Central Bureau for Astronomical Telegrams
IAUC 3428: INFRARED/OPTICAL/X-RAY OBSERYATIONS IN 1980; V471 Tau
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Circular No. 3428
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 617-864-5758
INFRARED/OPTICAL/X-RAY OBSERYATIONS IN 1980
W. Lewin and L. Cominsky, Massachusetts Institute of Technology,
write: "We recently invited optical astronomers to participate
in the 1980 simultaneous optical and x-ray observations of burst
sources (IAUC 3420). We heard from A. W. Jones et al. of confirmation
of the detection of infrared bursts from the Rapid Burster
(IAUC 3344; Kulkarni et al. 1979, Nature 280, 819). The average
luminosity at 2.2 um in the ~ 0.4-um bandwidth was ~ 10**30 J/s
(assumed isotropic emission). These extremely bright infrared bursts
are suspected to be associated with the Type I x-ray bursts from
the Rapid Burster that repeat on a timescale of hours; Type II
bursts repeat on a timescale of minutes or less (Nature 1978, 271,
630). If the infrared bursts are associated with Type I bursts,
they are also expected from other Type I burst sources, and they
would be much easier to detect than the optical bursts. Thus we
also urge infrared astronomers to participate in the 1980 worldwide
burst observations (IAUC 3420). To date, no infrared bursts have
been detected from the Rapid Burster simultaneously with x-ray
bursts, and the nature of the infrared bursts is still uncertain.
The next opportunity to make simultaneous infrared/x-ray observations
is expected to come some time in 1980 Feb.-Apr., when the
Rapid Burster is due for its next turn-on."
V471 TAURI
E. F. Guinan and E. M. Sion, Department of Astronomy, Villanova
University, write: "Three IUE short-wave spectra of the Hyades
white-dwarf eclipsing binary V471 Tau = BD +16 516 taken on Aug. 24
and Sept. 22 reveal the presence of a strong C IV 155.0-nm absorption
feature. The distribution of flux F_nu increases into the
ultraviolet, indicating that the emergent radiation arises from a hot
stellar photosphere, not from an accretion disk. This observation
represents the first detection of a metal line in the spectrum of a
hot white dwarf (Teff > 2 x 10**5 K). In addition, strong L-alpha
absorption is seen, and a Si IV 139.4-nm absorption feature may also be
present. The long-wave spectra in and out of eclipse exhibit strong
Mg II h + k 280-nm emission, presumably of chromospheric origin from
the K star. This system has an important bearing on the atmospheric
composition of hot white dwarfs and on the nature of novalike
variables. In addition, the cool component has several characteristics
in common with RS CVn variables."
1979 December 10 (3428) Brian G. Marsden
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