Gamma-Ray Bursts observed by XMM-Newton Paul O’Brien X-ray and Observational Astronomy Group, University of Leicester Collaborators:- James Reeves, Darach Watson, Julian Osborne, Ken Pounds, Alex Short, Martin Turner, Mike Watson, Keith Mason, Norbert Schartel, M Santos- Lleo, Matthaus Ehle.

The Compton Gamma Ray Observatory

GRB : BeppoSAX Observations 1997 February March 3 X-RAY IMAGES OF REGION CENTRED ON THE GRB X-ray and optical counterparts seen: z=0.695 (Djorgovski et al. 1999)

Optical Afterglows & Host Galaxies GRB Keck GRB HST host galaxy GRB

Possible Models for the Progenitor High energy (high mass), compact objects  two leading models collapse of giant star Predicted  duration ~ seconds merging neutron star binary Predicted  duration ~ 10s of seconds Both models produce an accreting black hole or a milli-second pulsar Both models have very high angular momentum Both models give beamed emission Jet internal/external shocks + interaction with surroundings  afterglow The models predict different line spectra

XMM-Newton Observation of GRB Reeves et al (2002): Nature, 416, 512 Reeves et al (2003): A&A, 403, 463 XMM-Newton EPIC NOT, R band image

Optical Follow-up of GRB GRB Host Redshift determined as z=2.140  Holland et al. (2002) HST:- GRB host galaxy (Fox 2002)

The X-ray Spectrum of GRB – first 5 ksec Power-law Fit (  =2.2)

Hydrogenic lines from Mg, Si, S, Ar and Ca detected in first 10ksec x10 Solar abundances, but no iron line (<1.4 Solar) – Supernova? Mg XI/XII Si XIV S XVI Ar XVIII Ca XX Lines are blueshifted: outflow velocity = km s -1 Sig. at 99.97%

Why is there no iron line in GRB ? Nucleosynthesis Synthesis model for a 40 solar mass progenitor star (e.g. Woosley & Weaver 1995) Iron line only dominates after t > 100 days. Nickel line dominates at t < 10 days.

X-ray afterglow of GRB A - 45 hrs after GRB  Soft excess line emission? Watson et al: 2002, A&A, 393, L1 Fading X-ray source P(const) = IPN error box Best PL with Galactic absorption  Line emission? Sig % Z x = /- 0.03

 ‘ Fe’ line X-ray afterglow of GRB hrs after GRB BeppoSAX error box Assumed afterglow P(const) = 0.06 Best PL with Galactic absorption Sig % Z x = 1.0 +/ Watson et al: 2002, A&A, 393, L1

X-ray afterglow of GRB hr after GRB Excess absorption  7.8 hr observation X-ray source fades as t -1.3 Need intrinsic absorption. At Z abs ~ 1.8, N H ~1.3x10 22 cm -2 Faint, fading optical transient No thermal emission apparent Watson et al: 2002, A&A, 395, L41

GRB detection of transient Si, S, Ar, Ca last 10ks only K  lines from Si, S, Ar and Ca  z=1.35  0.05 Detection significance = 5  No Fe or Ni/Co lines (<1.6 & <18 solar abundances, cf. 24 solar for light elements) Si S Ar Ca Total flux and line flux variation ~210 line photons (~115 in GRB ) Watson et al., 2003, ApJ, 595, L29

XMM-Newton GRB afterglows emission line summary

GRB afterglow evolution X-ray (1 keV) optical (R) radio (8.4 GHz) Optical + radio excess: Supernova (+?) Willingale et al., 2003, MNRAS, submitted

GSFC BAT XRT Spacecraft UVOT BAT UVOT XRT Spacecraft Launch in 2004 BAT 5x sensitivity of BATSE X-ray telescope has a MOS CCD Detect ~150 GRBs/year Response time ~ 100 seconds Swift – catching gamma ray bursts on the fly

Conclusions Soft X-ray lines detected in most, but not all, XMM-Newton GRB afterglow spectra. Theoretical models all assume reflection produces lines, but empirical fits prefer thermal models…?? XMM-Newton EPIC gives ~ x50 the count rate of the BeppoSAX MECS for a typical GRB afterglow spectrum. XMM-Newton will continue to play an important role in the Swift era – track long-term spectral evolution of the afterglow.