
with weak emission at ~T-45 sec with the peak at ~T+0.2 sec and ends 
at ~T+30 sec.  A second peak starts at ~T+75 and ends at ~T+135 sec.
T90 (15-350 keV) is 136 +- 14 sec (estimated error including systematics).
 
The time-averaged spectrum from T-4.8 to T+134.0 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.20 +- 0.22.  The fluence in the 15-150 keV band is 9.1 +- 1.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.34 sec in the 15-150 keV band
is 2.2 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/412081/BA/

D. Grupe (PSU) reports on behalf of the Swift-XRT team:

We have analyzed 1.9 ks of XRT data for GRB 100212A (Grupe et al.
GCN Circ. 10401
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 ), from 64 s to 7 ks after the BAT trigger. The
data comprise 409 s in Windowed Timing (WT) mode with the remainder
  in Photon Counting (PC) mode. The enhanced XRT position for this
  burst was given by Osborne et al. (GCN. Circ 10403).

The light curve is complicated displaying several strong flares up
to 700s after the burst. The underlying afterglow light curve
suggests a step decay slope of alpha=2.89+/-0.09. However, the data
of the second orbit indicate the beginning of the plateau phase with
a significantly flatter decay slope. Predictions of the further
development of the X-ray light curve are not reliable at this point.

A spectrum formed from the WT mode data can be fitted with an
absorbed power-law with a photon spectral index of 2.03 (+/-0.03).
  The best-fitting absorption column is 1.97 (+/-0.08) x 10^21 cm^-2,
   in excess of the Galactic value of 1.3 x 10^21 cm^-2 (Kalberla et
   al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux
   conversion factor deduced from this spectrum is 3.8 x 10^-11
   (5.6 x 10^-11) ergs cm^-2 count^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00412081.

This circular is an official product of the Swift-XRT team.

Sylvain Guiriec (UAH) and Dave Tierney (UCD/MPE)
report on behalf of the Fermi GBM Team:

"At 14:07:29 UT on 12 February 2010, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 100212A (trigger 287676444 / 100212588).

This GRB has also been detected independently with Swift/BAT and the
GBM location is consistent with the Swift/XRT location within the error bars

(Grupe et al. GCN Circ. 10401
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 ).

The angle from the Fermi LAT boresight is 15 degrees.

The GRB duration (T90) is about 2.30+/-0.14 s (8-1000 keV).
The time-averaged spectrum from T0-0.51 s to T0+0.26 s is
adequately fit by a power law with an index of -1.62+/-0.06
(Castor C-stat 394 for 363 d.o.f.).
It is also adequately fit by a power law function with an exponential
high energy cutoff. The power law index is -1.15 +/- 0.20 and
the cutoff energy, parameterized as Epeak, is 159.30 +/- 45.10 keV
(Castor C-stat 389 for 362 d.o.f.).

The event fluence (8-1000 keV) in the T90 time interval is
(3.81+/-0.06)E-7 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.7 s in the 8-1000 keV band is 3.16 +/- 0.22 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

M. Im (CEOU/Seoul National Univ) and Y. Urata (NCU)
  on behalf of EAFON team.

   We observed GRB100212A (Grupe et al. GCN 10401
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 ) in R and V
  using the 1.0m telescope at Mt. Lemmon (Arizona, US) operated by
  the Korea Astronomy Space Science Institute.
   The observation started at Feb. 13, 02:05:14 UT, about 12 hours
  after the BAT trigger.

   The stacked R-band image shows a marginal detection of
  the afterglow with R ~ 22.5 +- 0.2 mag, at the location reported by
  Malesani et al. (GCN 10402
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 ).  The mid-point for the R-band imaging
  is 02:17:36 UT. The object does not appear in a stacked V-band
  image, which was taken right after the R-band observation.
   Our obseravation shows that the afterglow candidate faded
  significantly since the report by Malesani et al. (GCN 10402
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 ),
  confirming that this is indeed a GRB afterglow.
   The photometry was calibrated against the USNO star (GCN 10402
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 ).

   We thank the LOAO operator, J. Yoon for her assistance of this
  observation.

The previous GCN 10408
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  dealt with GRB100212A, not GRB120212A as 
erroneously written. I apologize for the mistake.