SN 2005md is a Galactic cataclysmic variable
ATel #2750; D. C. Leonard
on 21 Jul 2010; 17:57 UT
Credential Certification: D. C. Leonard (leonard@astro.caltech.edu)
Subjects: Optical, Binary, Cataclysmic Variable, Nova, Supernovae, Transient, Variables
A fully reduced CCD spectrum (range 330-910 nm), obtained on 2005 December 31.8
UT with the Keck I 10-m telescope (+ LRISp), shows that the object, SN 2005md,
reported by Li, Wang, & Bian (CBET #332) and initially classified by Modjaz et
al. (IAUC # 8650 ) as a probable young type-IIb supernova (based on a featureless
spectrum obtained 3 days prior to this one), is in fact a new Galactic
cataclysmic variable. The object's spectrum shows features typical of
cataclysmic variables during outburst (e.g., the dwarf nova KS UMa; cf. Szkody
et al. 2004, AJ, 128, 1882): A blue continuum with strong Balmer absorption
lines possessing emission cores from H_alpha to at least H_eta. A weak He I
447.1 nm absorption is also evident. The Balmer line emission cores become
progressively weaker in the higher order lines (the H_alpha emission has a
measured HWZI of about 1000 km/s) and have an average redshift of about 300
km/s -- consistent with a Galactic origin and inconsistent with an origin in
NGC 2274 (z = 5072 km/s; Michel & Huchra 1988, PASP, 100, 1423), the putative
host galaxy of SN 2005md.
The CV classification of SN 2005md is consistent with the rebrightening
reported at the location (coincident to within 0.5") of SN 2005md by Li et
al. (CBET #1265) over two years after the initial discovery, and also resolves
the conundrum of having had a core-collapse supernova evidently occur in an
E-type galaxy with few signs of active star formation (cf. Hakobyan et
al. 2008, A&A, 488, 523).
