Late time observations Late time observations of GRB080319Bof GRB080319B

Nial TanvirNial Tanvir

University of LeicesterUniversity of Leicester

collaboration with Evert Rol, Andrew Levan, Andy Fruchter, Yoni Granot, Karl Svensson and

others

Reached visual magnitude 5.3!

Pi of Sky

Redshift = 0.94

REM & Tortora

Racusin et al. 2008Bloom et al. 2009

Was GRB 080319B exceptional in other ways?

Total energy (beaming corrected)?

Accompanying supernova?

Host galaxy?

Late time observations up to ~1 year post-burst.

HST/WFPC2 observations

T+19 days T+54 days T+107 days

Light curve (host subtracted photometry)

Light curve (host subtracted photometry)

Simple model:

1 =1.3, 2=2.35

=0.5

Sharp achromatic break at tb=11 days

Redder bands show late time excess.

Redder bands show late time excess.

Consistent with an additional supernova component reaching about 80% of the luminosity of SN 98bw (possibly slightly shorter duration).

i.e. similar to the properties of other GRB supernovae inferred from light curve “humps”.

Bright accompanying supernova and small host galaxy entirely typical of the very faintest GRBs!

Findings:

• Sharp, achromatic light-curve break at tb=11 days. If interpreted as a jet break, the implications for beaming corrected total energy depend on model, but most likely Etot <1052.5 erg.

• Accompanying supernova with magnitude similar to SN 98bw (best fit with a template somewhat fainter and redder).

• Dwarf host galaxy, which is at the faint end of the distribution of GRB hosts at comparable redshifts, and hence probably of lower metallicity.

Tanvir et al. ApJ submitted (arXiv:0812.1217)