[vsnet-alert 5985] SN 2001cn in IC 4758

[Hitoshi YAMAOKA <yamaoka@rc.kyushu-u.ac.jp>]

Dear SN watchers,

  R. Chassagne discovered his 8th SN 2001cn in the southern galaxy.
It is now around mag 15.0.  Congratulations, Robin!

  SN 2001cn was discovered on June 11.95 at mag about 14.8, and
remains at nearly the same magnitude until June 13.531 when R.
Sanrallo confirmed it.  The SN position is: R.A. = 18h46m17s.84, Decl.
= -65o45'41".8 (2000.0), which is about 2" west and 18" south of the
nucleus of the face-on spiral (Sc) galaxy IC 4758.  There are several
foreground stars around this galaxy nearly the same angular distance
from the nucleus as SN, so the identification needs care.

  The reported magnitude is somewhat brighter than the expected
maximum (V magnitude 15.4) of typical SN Ia for this galaxy's
recession velocity (4647 km/s).  It would possibly be caused that the
discoverer (and also confirmer) used ST-7E, which is sensitive for
blue light, and USNO-A2.0 r magnitude for the comparison stars. 
SNe in the early stage is usually bluer than the surrounding
comparison stars, so the blue-sensitive CCD (without filter) will
catch more photons from the young SN than stars whose r magnitude is
comparable with that of SN.  It is possible, however, that this SN is
intrinsically bright; further follow-up photometry (and of course the
spectral classification) will make it clear.

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan
yamaoka@kusastro.kyoto-u.ac.jp

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