GRB 971227

GRB 971227 optical observations:                                    #017

Paul Groot, Titus Galama (Univeristy of Amsterdam), Jan van Paradijs 
(UoA and University of Alabama in Hunstville), Chryssa Kouveliotou 
(USRA at NASA/MSFC), Nic Walton, (ING La Palma), Penny Sackett 
(Groningen), Arlin Crotts (Columbia University, NY), Simone Bianchi 
and Jonathan Davies (Cardiff, UK) report:
"Visual comparison of optical R-band observations made on December 
28.237 UT (1800s) and December 29.108 UT (900s) with the 2.5m Isaac 
Newton Telescope at La Palma of the inner 12'x12' region of the 
SAX WFC errorbox of GRB971227 shows no obvious varying object. 
Preliminary photometry shows that this corresponds to an upper limit 
on variability of 0.3 mags down to a limiting magnitude of R=22.8"

This message is citeable.

GRB 971227:                                                           #018

A. J. Castro-Tirado* and J. Gorosabel, Laboratorio de Astrofisica Espacially
   Fisica Fundamental (LAEFF-INTA), Madrid
J. Greiner, Astrophysikalisches Institut (AIP), Potsdam
M. R. Zapatero-Osorio, Instituto de Astrofisica de Canarias (IAC), Tenerife
   and
E. Costa, Istituto di Astrofisica Spaziale, Frascati (on behalf of the 
   BeppoSAX team)

Report: following the detection of GRB 971227 by BeppoSAX, R-band
images were obtained by Y. Aguilar and R. Kohley (Sternwarte der 
Universitat, Bonn) with the 2.2-m CAHA telescope (+CAFOS) at the German-
Spanish Calar Alto Observatory, on Dec 27.91, Dec 28.16 and Dec 29.12 .
A careful visual inspection of the three frames reveals no variable object 
(by more than 0.5 mag) above a R = 21.5 limiting magnitude within the entire 
BeppoSAX WFC error box (8' radius). Further observations are in progress.

* ajct@laeff.esa.es - though not easily reachable by e-mail from Dec 30 to
  Jan 10.

H. S. Park*                                                             #019
on behalf of the LOTIS collaboration:
 
R. Bionta, E. Ables, L. Ott, E. Parker (LLNL)
G. Williams, D. Hartmann (Clemson University)
S. Barthelmy, P. Butterworth, N. Gehrels, T. Cline (NASA/GSFC)
C. Kouveliotou, J. Fishman, C. Meegan (NASA/MSFC)
D. Band (U.C. San Diego)
K. Hurley (U. C. Berkeley)
D. Ferguson (CalState, Hayward)
 
"LOTIS (the  Livermore Optical Transient Imaging System), an automated,
wide-field-of-view telescope system dedicated to the search for
simultaneous GRB optical counterparts, was on-line on the night of Dec. 27
when BATSE detected GRB971227.  LOTIS received GCN coordinates
derived from BATSE telemetry approximately 4 seconds after the start of
the burst and obtained its first 10 second exposure, centered on the GCN
coordinates 6 seconds later (10 sec after the burst began: 27.3495 UT)
LOTIS continued taking 10 second exposures at the rate of 1 image
every 20 seconds for the next 20 minutes, then at the rate of once per
minute for the rest of the night.  Because of LOTIS's large,
17.4 x 17.4 degree field of view, the recorded images fully contain
the error box of the location of the associated x-ray transient
detected by BeppoSAX's NFI despite the 6.7 degree difference
between the location of the BeppoSAX NFI position and the
GCN BATSE-Original coordinates.  A computer-aided visual examination
of the area within the BeppoSAX NFI/WFC position error circle (8' radius)
revealed 10 objects brighter than a visual magnitude of mV ~ 12.3 +/- 0.3;
all of which were identified with known objects in the Guide Star Catalog and
the Digital Sky Survey, and none showing variations in brightness.
Further analysis is in progress."
 
*hpark@llnl.gov

GRB 971227                                                             #020

A. J. Castro-Tirado and J. Gorosabel, Laboratorio de Astrofisica Espacial y
   Fisica Fundamental, Madrid
J. Greiner, Astrophysikalisches Institut, Potsdam
M. R. Zapatero-Osorio, Instituto de Astrofisica de Canarias, Tenerife
   and
E. Costa, Istituto di Astrofisica Spaziale, Frascati (on behalf of the 
   BeppoSAX team)

Report: following the detection of GRB 971227 by BeppoSAX and BATSE (IAUC 
6796, 6798), R-band images were obtained by Y. Aguilar and R. Kohley 
(Sternwarte der Universitat, Bonn) with the 2.2-m CAHA telescope (+CAFOS) at 
the German-Spanish Calar Alto Observatory. Only the image taken on Dec 27.91 
includes the entire error box of 1SAX J1257.3+5924, presumably the GRB 971227
X-ray afterglow (IAUC 6797).  An object with R = 19.5 (preliminary magnitude) 
at the edge of the 16' field of view and inside the 1SAX J1257.3+5924 error 
box, is seen on the Dec 27.91 image, but it is not present on the images 
taken on Dec 30.16 at Loiano (see below), above a limiting magnitude R = 20.5.
Its position is AR(2000) = 12 57 10.6, Dec(2000) = +59 24 43 (+/- 3"). 
An identification-chart can be obtained via anonymous ftp at laeff.esa.es 
under /pub/users/ajct/grb971227.  Deeper observations are encouraged in order 
to confirm whether this is the optical counterpart of GRB 971227.

C. Bartolini, A. Guarnieri, M. Lolli, A. Piccioni and F. Zavatti, Universita 
di Bologna, 

Communicate: the object proposed by Castro-Tirado et al (this Circ.) is
undetectable on our R frames on Dec 30.16 which were taken at the 1.5m 
telescope of the Bologna Astronomical Observatory in Loiano.  The object
was therefore fainter than R=20.5 (mag limit of the images, preliminary 
value).  Data reduction is in progress.  Deeper imaging is highly recommended.

Optical Observations for GRB971227                                     #021

T.J. Galama, P.J. Groot (University of Amsterdam), T. von Hippel 
(University of Wisconsin) and A. Diercks (University of Washington, Seattle),
J. van Paradijs (UoA and University of Alabama in Huntsville), C. Kouveliotou 
(USRA at NASA/MSFC) report:
"R-band observations of the proposed OT to GRB971227 (Castro-Tirado 
et al., IAUC 6800) taken with the Kitt Peak 0.9m telescope at December 
29.53 UT and the 3.5m Apache Point Telescope at December 30.44 UT show this 
object at a constant level of R=20.4 +/- 0.1 mag, at a position 
RA=12h57m08.65s, Dec=+59d24'40" (J2000).  It is 1.4 magnitudes fainter than a 
relatively bright (R=19.0) star located at RA=12h57m04.8s, Dec=+59d24'42.0" 
(J2000).  Both object appear in the Digital Sky Survey with a relative 
magnitude difference comparable to this value.  In the Apache Point 
image the source appears to be slightly extended, which indicates it may be 
a galaxy.   
No object in the SAX NFI errorbox (Piro et al., IAUC 6797) appears to
vary at a level of more than 0.3 mag, down to a limiting magnitude of R=21.5".

Please direct communications to paulgr@astro.uva.nl

Howard E. Bond (Space Telescope Science Institute)                      #022
David Balam (University of Victoria)
Kailash C. Sahu (Space Telescope Science Institute)
report:

There seems to have been some confusion about possible optical counterparts of 
GRB 971227 in recent GCN e-mails.

We believe that this is because THREE different optical objects have been
mentioned in recent communications, as follows: 

Object            RA    (J2000)    Dec       Remarks

   1              12h57m10.6s   +59o24'43"   proposed as GRB counterpart by 
                                             Castro-Tirado et al., IAUC 6800

   2              12h57m08.6s   +59d24'40"   described as non-variable at 
                                             R=20.4 by Galama et al. (GCN 
                                             notice Dec 31) based on KPNO and 
                                             APO data

   3              12h57m04.8s   +59d24'42"   reference star with R=19.0 used 
                                             by Galama et al.


We note that objects 1 and 2 ARE NOT IDENTICAL.  Object 2 is in fact faintly
visible on direct examination of POSS-II films, in accordance with the above
report of non-variability.  Object 1 is NOT visible on POSS-I prints nor the 
POSS-II films.

A 630-sec CCD R-band exposure on the field was obtained on 1997 Dec 31.44
by D. Balam under poor observing conditions with the 1.8-m Plaskett reflector
of the Dominion Astrophysical Observatory; the limiting magnitude (S/N=3) is
R=20.5 (assuming Object 3 to have R=19.0). Object 2 is faintly visible, in
accordance with the above. 

Object 1, visible at R=19.5 in a Calar Alto image of Dec 27.91 posted on the
WWW by Castro-Tirado et al. (see IAUC 6800), and reported as NOT seen above
R=20.5 on Dec 30.16 by Bartolini et al. (GCN notice, Dec 30), is likewise NOT
visible above R=20.5 in Balam's image of Dec 31.44. 

This observation would appear to strengthen the reported variability of Object
1 and its identification with the GRB afterglow. 

Deeper images should urgently be obtained and monitoring should continue.

Dave Balam additionally reports:

  A precise optical position of Object 3 in our previous report has been 
  determined as follows:

              12h 57m 04s.93 +59o 24' 39".1 (J2000)

  The astrometric solution was obtained using 17 USNO catalog stars, 
  m.e. 0".41 (RA) and 0".32 (Dec)



[The "previous report" referred to above is attached below for reference. SDB]
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Howard E. Bond (Space Telescope Science Institute)
David Balam (University of Victoria)
Kailash C. Sahu (Space Telescope Science Institute)
report:

There seems to have been some confusion about possible optical counterparts of 
GRB 971227 in recent GCN e-mails.

We believe that this is because THREE different optical objects have been
mentioned in recent communications, as follows: 

Object            RA    (J2000)    Dec       Remarks

   1              12h57m10.6s   +59o24'43"   proposed as GRB counterpart by 
                                             Castro-Tirado et al., IAUC 6800

   2              12h57m08.6s   +59d24'40"   described as non-variable at 
                                             R=20.4 by Galama et al. (GCN 
                                             notice Dec 31) based on KPNO and 
                                             APO data

   3              12h57m04.8s   +59d24'42"   reference star with R=19.0 used 
                                             by Galama et al.


We note that objects 1 and 2 ARE NOT IDENTICAL.  Object 2 is in fact faintly
visible on direct examination of POSS-II films, in accordance with the above
report of non-variability.  Object 1 is NOT visible on POSS-I prints nor the 
POSS-II films.

A 630-sec CCD R-band exposure on the field was obtained on 1997 Dec 31.44
by D. Balam under poor observing conditions with the 1.8-m Plaskett reflector
of the Dominion Astrophysical Observatory; the limiting magnitude (S/N=3) is
R=20.5 (assuming Object 3 to have R=19.0). Object 2 is faintly visible, in
accordance with the above. 

Object 1, visible at R=19.5 in a Calar Alto image of Dec 27.91 posted on the
WWW by Castro-Tirado et al. (see IAUC 6800), and reported as NOT seen above
R=20.5 on Dec 30.16 by Bartolini et al. (GCN notice, Dec 30), is likewise NOT
visible above R=20.5 in Balam's image of Dec 31.44. 

This observation would appear to strengthen the reported variability of Object
1 and its identification with the GRB afterglow. 

Deeper images should urgently be obtained and monitoring should continue.

Optical Observations on GRB971227:                                       #024

A. N. Ramaprakash, S. R. Kulkarni, S. G. Djorgovski, R. R. Gal
(Caltech), and S. Perlmutter and B. Grossan (UCB/LBL), report on behalf
of the Caltech GRB collaboration:

"We have analyzed R-band images of the field of 1SAX J1257.3+5924,
proposed as the x-ray counterpart of GRB 971227, obtained at the
Keck-II telescope, on UT 1997 Dec 30.8  and UT 1998 Jan 01.8.  Our
analysis shows no objects brighter than R = 23 mag which have varied
significantly by more than 0.2 mag over this 2-day interval
(conservative limits).  For comparison, a source declining with a
standard 1/t power-law would have faded by about 0.5 mag in the same
time interval.  This upper limit is at least a factor of 10 fainter
than the optical transient associated with GRB 970508 at the same
relative epoch.

In addition, we have obtained r-band images at Palomar 60-inch
telescope on UT 1997 Dec 28.4, covering about 80 percent of the
1.5-arcmin radius error circle quoted for the x-ray source.  They show
no objects brighter than about R = 21 mag which were not also detected
in the subsequent Keck images.

More refined analysis is in progress."

This message may be cited.

Please send any comments to Shri Kulkarni (srk@astro.caltech.edu).

Optical Observations of the GRB971227 field:                            #025

S. G. Djorgovski, S. R. Kulkarni, A. N. Ramaprakash, (Caltech), and 
D. Frail (NRAO) report on behalf of the Caltech GRB collaboration:

"There has been some confusion regarding various objects in the field 
of 1SAX J1257.3+5924, the proposed x-ray counterpart of GRB 971227.
Keck R-band images of the field (obtained on UT 1997 Dec 30.8, limiting
magnitude R ~ 25.5) can be obtained at the following URL:

http://astro.caltech.edu/~george/grb/grb971227.html

There we mark several objects, whose positions (good to 0.4 arcsec,
on the basis of USNO A1.0 catalog) are:

Object   type      RA(J2000)     DEC(J2000)   R mag

   A     star     12 57 13.68   +59 23 36.7   19.1
   B     star     12 57 11.15   +59 24 45.4   22.1
   C     galaxy   12 57 08.74   +59 24 35.7   20.6
   D     star     12 57 04.95   +59 24 39.2   19.4
   E     galaxy   12 57 08.22   +59 24 52.4   21.4
   F     galaxy   12 57 08.30   +59 25 00.5   21.25

The magnitudes have been zero-pointed using a set of APM objects in the 
field; the zero-point is uncertain by at least 0.2 mag.

Star B is the closest object to the detection claimed by Castro-Tirado 
et al. (GCN 30
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 Dec97 [#020], and IAUC 6800), even though it is 4.8 arcsec away 
from their estimated position.  In particular, no object was detected 
within their nominal (3 arcsec radius) error circle down to a magnitude 
of R ~ 24 or even fainter in the Keck images of Dec 30.8 UT.  Star B 
remains constant in brightness over the time span of our data (cf. our earlier
GCN note [#024]), and indeed we detect no significantly variable objects 
in the entire error circle of the x-ray source down to the limits of our 
data.  If the detection claimed by Castro-Tirado et al. was real, it 
would imply a fading with a power-law slope of t^(-2.5) or steeper.

D is the comparison star mentioned by Galama et al. (GCN 31
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 Dec97 [#021]), even 
though it is about 3 arcsec away from their quoted position, and galaxy C 
is almost certainly the object they propose as the possible identification 
of the claimed detection by Castro-Tirado et al.

A is a convenient comparison/offset star.  E and F are random galaxies 
in the same area, also given here as comparisons.

We conclude that there is thus far no evidence for an optical transient
associated with this gamma-ray burst down to significantly faint magnitude
limits, similar to the cases of GRB 970815 and 970828.

This message can be cited."




[GCN Operator's Note:  I have attempted to correct a developing problem of how
to refer to earlier GCN Messages by retroactively adding serial numbers
to the messages contained in the archive files.  I have also added the
appropriate numbers to the three messages referenced in the above message --
that would be the numbers in square brackets [#0nn].  Starting with this
GCN Message, unique serial numbers will be added for reference purposes;
however, it is still wise to refer to the first author as well as the number.]

T.J. Galama, P.J. Groot (University of Amsterdam), S. Bianchi and J. Davies 
(Cardiff), T. von Hippel (University of Wisconsin) and A. Diercks 
(University of Washington, Seattle), J. van Paradijs (UoA and University of 
Alabama in Huntsville), C. Kouveliotou (USRA at NASA/MSFC) report:

"As noted by many, the identification (GCN #21
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 ) of a galaxy with the
optical counterpart to GRB971227 proposed by Castro-Tirado et al (GCN
note #20, IAUC 6800), is incorrect.  The galaxy is unrelated to the
proposed counterpart.  We sincerely apologize for the confusion this
has caused to the community. 

Comparison of the images taken with the Kitt Peak 0.9m telescope at 
Dec. 29.53 UT, the Apache Point Observatory 3.5m Telescope at Dec 30.44 UT
and a 2700s exposure with the 2.5m Isaac Newton Telescope at La Palma  
at Jan 03.10 UT of the region around the proposed OT, shows no variable 
object at a level of more than 0.3mag down to R=21.5.

Please direct communications to paulgr@astro.uva.nl  




[GCN Operator's Note:  The archive of GCN Messages for GRB971227
can be found at: http://gcn.gsfc.nasa.gov/gcn/other/971227.gcn3]

Near-IR follow-up on GRB971227:                           #028

Message from:   S. Klose, 
                Thueringer Landessternwarte Tautenburg, 
                Germany,
                klose@tls-tautenburg.de  

The 1.5 arcmin radius error box of GRB 971227 (Piro et al.,
IAUC 6797) was imaged with the Calar Alto 2.2-m telescope 
on January 9.1 UT using one of the MAGIC near-infrared cameras.
The total integration time was 5000 seconds in the K'-band 
and 5000 seconds in the J-band, centered at RA, DEC (J2000) 
= 12:57:15.0, 59:24:02. MAGIC was used in its wide-field mode
giving a field of view of 415 times 415 arcsec.  The sky was 
clear, but the sky conditions presumably not very photometric. 
Final images and final results of the data reduction will be 
published within about 2-4 weeks.

Preliminary results of the image reduction can already be 
obtained via http://www.tls-tautenburg.de/research/grb.html.
Both, the J and the K'-band image are obtained by combining
1000 frames taken at 5 overlapping positions.

If the optical counterpart of the GRB afterglow is strongly 
affected by extinction, then the most promising candidates for 
the NIR counterpart might be very red and faint objects.  Two such 
objects are visible in the GRB error box.  Both have only a 
faint counterpart on the Keck R-band image published 
by Djorgovski et al. (GCN #025
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 ). Coordinates are (+/- 2"):

    Object A: RA, DEC (J2000) = 12:57:10.3, 59:24:14
    Object B: RA, DEC (J2000) = 12:57:22.8, 59:23:48.

A photometry has still not been performed, but one can guess
that both objects might have K' = 19.0 +/- 1.0.  The most promising
object is object A.  Currently, it seems unlikely that this is an
artifact, but remind please, these are preliminary data.
At the moment it is impossible to decide whether one object
is physically related to GRB 971227, or whether both objects
are only very red objects in the field.  To be careful, one should
assume the latter.  ROSAT/HRI data could help.


This message may be cited.
Please send any communications to klose@tls-tautenburg.de