The faint afterglow and host galaxy of the short-hard GRB 060121

Abstract

We present optical and X-ray observations of the afterglow and host galaxy of the short-hard GRB 060121. The faint R-band afterglow is seen to decline as t^(-0.66) while the X-ray falls as t^-1.18, indicating the presence of the cooling break between the two frequencies. However, the R-band afterglow is very faint compared to the predicted extrapolation of the X-ray afterglow to the optical regime (specifically, beta_OX ~ 0.2), while the K-band is consistent with this extrapolation (beta_KX ~ 0.6), demonstrating suppression of the optical flux. Late time {\it HST} observations place stringent limits on the afterglow R-band flux implying a break in the R-band lightcurve. They also show that the burst occurred at the edge of a faint red galaxy which most likely lies at a significantly higher redshift than the previous optically identified short-duration bursts. Several neighboring galaxies also have very red colors that are similarly suggestive of higher redshift. We consider possible explanations for the faintness and color of the burst. Our preferred model is that the burst occurred at moderately high redshift and was significantly obscured; however, it is also possible that the burst lies at z > 4.5 in which case the faintness of the R-band afterglow could be attributed to the Lyman-break. We discuss the implications that either scenario would have for the nature of the progenitors of short bursts.

4 pages, 2 Figures - submitted to ApJ Letters

References in corpus (4)

• UV star-formation rates of GRB host galaxies
• Swift Identification of Dark Gamma-Ray Bursts
• A new definition of the intermediate group of gamma-ray bursts
• Are short gamma-ray bursts collimated? GRB050709, a flare but no break

Cited by in corpus (23)

• Discerning the physical origins of cosmological Gamma-ray bursts based on multiple observational criteria: the cases of z=6.7 GRB 080913, z=8.3 GRB 090423, and some short/hard GRBs
• A Comparison of the Afterglows of Short- and Long-Duration Gamma-Ray Bursts
• Different progenitors of short hard gamma-ray bursts
• Gamma-ray burst progenitors
• Discovery of the afterglow and host galaxy of the low redshift short GRB 080905A
• The optical afterglows and host galaxies of three short/hard gamma-ray bursts
• The Early-time Optical Properties of Gamma-Ray Burst Afterglows
• A Putative Early-Type Host Galaxy for GRB 060502B: Implications for the Progenitors of Short-Duration Hard-Spectrum Bursts
• GRB 060313: A New Paradigm for Short-Hard Bursts?
• The Prompt Gamma-Ray and Afterglow Energies of Short-Duration Gamma-Ray Bursts
• Multicolor observations of the afterglow of the short/hard GRB 050724
• A case of mistaken identity? GRB 060912A and the nature of the long -- short GRB divide
• GRB 060121: Implications of a Short/Intermediate Duration Gamma-Ray Burst at High Redshift
• Probing Kilonova Ejecta Properties Using a Catalog of Short Gamma-Ray Burst Observations
• 2900 square degree search for the optical counterpart of short gamma-ray burst GRB 180523B with the Zwicky Transient Facility
• On the nature of the short duration GRB 050906
• Redshift Filtering by Swift Apparent X-ray Column Density
• Exploring compact binary merger host galaxies and environments with $\mathrm{zELDA}$
• Are short gamma-ray bursts collimated? GRB050709, a flare but no break
• Short gamma-ray bursts from SGR giant flares and neutron star mergers: two populations are better than one
• Constraints on an optical afterglow and on supernova light following the short burst GRB 050813
• GRB 070707: the first short gamma-ray burst observed by INTEGRAL
• Light Curves of Swift Gamma Ray Bursts