GRB 011030

BeppoSAX ALERT: Possible X-ray rich GRB011030

On Oct. 30, 06:28:02 U.T. a  faint transient has been detected
by the WFC1 aboard BeppoSAX, without counterpart in the GRBM.

Preliminary  coordinates from WFC are:

R.A.(2000)= 310.927
DEC.(2000)= 77.293

The error radius at this stage of analysis is 5'.

A preliminary analysis of quick-look data shows that the event could be an
X-ray rich GRB, but the low galactic latitude and the presence of a faint
Rosat source (1RXS J204310.8+77172) inside the error box can not exclude
the x-ray burster nature of the source.
We are not planning a follow-up observation of this burst, due to the
on-going testing phase of gyroless attitude control system.

Giangiacomo Gandolfi
on behalf of
BeppoSAX Mission Scientist

[GCN OPS NOTE:  This distribution was delayed by about 1.5 hours because the
original submission address was invalid.  Apologies for the delay.]
[GCN OPS NOTE:  Due to confusion about active submitors accounts and delays
in the distributions, this was submitted twice and distributed twice.
The second copy (originally numbered 1119) was deleted from the archive
and the serial number sequence set back to waiting for the next submission.]

X-ray rich GRB011030: BeppoSAX refined positions

Refined coordinates from WFC are:

R.A.(2000) = 310.911
DEC.(2000) = 77.292

The error radius is 3'.

Giangiacomo Gandolfi
on behalf of BeppoSAX Mission Scientist

GRB 011030, R-band observations
--------------------------------

Vijay Mohan, S.B. Pandey, J.C. Pandey, Yogesh Joshi, Ram Sagar, UPSO
(Nainital)
Michel Creze (Univ. of Bretagne Sud)
Alberto J. Castro-Tirado, IAA-CSIC (Granada)
José María Castro Cerón, ROA (San Fernando)
Jochen Greiner, AIP (Potsdam)
Sylvio Klose, TLS (Tautenburg)
Juergen Fliri, USM (Munich)


report:

"We have just obtained several R-band exposures centred at
the GRB 011030 error box (Gandolfi et al. GCN#1119
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 ) starting
at 13:40 UT on 30 Oct 2001 with the  1.0-m telescope at Nainital
(India) and at 18:05 UT at the 1.23-m telescope at the
German-Spanish Calar Alto Observatory (CAHA).  A preliminary
analysis of the images reveal no optical counterpart within
a 5' radius down to R = 21 when comparing with the DSS-2 R-band
chart. Further R- and I-band observations are in progress."

Radio search for GRB011030

The Ryle Telescope (Cambridge, UK) was used for a 3-hour observation
centred on the refined position of GRB011030 (GCN 1119
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 ), from 21:15 UT 
on 2001 Oct 30. The field covered is 6' fwhm, resolution about 30", 
observing frequency 15 GHz. No source was detected, to a noise level
0.4 mJy rms.

Guy Pooley (MRAO, Cambridge)

G. B. Taylor, D. A. Frail (NRAO), and D. Fox (Caltech) report on
behalf of a larger collaboration:

"We have imaged the entire 3 arcmin WFC error circle of GRB 011030
(GCN 1118
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 ) with the VLA at 8.47 GHz on UT 2001 Oct. 31.13. We detect
two radio sources which we designate VLA J2042+7718 and VLA J2044+7717.
The coordinates of
VLA J2042+7718 are RA = 20h42m46.09s, DEC = 77d18'22.2" (J2000) and
VLA J2044+7717 are RA = 20h44m07.61s, DEC = 77d17'37.4" (J2000)
with conservative errors of 1 arcsec in each coordinate.  VLA J2044+7717
is well within the WFC error circle while VLA J2042+7718 is
right on the edge of the error circle. Preliminary flux densities are
0.9 mJy for VLA J2042+7718 and 0.3 mJy for VLA J2044+7717.  Neither
source is detected in the NRAO VLA Sky Survey (NVSS; Condon et
al. 1998, AJ, 115, 1693) above their flux limit of 1 mJy at 1.4 GHz.
We have searched the DSS and find a faint galaxy near VLA J2044+7717.
We encourage observers at other wavebands to check for counterparts at
the positions of these two radio sources.  Further radio observations
are planned."

This message may be cited.

J.J.M. in 't Zand, J. Heise (SRON, Utrecht), P. Lowes (SOC, Telespazio, Rome,
and SRON), G. Gandolfi, L. Piro, E. Costa (IAS, CNR, Rome), report:

"We have been able to further refine the position of GRB 011030 as obtained
with the Wide Field Camera unit 1 on BeppoSAX (GCN Circ. 1118
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 , 1119
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 ). The final
result is R.A. = 20h43m35.4s, Decl. = +77d17m20s (J2000.0) with an error
radius of 2.1 arcmin (99% confidence). We note that VLA J2044+7717 is at
1.8 arcmin from this WFC centroid and VLA J2042+7718 at 2.9 arcmin. Therefore,
the latter radio source is ruled out as counterpart to GRB 011030 by this
refinement. The WFC observation was performed during the testing phase of
the new gyro-less pointing mode. A preliminary analysis of all data collected
so far shows that the pointing accuracy in the gyro-less pointing mode is
consistent with or better than that during the one-gyro mode."

Evert Rol, Paul Vreeswijk, Isabel Salamanca, Lex Kaper (University of
Amsterdam), Ralph Wijers (SUNY Stony Brook), Richard Strom (UoA,
ASTRON), Tony Foley (ASTRON) report, on behalf a larger collaboration:

We have observed the error box of the possible GRB 011030 (Gandolfi,
GCN 1118
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 , 1119
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 ) at 4.8 GHz with the Westerbork Synthesis Radio
Telescope. We detect the two VLA sources found by Taylor et al. (GCN
1122
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 ).

Within the refined error circle (In't Zand, GCN 1123
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 ), we find only
one source, VLA J2044+7717. Our observations show this source to be
constant at 4.8 GHz, with a spectral index of 0.6 between our 4.8 GHz
flux and the VLA 8.6 GHz measurement:

    flux (mJy)    freq	     date
  0.23 +- 0.04	 4.8 GHz   Oct 30.68 
  0.20 +- 0.04	 4.8 GHz   Oct 31.71

Further observations are planned to see whether this source is the
counterpart to GRB 011030.

Molly Hammell (Dartmouth), J. P. Halpern, & N. Mirabal (Columbia U.) report
on behalf of the MDM Observatory GRB follow-up team:

"Using the MDM 1.3m, we obtained 120 minutes of exposure in the K band centered 
at Oct. 31.11 UT, 20 hours after the burst.  All of the 2.1' radius refined 
BeppoSAX error circle (in 't Zand et al., GCN #1123
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 ) was covered.  A follow-up 
observation was performed on Nov. 1.20 UT, with 40 minutes of exposure.  
Conditions were not photometric, and these images have not been calibrated.  
However, no afterglow candidate has been found to an approximate limiting 
magnitude K > 18.  Additional observations on Nov. 1 covering the position of 
the radio source VLA J2042+771 reported by Taylor et al. (GCN #1122
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 ) reveal no 
detection to a slightly deeper limiting magnitude.  A prominent galaxy is seen 
at the position of the radio source VLA J2044+7717 (see also Rol et al., GCN #1124
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 ).
It is constant to better than 0.05 mag.

I-band images were also obtained on both nights using the MDM 2.4m.  Results of
these will be reported subsequently.

A K-band image is posted at
http://www.astro.columbia.edu/~jules/grb/011030

This message may be cited."

J. P. Halpern, N. Mirabal (Columbia), Chris Burke, & D. L. DePoy (Ohio State),
report on behalf of the MDM Observatory GRB follow-up team:

"Using the MDM 2.4m, we obtained 15 minutes of exposure in the I band centered 
at Oct. 31.21 UT, 22.5 hours after the burst.  All of the 2.1' radius refined 
BeppoSAX error circle (in 't Zand et al., GCN #1123
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 ) was covered.  A follow-up 
observation was performed on Nov. 1.22 UT, with 15 minutes of exposure.  
Conditions were not photometric, and these images have not been calibrated.  
However, no afterglow candidate has been found to a limit approximately 1 mag
fainter than the POSS-II IVN plate, or I_c > 20.5.

An I-band image is posted at
http://www.astro.columbia.edu/~jules/grb/011030

This message may be cited."

G. B. Taylor (NRAO), D. A. Frail (NRAO/Caltech) and S. R. Kulkarni
(Caltech) report on behalf of the Caltech-NRAO-CARA collaboration:

"We have continued to monitor the WFC error circle of the X-ray
transient 011030 (GCN 1119
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 , 1123
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 ) with the VLA at 8.47 GHz.
Observations were made over four epochs on Oct. 31.13,
Nov. 1.79, Nov. 4.81, and Nov 8.80 UT.  Over this period the radio source
VLA J2044+7717 (GCN 1122
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 ) has remained constant, in agreement with the
4.8 GHz observations by Rol et al. (GCN 1124
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 ). On 2001 Nov 8.80 UT a
new source was detected with high significance with a flux density of
181 +/- 18 microJy. This new source is located near the center of the
WFC error circle at (epoch 2000) R.A.=20:43:32.3, Dec.=+77:17:18.9,
with a conservative error of +/-1 arcsec in both coordinates.

Little is known about the class of such X-ray rich transients. This is
the first detection of a counterpart at any other wavelength to an
X-ray rich transient. We will continue further radio observations and
urge observations at other wavelengths."

This message may be cited.

J. S. Bloom, A. Gil de Paz, F. A. Harrison and S. R. Kulkarni (Caltech)
report:

"Optical imaging observations were carried out at the Palomar 60-inch 
telescope on 9 November, 2001 (UT) by Armando Gil de Paz. Six images of
600 s duration were observed under non-photometric conditions. We found
no optical 
counterpart to a limiting magnitude of R=22.9 magnitude (5 sigma). 
Our photometry is based on assuming R=17.3 for the USNO A2.0 star
6-arcsecond to the northeast of the radio position. The astrometry is with
respect to more than 200 USNO A2.0 stars and the overall astrometric
accuracy is about 0.25 arcseconds (in each coordinate).  
We also note that the Galactic extinction towards this direction is high
(A_R about 1 magnitude)."

J. Heise (SRON, Utrecht), J.J.M. in 't Zand (Utrecht Univ. and SRON),
S.R. Kulkarni (Caltech), and E. Costa (CNR, IAS, Rome) report:

"We have carried out further investigations of SAX J2043.6+7717, the X-ray
rich transient of 30 October, 2001 discovered by BeppoSAX-WFC (GCN 1118
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 ).
The flash peaks at 0.26 Crab units (2-28 keV), while activity is detected for
about 1400 s (but we note that the observations started about 100 s before
the first activity from this source was detected). The spectrum is
characterized by a power law with a photon index of -1.9 +/- 0.1. A black
body fit is inconsistent with the data at 99.97% confidence. The 2-28 keV
fluence is estimated at 9E-7 erg/cm2. For X-ray light curve and spectrum,
we refer to http://wfc.sron.nl/flash/

What could SAX J2043.6+7717 be?

By several accounts, SAX J2043.6+7717 does not appear to be a traditional
GRB. First, the absence of detection of the X-ray transient in the Gamma-Ray
Burst Monitor on BeppoSAX means that the peak energy of the transient must be
lower than ~40 keV. In contrast, GRBs are distinguished by peaking in the 50
to 500 keV range. Second, GRBs with such long duration are rare, e.g. the
longest T90 listed in the 4th BATSE catalog (Paciesas et al. 2000, ApJS, 122,
465) out of 1234 bursts is 674 s (trigger 3458) and in general have strong
pulses. In contrast, SAX J2043.6+7717 lasted more than a thousand seconds long.

The second possibility, especially given the galactic latitude of
SAX J2043.6+7717 (b=+20.7 degrees), may argue for this source to be a Galactic
transient. However, the X-ray spectrum rules out SAX J2043.6+7717 being a type
I X-ray burst. This then leaves us with the possibility that SAX J2043.6+7717
is a Fast X-ray Transient (FXT; e.g., Grindlay 1999, ApJ, 510, 710). However,
FXTs usually last longer than an hour. More importantly, FXTs have been
identified with relatively bright quiescent optical/IR counterparts e.g.
RS CVns, nearby dMe stars, super flares from pre-main sequence stars and
black hole transients. However, as noted in GCN 1137
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 , there is no visible
optical counterpart to the radio source nor was a bright optical or IR
transient (GCN 1127
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 ) seen following the detection of the X-ray transient.

We conclude that most likely SAX J2043.6+7717 is a member of the newly
recognized class of X-ray flashes (Heise et al. 2001, in Proc. 'Gamma-Ray
Burst in the Afterglow Era', Rome, Oct. 17-20, 2000, in press).

Given that we know little about such events (with the 011030 flash possibly
being the first event localized to arcsecond accuracy; see GCN 1136
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 )
it is not appropriate to call such non-triggered transients as "X-ray rich,
gamma-ray poor" GRBs (or other equally oxymoronic names). Recognizing that
astronomical research is largely based on empiricism, we suggest that events
such as the one on 011030 characterized by the following criterion be
termed as "X-ray flashes" (XRF):  
  (1) Strong non-thermal emission in the X-ray (2-20 keV band;  this
      criterion distinguishes them from type I bursts);  
  (2) Weak in the traditional GRB gamma-ray band, 50-250 keV; this explains
      why typical XRFs do not trigger gamma-ray burst monitors. 
  (3) Durations less than a few thousand seconds; this differentiates XRFs from
      the so-called fast X-ray transients which have durations  of several
      hours (many of which are stars with intense coronal activity and some
      are binaries containing a compact object such as XTE J1819-254).
  (4) Display no strong quiescent optical/IR counterpart; this criterion
      distinguishes XRFs from stars with  strong coronal activity (e.g.
      strong flares from pre-main sequence stars, dMe stars, RSCVn stars,
      Be stars etc). 

The accurate position of this X-ray flash presents an excellent opportunity
to understand this new phenomenon which previously has never been detected
outside the X/gamma-ray regime. We strongly encourage multi-wavelength
observations."

This message may be cited.

J. P. Halpern, N. Mirabal (Columbia), C. Burke, D. L. DePoy (Ohio State), &
S. Gaudi (IAS), report on behalf of the MDM Observatory GRB follow-up team:

"Using the MDM 2.4m, we reobserved this location in the I band on Nov. 9.23 UT.
In two 8 minute exposures in seeing of 1.2 arcseconds, there is a possible
detection at the 2 sigma level of an object at position (J2000) 20:43:31.94,
+77:17:19.0, which is 1.2 arcseconds west of the position reported for the new 
radio source that appeared on Nov 8.80 (Taylor et al. GCN #1136
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 ).  Assuming
for a calibration that the faintest objects on the POSS-II IVN plates have 
I=19.5, this possible counterpart would have I=22.5.  Given the marginal
level of this detection and its absence on previous images of comparable
depth on Nov. 1, confirmation would be required.  Alternatively, this may
be considered an upper limit to the optical brightness of the radio source.

The new image is posted at
http://www.astro.columbia.edu/~jules/grb/011030

This message may be cited."

James E. Rhoads, Ingunn Burud, Andrew Fruchter, Chryssa Kouveliotou,
and Michael Wood-Vasey report on behalf of a larger collaboration:

We observed the error circle of GRB 011030 with the 3.5m WIYN telescope
and mini-mosaic imager on the nights of UT 011101, 011102, and 011103,
obtaining five 600 second images in the R band each night.

We find no source at the location of the new radio source reported by
Taylor et al (GCNC 1136).  If we adopt the R band zero point used by
Bloom et al (GCNC 1137), the corresponding 5 sigma upper limits are
R=23.61 (011101) and R=23.28 (011103).

In addition, we performed a seeing-matched image subtraction on the
011101 and 011103 data.  The difference image shows no significantly
variable sources.  The estimated photometric noise level in the
difference image (for a 1 arcsec radius aperture) is 0.5 microJansky
(1 sigma), corresponding to R=24.5 (1 sigma) or R=22.7 (5 sigma).

Further analysis of existing data is underway, and at least one
additional observation is planned.

We thank Doug Williams and Di Harmer for their help in these observations.

M. Brown, A. Dey (NOAO), A. Fruchter and J. Rhoads (STScI) report for
a larger collaboration:

The field of the radio transient (Taylor et al., GCN 1136
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 ) potentially
associated with GRB011030 was imaged at the KPNO 4-m using the
Multi-Aperture Red Spectrometer (MARS) through an RG830 (approximately
z-band) filter from 1:55 to 2:50 12 NOV 01 UT.  Due to significant
overhead associated with the instrument, the total exposure time was
600 seconds; the seeing was approximately 1."5.  No source was detected
at the position of the radio transient, or that of the potential I-band
object nearby reported by Halpern et al. (GCN 1139
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 ), down to a limiting
(Vega) magnitude of 22.5 (5-sigma).

S. Klose, B. Stecklum, A. Zeh (Thueringer Landessternwarte Tautenburg),
O. Fischer (Universitaets-Sternwarte Jena), 
U. Thiele (Calar Alto observatory, Spain),
R. Neuhaeuser, N. Huelamo,
   (Max-Planck-Institut fuer Extraterrestrische Physik, Garching),
J. Greiner (AIP Potsdam),
A. Castro-Tirado (LAEFF-INTA, Madrid, and IAA-CSIC, Granada), 
N. Masetti, E. Palazzi (ITeSRE, CNR, Bologna), 
E. Pian (Oss. Astron. Trieste),

report:


The error circle  of the X-ray transient 011030  (Gandolfi et al., GCN
#1118
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 ) was  imaged with  the Calar  Alto 3.5-m  telescope on  Oct. 30,
18:32 UT  - 19:33 UT  (i.e., about 12  hours after the  burst trigger)
using  the  near-infrared  camera   Omega  Cass  in  the  polarimetric
mode. The limiting magnitude in  the central part of the K'-band image
(mosaic) is about  K'=19.5 after adding all frames  taken at different
position angles  of the wire-grid polarizer. Since  standard stars are
not yet available we estimate the error of this magnitude limit to +/-
0.5  mag. The combined  image covers  about 90%  of the  revised error
circle (in 't Zand et al., GCN #1123
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 ).

At the position of the radio  transient reported by Taylor et al. (GCN
#1136
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 ) no source is detected (see also Hammell et al., #GCN 1126).

We do  not detect the  I-band source reported  by Halpern et  al. (GCN
#1139
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 ).


This message is quotable.

R. Hudec (Astronomical Institute Ondrejov), J. Polcar (Astronomical
Institute Ondrejov and Masaryk University Brno), M. Tichy and J. Ticha
(Klet Observatory) report:


The whole error box of GRB011030 was imaged with the Klet Observatory
0.57-meter f/5.2 telescope (+CCD camera SBIG ST-8) on 2001 Oct 31, 17:24
to 17:39 UT (10 exposures 60 sec each). No new and/or fading object has
been detected down to limiting magnitude of  19.5 (unfiltered), error
0.5 mag.

This message can be cited.

L.A. Antonelli, (INAF, Astr. Obs. Rome), F. Mannucci (CAISMI, CNR,
Firenze), E. Pian (INAF, Astr. Obs. Trieste), V. Testa, A. Di Paola,
L. Stella (INAF, Astr. Obs. Rome), I. Burud, A. Fruchter, J. Rhoads
(STScI), N.  Masetti, E. Palazzi, F. Frontera (ITeSRE, CNR, Bologna),
S. Covino (INAF, Astr. Obs. Brera, Milan), D. Lazzati (IoA, Cambridge),
L. Piro (IAS, CNR, Rome), J.  Licandro, F.  Ghinassi (TNG), S. Klose
(TLS, Tautenburg), on behalf of a larger collaboration, report:


"We imaged the field of XRF011030 (GCN 1118
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 ) with TNG equipped with the
near-IR camera NICS and K filter on Nov 10, 20:22 - 22:48 UT. During 
the observation the seeing was 1.5". The AS36 photometric standard was 
also observed and used for magnitude calibration.

No source is detected at the position of the radio transient reported
by Taylor et al. (GCN 1136
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 ) nor in the Chandra error box of the X-ray
source detected by Harrison et al. (GCN 1143
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 ) to a 5-sigma limiting
magnitude of K = 20.1.
 
This message may be cited."

A. Fruchter (STScI), S.  Pattel (MSFC), C. Kouveliotou (MSFC), J.
Rhoads (STscI), S. Holland (Notre Dame), I. Burud (STScI) and R. Wijers
(Stony Brook) report for the larger GOSH (Grb Optical Studies with Hst)
collaboration:

A field containing the reported X-ray (GCN 1143
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 ) and radio (GCN 1136
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 )
positions of XRF/GRB 011030 (GCN 1118
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 ) was observed with HST on 12
December 2001 using the STIS CCD camera both in open mode (50CCD) and
with a red-pass filter (LP).  Due to the low-galactic latitute (b=20.6)
of this field, the estimated foreground extintion is Av=1.2 (Schlegel,
Finkbeiner, Davis 1999).  Nevertheless, a 26th magnitude galaxy is
found to be coincident with both the X-ray and radio positions (within
the reported ~1" errors of both).

With the public release of the second epoch of Chandra observations
(taken on 29 November 2001), we have been able to determine that the
X-ray source fell between the two Chandra epochs approximately as
t^{-2} (using the time of the XRF/GRB as the zero-point), thus confirming
the association of this source with the XRF/GRB.

We have therefore attempted to refine the Chandra error circle.  We
aligned the first, deeper (9-November) Chandra observation with
wide-field R band images obtained on the 1 and 3 November on the WIYN
telescope using six point sources which are bright in both images.  We
find an r.m.s.  positional offset between sources in the two images of
~0."18.  As the XRF/GRB is brighter in the Chandra image than any source used
in the fit (though not visible in the WIYN image), we estimate that the 
error in transforming its position to the optical field should be no larger 
than 0."18, one sigma.   We have also been able to place the WIYN image on
the J2000 coordinate system to an accuracy of ~0."1, using both Naval
Observatory and Tycho standards.

We find that the 0."18 Chandra error circle overlaps the somewhat 
bluer, eastern end of the small irregular galaxy noted above.  The galaxy 
is approximately 0."5 across, and has a total magnitude of V~26.2, or
approximately V=25, after removal of the estimated foreground extinction.
This is comparable to the peak of the distribution of XRF/GRB host
magnitudes (Hogg and Fruchter 1999).  The color of the galaxy (again
after removal of the foreground extinction) is quite blue (consistent
with a power-law of nu^{-0.5}), suggesting both a relatively young
stellar population and that the galaxy has a redshift, z < 3.  XRF/GRB
011030 thus appears to be similar to GRBs in its probable redshift and
in its association with a faint, blue galaxy; this in turn suggests that 
XRFs are not a radically different class of object, but are very soft GRBs.

A. Fruchter (STScI) reports:

Images of the probable host galaxy of XRF/GRB 011030, described
in GCN 1268
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 , can be found at

http://www.stsci.edu/~fruchter/GRB/011030