GRB 071112C: A CASE STUDY OF DIFFERENT MECHANISMS IN X-RAY AND OPTICAL TEMPORAL EVOLUTION

We present a study on GRB 071112C X-ray and optical light curves. In these two wavelength ranges, we have found different temporal properties. The R-band light curve showed an initial rise followed by a single power-law decay, while the X-ray light curve was described by a single power-law decay plus a flare-like feature. Our analysis shows that the observed temporal evolution cannot be described by the external shock model in which the X-ray and optical emission are produced by the same emission mechanism. No significant color changes in multi-band light curves and a reasonable value of the initial Lorentz factor (Γ0 = 275 ± 20) in a uniform interstellar medium support the afterglow onset scenario as the correct interpretation for the early R band rise. The result suggests that the optical flux is dominated by afterglow. Our further investigations show that the X-ray flux could be created by an additional feature related to energy injection and X-ray afterglow. Different theoretical interpretations indicate the additional feature in X-ray can be explained by either late internal dissipation or local inverse-Compton scattering in the external shock.

[1]  N. Gehrels,et al.  Gamma-Ray Bursts , 2016, Stars and Stellar Processes.

[2]  W. T. Vestrand,et al.  Optical afterglows of Gamma-Ray Bursts: peaks, plateaus, and possibilities , 2010, 1009.3947.

[3]  T. Ohsugi,et al.  Infrared/optical – X-ray simultaneous observations of X-ray flares in GRB 071112C and GRB 080506 , 2010, 1006.0785.

[4]  R. Margutti,et al.  Gamma-ray burst long lasting X-ray flaring activity , 2010, 1004.3831.

[5]  P. Giommi,et al.  Unveiling the origin of X-ray flares in gamma-ray bursts , 2010, 1004.0901.

[6]  Bing Zhang,et al.  CONSTRAINING GAMMA-RAY BURST INITIAL LORENTZ FACTOR WITH THE AFTERGLOW ONSET FEATURE AND DISCOVERY OF A TIGHT Γ0–Eγ,iso CORRELATION , 2009, 0912.4800.

[7]  M. Nardini,et al.  Testing a new view of gamma-ray burst afterglows , 2009, 0907.4157.

[8]  Bing Zhang,et al.  A COMPREHENSIVE ANALYSIS OF SWIFT/X-RAY TELESCOPE DATA. IV. SINGLE POWER-LAW DECAYING LIGHT CURVES VERSUS CANONICAL LIGHT CURVES AND IMPLICATIONS FOR A UNIFIED ORIGIN OF X-RAYS , 2009, 0902.3504.

[9]  W. Zheng,et al.  A GRB Follow-up System at the Xinglong Observatory and Detection of the High-Redshift GRB 060927 ⋆ , 2008, 0906.2962.

[10]  W. T. Vestrand,et al.  Taxonomy of gamma‐ray burst optical light curves: identification of a salient class of early afterglows , 2008, 0803.1872.

[11]  H.-C. Lin,et al.  The Taiwanese-American Occultation Survey: The Multi-Telescope Robotic Observatory , 2008, 0802.0303.

[12]  A. J. Levan,et al.  THE AFTERGLOWS OF SWIFT-ERA GAMMA-RAY BURSTS. I. COMPARING PRE-SWIFT AND SWIFT-ERA LONG/SOFT (TYPE II) GRB OPTICAL AFTERGLOWS , 2007, 0712.2186.

[13]  T. Sakamoto,et al.  Testing the External-Shock Model of Gamma-Ray Bursts Using the Late-Time Simultaneous Optical and X-Ray Afterglows , 2007, 0707.2826.

[14]  D. N. Burrows,et al.  The First Survey of X-Ray Flares from Gamma-Ray Bursts Observed by Swift: Spectral Properties and Energetics , 2007, 0706.1564.

[15]  J. P. Osborne,et al.  An online repository of Swift/XRT light curves of Γ-ray bursts , 2007, 0704.0128.

[16]  C. Firmani,et al.  “Late Prompt” Emission in Gamma-Ray Bursts? , 2007, astro-ph/0701430.

[17]  P. Conconi,et al.  REM observations of GRB 060418 and GRB 060607A: the onset of the afterglow and the initial fireball Lorentz factor determination , 2006, astro-ph/0612607.

[18]  Bing Zhang.  Gamma-ray burst afterglows , 2006, astro-ph/0611774.

[19]  T. Soyano,et al.  Multicolor Shallow Decay and Chromatic Breaks in the GRB 050319 Optical Afterglow , 2006, astro-ph/0611323.

[20]  Bing Zhang,et al.  The Onset of Gamma-Ray Burst Afterglow , 2006, astro-ph/0608132.

[21]  N. Gehrels,et al.  The Giant X-Ray Flare of GRB 050502B: Evidence for Late-Time Internal Engine Activity , 2005, astro-ph/0512615.

[22]  N. Gehrels,et al.  Evidence for a Canonical Gamma-Ray Burst Afterglow Light Curve in the Swift XRT Data , 2005, astro-ph/0508332.

[23]  N. Gehrels,et al.  Physical Processes Shaping Gamma-Ray Burst X-Ray Afterglow Light Curves: Theoretical Implications from the Swift X-Ray Telescope Observations , 2005, astro-ph/0508321.

[24]  Y. Urata,et al.  Optical Afterglow Observations of the Unusual Short-Duration Gamma-Ray Burst GRB 040924 , 2005, astro-ph/0506232.

[25]  N. Gehrels,et al.  Bright X-ray Flares in Gamma-Ray Burst Afterglows , 2005, Science.

[26]  Bing Zhang,et al.  Gamma-Ray Bursts: Progress, Problems & Prospects , 2003, astro-ph/0311321.

[27]  E. Rykoff,et al.  The ROTSE‐III Robotic Telescope System , 2002, astro-ph/0210238.

[28]  P. Mészáros,et al.  Theories of Gamma-Ray Bursts , 2001, astro-ph/0111170.

[29]  E. Ramirez-Ruiz,et al.  Was GRB 990123 a unique optical flash , 2001, astro-ph/0110519.

[30]  T. Piran.  Gamma-ray bursts – a puzzle being resolved ☆ , 1999, astro-ph/9907392.

[31]  Tsvi Piran,et al.  Predictions for the Very Early Afterglow and the Optical Flash , 1999, astro-ph/9901338.

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

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

[34]  K.,et al.  Multi-color Shallow Decay and Chromatic Breaks in the GRB 050319 Optical Afterglow , 2006 .

[35]  ApJ in press Preprint typeset using L ATEX style emulateapj v. 04/03/99 GAMMA-RAY BURST EARLY OPTICAL AFTERGLOWS: IMPLICATIONS FOR THE INITIAL LORENTZ FACTOR AND THE CENTRAL ENGINE , 2003 .

[36]  to be published in THE ASTROPHYSICAL JOURNAL LETTERS OFF-AXIS AFTERGLOW EMISSION FROM JETTED GAMMA-RAY BURSTS , 2002 .