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Title: The high-redshift gamma-ray burst GRB 140515A

High-redshift gamma-ray bursts (GRBs) offer several advantages when studying the distant Universe, providing unique information about the structure and properties of the galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge of this kind of distant events. We present the multi-wavelength analysis of the high-zSwift GRB GRB 140515A (z = 6.327). The best estimate of the neutral hydrogen fraction of the intergalactic medium towards the burst is x HI ≤ 0.002. The spectral absorption lines detected for this event are the weakest lines ever observed in GRB afterglows, suggesting that GRB 140515A exploded in a very low-density environment. Its circum-burst medium is characterised by an average extinction (AV ~ 0.1) that seems to be typical of z ≥ 6 events. The observed multi-band light curves are explained either with a very hard injected spectrum (p = 1.7) or with a multi-component emission (p = 2.1). In the second case a long-lasting central engine activity is needed in order to explain the late time X-ray emission. Furthermore, the possible origin of GRB 140515A in a Pop III (or in a Pop II star with a local environment enriched by Pop III) massive star is unlikely.
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  1. INAF-Osservatorio Astronomico Brera, Merate (Italy)
  2. Instituto de Astrofisica de Andalucia (IAA-CSIC), Granada (Spain); Univ. del Pais Vasco (UPV/EHU), Bilbao (Spain); Basque Foundation for Science, Bilbao (Spain)
  3. INAF-Osservatorio Astronomico Brera, Merate (Italy); Univ. degli Studi dell'Insubria, Como (Italy)
  4. The Hebrew Univ. of Jerusalem, Jerusalem (Israel)
  5. Univ. of Ljubljana, Ljubljana (Slovenia)
  6. Instituto de Astrofisica de Andalucia (IAA-CSIC), Granada (Spain); Univ. of Copenhagen, Copenhagen (Denmark)
  7. Instituto de Astrofisica de Andalucia (IAA-CSIC), Granada (Spain)
  8. ASI - Science Data Center, Roma (Italy); INAF - Osservatorio Astronomico di Roma, Monte Porzio Catone (Italy)
  9. Stockholm Univ., Stockholm (Sweden)
  10. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Univ. of Chicago, Chicago, IL (United States)
  11. Univ. Paris Diderot, Paris (France)
  12. Univ. of Copenhagen, Copenhagen (Denmark)
  13. INAF - IASF Milano, Milano (Italy)
  14. INAF-Osservatorio Astronomico Brera, Merate (Italy); Univ. Paris Diderot, Meudon (France)
  15. Chinese Academy of Sciences (CAS), Beijing (China); Univ. of Copenhagen, Copenhagen (Denmark)
Publication Date:
Report Number(s):
Journal ID: ISSN 0004-6361; arXiv eprint number arXiv:1506.03079
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Astronomy and Astrophysics
Additional Journal Information:
Journal Volume: 581; Journal Issue: 9; Journal ID: ISSN 0004-6361
EDP Sciences
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; gamma-ray burst: general; gamma-ray burst: individual: GRB 140515A; galaxies: high-redshift; intergalactic medium
OSTI Identifier: