[Vsnet-alert 8398] GRB 050509b and possible SN association?

[Taichi Kato]

   Forwarded message from the GCN.  Perhaps we don't need to wait for huge
telescopes to move.  What magnitude would be expected now, assuming the SN Ia
hypothesis, Yamaoka-san?

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3423
SUBJECT: GRB 050509B and short GRB-SN association?
DATE:    05/05/15 08:56:20 GMT
FROM:    Arnon Dar at Technion-Israel Inst. of Tech  <arnon at physics.technion.ac.il>

S. Dado (Technion) and A. Dar (Technion) report:

The leading scenarios for the production of short-duration GRBs involve
(a) neutron-star mergers [1] (b) super flares from SGRs (GCN 2942 and [2])
(c) gravitational collapse of neutron-stars to strange-quark stars [3] (d)
gravitational collapse of C/O white dwarfs to neutron stars (GCN 2174) and
[3]). While scenarios (a),(b) are not associated with standard optical
SNe, scenarios (c),(d) are expected to produce a standard optical SN. 
In particular, in scenario (d), a bright SNIa is expected at the GRB
location with a standard rest frame optical light curves which peak around
20 days after burst with un-reddened absolute rest frame magnitudes,
Bmax~-19.47, Vmax~-19.42, Rmax~-19.42 and Imax~-19.06 (+\-0.15 magnitude).


GRB050509B (GCN 3381) is the first well localized short-duration (~30 ms)  
GRB. It allows a late time search of an SN associated with a short
duration GRB. In the observer frame the expected un-reddened spectral
energy density at a frequency nu and a time t after burst is:

    F(nu,t)=((1+z) [D_L(z')]^2 / (1+z')[D_L(z)]^2) Ftsn(nu',t')

where z' is the redshift of the template SNIa whose spectral energy
density is Ftsn and nu'=[(1+z)/(1+z')] nu, t'=[(1+z')/(1+z)] t. 
If GRB050509B was produced in an SNIa in the galaxy cluster NSC
J123610+285901 at a redshift z~0.225 (GCN 3390), its observed V-band light
curve should peak near t=25 days after burst with Vmax~20.43+/- 0.15
(extinction in the host galaxy is not included, but Galactic extinction in
the direction of GRB 050509B, Av~0.06 [5] is included).

Despite the failures so far to detect an optical afterglow
within/near the refined XRT error circle (GCN 3395)  of GRB 050509B, an SN
search within/near the burst XRT error circle, with the most powerful
telescopes such as Keck, VLT, Subaru and HST, is highly encouraged.

[1]  Goodman, J, Dar, A, & Nussinov, S. 1987, ApJ, 314, L7 
[2]  Hurley, K., et al. 2005, astro-ph/0502329
[2]  Dar, A.   1999, A&AS, 138, 505 
[3]  Dar, A. & De Rujula, A. 2004, Physics Reports, 405, 203 
[4]  Germany, L. M., et al. 2004, A&A 415, 863 
[5]  Schlegel, D. J.; Finkbeiner, D. P. & Davis, M. 1998, ApJ, 500, 525