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Gamma Ray Bursts and LIGO Emelie Harstad University of Oregon HEP Group Meeting Aug 6, 2007

Gamma Ray Bursts and LIGO Emelie Harstad University of Oregon HEP Group Meeting Aug 6, 2007. Outline. What are GRBs? GRB detection, types, and light curves GRB progenitors LIGO's interest in GRBs GWs from GRBs Targeted search using GRBs Etc. What are GRBs?.

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Gamma Ray Bursts and LIGO Emelie Harstad University of Oregon HEP Group Meeting Aug 6, 2007

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  1. Gamma Ray Bursts and LIGO Emelie Harstad University of Oregon HEP Group Meeting Aug 6, 2007

  2. Outline • What are GRBs? • GRB detection, types, and light curves • GRB progenitors • LIGO's interest in GRBs • GWs from GRBs • Targeted search using GRBs • Etc...

  3. What are GRBs? • Most luminous events in the universe since the Big Bang. • Energy output 1051-1054 erg/s (comparable to E emitted by Milky Way over 100 yrs.) • Flashes of high energy photons (~MeV) which 'light up' the sky ~3 times per day. • Lasting 10-3 to 103 seconds (followed by longer wavelength afterglows). • Isotropic distribution

  4. Satellite Detection of GRBs • 1969: Vela (first discoverd GRBs) • 1991: Compton Gamma-Ray Observatory / BATSE • Showed isotropic/cosmological distribution • 1997: Beppo-SAX • Detected x-ray afterglows –> accurate sky positions –> optical and radio observations –> red-shift measurements • 2000: HETE-2 • 2002: INTEGRAL • 2004: Swift / BAT / XRT / UVOT • Early afterglows • Detected first short GRB afterglow http://heasarc.gsfc.nasa.gov/docs/swift/swift.html

  5. GRB Types and Light Curves • Light curves vary in shape, number of peaks, decay rate, peak luminosity, etc. • Fall into 2 general categories: • Short (<2ms) • Long (>2ms) • Third category possibly exists – GRB 060614 • Long duration (~102 s) • Temporal lag and peak luminosity of short GRB • No associated SNe http://imagine.gsfc.nasa.gov/docs/science/know_l1/grb_profiles.html

  6. GRB Jets • GRBs thought to be beamed because of jet breaks in afterglow light curves. • Due to relativistic beaming (G~1/q) and deceleration of ejected matter. • Reduces total energy requirement of GRB by a few orders of magnitude (q~5-20). http://www.lbl.gov/Science-Articles/Archive/sabl/2005/August/05-GRB-supernovae.html http://www.mpe.mpg.de/~jcg/grb060814.html

  7. Short GRB Progenitors • Found on outskirts of elliptical type galaxies where star formation is low • Afterglows show no association with supernovae • NS-NS or NS-BH inspirals are most likely candidates • Merger results in black hole or hypermassive NS surrounded by accretion torus –> relativistically expanding fireball –> gamma rays http://www.astro.exec.ac.uk/people/dprice/research/nsmag/

  8. Long GRB Progenitors • Found in active star-forming regions in galaxies • Several afterglow light curves directly linked to supernovae • Massive star collapse –> supernova, or 'failed supernova' (hypernovae, collapsar) • Supernova results in BH with accretion disk –> expanding fireball –> gamma rays http://imagine.gsfc.nasa.gov/docs/science/know_l1/bursts.html

  9. Fireball Shock Scenerio http://www.oamp.fr/ECLAIRS/01home/home.htm

  10. What is it to LIGO? • The same objects that produce GRBs will also produce gravitational waves. • Interferometric gravitational detectors are designed to detect GWs by sensing differences in arm lengths: • Binary systems have large non-spherical kinetic energy and coalese in LIGO peak sensitivity band. • Supernovae develop non-spherical mass distributions (particularly if spinning) which can significantly contribute to non-spherical kinetic energy.

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