GRB 001109

BeppoSAX ALERT: GRB001109

On Nov. 09, 09:23:17 U.T. a GRB (GRB001109) has been detected
simultaneosly by the GRBM and WFC1 aboard BeppoSAX.

Preliminary  coordinates from WFC are:

R.A.(2000)= 277.507
DEC.(2000)= 55.307

The error radius at this stage of analysis is 4'.

We are planning a BeppoSAX-NFI observation.


G. Gandolfi on behalf of
BeppoSAX Mission Scientist

GRB001109: BeppoSAX refined WFC position

Refined  coordinates of GRB001109 from WFC are:

R.A.(2000)= 277.531
DEC.(2000)= +55.301

The error radius is 2.5'.

G. Gandolfi
on behalf of BeppoSAX Mission Scientist

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

"We have imaged the entire 2.5 arcmin WFC error circle of GRB 001109
(GCN 879
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 ) with the VLA at 8.47 GHz on UT 2000 Nov. 9.80. We detect one
radio source which we designate VLA J1830+5518.  The coordinates of
VLA J1830+5518 are: RA = 18h30m06.51s, DEC = 55d18'35.7" (equinox
J2000) with conservative errors of 0.1 arcsec in each coordinate.  The
flux density on Nov. 9.8 is 236 +/- 31 microJy. The size of VLA
J1830+5518 is less than 0.4 arcsec.  No 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.  The density of sources on the sky
stronger than 250 microJy at 8.4 GHz is 0.0145 arcmin**-2.  We
computed an astrometric solution for the DSS-2 image of the field
using the USNO-A2.0 catalogue and found no obvious optical point
source at the position of the radio object."

This message may be cited.

K. Z. Stanek (CfA), P. Garnavich (Notre Dame), K. L. Luhman and
B. A. McLeod (CfA) report:

We imaged the WFC error box (GCN 879
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 ) of GRB001109 with the FLWO 1.2m
telescope and R-band filter starting on 2000 Nov. 10.087 (UT).  We
obtained 2x600-sec R-band exposures. Near the position of the radio
source reported by Taylor et al. (GCN 880
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 ) we detect faint optical
source, R~21.0, located at RA=18:30:06.63, DEC=55:18:34.95 (2000.0).
The magnitude estimate for this source was obtained by comparing to
USNO star ``A'' at RA=18:30:06.38, DEC=55:19:05.8 (2000.0),
R=19.0. This faint optical source near the position of the radio
source is also marginally visible at the POSS-II red plate, and thus
most likely is not an optical counterpart to GRB001109. Within the WFC
error box we do not see any ``new'' sources brighter than R~20.5.

Our composite 1200-sec R-band image is available at
http://cfa-www.harvard.edu/cfa/oir/Research/GRB/, along with the
POSS-II finding chart with positions of the sources marked.

This message can be cited.

GRB001109: BeppoSAX/NFI Observations

A BeppoSAX TOO observation (20 ksec) of GB001109 has started about 16
hours after the GRB.
Preliminary analysis of the first three orbits shown a
bright and unknown source in the MECS(1.6-10 keV) image.

The position is:

RA = 277.525
Delta = 55.309

The error radius is 1.5 arcminutes.

At this stage still we don't detect an unambiguous fading behaviour of
this X-ray source.

G. Gandolfi
on behalf of BeppoSAX Mission Scientist

V.Rumjantsev and L.Pavlenko (on behalf of Crimean Observatory and Space
Research Institute (Moscow) GRB follow-up teams) report:

"We have imaged of the error box for GRB 001109 (G. Gandolfi et al., GCN 878
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 ) with the 0.64-m 
and the 0.38-m Cassegrain telescopes of Crimean Astrophysical Observatory. 
A first frame was obtained on Nov 9 15:50:21 UT (i.e. 6.5 hours after the GRB). 
Conditions were not so good. Our images cover all but the square half degree.
No new objects are seen within the error box when comparing to the DSS-2 (R-band), 
brighter a limiting integral magnitude of 20 mag (at 0.64-m telescope) and also 
brighter then 17 mag in V (at 0.38-m telescope)."

L. Amati, F. Frontera, and E. Pian, Istituto Tecnologie e
Studio Radiazioni Extraterrestri, CNR, Bologna; P. Giommi and M.
Capalbi, BeppoSAX Science Data Center, Rome; E. Costa and G.
Gandolfi, Istituto di Astrofisica Spaziale, CNR, Rome; J. J. M. in
't Zand, Space Research Organization Netherlands; C. Guidorzi,
Universita di Ferrara; S. Granata and A. Paolino, BeppoSAX Science
Operation Center, Rome, report:  "The 2'.5 error box of GRB 001109
provided by the BeppoSAX Wide Field Cameras was observed with
the BeppoSAX Narrow Field Instruments from Nov. 10.0762 (16.5 hr
after the gamma-ray burst) to 10.9847 UT.  A previously unknown
source lying inside the error box has been detected by the Medium
Energy Concentrator Spectrometer.  The source, designated 1SAX
J1830.1+5517, is located at R.A. = 18h30m07s.8, Decl. = +55o17'56"
(equinox 2000.0; error radius 50") and has an average count rate of
0.00914 +/- 0.0007 count/s in the two MECS units, corresponding to
a 2-10-keV flux of (7.1 +/- 0.5) x 10**-13 erg cm**-2 s**-1.  The
flux decreases by a factor of about 2 during the first 20 000 s of
the observation.  Due to its fading behavior, 1SAX J1830.1+5517 is
likely the x-ray afterglow of GRB 001109.  We remark that the
position of this source is consistent with that of the previously
unknown radio source detected in the GRB 001109 error box by Taylor
et al. (GCN 880
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 ).  A second BeppoSAX NFI observation of the field
is in progress."


This message can be cited

P. Vreeswijk, E. Rol (U. of Amsterdam), C. Packham (U. of Florida),
N. Tanvir (U. of Hertfordshire), C. Kouveliotou (MSFC/USRA), R. Wijers
(SUNY) and J. Knapen (ING/U. of Hertfordshire), report on behalf of a
larger collaboration:

We observed the field of GRB 001109 [1] in J, H and Ks with INGRID on
the 4.2m William Herschel Telescope on La Palma, Canary Islands on
Nov. 9.8 and 11.8 UT, respectively 10 and 59 hours after the burst.
The 50" radius error circle of the reported X-ray afterglow of 
GRB 001109 [2] is located at the center of our 4.2'x4.2' images.

We observed the UKIRT faint standard #30 [see 3] to calibrate the
field. The stellar FWHM in the co-added frames ranges from 0.9" to
1.3" (pixelsize=0.25").  The first table below shows the log of the
observations, including the estimated 3-sigma limiting magnitude
(using an aperture diameter twice the size of the FWHM).

At the position of the radio source detected in the field [4], we
observe extended emission, consisting of a bright component (with a
PSF FWHM significantly larger than that of point sources in the
field), and a fainter peak, separated by roughly 1". The magnitudes
that we measure for this emission (using an aperture radius of 2.5"),
are also listed in the table. Within the errors (which do not include
the uncertainty in the calibration), this source does not vary. This
confirms the expectation [5] that the emission from this location is
probably not related to the GRB.


         UT date   filter  exptime   lim. mag.  radio source
 -----------------------------------------------------------
 2000 Nov.  9.81     J       300s      21.3	18.64 (0.05)
	    9.80     H       750s      21.0	17.96 (0.03)
	    9.79     Ks      750s      19.9	16.96 (0.04)

	   11.86     J       600s      21.4	18.70 (0.05)
	   11.82     H       600s      20.7	17.93 (0.08)
	   11.83     Ks      600s      19.4	17.07 (0.07)


Furthermore, after close inspection of the images by eye and by
comparing the aperture magnitudes of all the detectable objects
between the two epochs, we do not find an afterglow candidate.

To our knowledge, our images present the deepest near-infrared upper
limit on a GRB afterglow brightness to date. The table below shows all
GRB afterglow near-IR detections and upper limits (that we could find)
with observations performed within 3 days of the burst occurrence.  It
is clear that our early deep observations would have easily discovered
any of the detections in the table, and that they are both earlier and
deeper than the reported upper limits. This result suggests that at
least some bursts are intrinsically faint in the near-IR and that the
dust obscuration explanation for the GRB afterglow non-detections in
the optical may not be valid in all cases, unless this burst occurred
at a redshift large enough for the optical/UV extinction in the rest
frame to move into the K band regime in the observer's frame.


 GRB		magnitude	       hrs. since burst	    reference
 --------------------------------------------------------------------
 971214		J=20.3			     11		      [6]
 980329		J~19.2			     16		      [7]
 980703		H=17.6			     30		      [8]
 990123		K=18.3			     29		      [9]
 990510		J=17.1, H=16.4, K=16.6	     14		      [10]
 990705		H=16.6		 	      7		      [11]
 991216		J=16.8, K=15		     13		      [12]
		H=17.2			     35		      [13]
 000214		K>18.2			     32		      [14]
 000301C	K~17.4			     50		      [15]
 000418		K~17.5			     60		      [16]
 000516		J>20.5, K>17.5		     17		      [17]
 000615		H>20.5			     17		      [18]
 000926		K~19			     72		      [19]


Finally, we estimate a rough optical upper limit by extrapolating our
H band upper limit to the R band, assuming a typical unreddened
afterglow spectrum with a slope of -0.8, obtaining R > 23.1.
Extinction intrinsic to the burster host galaxy is not included, which
can substantially increase this R band limit.

 References:

 1. Piro, L. et al. 2000, GCN No. 879
 2. Amati, L. et al. 2000, IAU Circ. 7519
 3. http://www.jach.hawaii.edu/JACpublic/UKIRT/astronomy/calib/fs_newJHK.html
 4. Taylor, G.B. et al. 2000, GCN No. 880
 5. Stanek, K.Z. et al. 2000, GCN No. 881
 6. Tanvir, N. et al. 1997, IAU Circ. 6796
 7. Mannucci, F. et al. 1998, GCN No. 46
 8. Vreeswijk, P. et al. 1999, ApJ, 523, 171
 9. Bloom, J.S. et al. 1999, GCN No. 240
10. Rol, E. et al. 2001, in prep.
11. Masetti, N. et al. 2000, A&A, 354, 473
12. Garnavich, P. et al. 2000, ApJ, 543, 61
13. Rol, E. et al. 2001, in prep. 
14. Rhoads, J. et al. 2000, GCN No. 564
15. Klose, S. et al. 2000, GCN No. 572
16. Stecklum, B. et al. 2000, GCN No. 654
17. Antonelli, A. et al. 2000, GCN No. 708
18. Palazzi, E. et al. 2000, GCN No. 727
19. Kobayashi, N. et al. 2000, GCN No. 821

J. Greiner (AIP, Potsdam), B. Stecklum, S. Klose (both TLS, Tautenburg), 
A.J. Castro-Tirado (LAEFF-INTA, Madrid and IAA-CSIC, Granada), 
F.J. Vrba, A.A. Henden (both US Naval Observatory, Flagstaff),
M. Feldt (MPIA, Heidelberg), L. Montoya, A. Aguire (both Calar Alto),
J. Fliri (LMU, Muenchen), J.M. Castro Ceron (ROA, San Fernando), 
report:

Starting at about 9 hrs after the  occurence of GRB 001109 we have observed its
50 arcsec radius error box (GCN #879
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 , #885
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 , IAUC 7519) in the B, R, I and H 
band with the Calar Alto (CA), and Naval Observatory Flagstaff Station (NOFS) 
telescopes  as detailed below:

--------------------------------------------------------------------
   Date (UT)      Telescope    filter  exposure    seeing   limiting
   (Start)                              (sec)     (arcsec)    mag.
--------------------------------------------------------------------
  Nov. 09.7712    CAHA 1.23      R      7 * 500      1.0     20.9
  Nov. 09.7846    CAHA 1.23      B      3 * 600      1.0     19.8
  Nov. 10.0980    NOFS 1.0       I       1800        1.9     21.0
  Nov. 10.7623    CAHA 1.23      R      9 * 500      1.0     20.9
  Nov. 10.8379    CAHA 3.5       H     10 * 300      1.5     20.5
  Nov. 13.0664    NOFS 1.0       I       1800        2.6     21.0
--------------------------------------------------------------------

Photometric calibration of the images was done based on USNO magnitudes 
in the B and R band, and with selected area SA 113 for the I band.
A comparison of the two epochs of (summed) R-band and I-band images, 
respectively, reveals no fading object in the GRB error box down to the 
limiting magnitudes as given in the table. The summed B band image does not 
contain any source which is not visible on the blue DSS-2. The H band image, 
when compared to the H band images of Vreeswijk et al. (GCN #886
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 ) also 
shows no fading object in the GRB error box.

The optical source coincident with the radio source mentioned in GCN #880
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  is 
detected at R=20.70+/-0.15 (Nov. 9), I=20.07+/-0.1 and R=20.63+/-0.15 (Nov. 10)
and I=20.13+/-0.1 (Nov. 13). The constancy of this source as well as the
extended shape (GCN #886
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 ) make it possible that it could be the host galaxy of
GRB 001109. If true, (i) this burst could be similar to GRB 981226 with a 
radio, but no optical/IR counterpart, and (ii) it would be the brightest host 
galaxy of any GRB. If, in addition, the GRB occured within that galaxy without
substantial offset, the optical afterglow would not have to be particularly
faint to be hidden by the light of the galaxy. Under these assumptions,
we estimate that we can place a limit of only R > 21.5 mag at 9 hrs and
I > 22 mag at 17 hrs after the GRB.

We finally note that we don't see very many obvious galaxies in these images.  
Perhaps there is higher extinction than would normally be expected at this
high galactic latitude (bII=+24.96).

E. Rol, P. Vreeswijk (U. of Amsterdam), R. Strom (U. of Amsterdam,
ASTRON), E. Richards (Hubble fellow at UAH), R. Wijers (SUNY),
L. Kaper (U. of Amsterdam) C. Kouveliotou (MSFC/USRA) report on behalf
of a larger collaboration:

We observed the WFC error circle of GRB001109 (Gandolfi, GCNs #878
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 ,
#879
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 ) with the Westerbork Synthesis Radio Telescope at 4.8 GHz, on
Nov. 11.6, 13.7 and 19.7 UT. The flux density detection limits for
these three epochs are 0.043 mJy, 0.048 mJy and 0.059 mJy,
respectively. Within the NFI error circle (Amati et al., IAUC #7519),
we do not detect any sources down to a 4 sigma limit for the first two
epochs, and 5 sigma for the last epoch.

Assuming a low value for the spectral slope of an extra-galactic radio
source of -0.5, the reported VLA 8.4 GHz flux density of 0.24(3) mJy
(Taylor et al., GCN #880
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 ), implies a 4.8 GHz flux of about 0.32 mJy on
Nov. 9.8 UT. Then this source has decreased by at least a factor of
about two in flux density (from 0.32 mJy to below our 4 sigma limit of
0.17 mJy on Nov. 11.6) between 0.4 days and 2.2 days after the
burst. If the radio source is an extragalactic object of constant
flux, then our measurement requires its spectral index to be +0.6 or
steeper, which is well outside the usual range -1 to -0.5 for
extragalactic sources.

Therefore, it is more likely that the source has actually faded,
making this source the probable counterpart of GRB001109. The radio
behavior is then reminiscent of the short radio flare counterparts,
like those of GRB970828 and GRB990123. Assuming a radio spectral index
during the fading phase of -0.8, the temporal decay has to be faster
than t**-0.5.  This is consistent both with a reverse-shock and
forward-shock origin of the radio emission.

Further radio measurements are required to exclude or confirm that 
the radio source is a variable extragalactic object of some kind.

We thank the WSRT staff for their assistance.

V.Petkov, on behalf of the peak Terskol Observatory GRB followup team.

We acquired on Nov 9.796 UT one R-band (300s exposure) image and 
one I-band (600s exposure) image of the GRB001109 error box
(GCN #885
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 ) using the CCD camera of the 2m peak Terskol Observatory telescope. 
Photometric calibration of the images was done based on USNO-A2.0
magnitudes in the R-band and with selected areas SA 113 and SA 92 
for the I band.
A comparison with Nov 15.653 (1200s exposure) images reveals no fading object
in the GRB error box down to R=19.6 and I=19.8.

V. Afanasiev, T. Fatkhullin, S. Dodonov, V. Sokolov, (SAO RAS),
A. Castro-Tirado (IAA-CSIC Granada; LAEFF-INTA, Madrid), V. Komarova,
A. Moiseev (SAO RAS), A. Cherepashchuk, K. Postnov (SAI-MSU Moscow)
report:

"On July 24, 2001 UT, we observed the field of GRB 001109 (Gandolfi, GCNs #878
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 ,
#879
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 ). The photometric conditions were good with a seeing of about 1.3 arcsec. 
We have obtained three 180-s R-band images with the SCORPIO instrument
(http://www.sao.ru/~moisav/scorpio/scorpio.html) at the 6-m telescope of SAO
RAS. At the position of the VLA radiosource (Taylor et al. GCN #880
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 ) which
is presumably a radio afteglow (Rol et al. GCN #889
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 ) we detected an extended
object as already reported by Vreeswijk et al. (GCN #886
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 ) and Greiner et al. 
(GCN#887
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 ), most likely double. Spectroscopic observations (12 x 600-s 
exposures) were obtained with the 300 lines/mm grating giving a spectral 
resolution (FWHM) of about 20 A and an effective wavelength coverage of 
3500 - 9500 A. The slit was placed along the extended object. The analysis 
revealed that the object is double with a spectra showing the continua
with clearly detected Balmer break. The redshift for each component is:

Object A:  z = 0.398 +/- 0.002, based on identification of the Halfa 6563A,
           O[III] 4959,5007AA emission lines (brighter component)


Object B:  z = 0.3399 +/- 0.0005, based on identification of the Halfa 6563A,
           Hbeta 4861AA, emission lines (fainter component)

If the radio transient is related to GRB 001109 indeed, then this is the
nearest host galaxy detected so far.

The R-band image can be seen at:
http://www.sao.ru/~sokolov/GRB/HOSTS/GRB001109/GRB001109.html

This message may be cited".

-Vladimir Sokolov, on behalf of the RAS Special Astrophysical Observatory
GRB followup team.

V. Sokolov, T. Fatkhullin, V. Komarova (SAO RAS) report:

"Using the images obtained on July 24, 2001 (GCN #1090
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 ), we performed the
astrometry to reveal where the VLA radiosource
(Taylor et al. GCN #880
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 ; RA = 18h30m06.51s, DEC = 55d18'35.7", equinox J2000)
has been placed.  We used 10 USNO stars not saturated on the images
and the astrometrical uncertainty is found to be about 0.5 arcsec,
including statistic and systematic errors.
The astrometry showed that radiosource is placed on the West
outskirt of the brighter component A (GCN #1090
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 ).
If the VLA radiosource is indeed located in this galaxy and related to
GRB 001109 than the redshift of the GRB event is 0.398 +/- 0.002
(see GCN #1090
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 ).

The image can be seen at
http://www.sao.ru/~sokolov/GRB/HOSTS/GRB001109/GRB001109.html

This message can be cited".

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

"We have continued to monitor the radio source detected by Taylor et
al. (VLA J1830+5518; GCN #880
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 ) inside the BeppoSAX error box of
GRB001109 (GCN #878
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 ) at 1.43, 4.86, and 8.46 GHz with the VLA. This
source had previously been claimed to be the afterglow of GRB001109 by
Rol et al. (GCN #889
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 ). Although the mean flux density of the source at
8.46 GHz varies by 10-20%, there has been no secular decrease in the
flux density over a period of 390 days. A similar behavior is observed
at 1.43 and 4.86 GHz.  Moreover, the flux density at 1.43 GHz is
consistently brighter than at 8.46 GHz, with a spectral slope typical
of extragalactic radio sources.  We conclude that this source is not
the afterglow of GRB001109, and therefore the optical galaxy at
z=0.398 associated with it (Vreeswijk et al. GCN #886
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 ; Greiner et al.
GCN #887
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 ; Afanasiev et al. GCN #1090
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 ; Sokolov et al. GCN #1092
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 ) is not
a GRB host galaxy."

This message may be cited.