Paper: astro-ph/0507502
Date: Thu, 21 Jul 2005 10:08:19 GMT (156kb)

Title: The Progenitor of SN 2005cs in the Whirlpool Galaxy

Authors: J.R. Maund (Institute of Astronomy), S.J. Smartt (Queen's University
Belfast) and I.J. Danziger (INAF, Trieste)
Comments: Submitted to MNRAS Letters
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The progenitor of SN 2005cs, in the galaxy M51, is identified in
pre-explosion HST ACS WFC imaging. Differential astrometry, with post-explosion
ACS HRC F330W images, permitted the identification of the progenitor with an
accuracy of 0.01". The progenitor was detected in the F814W pre-explosion image
with I=23.3+/-0.2, but was below the detection thresholds of the F435W and
F555W images, with B<24.8 and V<25 at 5sigma. Limits were placed on the U and R
band fluxes of the progenitor from pre-explosion HST WFPC2 F336W and F675W
images. Deep images in the infra-red from NIRI on the the Gemini telescope were
taken 2 months prior to explosion, but the progenitor is not clearly detected
on these. The upper limits for the JHK magnitudes of the progenitor were
J<21.9,H<21.1 and K<20.7. Despite having a detection on only one band, a
restrictive spectral energy distribution of the progenitor star can be
constructed and a robust case is made that the progenitor was a red supergiant
with spectral type between mid K-type to late M-type type. The spectral energy
distribution allows a region in the theoretical HR diagram to be determined
which must contain the progenitor star. The initial mass of the star is
constrained to be M(zams)=9 +3/-2 Msol, which is very similar to the identified
progenitor of the type IIP SN 2003gd, and also consistent with upper mass
limits placed on five other similar SNe. The upper limit in the deep K-band
image is significant in that it allows us to rule out the possibility that the
progenitor was a significantly higher mass object enshrouded in a dust cocoon
before core-collapse. This is further evidence that the trend for type II-P SNe
to arise in low to moderate mass red supergiants is real.

\\ ( http://arXiv.org/abs/astro-ph/0507502 , 156kb)