M. Templeton, A. Henden, W. Goff, S. Smith, R. Sabo, G. Walker, R. Buchheim, G. Belcheva, T. Crawford, M. Cook, S. Dvorak, B. Harris
We present a modern ephemeris and modern light curve of the first-discovered
Cepheid variable in M31, Edwin Hubble's M31-V1. Observers of the American
Association of Variable Star Observers undertook these observations during the
latter half of 2010. The observations were in support of an outreach program by
the Space Telescope Science Institute's Hubble Heritage project, but the
resulting data are the first concentrated observations of M31-V1 made in modern
times. AAVSO observers obtained 214 V-band, Rc-band, and unfiltered
observations from which a current ephemeris was derived. The ephemeris derived
from these observations is JD(Max) = 2455430.5(+/-0.5) + 31.4 (+/-0.1) E. The
period derived from the 2010 data are in agreement with the historic values of
the period, but the single season of data precludes a more precise
determination of the period or measurement of the period change using these
data alone. However, using an ephemeris based upon the period derived by Baade
and Swope we are able to fit all of the observed data acceptably well.
Continued observations in the modern era will be very valuable in linking these
modern data with data from the 1920s-30s and 1950s, and will enable us to
measure period change in this historic Cepheid. In particular, we strongly
encourage intensive observations of this star around predicted times of maximum
to constrain the date of maximum to better than 0.5 days.
View original:
http://arxiv.org/abs/1111.0262
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