Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hubble Space Telescope Imaging of the Optical Transient Associated with
  GRB970508   We report on Hubble Space Telescope (HST) observations of the optical
transient (OT) discovered in the error box of the gamma-ray burst GRB970508.
The object was imaged on 1997 June 2 with the Space Telescope Imaging
Spectrograph (STIS) and Near-Infrared Camera and Multi-Object Spectrometer
(NICMOS). The observations reveal a point-like source with R = 23.1 +- 0.2 and
H = 20.6 +- 0.3, in agreement with the power-law temporal decay seen in
ground-based monitoring. Unlike the case of GRB970228, no nebulosity is
detected surrounding the OT of GRB970508. We set very conservative upper limits
of R ~ 24.5 and H ~ 22.2 on the brightness of any underlying extended source.
If this subtends a substantial fraction of an arcsecond, then the R band limit
is ~25.5. In combination with Keck spectra that show Mg I absorption and [O II]
emission at a redshift of z = 0.835, our observations suggest that the OT is
located in a star-forming galaxy with total luminosity one order of magnitude
lower than the knee of the galaxy luminosity function, L*. Such galaxies are
now thought to harbor the majority of star formation at z ~ 1; therefore, these
observations may provide support for a link between GRBs and star formation.

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The categories of this paper are: econ
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The categories of this paper are: gr-qc
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The categories of this paper are: math
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The categories of this paper are: chao-dyn
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The categories of this paper are: eess
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The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: cs
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: patt-sol