Columbia University Astronomy and 

MDM Observatory GRB Team

GRB 060218: Optical follow-up

GCN Circular #4783
GRB 060218: Pre-burst detection of a possible host galaxy
N. Mirabal (U. Michigan) reports:

"Analysis of the SDSS pre-burst observations of the GRB 060218 field
(Cool et al. GCN #4777) reveals an extended object at 03h21m39.68s
+16o52'01.66" (J2000). Given the proximity of this object to the reported
XRT and UVOT positions for a candidate afterglow (Cusumano et al. GCN
#4775, Marshall et al. GCN #4779), this should be considered a potential 
host galaxy of a low-redshift GRB. Further multiwavelength observations 
are encouraged to confirm the reality of this trigger (Barbier et al. GCN 
#4780), and its possible association with this nearby galaxy. I 
acknowledge useful conversations with Richard Cool."

GCN Circular #4784
GRB 060218: MDM Observations
N. Mirabal (U. Michigan) reports on behalf of the MDM Observatory GRB 
follow-up team:

"I observed the candidate optical afterglow of Swift GRB 060218 detected
by the Swift UVOT (Cusumano et al. GCN #4775, Marshall et al. GCN #4779, 
Quimby et al. GCN #4782) with the MDM 2.4m telescope and RETROCAM imager 
under partly cloudy conditions. Calibration with SDSS pre-burst 
observations (Cool et al. GCN #4777) yields r = 17.55 +/- 0.1 on Feb. 
19.1438 UT for the OT. This is brighter than the pre-burst observations 
and confirms it as the OT of GRB 060218."

MDM 2.4m
(J2000) 03h 21m 39.7s, +16° 52′ 02″

GCN Circular #4792
GRB 060218: MDM Redshift
N. Mirabal (U. Michigan) and J. P. Halpern (Columbia U.) report on behalf
of the MDM Observatory GRB follow-up team:

"We obtained a low-resolution spectrum of the optical afterglow and
host galaxy of GRB 060218 using the MDM 2.4m telescope and Boller &
Chivens (CCDS) Spectrograph on Feb. 20 02:20 UT.  Strong, narrow emission
lines of H-beta, [O III] 4959,5007, and H-alpha at z=0.0331 are seen,
superposed on a blue continuum, which is still much brighter than the
SDSS pre-burst magnitudes.  The line ratios are typical of a high-excitation 
starburst.  This confirms the low-redshift, extragalactic nature of this
unusual GRB.

This message may be cited."


Nestor Mirabal
Jules Halpern
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Last Modified: February 25, 2006