Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-12-15
Astron.Astrophys.451:777-787,2006
Astronomy and Astrophysics
Astrophysics
14 pages, 7 figures, accepted for publication on A&A
Scientific paper
10.1051/0004-6361:20053913
We present Swift and XMM observations of GRB 050326, detected by Swift-BAT. The fluence was 7.7x10^-6 erg cm^-2 (20-150 keV), and its spectrum was hard, with a power law photon index 1.25. The afterglow light curve did not show any break nor flares between ~1 hr and ~6 d after the burst, and decayed with a slope 1.70. The afterglow spectrum is well fitted by a power-law model, suffering absorption both in the Milky Way and in the host galaxy. The rest-frame Hydrogen column density is significant, N_H_z > 4x10^21 cm^-2, and the redshift of the absorber is z > 1.5. There was good agreement between the Swift-XRT and XMM results. By comparing the prompt and afterglow fluxes, we found that an early break occurred before the XRT observation. The properties of the GRB 050326 afterglow are well described by a spherical fireball expanding in a uniform external medium, so a further steepening is expected at later times. The lack of such a break constrains the jet angle to be >7 deg. Using the redshift constraints provided by the X-ray analysis, we also estimated that the beaming-corrected gamma-ray energy was >3x10^51 erg, at the high end of GRB energies. Despite the brightness in X rays, only deep limits could be placed by Swift-UVOT at optical/UV wavelengths. Thus, this GRB was "truly dark", with the optical-to-X-ray spectrum violating the synchrotron limit. The optical and X-ray observations are consistent either with an absorbed event or with a high-redshift one. To obey the Ghirlanda relation, a moderate/large redshift z>4.5 is required. (abridged)
Angelini Leonardo
Banat Piotr
Barbier Louis
Barthelmy Scott D.
Beardmore Andrew
No associations
LandOfFree
Swift and XMM observations of the dark GRB 050326 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Swift and XMM observations of the dark GRB 050326, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Swift and XMM observations of the dark GRB 050326 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-167586