TITLE:   GCN CIRCULAR
NUMBER:  7189
SUBJECT: Transient 080109/ SN 2008D, metallicity of the host galaxy
DATE:    08/01/16 20:39:34 GMT
FROM:    Krzysztof Z. Stanek at CfA  <kstanek@cfa.harvard.edu>

J. L. Prieto (Ohio State) reports:

The host galaxy of SN 2008D, NGC 2770, is included in the latest version
of our catalog of supernova hosts:

http://www.astronomy.ohio-state.edu/~prieto/snhosts/sort_name.html#2008D

The central oxygen abundance of NGC 2770, as measured by Tremonti et al.
(2004, ApJ, 613, 898) using nebular emission lines, is 12 + log(O/H) = 9.0
and its absolute magnitude is MB = -20.7 (HyperLeda catalog), putting this
Sc galaxy on the luminosity-metallicity relationship of star forming
galaxies (e.g., Tremonti et al. 2004). These characteristics are typical
of the hosts of other type Ib/c supernovae (Prieto, Stanek & Beacom 2008,
ApJ, in press, arXiv: 0707.0690), and in contrast with the low-metallicity
of the hosts of long-GRBs with supernovae (e.g., Stanek et al. 2006, AcA,
56, 333). We note, however, that SN 2008D exploded fairly far from the
center of NGC2770 (galactocentric distance of ~10kpc), which may have a
strong metallicity gradient, as suggested by its late-type Sc
classification. From the measured radial metallicity gradients of galaxies
with similar morphological class (Zaritsky, Kennicutt, & Huchra 1994, ApJ,
420, 87), we estimate an oxygen abundance of 8.4 < 12 + log(O/H) < 8.8 (in
the scale of Tremonti et al.) at the site of the supernova explosion. Even
though this is only an approximation, this value is consistent with the
metallicities measured at the sites of broad-lined SN Ic without GRBs
(Modjaz et al. 2008, AJ, in press, astro-ph/0701246).

Indepently of the true nature of the X-ray transient associated with the
peculiar type Ic supernova 2008D (e.g., Blondin et al., CBET 1205), an XRF
or shock breakout (Burrows et al., GCN Circ. 7179), its remarkable
star-forming host, NGC 2770, deserves to be studied in detail: it has
produced three supernovae of type Ib/c in less than 10 years (SN 1999eh,
2007uy, and 2008D), which most likely result from death of very massive
stars (mass > 30 Msun, e.g., Heger et al. 2003, ApJ, 591, 288).

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