Maqola

GRB 070125: The First Long‐Duration Gamma‐Ray Burst in a Halo Environment

S. B. CenkoSpace Radiation Laboratory, MS 220-47, California Institute of Technology, Pasadena, CA 91125D. B. FoxDepartment of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802B. E. PenprasePomona College Department of Physics and Astronomy, 610 North College Avenue, Claremont, CA 91711A. CucchiaraDepartment of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802P. A. PriceInstitute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822E. BergerHubble FellowShri KulkarniDivision of Physics, Mathematics, and Astronomy, 105-24, California Institute of Technology, Pasadena, CA 91125Fiona A. HarrisonSpace Radiation Laboratory, MS 220-47, California Institute of Technology, Pasadena, CA 91125A. Gal‐YamAstrophysics Group, Faculty of Physics, Weizmaun Institute of Science, Rehovot 76100, IsraelE. O. OfekDivision of Physics, Mathematics, and Astronomy, 105-24, California Institute of Technology, Pasadena, CA 91125A. RauDivision of Physics, Mathematics, and Astronomy, 105-24, California Institute of Technology, Pasadena, CA 91125P. ChandraDepartment of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903D. A. FrailNational Radio Astronomy Observatory, Socorro, NM 87801M. M. KasliwalDivision of Physics, Mathematics, and Astronomy, 105-24, California Institute of Technology, Pasadena, CA 91125B. SchmidtResearch School of Astronomy and Astrophysics, Australian National University, Mt. Stromlo Observatory, via Cotter Road, Weston Creek, ACT 2611, AustraliaAlicia SoderbergDivision of Physics, Mathematics, and Astronomy, 105-24, California Institute of Technology, Pasadena, CA 91125P. B. CameronDivision of Physics, Mathematics, and Astronomy, 105-24, California Institute of Technology, Pasadena, CA 91125Kathy RothGemini Observatory, 670 North A`ohoku Place, Hilo, HI 96720

2008en

ABI

Annotatsiya

We present the discovery and high signal-to-noise spectroscopic observations of the optical afterglow of the long-duration gamma-ray burst GRB 070125. Unlike all previously observed long-duration afterglows in the redshift range 0.5 ≾ z ≾ 2.0, we find no strong (rest-frame equivalent width W_r ≳ 1.0 Å) absorption features in the wavelength range 4000–10000 Å. The sole significant feature is a weak doublet that we identify as Mg II λλ 2796 (W_r = 0.18±0.02 Å), 2803 (Wr = 0.08±0.01 Å) at z = 1.5477±0.0001. The low observed Mg II and inferred H I column densities are typically observed in galactic halos, far away from the bulk of massive star formation. Deep ground-based imaging reveals no host directly underneath the afterglow to a limit of R>25.4 mag. Either of the two nearest blue galaxies could host GRB 070125; the large offset (d ≳ 27 kpc) would naturally explain the low column densities. To remain consistent with the large local (i.e. parsec scale) circum-burst density inferred from broadband afterglow observations, we speculate GRB 070125 may have occurred far away from the disk of its host in a compact star-forming cluster. Such distant stellar clusters, typically formed by dynamical galaxy interactions, have been observed in the nearby universe, and should be more prevalent at z>1 where galaxy mergers occur more frequently.

Hali tarjima qilinmagan

Identifikatorlar

DOI: 10.1086/526491

Iqtiboslar va manbalar

2 ta iqtibos0 ta foydalanilgan manba

Koʻrsatkichlar — AkademScholar