GRB 010213

G. Ricker, D. Lamb, and S. Woosley on behalf of the HETE Science Team;

R. Vanderspek, G. Crew, J. Doty, G. Monnelly, J. Villasenor; N. 
Butler, T. Cline, J.G. Jernigan, A. Levine, F. Martel, G. Pizzichini, 
and G. Prigozhin, on behalf of the HETE Operations and HETE 
Optical-SXC Teams;

N. Kawai, M. Matsuoka, Y. Shirasaki, T. Tamagawa, A. Yoshida, E. 
Fenimore, M. Galassi, and  C. Graziani, on behalf of the HETE WXM 
Team;

J-L Atteia, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf 
of the HETE FREGATE Team;

write:

On 13 February 2001 at 12:35:35 UTC, a soft spectrum, high energy 
transient at high galactic latitude was detected and localized by 
HETE.  Both the WXM and the FREGATE instruments detected the event. 
Although the WXM and FREGATE cover extremely broad energy bands (WXM: 
2-25 keV; FREGATE: 6-500 keV), the burst event was only detectable in 
the 2-18 keV band by WXM, and in the 6-10 keV band by FREGATE. 
Because of the unusual spectrum of the transient, neither instrument 
triggered.

The preliminary coordinates of the burst are RA= 10h 31m 36s, Dec= 
+5d 30' 39" (J2000), derived from combining data from the WXM and 
Boresighted Optical Cameras.  The statistical error radius in the WXM 
localization is 3.5 arcmin (95% confidence).  In addition, we estimate 
a systematic error radius at present of 30 arcmin about this 
location.  The spacecraft aspect was known to an accuracy of +/- 30 
arcsec (95% confidence) from the optical cameras, and will be 
improved.

The burst exhibited a double-peaked structure and lasted about 30 
seconds.  The incident flux measured with the WXM (2-18 keV) at the 
first peak is about 0.7 Crab, and at the second peak is about 2.4 
Crab.  The spectrum in the 2-18 keV range was harder than that of the 
Crab nebula at the first peak, and softer than that of the Crab at 
the second peak.  The peak flux seen with FREGATE (6-10 keV) was ~2
Crab.  Assuming a Crab-like spectrum, the peak energy flux was ~1.5
E-8 erg/cm^2/sec in the 6-10 keV range.

The high galactic latitude of the source, well away from the Galactic 
Bulge, and the shape of its light curve suggest that it is a 
gamma-ray burst with a very unusual spectrum, perhaps similar to 
those reported for "X-ray rich" GRBs by Heise et al (2001) from 
BeppoSAX observations.  Conceivably, it could instead be a nearby 
X-ray burst source.  A preliminary catalog search of the WXM error 
circle revealed no correspondence with known globular sources, 
cataclysmic variables, low mass X-ray binaries, or flare stars.

Follow-up observations of this unusual transient are encouraged.

Additional information on the 13 February high energy transient 
(including light curves, the WXM error box and results from the 
preliminary catalog searches), as well as the HETE mission, is 
available at:

http://space.mit.edu/HETE/

Acronyms:
HETE=High Energy Transient Explorer
FREGATE=French Gamma Ray Telescope
WXM=Wide Field X-ray Monitor
SXC=Soft X-ray Camera

This message may be cited.

M. Boer, J.-L. Atteia, and A. Klotz, on behalf of the TAROT team report:

TAROT observed the source of  GRB 010213 (Ricker et al., GCN Circ  934
Loading...
 
 ).
The observations were performed between 1h48 and 2h00 on Feb. 15, 2001,
i.e. about 38 hours after the burst, with a limiting magnitude of 17 (no
filter). A comparison with the USNO A2.0 catalog does not show any new
source 30arcmin around the center of the HETE error box.

This message may be cited.
--
===================================================================
Michel Boer
Centre d'Etude Spatiale des Rayonnements (CESR/CNRS)
BP 4346
31028 Toulouse Cedex 4
France
Telephone: (33) (0) 5 61 55 66 40  - Telefax: (33) (0) 5 61 55 67 01
http://www.cesr.fr/~boer   Visit TAROT server: http://tarot.cesr.fr
===================================================================

A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:

We have imaged the inner 6.5x6.5 arcmin portion of the
HETE error circle with the USNOFS 1.55-m telescope and the
ASTROCAM infrared camera at H-band, starting at 010215.42 UT.
Poor seeing conditions limited the depth of the image,
but the limiting magnitude is approximately equivalent to
that of the POSS-IIF red plate for this field.
  We find no object that does not have a counterpart
on the POSS-II plate.

R. Hudec, M. Jelinek, Astronomical Institute Ondrejov, Czech Republic,
M. Tichy, J. Ticha, Klet Observatory, Czech Republic, report:

Unfiltered optical images of the GRB010213 HETE error box (GCN#934
Loading...
 
 ) were
acquired on 2001 February 15.09 with the 0.57-meter f/5.2 telescope (+CCD
camera SBIG ST-8) of the Klet Observatory, Czech Republic, for a total
exposure time of 600 sec.

No new or noticeable object down to a magnitude ~20.5 is detected inside
the trigger error box when we compare our summed frame with the DSS-II
Digital Sky Survey.

This message can be cited.

[GCN OPS NOTE(15feb01): A typo on the date was corrected.  The "January 15.09"
date was changed to "February 15.09".]

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

"Beginning on February 15.42 UT we observed the inner ~25% of the HETE II
error circle of GRB010213 (GCN#934
Loading...
 
 ) with the VLA at 1.43 GHz.  Inside this
region we detect one weak source, which is not cataloged in the NRAO VLA
Sky Survey (NVSS), at RA=10:31:08.08, DEC=5:32:08.26 with a conservative
error of 0.5" in each.  In addition, we detect several sources which
correspond to cataloged NVSS sources.  We note that the uncataloged source
is at the detection threshold of NVSS.  Further observations with the VLA
are planned, and we urge optical observers to try to confirm this
detection."

This message may be cited.

GRB010213 Optical Observation

J. Zhu, on behalf of the Beijing Astronomical Observatory GRB team, report:

"The 58 x 58 arcmin area centered at the HETE II error circle of GRB010214
(G. Ricker et al, GCN #934
Loading...
 
 ) were imaged on Feb. 15.5 (48 hours after the 
burst) with the BAO 0.6-m Schmidt telescope. 13 images were taken (30 min. 
exposure for each) with the BATC-i filter, and the detection limitation 
of the combined image is about R=22.

There is no optical counterpart at the position of the radio source 
mentioned by E. Berger and D. A. Frail (GCN #945
Loading...
 
 ) for our detection 
threshold.  (An epoch 2000.0 is assumed for their coordinates.)

The image will be compared with further observations for any variable
object.

This report may be cited."

-- 
========================================================================
Jin Zhu                          | Tel.:  +86-10-62751286 (O)
Beijing Astronomical Observatory |        +86-314-5520267 (Schmidt dome)
Chinese Academy of Sciences      | Pager: +86-10-96301682333
P. R. China                      | Fax :  +86-10-62765031
------------------------------------------------------------------------
Room 2919, No. 2 Science Building, CAS-PKU Beijing Astrophysics Center,
Peking University, Beijing 100871, P. R. CHINA.
------------------------------------------------------------------------
email: zj@bac.pku.edu.cn                  http://vega.bac.pku.edu.cn/~zj
========================================================================

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

"On February 18.24 UT we conducted a second observation of the central
region of the HETE II error circle of GRB010213 (GCN#934
Loading...
 
 ) with the VLA
at 1.43 GHz. The weak radio source reported in GCN#945
Loading...
 
  is still
present at approximately the same flux level (~1 mJy) as measured on
February 15.42 UT. Furthermore, there is a weak (6-sigma) source
present at this position in 1.4 GHz images taken as part of the FIRST
survey (http://sundog.stsci.edu/top.html). We no longer consider this
radio source to be a viable afterglow candidate."

This message may be cited.