[vsnet-alert 4357] Re: very curious spectra of SN 2000H

[Brian Skiff <bas@lowell.edu>]

     A couple of other routes are possible as well toward getting stars
near the galaxy calibrated reasonably well.  Besides Arne's sequence nerar
the GRB, there is also the GSPC sequence P481, which lies about half a
degree due east of the SN.  Some quick A/B comparisons with these stars using
a CCD could provide V magnitudes for the stars in the field of the galaxy.
     Similarly, the Tycho-2 catalogue photometry can be used to set zero-points
directly in the same field if the CCD covers a large enough area.  A quick
search in VizieR shows nine Tycho-2 stars within 10' radius of the supernova.
Of these, three probably have small enough errors to use to obtain on-chip
differential magnitudes in the V system:

GSC 0755-1135   6 51 31.00  +12 55 07.7    10.52
GSC 0755-0275   6 51 36.15  +12 53 51.6    10.39
GSC 0755-1471   6 50 54.75  +12 47 18.8    11.08

...where the final column are Tycho V corrected to the standard system.
The first of these stars is 5'.7 nearly due east of the supernova.  The
internal errors on the photometry for these stars is ~0.08 mag., not much
different than for the USNO stars, so again using these will provide only
a rough adjustment to the standard system.

\Brian

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