Evidence for a Supernova in Reanalyzed Optical and Near-Infrared Images of GRB 970228

We present B-, V-, RC-, IC-, J-, H-, K-, and K'-band observations of the optical transient (OT) associated with GRB 970228, based on a reanalysis of previously used images and unpublished data. In order to minimize calibration differences, we have collected and analyzed most of the photometry and consistently determined the magnitude of the OT relative to a set of secondary field stars. We confirm our earlier finding that the early decay of the light curves (before 1997 March 6) was faster than that at intermediate times (between 1997 March 6 and April 7). At late times the light curves resume a fast decay (after 1997 April 7). The early-time observations of GRB 970228 are consistent with relativistic blast-wave models, but the intermediate- and late-time observations are hard to understand in this framework. The observations are well explained by an initial power-law decay with α = -1.51 ± 0.06 modified at later times by a Type Ic supernova light curve. Together with the evidence for GRB 980326 and GRB 980425, this gives further support for the idea that at least some γ-ray bursts are associated with a possibly rare type of supernova.

[1]  L. A. Antonelli,et al.  Discovery of an X-ray afterglow associated with the γ-ray burst of 28 February 1997 , 1997, Nature.

[2]  Bradley E. Schaefer,et al.  The Late‐Time Light Curve of SN 1998bw Associated with GRB 980425 , 1999, astro-ph/9904397.

[3]  H. L. Johnson,et al.  Astronomical Measurements in the Infrared , 1966 .

[4]  Arlo U. Landolt,et al.  UBVRI Photometric Standard Stars in the Magnitude Range 11 , 1992 .

[5]  Stefano Casertano,et al.  THE PERFORMANCE AND CALIBRATION OF WFPC2 ON THE HUBBLE SPACE TELESCOPE , 1995 .

[6]  Eli Waxman,et al.  Gamma-Ray-Burst Afterglow: Supporting the Cosmological Fireball Model, Constraining Parameters, and Making Predictions , 1997, astro-ph/9704116.

[7]  M. Bessell,et al.  UBVRI PHOTOMETRY WITH A GA-AS PHOTOMULTIPLIER. , 1976 .

[8]  Eric W. Deutsch,et al.  CC BOOTIS: QSO, NOT VARIABLE HALO GIANT , 1997 .

[9]  S. Djorgovski,et al.  The unusual afterglow of the γ-ray burst of 26 March 1998 as evidence for a supernova connection , 1999, Nature.

[10]  M. Livio,et al.  The optical counterpart to γ-ray burst GRB970228 observed using the Hubble Space Telescope , 1997, Nature.

[11]  I. Smail,et al.  The X-Ray, Optical, and Infrared Counterpart to GRB 980703 , 1999, astro-ph/9904286.

[12]  M. Rees,et al.  Shocked by GRB 970228: the afterglow of a cosmological fireball , 1997, astro-ph/9704153.

[13]  S. Woosley.  Gamma-ray bursts from stellar mass accretion disks around black holes , 1993 .

[14]  F. J. Castander,et al.  A Photometric Investigation of the GRB970228 Afterglow and the Associated Nebulosity , 1998, astro-ph/9807195.

[15]  D. Reichart.  GRB 970228 Revisited: Evidence for a Supernova in the Light Curve and Late Spectral Energy Distribution of the Afterglow , 1999, astro-ph/9906079.

[16]  S. Woosley,et al.  Gamma-Ray Bursts and Type Ic Supernova SN 1998bw , 1998, astro-ph/9806299.

[17]  S. Djorgovski,et al.  The unusual afterglow of GRB 980326: evidence for the gamma-ray burst/supernova connection , 1999, astro-ph/9905301.

[18]  David W. Hogg,et al.  Deep Optical Galaxy Counts with the Keck Telescope , 1995, astro-ph/9506095.

[19]  M. Feroci,et al.  Discovery of the X-Ray Afterglow of the Gamma-Ray Burst of February 28 1997 , 1997 .

[20]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

[21]  D. Reichart.  Submitted to The Astrophysical Journal Letters Observations and Theoretical Implications of GRB 970228 , 1997 .

[22]  Arnon Dar,et al.  Gamma Ray Bursts from Minijets , 1994 .

[23]  F. J. Castander,et al.  The Extinction toward the GRB 970228 Field , 1999 .

[24]  J. Mathis,et al.  The relationship between infrared, optical, and ultraviolet extinction , 1989 .

[25]  Brian P. Schmidt,et al.  SN 1997cy/GRB 970514: A New Piece in the Gamma-Ray Burst Puzzle? , 1999 .

[26]  T. Piran,et al.  Spectra and Light Curves of Gamma-Ray Burst Afterglows , 1997, astro-ph/9712005.

[27]  A. S. Fruchter,et al.  The fading optical counterpart of GRB 970228, 6 months and 1 year later , 1998 .

[28]  Shri R. Kulkarni,et al.  Implications of the Radio Afterglow from the Gamma-Ray Burst of 1997 May 8 , 1998 .

[29]  E. Ofek,et al.  The effect of magnetic fields on γ-ray bursts inferred from multi-wavelength observations of the burst of 23 January 1999 , 1999, Nature.

[30]  N. Masetti,et al.  The Discovery and Broadband Follow-up of the Transient Afterglow of GRB 980703 , 1998 .

[31]  D. Frail,et al.  Radio emission from the unusual supernova 1998bw and its association with the γ-ray burst of 25 April 1998 , 1998, Nature.

[32]  Andrew S. Fruchter,et al.  Galactic Extinction from Colors and Counts of Field Galaxies in WFPC2 Frames: An Application to GRB 970228 , 1998, astro-ph/9807291.

[33]  B. Paczyński.  Are Gamma-Ray Bursts in Star-Forming Regions? , 1997, astro-ph/9710086.

[34]  M. Rees,et al.  Optical and Long-Wavelength Afterglow from Gamma-Ray Bursts , 1996, astro-ph/9606043.

[35]  C. Kouveliotou,et al.  Transient optical emission from the error box of the γ-ray burst of 28 February 1997 , 1997, Nature.

[36]  Stefano Casertano,et al.  THE PHOTOMETRIC PERFORMANCE AND CALIBRATION OF WFPC2 , 1995 .