Central Bureau for Astronomical Telegrams
IAUC 3923: Her X-1; H0139-68
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Circular No. 3923
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
HERCULES X-1
J. Trumper, P. Kahabka, H. Ogelman, W. Pietsch and W. Voges,
Max-Planck-Institut fur Extraterrestrische Physik, Garching; and
M. Gottwald and A. Parmer, EXOSAT Observatory Team, telex: "EXOSAT
observations of Her X-1 = HZ Her during Mar. 1.5-1.8 UT detected
the source in the high state with an average flux of ~ 80 Uhuru
flux units in the 1-10-keV range. Preliminary analysis indicates
strong 1.24-s pulsations. The last detection of the 35-day on-off
cycle was reported by Tenma for the period 1983 May 20-June 1
(IAUC 3852). Ten different subsequent observations by EXOSAT
between 1983 June 28.1 and Oct. 22.9 had failed to detect any on-
state of the 35-day cycle, suggesting that the source had entered
a prolonged off-state (IAUC 3841 and subsequent observations). We
are currently observing a complete cycle of Her X-1 at ~ 4-day
intervals. We urge optical observers to monitor this source."
H0139-68
N. Visvanathan, M. S. Bessell and D. T. Wickramasinghe, Mount
Stromlo Observatory, telex: "Our photometric and spectroscopic
observations at the Anglo-Australian Telescope on 1983 Sept. 25, Oct.
24 and Dec. 15 show that the AM-Her system H0139-68 (cf. IAUC 3833)
continued to be in an unusually active state. Magnitudes were:
Sept. 25, V = 17.64, [1.05 microns] = 15.58; Dec. 15, 17.29, 15.42. On
Oct. 24 (when V was estimated at 17.0) the spectrum in the range
510-885 nm obtained with the aid of the faint-object red spectrograph
and CCD detector revealed the TiO bands at 759, 843 and 705
nm, as well as a weak CaH+TiO feature centered near 660 nm. The
continuum fell from 885 to 660 nm, then rose quickly toward 510
nm, indicating that the spectral region near 510-540 nm is dominated
by the white dwarf and that the spectral region redward of 660
nm is dominated by the late-type star. The depth of the 759-nm TiO
bands gives the spectral type of the secondary as dM3-4. This is
the second AM-Her-type system for which the characteristics of the
secondary star have been determined. Assuming that our [1.05 microns]
magnitude is little contaminated by the white dwarf and cyclotron
components of the system--this is indicated by the constancy of
[1.05 microns] in Sept. and Dec.--we derive a distance modulus for the
H0139-68 system as 6.1 mag, which corresponds to 166 pc. An absolute
visual magnitude of 12.2 has been assumed for the secondary."
1984 March 8 (3923) Brian G. Marsden
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