////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1147
SUBJECT: BEPPOSAX GRB011121
DATE:    01/11/21 22:15:21 GMT
FROM:    SAX Science Operations at IAS/CNR Frascati  <saxsci@ias.rm.cnr.it>

On Nov. 21, 18:47:21 UT a very bright GRB (011121) has been simultaneously
detected in the BeppoSAX GRBM and WFC

Preliminary  coordinates from WFC are:

R.A.(2000)= 173.326
DEC.(2000)= -76.033

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

Luigi Piro
BeppoSAX Mission Scientist

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1148
SUBJECT: IPN triangulation of GRB011121
DATE:    01/11/21 23:47:30 GMT
FROM:    Kevin Hurley at UCBerkeley/SSL  <khurley@sunspot.ssl.berkeley.edu>

K. Hurley and T. Cline, on behalf of the Ulysses GRB team, and
C. Guidorzi, E. Montanari, F. Frontera, and M. Feroci, on behalf
of the BeppoSAX GRBM team, report:

Ulysses and the BeppoSAX GRBM observed GRB011121 (GCN 1147).  As
observed by Ulysses, this event had a 25-100 keV fluence of 2 x 10^-5
erg/cm^2, and a peak flux over 0.25 s of 2 x 10^-6 erg/cm^2 s.  We have
triangulated it to a preliminary annulus centered at RA(2000),
Decl(2000)=65.922 o, -54.971 o, whose radius is 41.220 +/- 0.067 o (3
sigma).  This annulus intersects the BeppoSAX error circle at just two points:

RA(2000)     		Decl(2000)
11 h 34 m 21.3 s     -76 o 05 ' 14 "
11 h 32 m 52.8 s     -75 o 57 ' 13 "

This limits the location to the north-eastern segment
of the circle.

This result may be refined.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1149
SUBJECT: GRB011121: BeppoSAX-WFC refined positions
DATE:    01/11/22 01:29:58 GMT
FROM:    SAX Science Operations at IAS/CNR Frascati  <saxsci@ias.rm.cnr.it>

GRB011121: refined positions

Refined coordinates from WFC are:

R.A.(2000)= 173.6059
DEC.(2000)= -76.027

The error radius  is 2'

BeppoSAX could not perform a TOO due to constraints on visibility

Luigi Piro
BeppoSAX Mission Scientist

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1150
SUBJECT: GRB011121: possible optical counterpart
DATE:    01/11/22 06:47:19 GMT
FROM:    Krzysztof Z. Stanek at CfA  <kstanek@cfa.harvard.edu>

Lukasz Wyrzykowski (Warsaw University Observatory), K. Z. Stanek
(Harvard-Smithsonian CfA) and P. M. Garnavich (Notre Dame) report:

R-band observations of the optical afterglow of the GRB011121 carried
out with the OGLE 1.3m telescope (+8kx8k OGLE-III mosaic) at the Las
Campanas Observatory, starting at UT 011122 05:08 (10.3 hours after
the burst), reveal a new, bright source in the refined BeppoSAX-WFC
error box (GCN 1149). Its position, based on the GSC, is: 11:34:30.38,
-76:01:41.3 (J2000).

Comparing to star "A" (R=17.4) from the USNO catalog (located at
11:34:18.9, -76:01:38.1, J2000), we estimate the R-band magnitude of
the possible GRB011121 afterglow to be R=18.3\pm 0.1 (subject to
possible systematic error due to the calibration of the catalog).

Additional data will be obtained.

The E(B-V) Galactic reddening from Schlegel et al. is E(B-V)=0.5, or
A_R=1.33.

This message can be cited.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1151
SUBJECT: GRB011121: fading behavior
DATE:    01/11/22 08:04:55 GMT
FROM:    Krzysztof Z. Stanek at CfA  <kstanek@cfa.harvard.edu>

K. Z. Stanek (Harvard-Smithsonian CfA), P. M. Garnavich (Notre Dame)
and Lukasz Wyrzykowski (Warsaw University Observatory) report:

Further R-band observations of the possible optical afterglow of the
GRB011121 carried out with the OGLE 1.3m telescope (+8kx8k OGLE-III
mosaic) 12.5 hours after the burst, indicate a fading behavior of the
new source at 11:34:30.38, -76:01:41.3 (J2000) reported by Wyrzykowski
et al. (GCN 1150):

HJD-2450000         UT           R_c       exp
2235.71890    011122 05:19  18.31+-0.03  200 sec
2235.80322    011122 07:20  18.64+-0.03  200 sec

Errors in the magnitudes are statistical only.  The R-band magnitudes
are relative to star "A" (11:34:18.9, -76:01:38.1, J2000), assuming
its magnitude R=17.4 (see GCN 1150).

Inspection of the Digitized Sky Survey shows a faint object 0.5" to
the northeast of the OT. The source, possibly the host galaxy has a
magnitude of approximately R=20.4 based on the assumed brightness of
star A.

We have also obtained BVI observations of the afterglow, reductions
of which are under way.

This message can be cited.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1152
SUBJECT: GRB011121: possible redshift, continued decay
DATE:    01/11/22 12:10:45 GMT
FROM:    Krzysztof Z. Stanek at CfA  <kstanek@cfa.harvard.edu>

L. Infante (Pontificia Univ. Catolica de Chile), P. M. Garnavich
(Notre Dame), K. Z. Stanek (Harvard-Smithsonian CfA) and Lukasz
Wyrzykowski (Warsaw University Observatory) report:

Spectra of the possible OT (Wyrzykowski et al.: GCN 1150) obtained
with the Magellan Walter Baade 6.5m telescope and the LDSS-2
spectrograph on Nov. 22.3 (UT) show a smooth continuum with a peak
flux near 650 nm. Narrow emission lines, likely from the host galaxy,
are seen at 507.58 nm and 681.0 nm, which may correspond to [O II]
372.7 and [O III] 500.7 nm at a redshift of 0.36. The depressed blue
end of the spectrum is most likely due to strong Galactic dust
extinction.

Also, additional R-band observation of the GRB011121 field carried out
with the OGLE 1.3m telescope 13.75 hours after the burst indicates
continuing fading behavior of the afterglow, as seen already by Stanek
et al. (GCN 1151):

HJD-2450000         UT           R_c       exp
2235.85176    011122 08:30  18.80+-0.03  600 sec

This behavior is consistent with a power-law decay with an index of
-1.65. The R-band magnitudes are relative to star "A" of Wyrzykowski
et al. (see finding chart at
http://cfa-www.harvard.edu/cfa/oir/Research/GRB/).

The faint object 0.5" to the northeast of the OT reported by Stanek et
al. is easily visible in 600 sec R-band exposure.

Relatively low redshift and fast decay of its afterglow make GRB011121
an attractive search target for a possible supernova associated with
this burst.

This message can be cited.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1153
SUBJECT: GRB 011121: Detection of Bright IR Counterpart
DATE:    01/11/22 12:38:21 GMT
FROM:    Paul Price at RSAA, ANU at CIT  <pap@srl.caltech.edu>

P.A. Price, P. McCarthy, D.W. Fox, K. Koviak and J.S. Bloom report on
behalf of the REACT GRB collaboration:

On 2001 November 22.36 UT, K. Koviak observed the field of GRB 011121
(GCN #1149) with the du Pont 2.5m telescope at Las Companas Observatory.
In a single 90 sec sky-subtracted observation in J-band, a source at the
position of Stanek's transient (GCN ##1150,1151) is strongly detected
at the 10-sigma level.  We estimate the magnitude as J ~ 16 mag.
Reductions of the nearly 2 hours of J and Ks band imaging are in progess,
but clearly the source is bright in the NIR.

Given the large Galactic extinction towards this source, we strongly
encourage NIR observations of this afterglow.  Further observations
are in progress.

This message may be cited.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1154
SUBJECT: GRB011121: continued decay
DATE:    01/11/23 07:33:52 GMT
FROM:    Krzysztof Z. Stanek at CfA  <kstanek@cfa.harvard.edu>

L. Wyrzykowski (Warsaw University Observatory) and K. Z. Stanek
(Harvard-Smithsonian CfA) report:


Additional R-band observations of the GRB011121 OT carried out with
the OGLE 1.3m telescope indicate continuing fading behavior of the
afterglow (GCNs 1151, 1152):

HJD-2450000         UT           R_c       exp
2236.71036    011123 05:06   20.35+-0.07  3x600 sec

This measurement might be somewhat contaminated by the possible host
galaxy.  Combined with the last night data, this is consistent with a
power-law decay with an index of -1.55, similar to -1.65 obtained from
first night data alone (GCN 1152).  The R-band magnitudes are relative
to star "A" of Wyrzykowski et al. (see finding chart at
http://cfa-www.harvard.edu/cfa/oir/Research/GRB/).


This message can be cited.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1155
SUBJECT: GRB 011121 J-Band Astrometry
DATE:    01/11/23 23:35:28 GMT
FROM:    Shri Kulkarni at Caltech  <srk@astro.caltech.edu>

P.A. Price, D.W. Fox, J. S. Bloom & S.R. Kulkarni, California Institute
of Technology, Pasadena report on behalf of a larger collaboration:

"We have registered the J-band images of the field of GRB 011121
(GCN 1147, GCN 1148) obtained at Las Campanas Observatory by K.
Koviak (see GCN 1153) against nearly one hundred stars whose stellar
positions are listed in the USNO-A2.0 catalog.  Individual RMS errors
for this registration, are 0.24" and 0.20" respectively in RA and Dec.

From this analysis we derive the following position for the NIR
transient reported in GCN 1149:  

(J2000) RA 11:34:29.669, Dec -76:01:41.56. 

The nominal uncertainty in each coordinate is about 0.30 arcsec; this
includes the 0.17 arcsec uncertainty between USNO-A2.0 and the ICRF
(the latter defines the radio frame).  It is clear that the transient
reported in GCN 1153 is the NIR counterpart of the optical transient
first reported by Wyrzykowski et al. (GCN 1150).  We therefore conclude
that the coordinates reported in GCN 1150 (and based on the GSC) are in
error by 2.6 arsec (east-west axis). While this difference is more than
three times the nominal error for positions derived from the GSC
(Deutsch 1999) we believe that our astrometry based on USNO-A2.0 is
secure."

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1156
SUBJECT: GRB 011121: Radio Observations
DATE:    01/11/24 00:09:06 GMT
FROM:    Shri Kulkarni at Caltech  <srk@astro.caltech.edu>

R. Subrahmanyan, Australia Telescope National Facility,
S. R. Kulkarni & E. Berger, California Institute of Technology, and 
D. A. Frail, National Radio Astronomy Observatory report 
on behalf of a larger collaboration:

"We imaged the error circle of GRB 011121 (GCN 1147, 1148) with the
Australia Telescope Compact Array (ATCA), Narrabri, Australia. The
observations were conducted in the 3-cm band.  The observations started
at UT 1600, November 22 2001 and lasted 12 hours.

The rms of the combined 8640 & 8768 MHz image is 35 microJy and the
beam is 1.37x1.21 arcsec (PA=-27 deg).  Only one source is detected in
the general vicinity of the optical transient (OT) reported by
Wyrzkyowski et al. (GCN 1150).  This source, hereafter
ATCA 113429.6-760141, is is located at 11h 34m 29.63s -76d 01m 41.5s
(J2000, uncertainty of about 0.2 arcsec).  It has a peak flux of 0.2
mJy and is embedded in some radio nebulosity; the integrated flux is
0.25 mJy. 

The discrepancy between the position of ATCA 113429.6-760141 and the
position of the optical transient (GCN 1150) motivated us to
reinvestigate the optical/IR astrometry. As reported in GCN 1155, the
coordinates of the OT as given in GCN 1150 are likely to be in error
and that the true position of the OT/NIRT is, within errors, the same
as that of ATCA 113429.6-760141.  We conclude that ATCA 113429.6-760141
is the radio afterglow of GRB 011121. 

Separately, we note that the radio frame does not suffer from zonal
errors. In contrast, GSC suffers from such errors (and USNO less so).
Thus the position of ATCA 113429.6-760141 is quite secure and
with additional observations the source will be located to an accuracy
better than the usual radio-optical frame tie.

The 2-arcsec nebulosity is likely the radio host galaxy of GRB 011121.
If so, assuming that the nebulosity is 0.05 mJy (a lower limit; we
could be missing some extended flux) and a typical spectral index of
-0.5 (between 1.4 and 8.5 GHz) we obtain Star Formation Rate (SFR, M>5
solar masses; Salpeter IMF) of 13 solar masses per year or SFR(M > 0.1
Msun) of 70 solar masses per year. 

We encourage deep optical/IR imaging to fully reveal the extent
of the presumed host galaxy."

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1157
SUBJECT: GRB011121
DATE:    01/11/24 04:49:38 GMT
FROM:    Knut Olsen at CTIO  <kolsen@ctio.noao.edu>

K. Olsen, M. Brown, R. Schommer (NOAO), and C. Stubbs (U. Washington)
report:

On November 22 UT, we observed the OT associated with GRB011121
(Wyrzykowski, Stanek, and Garnavich: GCN 1150) with the CTIO 0.9-m
telescope and UBVRI filters.  The bright OT is clearly detected in
each band.  We performed aperture photometry on the transient through
2" apertures.  We calibrated the photometry with observations, taken
at nearby time and airmass, of stars E5-c and E5-59Y from Graham 1982,
PASP, 94, 244.  These stars have similar colors to the OT (E5-59Y: U-B
= -0.02; E5-c: B-V = 0.89, V-R = 0.49, V-I = 0.96).  We find:

  U = 20.7  +/- 0.2     at 08:19 UT
  B = 20.86 +/- 0.05    at 06:59 UT
  V = 20.00 +/- 0.05    at 07:10 UT
  R = 19.25 +/- 0.05    at 06:35 UT
  I = 18.66 +/- 0.05    at 06:48 UT

where the errors reflect both random error and the estimated
uncertainty in the absolute calibration.  These magnitudes have been
lowered by 0.051, 0.019, 0.03, 0.015, and 0.013 magnitudes in UBVRI,
respectively, to account for the small difference in airmass at which
the OT and the standards were observed.  We assume "typical" CTIO
extinction coefficients of 0.45 (U), 0.28 (B), 0.15 (V), 0.08 (R), and
0.11 (I) magnitudes per airmass.  We have not attempted to adjust the
magnitudes for difference in color between the OT and the standards;
we estimate that such effects will be smaller then 0.01 magnitudes in
BVRI, but perhaps as large as 0.05 magnitudes in U.

Comparing the magnitude of the OT in R to that of star "A" (R=17.4;
Wyrzykowski et al., GCN 1150) we find the R magnitude of the OT to be
18.46 +/- 0.02 (internal error only).  There is thus a zero point
difference of 0.79 magnitudes between our photometry and that of
Wyrzykowski et al.

Assuming E(B-V) = 0.5 (Schlegel et al. 1998) and adopting the
extinction curve of Cardelli, Clayton, & Mathis (1989), we find
extinctions of A_U = 2.43, A_B = 2.07, A_V = 1.55, A_R = 1.16, and A_I
= 0.74.  The intrinsic colors of the OT are thus (U-B)=-0.52,
(B-V)=0.34, (V-R)=0.36, and (V-I)=0.53.

Astrometry of the object, tied to the USNO-A2 catalog, shows the OT to
be at 11 34 29.61 -76 01 41.5 (2000.0).  This position agrees with
that of Price et al. (GCN 1155), and is 2."4 further west than that of
Wyrzykowski et al.

This message may be cited.


////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1158
SUBJECT: GRB011121: UBRI Observations
DATE:    01/11/24 18:12:47 GMT
FROM:    Michael Brown at NOAO  <mbrown@noao.edu>

M. Brown, R. Schommer, K. Olsen, B. Jannuzi, A. Dey (NOAO), A. Fruchter,
J. Rhoads (STSci) and the NOAO Deep Wide Field Survey Team. 

The GRB011121 optical transient (Wyrzykowski et al. GCN 1150) was imaged
with the CTIO Blanco 4m with Chip2 of Mosaic-II in UBRI between 7:32 and
8:21 23 Nov 2001 UT. 

Two objects within 2" of each other were detected near the position
reported in GCN 1150.  The brighter object (located at 11:34:29.66
-76:01:41.49 J2000) is the optical transient while the fainter object
(located at 11:34:30.15 -76:01:42.26 J2000) could be the host or a
companion galaxy.

Aperture photometry of the optical transient, candidate host/companion and
Star A from GCN 1150 is provided below. The photometry is in the
Johnson-Kron-Cousins system and has been calibrated with Landolt (1992)
standards from regions SA113 and SA95.  The photometry has been corrected
for atmospheric extinction (to airmass 0) but has not been corrected for
galactic extinction where the Schlegel et al. (1998) dust maps predict
dust reddening of E(B-V)=0.496 magnitudes. 

The 1" aperture photometry misses approximately 0.6 magnitudes of the total
flux while 3" aperture photometry of the candidate host/companion galaxy
suffers from contamination from the optical transient.  Star A is ~0.8
magnitudes fainter in R-band than originally reported in the USNO
catalogue (and GCN 1150) and estimates of the fading of the optical
transient should be corrected accordingly.

Object	Band  Seeing   UT       1" radius    2" radius     3" radius
              (arcsec) (23 Nov) ap. mag.     ap. mag       ap mag.

OT      U     1.95     7:59     23.6 +/- 0.2  22.4 +/- 0.1  22.1 +/- 0.1
OT      B     1.45     7:45     23.3 +/- 0.1  22.6 +/- 0.1  22.4 +/- 0.1
OT      R     1.45     7:32     21.8 +/- 0.1  21.1 +/- 0.1  20.8 +/- 0.1
OT      I     1.50     8:16     21.2 +/- 0.1  20.3 +/- 0.1  20.0 +/- 0.1

Host?	U     1.95     7:59     24.6 +/- 0.4  23.4 +/- 0.3  22.6 +/- 0.2
Host?	B     1.45     7:45     24.4 +/- 0.1  23.1 +/- 0.1  22.5 +/- 0.1
Host?	R     1.45     7:32     22.2 +/- 0.1  21.2 +/- 0.1  20.9 +/- 0.1
Host?	I     1.50     8:16     21.3 +/- 0.1  20.3 +/- 0.1  20.0 +/- 0.1

Star A	U     1.95     7:59     21.7 +/- 0.1  20.9 +/- 0.1  20.7 +/- 0.1
Star A	B     1.45     7:45     20.5 +/- 0.1  20.0 +/- 0.1  20.0 +/- 0.1
Star A	R     1.45     7:32     18.7 +/- 0.1  18.3 +/- 0.1  18.2 +/- 0.1
Star A	I     1.50     8:16     17.6 +/- 0.1  17.6 +/- 0.1  17.5 +/- 0.1

The reduced images are available from the 1st author upon request
(mbrown@noao.edu).

This message can be cited.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1159
SUBJECT: Correction: GCN1157 (GRB 011121)
DATE:    01/11/24 21:23:49 GMT
FROM:    Knut Olsen at CTIO  <kolsen@ctio.noao.edu>

The values of the R and I-band extinctions reported in GCN 1157
incorrectly used the ratios of total to selective absorption appropriate

for Johnson, rather than Cousins, filters.  The correct extinction
values are A_R=1.328 and A_I=0.964, rather than A_R = 1.16 and A_I =
0.74.  The intrinsic colors are then (V-R) = 0.53 and (V-I) = 0.75.
Many thanks to Kris Stanek for pointing out the mistake.

Knut Olsen

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1160
SUBJECT: GRB011121: fainter still
DATE:    01/11/25 00:14:55 GMT
FROM:    Krzysztof Z. Stanek at CfA  <kstanek@cfa.harvard.edu>

K. Z. Stanek (Harvard-Smithsonian CfA) and L. Wyrzykowski (Warsaw
University Observatory) report:


Additional R-band observations of the GRB011121 OT carried out with
the OGLE 1.3m telescope indicate continuing fading behavior of the
afterglow (GCNs 1151, 1152, 1154):

HJD-2450000         UT           R_c       exp
2237.8276     011124 07:47  21.97+-0.07  6x900 sec

The R-band magnitudes are relative to star "A" of Wyrzykowski et
al. (GCN 1150), which we now take to be R=18.2 after correction by 0.8
mag determined by Olsen et al. (GCN 1157) and Brown et al. (GCN 1158).

This measurement might be fairly significantly contaminated by the
possible host galaxy. It was derived with DaoPhot/Allstar PSF-fitting
software (Stetson 1992), which near the OT finds another source
located about 0.8"S and 1.8"E (see deep finding chart and PSF-fitting
residua at http://cfa-www.harvard.edu/cfa/oir/Research/GRB/) with
magnitude R=21.91+-0.07.

We also correct our previous measurements by 0.8 mag:

HJD-2450000         UT           R_c       exp
2235.71890    011122 05:19  19.11+-0.03  200 sec
2235.80322    011122 07:20  19.44+-0.03  200 sec
2235.85176    011122 08:30  19.60+-0.03  600 sec
2236.71036    011123 05:06  21.15+-0.07  3x600 sec

Further, deep observations of the OT are strongly encouraged. We
designate fainter comparison star "C" (see the WWW finding chart),
which by comparison to "A" we measure to be R=20.09+-0.02 (statistical
error only, no color term correction included).


This message can be cited.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1161
SUBJECT: GRB 011121: HST Scheduled
DATE:    01/11/27 04:31:24 GMT
FROM:    Shri Kulkarni at Caltech  <srk@astro.caltech.edu>

S. R. Kulkarni, T. J. Galama and J. S. Bloom, California Institute of
Technology reports on behalf of a large collaboration,

"As a part of our AO-10 large program on GRBs we have triggered HST
observations of GRB 011121.  We will observe the  optical afterglow of
this GRB (GCN 1150) with WFPC2 on five different occasions (with the
first visit being December 4, 2001). The sequence of observations is
designed to either detect or place significant upper limits on possible
underlying supernova component. We encourage overlapping ground-based
observations over the next three weeks, particularly in the VRIZ
bands."

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1163
SUBJECT: GRB 011121: NIR observations, host galaxy?
DATE:    01/11/29 01:12:02 GMT
FROM:    Paul Price at RSAA, ANU at CIT  <pap@srl.caltech.edu>

S. Ryder (AAO), K. Gunn and N. Seymour (University of Southampton)
with P.A. Price, B.P. Schmidt and T.S. Axelrod (RSAA, ANU) report:

We have observed the field of the afterglow of GRB 011121 (GCN #1150)
with the newly-commissioned Infra-Red Imager and Spectrograph (IRIS2)
on the Anglo-Australian Telescope at 2001 Nov 28.7 UT.  Preliminary
reduction of 40 individual 60 sec images in Ks with 1.8 arcsec seeing
reveal a faint source at the position of the afterglow (GCN #1155),
on the outskirts of a galaxy centered approximately 1.5" E and 0.7" S
(ie 9 kpc at z=0.36).  At the resolution and depth of our observations,
we cannot distinguish between this source being distinct from the
galaxy or corresponding to an extension of the galaxy.  We estimate
our limiting magnitude as K = 19.1 mag.

This message may be cited.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1164
SUBJECT: GRB 011121: J-band observations
DATE:    01/11/29 23:13:15 GMT
FROM:    Saurabh Jha at Harvard-Smithsonian CfA  <sjha@cfa.harvard.edu>

M. M. Phillips (Carnegie), K. Krisciunas (CTIO), P. M. Garnavich,
S. Holland (Notre Dame), S. Jha, K. Z. Stanek (Harvard-Smithsonian
CfA) and P. McCarthy (Carnegie) report:

We have observed the field of GRB 011121 with the 6.5m Magellan I
Baade telescope (+ IR imager) on UT 2001 Nov 29.3 for a total of 
4320s in the Js passband with 0.5" seeing in the combined image.

A finder chart of the combined image is available at:
http://cfa-www.harvard.edu/cfa/oir/Research/GRB/.

The data have been calibrated via three IR standard stars also
observed over the course of the night, from the list of Persson et al.
(1998, AJ, 116, 2475). The Js passband is slightly narrower than the
standard J, but we make no color correction and adopt Js = J because
we lack sufficient data (both for the standard stars and the objects
in the GRB field). The effects of the slight filter mismatch are
expected to be small (see, for example, Krisciunas et al. 2001, AJ,
122, 1616). For the bright stars marked in the finder, we measure J =
17.82 +/- 0.03 (star D) and J = 18.59 +/- 0.03 (star E).

A source at the position of the GRB afterglow is marginally detected,
but because of its faintness, it is difficult to separate a possible
point source from the underlying fuzz. Differential PSF-fitting
photometry relative to the bright stars in the field yields J = 21.9
+/- 0.1 for the source at the position of the GRB afterglow. Because
of the marginal detection, this should be viewed as an upper limit.

Two other sources are detected near the GRB position. One bright
source is located 0.8"S and 2.0"E of the GRB with J = 19.98 +/- 0.04.
This object may be the core of the GRB host galaxy, but it is not
clearly resolved -- it might be a foreground star. The other source
(the "blob") located 1.6"S and 2.6" E of the GRB is clearly detected
at J = 21.57 +/- 0.07, and is possibly extended.

Adopting J ~ 16 mag for the GRB afterglow on Nov 22.36 (GCN 1153), the
reported optical decay slope (GCN 1160) would predict J ~ 21 for the
afterglow at the time of these observations.

This message may be cited.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1166
SUBJECT: GRB 011121
DATE:    01/11/30 16:55:44 GMT
FROM:    Jochen Greiner at Astrophys.Inst. Potsdam,Germany  <jgreiner@aip.de>

J. Greiner (AIP Potsdam, Germany), S. Klose, A. Zeh (both TLS Tautenburg, 
Germany), G. Lamer, R.D. Scholz, N. Lodieu (all AIP Potsdam, Germany),
E.v.d. Heuvel, P. Vreeswijk, L. Kaper (all  Univ. Amsterdam, The Netherlands),
A.J. Castro-Tirado (IAA Granada, Spain), A. Fruchter (STScI, USA),
J. Hjorth (Copenhagen, Denmark), and E. Pian (Oss. Astr. Trieste, Italy),
V. Doublier, O. Hainaut, S. Hubrig, R. Johnson, A. Kaufer, M. Kuerster, 
E. Pompej, (all ESO, Chile),
report for the large European GRB-Afterglow collaboration:


Observations of the afterglow of GRB 011121 (GCN #1147 - #1161)
have been performed at ESO (Chile) starting 8.4 hrs after the GRB,
and continuing over 4 days. In particular, K band imaging has been
obtained with SOFI at NTT (La Silla) and with ISAAC at Antu (Paranal)
at 0.4-0.9 arcsec seeing conditions. The best-seeing images (taken Nov. 24, 
starting at 06:24 UT) resolve the afterglow and the surrounding emission to
hitherto unprecedented resolution. We do not see any diffuse emission.
Instead, besides the afterglow and the other "faint source" at 2 arcsec
distance reported earlier in GCN #1160 and #1163 (which we denote as
object "2"), we find two more sources (see the Figures at 
http://www.aip.de/grb011121): one in between these two objects, 
about 0.9 arcsec East of the afterglow (and denoted as "1" in the following),
and one about 1 arcsec south-east of the "faint source" (denoted "3").
The location and relative brightness of these objects 1 and 3 make
us believe that they are the cause for the earlier reports on "diffuse
emission" (see Figure 3). Thus, it is conceivable that object "2" is not 
related to the GRB or its host. The source of the radio nebulosity (GCN #1156)
remains to be resolved.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1167
SUBJECT: GRB 011121: Errata URL
DATE:    01/11/30 19:58:34 GMT
FROM:    Jochen Greiner at Astrophys.Inst. Potsdam,Germany  <jgreiner@aip.de>

Errata GCN #1166:

Sorry, the correct URL should read: http://www.aip.de/~jcg/grb011121.html

Jochen Greiner

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1172
SUBJECT: Detection of the X-ray afterglow of GRB011121 by BeppoSAX 
DATE:    01/12/03 12:39:11 GMT
FROM:    SAX Science Operations at IAS/CNR Frascati  <saxsci@ias.rm.cnr.it>

Detection of the X-ray afterglow of GRB011121 by BeppoSAX
 
L. Piro, P. Soffitta (IAS/CNR-Rome), L.A. Antonelli (OAR-Roma), J. in 't
Zand, J. Heise (SRON, Utrecht), L. Nicastro (IFCAI/CNR, Palermo), L. Amati
(ITeSRE/CNR, Bologna), F. Frontera, C. Guidorzi, E. Montanari (Ferrara
Univ.), L. Reboa (BeppoSAX SDC, Telespazio, ROma), M. Corsi, S. Granata
(BeppoSAX SOC, Roma), G. Gennaro (BeppoSAX OCC, Roma), S. Rebecchi (ASI
SDC, Roma), L. Salotti (ASI, Roma)
 
 
We have successfully performed a follow-up observation of GRB011121 with
BeppoSAX starting on Nov.22, 16.01 UT. This is the first TOO (Target of
Opportunity) observation of a GRB after the new gyroless mode was
installed in October and being tested.
 
We have detected the fading X-ray afterglow of GRB011121 with NFI (1SAX
J113426-7601.4) at a position RA(2000)= 11h34m25.8s, Decl(2000)=-76 01'
22", with an error radius of 50". This position is 25" away from the
optical transient (GCN#1150), well within the error, verifying the good
quality of the aspect reconstruction in this new pointing mode.  A
detailed data analysis is in progress.glow of GRB011121 with NFI (1SAX
J113426-7601.4) at a position RA(2000)= 11h34m25.8s, Decl(2000)=-76 01'
22", with an error radius of 50". This position is 25" away from the
optical transient (GCN#1150), well within the error, verifying the good
quality of the aspect reconstruction in this new pointing mode.  A
detailed data analysis is in progress.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1260
SUBJECT: HST Imaging of the afterglow and host of GRB 011121
DATE:    02/03/06 03:05:01 GMT
FROM:    Josh Bloom at CIT  <jsb@astro.caltech.edu>

HST Imaging of the afterglow and host of GRB 011121

J. S. Bloom, on behalf of the Caltech-NRAO-CARA GRB Collaboration,
reports:

"The afterglow of GRB 011121 (GCN #1150) has been detected in a series
of HST observations (see GCN #1161) which began on 4 Dec 2001 and will
continue until April 2002. The afterglow appears to have faded in a
manner consistent with the extrapolation of early-time optical
observations. Preliminarily, we find no evidence of an
intermediate-time light curve bump (from an underlying supernova,
etc.).

Source 1 (Greiner et al., GCN #1166 == 'Blob' of Phillips et al.,
#1164) is a red point source and source 2 appears to be a foreground
star with colors similar to other stars in the field. Source 3 is
clearly extended in the HST images and is likely the host galaxy of
GRB 011121 (as suggested by Phillips et al., GCN #1164).

The low redshift and large angular extent of the host make it one of
the better GRB host candidates for determining detailed morphology
(see also, e.g., the analysis of GRB 980703 by Holland et al. A&A,
371, 52, 2001).  A PSF-subtraction of the nearby point sources
(including the afterglow) in the latest F814W image reveals the host
to be a fairly smooth galaxy with a half-light radius of ~0.88 arcsec
(4.8 kpc in projection at a redshift of z=0.36, GCN #1152). Using the
IRAF task GIMFIT2D to find the structural parameters of the host
galaxy, we find the light is well fit by an exponential disk-bulge
model. The bulge (Sersic index = 4; i.e., a de Vaucouleurs profile)
accounts for 13 +/- 3% (1 sigma) of the light and the exponential disk
(~10 deg inclined from face-on) accounts for the remainder.  This
provides some of the first morphological evidence for a significant
mass from an old stellar population in a GRB host (see also Chary,
Becklin & Armus ApJ, 556, 229, 2002 for a compilation of photometric
evidence to this effect)."

A series of images of the OT+host system (5 WFPC filters) may be found
at:
  http://www.astro.caltech.edu/~jsb/grb011121-hst-ep1.gif

This message may be cited.



////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1273
SUBJECT: GRB011121, possible supernova association
DATE:    02/03/15 17:16:11 GMT
FROM:    Peter Garnavich at U of Notre Dame  <pgarnavi@miranda.phys.nd.edu>

P. M.  Garnavich, S. T. Holland (Notre Dame), S. Jha, R. P. Kirshner, 
   D. Bersier, and K. Z. Stanek (CfA)

We have reanalyzed R-band images of GRB 011121 obtained with the
Walter Baade 6.5m Magellan telescope on 2001 Dec. 4.32  in light
of the recently released HST images taken near the same time
(Bloom, GCN 1260). The brightness of the afterglow in the Magellan
data deviated from the steep powerlaw decline seen in the
first three days after the burst and we attributed this to contamination
from the host galaxy (e.g. Phillips et al. GCN 1164). However the Magellan
magnitude of R=23.0+\-0.1, obtained by point-spread-function fitting is
consistent with the WFPC2 magnitude of f702w=23.16+\-0.08 which
has minimal host contamination. Both observations are nearly
2 magnitudes brighter than the early-time extrapolation. 

The full light curve is well fit by an initial powerlaw with
index of 1.71+\-0.05  plus the light curve of SN 1998bw stretched
and faded to a redshift of z=0.36 (Infante et al. GCN 1152). The
Dec. 4 data is 10 days after explosion in the rest frame, while
SN 1998bw peaked 17 days after GRB 980425, so later epochs
may show a small rise in the f702w magnitude before final
fading. The light curve can be viewed at

http://www.nd.edu/~pgarnavi/grb011121/grb011121_sn.ps

Assuming a flat cosmology with Omega_m=0.3 and a Hubble
parameter of 65 km/s/Mpc, we derive an absolute magnitude for
the possible supernova on Dec. 4 of Mv=-19.3+\-0.2 (corrected
for a large Galactic extinction but not for host extinction), consistent
with SN 1998bw near maximum.  These observations could be strong
evidence for a SN-GRB connection.

This message may be cited.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1274
SUBJECT: GRB 011121: HST Observations reveal an intermediate-time multicolor
DATE:    02/03/18 05:24:55 GMT
FROM:    Josh Bloom at CIT  <jsb@astro.caltech.edu>

GRB 011121: HST Observations reveal an intermediate-time multicolor bump

J. S. Bloom, P. A. Price, S. R. Kulkarni, D. E. Reichart (Caltech), D. A.
Frail (NRAO), E. Berger on behalf of the Caltech-NRAO-CARA GRB
Collaboration, report:

As a part of our AO-10 HST GRB program, we observed the afterglow
(Wyrzykowski et al.; GCN #1150) of GRB 011121 (Piro et al.; GCN #1147). We
obtained WFPC2 observations through multiple filters, designed to detect
or constrain underlying supernovae following low-redshift GRBs.  The
observations presented here were obtained on 2001 Dec 4-5 and 2001 Dec
14-16.

Recently, Garnavich et al. (GCN #1273) noted that the optical afterglow of
GRB 011121 on day 13 showed an excess in the F702W filter over an
extrapolation of fluxes measured at earlier epochs in the R-band filter.
They suggested this excess is indicative of a contribution from an
underlying supernova (SN) as has been discussed for some GRBs (e.g. GRB
980326, GRB 970228). Here we report further analysis of the HST data.

In the following, we give the PSF-fit photometry for the first two epochs
of our program in an 0.5 arcsec radius using the current WFPC zero-points
from Dolphin (see http://www.noao.edu/staff/dolphin/wfpc2_calib/ ).  The
magnitudes have been corrected for the (sometimes considerable)
charge-transfer inefficiency using the Dolphin methodology but not
corrected for Galactic extinction; the uncertainties do not reflect the
errors in the absolute zero-points.  These brightnesses also include an
uncertain contribution from the host galaxy at the position of the
transient. As per the discussion in Holtzmann et al. 1995, the "infinite
aperture" magnitudes will be ~0.1 mag brighter,

Epoch  delta T      Filter    ST Magnitude
       (days)
---------------------------------------------
1     13.09         F450W    24.64 +/- 0.07
1     13.16         F555W    23.88 +/- 0.05
1     13.23         F702W    23.16 +/- 0.05
1     14.02         F814W    22.79 +/- 0.03
1     14.15         F850LP   22.51 +/- 0.06
2     23.03         F555W    24.43 +/- 0.04
2     23.09         F702W    23.33 +/- 0.03
2     24.83         F814W    22.98 +/- 0.03
2     24.96         F850LP   22.59 +/- 0.09
---------------------------------------------

We confirm that the excess seen on day 13 in F702W is also present in
other filters (F450W, F555W, F814W, and F850LP). Second, the excess is
seen even at epoch 2 (day 23-25).  Thanks to our extensive multi-band
data, this is the first unambiguous detection of an intermediate-time bump
(>~ 10 days) in a GRB afterglow simultaneously in more than 3 filters.

As is common in the SN interpretation, we took the multi-band light curves
of SN 1998bw and transformed the same to the redshift of GRB 011121 (z =
0.36, GCN #1152).  In the SN 1998bw interpretation, one would expect the
brightness to have increased by 0.03 mag in the F555W filter, 0.23 mag in
the F702W filter, 0.30 mag in the F814W filter, and 0.19 mag in the F850LP
filter between these two epochs.  Instead, we find the brightness to
decrease by 0.55 +/- 0.06 mag in the 555W filter, 0.17 +/- 0.06 mag in the
702W filter, 0.19 +/- 0.04 mag in the 814W filter, and 0.08 +/- 0.11 mag
in the 850LP filter.  Thus this curious bump is inconsistent with an
underlying SN similar to SN 1998bw.

We caution that all these excesses are measured with respect to
extrapolations of early time ground based data and such extrapolations
have not included possible jet breaks."

This message can be cited.






////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1276
SUBJECT: GRB 011121: Third HST Epoch
DATE:    02/03/19 07:14:41 GMT
FROM:    Shri Kulkarni at Caltech  <srk@astro.caltech.edu>

S. R. Kulkarni, J. S. Bloom, P. A. Price, D. E. Reichart, Caltech
and B. Schmidt, Mount Stromlo Observatory  report
on behalf of a larger collaboration:

Here we report on the third HST epoch (19 Dec 2001 UT) of WFPC2 images of
GRB 011121 (see GCN 1274). The third epoch was requested for observations
1 week after the second epoch but HST scheduling restrictions resulted
in the data being taken earlier.

We have performed PSF-fitting photometry on the transient and using
the prescription of Dolphin and Holtzman (D-H) we measure the following
magnitudes:

Epoch  delta T      Filter   D-H Magnitude
       (days)
---------------------------------------------
3       27.24       F555W    25.08 +/- 0.07
3       27.30       F702W    23.65 +/- 0.04
3       28.10       F814W    23.16 +/- 0.06
3       28.16       F850LP   22.72 +/- 0.06
---------------------------------------------
Note:  (1) These magnitudes are measured magnitues and have not been
corrected for extinction. (2) The magnitude system here is the same
as that in GCN 1274.

We have converted these magnitudes to fluxes and the light curve can be
found at http://www.astro.caltech.edu/~der/1121lc_0.75mag.eps.  We
assumed that the excess over the power law decay of the afterglow is
due to an underlying SN. To this end, we assumed assumed  an SN 1998bw
template (corrected for extinction of A_V=0.19), redshifted to that of
the host galaxy of GRB 011121 (z=0.36, GCN 1152) and subject to the
estimated Galactic extinction of A_V=1.64 towards GRB 011121 (see GCN
1158). A simple fit ("chi-by-eye") requires the 1998bw contribution to
be dimmed by 0.75 mag. Even so, the fit is only approximate  with clear
deviations in some bands (e.g. F555W).

A full-fledged proper fitting of the data must address two points.
First (a minor concern) is the heavy extinction towards this direction.

Second (a major issue) is that there is great evidence that cosmologically
located GRBs are not spherical but jetted sources with opening angles of
only a few degrees (e.g. Frail et al. 2001, ApJ 562, 55).  In contrast,
the asymmetry in SN 1998bw is sufficiently mild that this issue has been
debated for some time in the literature.

The fact that we see GRB 011121 means that we are seeing the explosion
along the symmetry axis (or close to it).  [The opening angle for GRB
011121, as with other GRBs, can be estimated from broad-band data.
Indeed, if the true gamma-ray energy release from GRB 011121 is similar
to those estimated from other cosmologically located GRBs then
we estimate an opening angle of over 8 degrees].
 
Continuing, if cosmologically GRBs have an underlying SN then these SN
are likely to be severely asymmetric. These strong asymmetries, more than
any any other quantity (e.g., the amount of synthesized Nickel), will
strongly affect the light curve (see Hoflich et al. 1999, ApJ 524, L107).
Rapid rise in the SN light is easily explained by rapid expansion along
the polar axis and the decline can be expected to be rapid as well. Thus
we should be prepared to see a large diversity in the light curves of the
underlying SN in cosmologically located GRBs. Within these expectations,
it appears that the case for an underlying SN in GRB 011121 is 
well established.

////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1288
SUBJECT: GRB 011121: Fourth Epoch of HST Imaging
DATE:    02/03/22 00:37:58 GMT
FROM:    Josh Bloom at CIT  <jsb@astro.caltech.edu>

GRB 011121: Fourth Epoch of HST Imaging

J. S. Bloom, S. R. Kulkarni, D. E. Reichart, P. A. Price, on behalf of
the Caltech-NRAO-CARA GRB Collaboration and co-investigators on the
large HST Cycle 10 GRB program (#9180), report:

Following the discussion from Kulkarni et al. (GCN #1276) the fourth epoch
of HST imaging (4 Feb 2002 UT) of the afterglow of GRB 011121 has revealed
continued fading of the intermediate-time red bump (Garnavich et al. GCN
#1273; Bloom et al. GCN #1274; GCN #1276).  Following are the magnitudes
and fluxes of the transient bump plus host contribution:

Filter  delta T    lambda_eff   f_nu(lambda_eff)   Vega mags
         (days)      (Ang)           (microJy)       (mag)
---------------------------------------------------------------------
F555W    77.33      5604.61     0.123 +/- 0.014  V = 26.173 +/- 0.118
F702W    76.58      7042.09     0.224 +/- 0.019  R = 25.264 +/- 0.092
F814W    77.25      8149.18     0.294 +/- 0.020  I = 24.762 +/- 0.073
---------------------------------------------------------------------

These fluxes and magnitudes have not been corrected for Galactic or host
extinction.  The host galaxy contributes significantly to the flux at
these late times.  We estimate this contribution from the host to be
f_nu(F555W) = (0.087 +/- 0.027) microJy, f_(F702W) = (0.127 +/- 0.026)
microJy and f_nu(F814W) = (0.209 +/- 0.059) microJy.  More information
about the reductions may be found in:
http://www.astro.caltech.edu/~jsb/Papers/grb011121-paper1.ps

This message may be cited.






////////////////////////////////////////////////////////////////////////
TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1463
SUBJECT: HST Imaging of the Host of GRB 011121
DATE:    02/08/02 19:02:08 GMT
FROM:    Josh Bloom at CIT  <jsb@astro.caltech.edu>

HST Imaging of the Host of GRB 011121

J. S. Bloom (Caltech, Harvard/CfA) and P. A. Price (RSSA, ANU) report:

"Deep late-time images of the field of GRB 011121 were acquired with the
Hubble Space Telescope in from 21 April to 2 May 2002 UT as part of the
large GRB program #9180 (Kulkarni, PI).  Five filters were used---F450W,
F555W, F702W, F814W, F850LP---with a total integration time of 4500 sec
per filter.

The transient afterglow plus intermediate-time bump, suggested elsewhere
as an accompanying supernova (SN) to the GRB (Bloom et al. 2002, Garnavich
et al. 2002), faded beyond detection in each filter. There is no apparent
persistent emission at the burst location aside from diffuse light from
the host galaxy. In Bloom et al. (table 1) we noted the estimated the
contribution of this diffuse light to the total measured flux of the
OT/SN; using the host images as a template for subtraction from earlier
epochs, we confirm those estimations were correct to within the stated
errors; here we provide a direct measurement of the diffuse host flux
contributing to the 0.5" radius aperture PSF photometry: f_nu(host)[F450W,
F555W, F702W, F814W, F850LP] = (0.038 +- 0.048), (0.067 +- 0.034), (0.154
+- 0.035), (0.195 +- 0.067), (0.305 +- 0.184) microJy. These fluxes have
not been corrected for Galactic extinction.

Two rather blue compact knots of emission are detected West of the galaxy
core, near to the OT/SN. Knot #1 is positioned at 0.52"E, 0.01"N and knot
#2 is 0.08"E, 0.28"N relative to the OT/SN location. [For reference, the
OT/SN was 1.99" W, 0.85" N of the star labeled as "B" in figure 1 of Bloom
et al.]. At the redshift of the host (z=0.362; Garnavich et al.)  even the
closest of these knot lies 1.5 kpc in projection from the burst site.

A close-in color image of the host may be found at:
       http://cfa160.harvard.edu/~jsbloom/grb011121

Though we cannot rule out these knots as background galaxies, given the
detection of Hydrogen Balmer-line and [OII] emission in the spectrum of
the larger "host" galaxy, these knots are likely strong pockets of star
formation in the host itself."

This message may be cited.

Paper References:
-----------------
1. Bloom et al., 2002, ApJ Letters, v572, 45-49
2. Garnavich et al., 2002, submitted to ApJ, (astro-ph/0204234)