Paper

{
  "raw_xml": "<entry>\n    <id>http://arxiv.org/abs/2603.01633v1</id>\n    <title>Episode-wise spectro-polarimetry of GRB 220107A: Testing the hypothesis of evolving radiation mechanisms</title>\n    <updated>2026-03-02T09:08:53Z</updated>\n    <link href='https://arxiv.org/abs/2603.01633v1' rel='alternate' type='text/html'/>\n    <link href='https://arxiv.org/pdf/2603.01633v1' rel='related' title='pdf' type='application/pdf'/>\n    <summary>We investigate the spectro-polarimetric properties of the long-duration GRB~220107A, which exhibited two distinct emission episodes separated by a 40 s quiescent gap, to test whether such multi-episode bursts show evidence for evolution in their underlying radiation mechanisms. We analyzed prompt emission data from AstroSat/CZTI, Fermi/GBM, and Konus-Wind, performing spectro-polarimetric analysis for each emission episode. The time-integrated polarization analysis shows no significant detection (PF$ &lt; 38 \\%$, $2σ$). Time-resolved analysis reveals clear spectral evolution between the two episodes, with episode 1 exhibiting a hard low-energy photon index and episode 2 showing substantial spectral softening ($α\\sim -0.72$). Regarding polarization: Episode 1 shows a low polarization upper limit (&lt; 52\\%), consistent with expectations for photospheric emission dominated by quasi-thermal Comptonization in a baryon-rich outflow. Episode 2 also shows overall low polarization (PF$ &lt; 55 \\%$, $2σ$), though sliding-window analysis yields a marginally elevated signal (PF$= 70 \\pm 30\\%$, BF = 2.8) between T0+76 to T0+88 s. The robust spectral softening between episodes could arise from sub-photospheric dissipation, optically thin synchrotron radiation in small-scale magnetic fields, or if the tentative polarization enhancement proves intrinsic, it would favor synchrotron emission in large-scale ordered magnetic fields. The spectral evolution of GRB 220107A, combined with our polarimetric constraints, demonstrates the diagnostic potential of time-resolved spectro-polarimetry for constraining GRB prompt emission physics. We present GRB 220107A as a test case illustrating how future higher sensitivity observations could discriminate between competing emission models for multi-episode bursts. Our results emphasize both the promise and current limitations of prompt phase polarimetry.</summary>\n    <category scheme='http://arxiv.org/schemas/atom' term='astro-ph.HE'/>\n    <published>2026-03-02T09:08:53Z</published>\n    <arxiv:comment>16 pages, 10 figures, 6 tables, accepted for the publication in Astronomy and Astrophysics</arxiv:comment>\n    <arxiv:primary_category term='astro-ph.HE'/>\n    <author>\n      <name>Rahul Gupta</name>\n    </author>\n    <author>\n      <name>Rushikesh Sonawane</name>\n    </author>\n    <author>\n      <name>Shabnam Iyyani</name>\n    </author>\n    <author>\n      <name>D. Frederiks</name>\n    </author>\n    <author>\n      <name>Judith Racusin</name>\n    </author>\n    <author>\n      <name>Tanmoy Chattopadhayay</name>\n    </author>\n    <author>\n      <name>A. J. Castro-Tirado</name>\n    </author>\n    <author>\n      <name>A. F. Valeev</name>\n    </author>\n    <author>\n      <name>Soumya Gupta</name>\n    </author>\n    <author>\n      <name>Mayuresh Tembhurnikar</name>\n    </author>\n    <author>\n      <name>A. Ridnaia</name>\n    </author>\n    <author>\n      <name>D. Svinkin</name>\n    </author>\n    <author>\n      <name>S. B. Pandey</name>\n    </author>\n    <author>\n      <name>Dipankar Bhattacharya</name>\n    </author>\n    <author>\n      <name>Vidushi Sharma</name>\n    </author>\n    <author>\n      <name>Varun Bhalerao</name>\n    </author>\n    <author>\n      <name>G. C. Dewangan</name>\n    </author>\n    <author>\n      <name>Santosh Vadawale</name>\n    </author>\n    <author>\n      <name>R. Sánchez-Ramírez</name>\n    </author>\n    <author>\n      <name>Anastasia Tsvetkova</name>\n    </author>\n  </entry>"
}