GRB 000418
GCN Circular 1182
Subject
Sub-mm and Centimeter Detections of the Host Galaxy of GRB000418
Date
2001-12-06T22:54:20Z (24 years ago)
From
Edo Berger at Caltech <ejb@astro.caltech.edu>
E. Berger (Caltech), L. Cowie, H. Aussel, A. Barger (U of Hawaii), S. R.
Kulkarni (Caltech), and D. A. Frail (NRAO), report:
We observed the position of GRB000418 with the Sub-millimeter Common User
Bolometer Array (SCUBA) on the James Clark Maxwell Telescope (JCMT) at 850
and 450 microns on the nights of Oct 30th through Nov 1st, 2001. We find
a source with a flux density of 3.4+/-0.8 mJy at 850 microns and 38+/-10
mJy at 450 microns. The spectral index between 850 and 450 microns,
beta~3.8 (F_nu~nu^beta), is indicative of thermal emission from dust, as
observed from other SCUBA galaxies.
In addition, observations with the VLA conducted during the month of June
reveal a 4-sigma source at 8.46 GHz at the position of GRB000418, whereas
an extrapolation of the power-law decay of the afterglow indicates that
the flux density of the afterglow at this frequency should be well below
the detection limit of the VLA (Berger et al. 2001).
Based on the astrometric accuracy of the of the VLA detection (+/-0.6
arcsec) and the spectral characteristics of the SCUBA source, we conclude
that we have detected the host galaxy of GRB000418. This is the third GRB
host galaxy, the other two being GRB980703 (Berger, Kulkarni, & Frail
2001) and GRB010222 (Frail et al. 2001), which shows significant emission
at submillimeter and centimeter wavelengths, indicating the presence of
high levels of star formation. The star formation rate estimated in the
usual manner (Carilli & Yun, 1999) is ~500-1000 Msun/yr (using a Salpeter
IMF), typical of the sample of dusty, high redshift starburst galaxies
(Smail et al. 2000).
References:
Berger, E., et al., 2001, ApJ, 556, 556.
Berger, E., Kulkarni, S. R., and Frail, D. A. 2001, ApJ, 560, 652.
Carilli, C. L., and Yun, M. S. 1999, ApJ, L13.
Frail, D. A., et al. 2001, Accepted to ApJ; astro-ph/0108436.
Smail, I., et al. 2000; astro-ph/0008237
GCN Circular 1061
Subject
GRB000418: HST/STIS Second-epoch Observations
Date
2001-05-12T21:37:22Z (24 years ago)
From
Andrew S. Fruchter at STScI <fruchter@stsci.edu>
A. Fruchter and M. Metzger report for a larger HST GRB Collaboration:
The field of GRB 000418 was re-observed by the Hubble Space Telescope
starting on UT 2001 Feb 11.64 using the STIS camera in open (50CCD)
mode. The individual exposures were combined using Drizzle for a total
exposure time of 5120 s.
When this image is subtracted from that obtained by HST on 2000 June
4.17 a small residual of magnitude R~28 is found at the position of the
compact galaxy believed to be the host galaxy (GCN 669); however, the
residual is sufficiently faint to be consistent with no detection at
about the 2 sigma level. Taking into account the varying brightness of
the host galaxy we find an upper limit to the brightness of the OT on
2000 June 4.2 of R > 27.5.
This upper limit on the R-band flux implies that the decay of the
optical transient steepened to at least t ^ -1.75 to -2 at late times,
in agreement with the result obtainted primarily from radio data by
Berger et al (20001, astro-ph/0102278).
The images of the STIS field, with transient location indicated, can be
seen at http://www.stsci.edu/~fruchter/GRB/000418.
This message may be cited.
GCN Circular 733
Subject
GRB000418, HST/STIS Observations
Date
2000-06-29T07:06:01Z (25 years ago)
From
Mark R. Metzger at CIT <mrm@astro.caltech.edu>
M. Metzger, A. Fruchter, N. Masetti, E. Palazzi, E. Pian, S. Klose,
and B. Stecklum report for a larger HST GRB Collaboration:
The field of GRB 000418 was observed by the Hubble Space Telescope
using the STIS camera in open (50CCD) mode on UT 2000 June 4.17. The
position of the transient with respect to the STIS image was made by
performing relative astrometry of early infrared images of the
transient from the Calar Alto 3.5m (GCN 645) and optical images on Apr
20.9 UT from the Telescopio Nazionale Galileo 3.5m with deep late-time
images from Keck (GCN 669). The transient position on the Keck images
was then transformed to the STIS image.
Near the position of the transient, a compact galaxy with half-light
radius of 0.13 arcsec is detected with R = 23.9 +- 0.2 mag (where much
of the photometric uncertainty is due to the uncertain spectral energy
distribution of the galaxy). The best fit position of the OT is
approx 0".08 +- 0".15 arcsec east of the center of this galaxy, which
we infer is the likely host. The magnitude measured is within a few
tenths of a magnitude of the May 6 Keck measurement (GCN 669