J/ApJ/491/93 JHK photometry of 9 gamma-ray burst fields (Larson+ 1997)
Extragalactic content of gamma-ray burst localizations
Larson S.B., McLean I.S.
<Astrophys. J. 491, 93 (1997)>
=1997ApJ...491...93L 1997ApJ...491...93L
ADC_Keywords: Galaxies, photometry ; Gamma rays ; Photometry, infrared
Keywords: galaxies: photometry - gamma-ray: bursts - infrared: galaxies -
surveys
Abstract:
Results of a deep, near-infrared survey of a predetermined, consistent
sample of gamma-ray burst localizations are presented. This systematic
study, conducted from 1994 to 1996, is the first to be designed
specifically to examine the extragalactic content of these regions of
sky. JHK images of nine of the smallest error boxes from the third
Interplanetary Network together with 70arcmin2 of control fields
were obtained reaching levels up to 200 times fainter than those
reached by previous infrared studies of burst locations. Photometric
measurements and star/galaxy separation measurements of more than 3000
detected objects were made. An overabundance of brighter galaxies
exists in the gamma-ray burst images at the 98% confidence level,
which indicates that the bursts are cosmological. Both the level of
this enhancement and the galaxy brightness, where it appears, match
what is expected for host galaxies. As a group, the brightest galaxy
within each error box is slightly brighter than normal but is still
consistent with a random population of galaxies. Their positions
within the boxes are also consistent with a random distribution, with
no preference toward the center. The bright galaxy excess in these
regions of sky, combined with a seemingly random population of
brightest error box galaxies, suggest that either the true host
galaxies are fainter or the error boxes do not point accurately to
the hosts.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
grbcat.dat 72 1892 Catalogue of sources in 9 γ-ray burst fields
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See also:
IX/20 : The Fourth BATSE Burst Catalog (Paciesas+ 1998)
Byte-by-byte Description of file: grbcat.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- GRB GRB field (name of the GRB)
8- 10 I3 --- No Object number in GRB field
12- 15 I4 pix Xpos X coordinate
17- 19 I3 pix Ypos Y coordinate
21- 28 F8.4 deg RAdeg Right ascension (J2000) (1)
30- 37 F8.4 deg DEdeg Declination (J2000) (1)
39- 43 F5.2 mag Jmag ? J (1.25 micron) magnitude of the object (2)
45- 48 F4.2 mag e_Jmag ? 1-sigma error in the J magnitude (3)
50- 54 F5.2 mag Hmag ? H (1.65 micron) magnitude of the object (2)
56- 59 F4.2 mag e_Hmag ? 1-sigma error in Hmag
61- 65 F5.2 mag K'mag Either the K' (2.11 micron) or Ks (2.16 micron)
magnitude of the object (2) (4)
67- 70 F4.2 mag e_K'mag ? 1-sigma error in K' or Ks
72 A1 --- S/G [SG] Identifies whether the object has been
classified as a star (S) or a galaxy (G)
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Note (1): The right ascension and declination (J2000) of the object using
the pixel coordinates and a minimal astrometry model. These
coordinates should be accurate to better than 1 arcsec.
Note (2): Empty magnitude cells mean that no photometric information
is available. Magnitudes equal to 0 mean that the object is saturated.
Note (3): 1 sigma error, derived by adding the zeropoint and statistical
errors in quadrature.
Note (4): Fields GRB 910219, 920325, 920711, 920720, and 920723 are K'
magnitudes. The others are Ks magnitudes
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Acknowledgements: Samuel B. Larson
(End) Patricia Bauer [CDS] 13-Feb-1998