[vsnet-sequence 126] SN 2002ap preliminary sequence (Henden)

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

SN 2002ap preliminary sequence (Henden)

   The following message was relayed from Arne Henden, as originally posted
to AAVSO-GRB:

I've posted on
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/sn2002ap.dat
a BVRI field photometry file from last night.  Much as I begged
the clouds to go away, there remained scattered cirrus at the
time these observations were made.  My estimate is perhaps
a 0.1mag external error on these numbers.
  The photometry is inconsistent with the Vmag frame extraction
that I gave Mike Simonsen to make the AAVSO chart for this field,
with the new photometry about 0.25mag brighter at V.  Brian Skiff
was good enough to give me 3 stars that Harold Corwin measured
many moons ago near the center of M74; that photometry was pretty
poor, but indicated that the chart mags were too faint by 0.17mag.
So bottom line is that I would trust the sn2002ap.dat magnitudes
more than the current chart magnitudes, but both sets are under
suspicion until a decent night is available.
  However, the supernovae does appear in the .dat file at
  RA  (J2000) DEC      RA             DEC       V     B-V    V-R    R-I
24.099676  15.753692 01:36:23.92  +15:45:13.3 12.987  0.558  0.018 -0.212

The spectra indicate a rather blue continuum with broad absorption
at 448.0, 557.5, and 719.5 nm, or roughly the center of B and V,
and inbetween R and I.  Depending on the depths of these absorptions,
the broadband colors can be almost anything, as evidenced above.
VRI indicate a pretty blue object; B is fainter than expected, but
probably due to the 448.0 absorption.

Note that the position above is very close to the radio position,
right-on in RA and 0.4arcsec off in DEC.
Arne

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