[vsnet-chat 3860] mu Cephei historical data

[Brian Skiff <bas@lowell.edu>]

     Following on the recent query to the AAVSO discussion list about whether
mu Cephei is an irregular or semiregular variable, I have keyed-in much of the
historical archive of observations available from the literature.  As far as I
know none of this is available in machine-readable form, and given the relative
obscurity of the publications involved, few will have ready access to the paper
copies.  Along with submitting them via Taichi Kato to 'vsnet-obs', I have
copied the files out to the Lowell ftp area:

http://ftp.lowell.edu/pub/bas/varseq/mucep.archive   (56Kb)
http://ftp.lowell.edu/pub/bas/varseq/mucep.hassen    (10Kb)
http://ftp.lowell.edu/pub/bas/varseq/mucep.larsson   (6Kb)

These are plain ASCII lists in vsnet-ish format, although JDs are given (taken
directly from the source material) rather than UT.  The sources for these lists
are Hassenstein's "famous" monograph on mu Cep, a later summary of his
photoelectric observations, and Gunnar Larsson-Leander's five-year series of
two-color photoelectric observations:

1938POPot..29a...3H
HASSENSTEIN W.
Publ. Astrophys. Obs. Potsdam, 29, heft 1, 3 (1938)
Untersuchungen uber den lichtwechsel von mu. Cephei.

1954POPot..29e...1H
HASSENSTEIN W.
Publ. Astrophys. Obs. Potsdam, 29, heft 5, 3 (1954)
Photometrische beobachtungen von veranderlichen sterne.

1963ArA.....3..285L
LARSSON-LEANDER G.
Arkiv for Astron., 3, 285-297 (1963)
Photoelectric observations of mu Cephei.

     As best I can tell from the second edition of the 'GuL', this is basically
all the published visual and photoelectric photometry of the star apart from
isolated modern observations.  The coverage is complete from 1848 to 1940
apart from somewhat more than a year in 1866-67, and the ten years ending in
1882, when Plassmann started observing the star.  Important early observations
were made by Julius Schmidt, Friedrich Argelander, and Eduard Heis.
     The first cited item is the place where Hassenstein provides about 2100
means of visual observations made between 1848 and 1938.  Notably this includes
Plassmann's remarkable series of over 5000 observations covering a 55-year
interval.  Roughly another 5000 observations are summarized; about half a dozen
individual observations spanning ~20 days goes into each mean value.  The whole
collection is placed on a common photometric zero-point, which from internal
evidence turns out to be very nearly 0.1 mag. fainter than standard V.  I have
excluded from the file most of the data given only in the text (rather than the
main table of the appendix), since these add very little, and are often noted
by Hassenstein as being unsatisfactory (just too scattered) after systematic
errors are taken into account.
     The 1938 monograph and the 1954 follow-up include some 200 photoelectric
observations made by Hassenstein with an unfiltered blue-sensitive tube.  The
magnitude differences he supplies for the comparison stars (the red giants
12 Cep and 20 Cep) match the standard B system within 0.01 mag., so I have used
modern B magnitudes for those stars to derive B for mu Cep in the lists.
(Confusingly, Hassenstein published magnitudes with the zero-point adjusted to
that of the visual system of the 1938 monograph.)  The night-to-night rms
scatter in this data is about +/-0.03 mag.  The main value in the photoelectric
data is to show that the visual observations by Plassmann and by the well-known
astronomer Dean McLaughlin in the 1930s are excellent, and to extend the
dataset until 1940.
     Larsson-Leander obtained about five years of V and P-V (similar to B-V)
photoelectric observations of high-quality (rms ~0.012 in V) in the late 1950s.
The data density is such that it can replace the visual record for this
interval.
     These lists combined with the recent APT data might justify revisiting
the supposed periodicies of the star.  The ~850-day cycle is _usually_ present
in the long historical record, but Larsson-Leander's lightcurve confirms there
are long stretches (often 200 days or more) where the star is essentially
constant.

\Brian

VSNET Home Page

Return to Daisaku Nogami

---

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