[vsnet-chat 4828] Re: "Unknown" Variable Stars

[Brian Skiff <bas@lowell.edu>]

     As John Isles notes, HD 37519 = NSV 2537 was suspected of flaring on
photographs by Andrews in the early 60s.  There is a recent follow-up paper
by Andrews himself in the Irish Astronomical Journal (which he edited and wrote
much of the contents of).  This is not a widely circulated journal, but it is
nevertheless the third entry in the biblio listing for the star in SIMBAD....

1996IrAJ...23..189A: ANDREWS A.D. <Irish Astron. J., 23, 189-193 (1996)>
    A re-examination of the suspected early-type flare star BD+31 1048
    (BS 1938) in Auriga: a skeleton from the cupboard.

In his review, Andrews overlooks essentially all the literature published
since his original paper (and folks wonder why scientific papers are refereed,
which this one almost certainly wasn't).  Among these is high-precision
photometry by Mike Jerzykiewicz [jer-zi-kay-vich] (1993A&AS...97..421J), who I
would nominate as the world's best living photometrist.  From 17 observations
over 13 nights, he found HD 37519 and another nearby star constant with an rms
scatter of 2.1 millimags.  Andrews quotes "unpublished" visible and near-IR
photometry by Mendoza, inferring from it unusual colors and a faint V
magnitude.  The data were in fact published later, and the star colors shifted
around by small amounts (perhaps from re-reduction) such that the colors are no
longer anomalous, and the V magnitude changed to be more nearly in line with
other observations.  The Hipparcos catalogue specifically flags the star as
being constant, having an rms scatter in the Hp magnitude of 4 millimags.
Andrews also overlooked a good, high-dispersion MK classification by Anne
Cowley (1972AJ.....77..750C), who finds it to be B9.5III-IV(p), the 'p'
indicating in this case the presence of strong mercury and magnesium lines.
These are not terribly rare, and the incidence of variability among such stars
is not different from ordinary late-B/early-A stars.  The spectral type also
makes the photometric colors less anomalous than Andrews claims in his 1996
review based on an assumed type of B7V (which comes from a low-dispersion
objective-prism plate).  None of this of course excludes the one-off flare that
Andrews found, which was supposedly as large as 2 full magnitudes.  Yes, I'd be
skeptical, too.

     That Zinner listed delta-1 Lyr as variable almost automatically makes it
suspect.  These are mostly claims of quite small-amplitude variables found
visually with binoculars.  Some of the stars are of course variable, but not
in the way claimed by Zinner.  The star has not been observed as a variable
since Zinner's report, only as a close binary and as a nominal member of the
delta Lyrae open cluster.  Kevin West used it as a comp star for delta-2 Lyr
(http://vsnet.konkoly.hu/cgi-bin/IBVS?4335), obtaining an rms scatter of about
0.02 mag. (commendably small, observing from cloudy England), which does not
suggest much is happening.  Again the Hipparcos photometry suggests constancy:
the rms scatter is all of 7 mmag, but in this case the binarity is likely to
have caused some problems (the 5th/95th percentile range in the Hipparcos data
is only 0.02 mag.).  The NSV claims an amplitude of only 0.06 mag.  Sebastian?!

     I found all this information using SIMBAD, VizieR, and ADS, without
leaving my desk except to read the Andrews paper (the only one that is not
available on-line).  Please don't say there was nothing to find out from
the various on-line sources.

\Brian

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp