Central Bureau for Astronomical Telegrams
IAUC 4039: EXO 0748-676; T Tau
The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).
Read IAUC 4040
Circular No. 4039
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
EXO 0748-676
A. N. Parmar, N. E. White, P. Giommi and F. Haberl, EXOSAT
Observatory, telex: "EXOSAT discovered a bright (0.03 Crab) transient
x-ray source on Feb. 15. The preliminary position is R.A. =
07h48m24s5, Decl. = -67deg37'23" (equinox 1950.0), with an error radius
of 15". The source shows bursts, irregular intensity dips and
periodic total eclipses. The first observed eclipse was centered
on Feb. 15d01h46m57s UT (barycentric), with a duration of 500 s.
The eclipses recur with a period of 3.824 +/- 0.001 hr. The intensity
dips occur between phases 0.5 and 1.0, where 0.0 is the center
of eclipse. Further EXOSAT observations are planned to follow
the evolution of the outburst, and an optical search of the error
region is strongly urged. A further observation on Feb. 19 showed
the source to be at a similar intensity level."
H. Pedersen, European Southern Observatory; and M. Mayor,
Geneva Observatory, using CCD photometry obtained at the 1.54-m
Danish telescope at La Silla, have identified EXO 0748-676 with a
blue variable star at a position consistent with that of the x-ray
source. At maximum V = 16.9, B-V = +0.1. The source was followed
during Feb. 19d01h22m-19d06h41m UT using a time resolution of 5
min. During this period there were two eclipses, and the times
fit the x-ray ephemeris; the amplitude of variability is 0.6 mag.
T TAURI
M. Karovska, P. Nisenson, R. Noyes, C. Papaliolios and R.
Stachnik, Center for Astrophysics, write: "Speckle image
reconstructions of T Tau show a second, unresolved source located ~
0"35 from T Tau at p.a. ~ 5 deg. The source was first detected at
the Steward Observatory's 2.3-m telescope in 1983 Nov., and it was
detected again using the 2.5-m telescope at Mt. Wilson Observatory
in 1984 Nov., thus confirming its reality. Both sets of data were
obtained through broad-band filters centered near 660 nm (and including
H=alpha), using a two-dimensional photon-counting PAPA detector.
The source appears to be ~ 4 mag fainter than T Tau itself in
this wavelength band. We note that this appears to be a third
component of the T Tau system; it is not the object reported by
infrared and radio observers as being south of T Tau. Further
optical or infrared observations of T Tau during the remainder of
this observing season would be most useful."
1985 February 22 (4039) Brian G. Marsden
Read IAUC 4040
Our Web policy. Index to the CBAT/MPC/ICQ pages.
