Central Bureau for Astronomical Telegrams
IAUC 6261: AX J2315-592; 51 Peg
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Circular No. 6261
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
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AX J2315-592
H.-C. Thomas, Max-Planck-Institut fur Astrophysik, Garching;
and K. Reinsch, Universitats-Sternwarte Gottingen, write: "We have
identified the newly-discovered x-ray source AX J2315-592 (IAUC
6260) as a new AM Her binary. The star (V = 17.1) located 15"
north of the x-ray position at R.A. = 23h15m18s.4, Decl. =
-59o10'27" (equinox 2000.0) has been observed with the ESO/MPI 2.2-
m telescope (+ EFOSC2) at La Silla on Nov. 12 and 13. The spectra
display strong emission lines of the Balmer series and of helium.
A radial-velocity variation with an amplitude of 200 km/s and an
intensity variation between mag 14.4 and 16.2 in the Gunn i filter
have been found with a period of 5360 +/- 10 s. The variation in
brightness decreases toward shorter wavelengths, indicating strong
cyclotron radiation to be present at long wavelengths. No
cyclotron harmonics could be distinguished, and this must be due to
a rather low magnetic field strength at the white dwarf's surface.
At certain phases, the emission lines have extended blue wings. No
features of the M star have been detected in the spectra."
51 PEGASI
E. Guinan, Villanova University, writes: "High-precision
photoelectric photometry of 51 Peg has been carried out at Mount
Hopkins by R. Dukes, H. Nations, and D. Buzasi (College of
Charleston) and by E. Guinan and G. McCook since Oct. 14. No
significant light variations have been detected for 51 Peg to the
level of the photometric precision (0.0018 mag). Some of the
photometry was carried out near the expected times of the
companion's transit eclipse. Several nearby comparison and check
stars have been used for this differential photometry. As a
cautionary note to other observers, one of the most logical primary
comparison stars for the photometric study of 51 Peg, HD 217813 (V
= 6.60, B-V = +0.61; spectral type G5 V), was found by both groups
to be a variable star, showing quasi-sinusoidal light variations
with a period of about 8.5 days and brightness ranges of 0.012 mag
in V and 0.020 mag in U; the period and wavelength dependence are
consistent with the rotational modulation in brightness by
starspots from a Hyades-age solar-type star. Another possible
photometric reference star near the position of 51 Peg, HD 218396
(= HR 8799; A7-F0 V; V = 5.99, B-V = +0.25), is also a small-
amplitude variable (see Rodriguez and Zerbi, IBVS No. 4170). HD
217924 (V = 7.3, B-V = +0.6; G0 V) shows no indications of
photometric variations greater than about 0.002 mag and seems to be
suitable as a comparison star for the study of 51 Peg."
1995 November 14 (6261) Daniel W. E. Green
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