Thumbnail - Colorized image of the field around the GRB position. Click for full version. Labels are color-coded: blue indicates an X-ray position, violet a UVOT position, orange an optical position, red an IR position, and yellow a radio/millimeter position. Green indicates a labeled object, where "H" indicates a probable host.
N - Sequential index of the GRB in our observations.
GRB - Name of the GRB, following the usual YYMMDDN convenrtion.
filt - The standard filter system to which the photometry was calibrated to (UBV are Johnson, RI are Cousins). (As distinguished from "filter" later in the table.)
lim.mag - Point-source limiting magnitude of the image and uncertainty. The uncertainty is purely photometric (and is based on the sky RMS) and does not include calibration uncertainties or other systematics. This does not currently include any color terms.
host mag - Magnitude of the host galaxy or probable host galaxy, if present. The host is always labeled H (or occasionally H? if relatively ambiguous) in the thumbnail. No magnitude is given if there is not a clearly favored host candidate.
calsys - Photometric calibration method. In approximate order of accuracy: "sdss" = Sloan Digital Sky Survey, "nickel" = Lick 1m calibration program from our survey, "p60" = Palomar 60-inch calibration, either from this survey or from previous work of Cenko et al. (2009), "landolt" = Measured zeropoint from observations of Landolt standards that night, "usno" = USNO B1.0 survey, "zeropt" = Archival zeropoint from observations of Landolt standards on other nights.
camera - Instrument used, including (when relevant) which arm of LRIS (B=blue, R=red) and the version of the LRIS-red CCD (1,2, or 3).
filter - The actual filter employed (as distinct from the standard filter calibrated to). We have not yet carried out a careful quantitative study of filter terms for the Keck filters employed in this study, but a preliminary investigation shows that even without color terms, systematic errors are less than 10 percent in nearly all cases (and more typically only a few percent.)
dichroic - Dichroic employed (relevant only to LRIS).
date obs - Date of observation.
UT obs - Time of observation.
total exp - Total integration time for frames used in the analysis.
avg. exp - Median time of an individual exposure.
airmass - Average airmass.seeing - Average seeing during the observation as measured by the photometric pipeline. Seeing measurements exist for all fields, but some have not been propagated to this automatically-generated page. Future versions will correct this.
trans dev - Median deviation of the relative transmission of each image. If greater than 0.02 this generally indicates nonphotometric conditions during the observation.
1. Photometric analysis calibration are
2. Host galaxies are extended objects and the inferred magnitude may depend on the chosen aperture and seeing. These systematics have *not* been included in the uncertainty measurements.
3. Host identification is not always definite, especially when only XRT positions are avalable. Given magnitudes are for the object designated "H" in the thumbnail. If no magnitudes are given, this can mean (1) there is no host consistent with the best error circle(s).