GRB021004 Afterglow

NEAT Epoch 1	DPOSS

Images

GCN Circulars

GCN #1564

D.W. Fox reports on behalf of the Caltech-NRAO GRB Collaboration:  

"We have observed the error box of GRB021004 (HETE Trigger 2380;
trigger time 12:06:13.57 UT) with the 48-inch Oschin/NEAT robotic
telescope at Palomar Observatory, with three 60-second integrations
beginning at 12:15:11, 12:17:45, and 12:22:52 UT.  We identify a new,
stationary, fading, point-like object by comparison with the Digitized
Sky Survey.  The object coordinates are:

    RA 00:26:54.689, Dec +18:55:41.3   (J2000)

with an uncertainty of less than 0.5" in each coordinate.  Deriving an
R-band photometric zero-point for our unfiltered observations by
reference to the USNO star at 00:26:58.713 +18:56:56.61, which we
assume to have magnitude R=15.3, we find object magnitudes at our
three mean epochs of:

         Mean Epoch  
       UT      From GRB   Magnitude
  ========================================
    12:15:41 UT   567 s   15.34 mag
    12:18:15      721     15.49
    12:23:22     1028     15.78
  ========================================

Given the source brightness and fading behavior we identify the object
as the likely optical afterglow of GRB021004.  A finding chart from
these observations may be found at

    http://www.astro.caltech.edu/~derekfox/grb021004/finder.ps.gz

and a web page presenting the observations will be available soon at
http://www.astro.caltech.edu/~derekfox/grb021004/."

GRB021004: Absorption redshift

GCN #1569

D.W. Fox, A.J. Barth, A.M. Soderberg, and P.A. Price (Caltech), with
H. Buttery (Cambridge) and T. Mauch (U. Sydney), report on behalf of
the Caltech-NRAO GRB Collaboration:

"We have observed the optical afterglow (Fox, GCN 1564) of GRB021004
(Shirasaki et al., GCN 1565) with the Siding Springs Observatory 2.3m
telescope and double-beam spectrograph.  Reduction of a single 1200s
spectrum of the source reveals two distinct absorption-line systems,
with redshifts and line identifications as follows:

    Line       Rest Wavelength (Ang)    Redshift
  ================================================
    Mg II      2796.4, 2803.5           1.38
    Mg II      2796.4, 2803.5           1.60
    Mg I       2853.0                   1.60
  ================================================

We have also identified Mn II and Fe II absorption features associated
with the z=1.60 system.  We conclude that the redshift of GRB021004 is
greater than or equal to 1.60."