Central Bureau for Astronomical Telegrams
IAUC 4486: EXO 033319-2554.2; 1987A
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Circular No. 4486
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 033319-2554.2
P. Giommi, L. Angelini, J. Osborne, L. Stella, and G.
Tagliaferri, EXOSAT Observatory, report: "The soft X-ray source
EXO 033319-2554.2, serendipitously discovered in two EXOSAT CMA
observations at R.A. = 3h33m19.9, Decl. = -25 54'14" (equinox 1950.0; error
radius 20"), shows a 100-percent modulation of its x-ray flux with
a period of 127.6 +/- 3.0 min. The lightcurve displays an on-off
behavior similar to that of VV Pup, with the bright part of the cycle
lasting 0.56 in phase. It also shows an eclipse-like feature,
lasting 8.0 +/- 0.5 min with unresolved ingress and egress, 0.13 in
phase after maximum intensity. Bright phase countrates were 0.71
and 0.65 cts/s in 1983 Aug. (polypropylene filter) and 1986 Jan.
(3000 lexan filter), respectively. The soft x-ray color is
inconsistent with blackbody temperatures > 25 eV. No detection was
achieved in the medium energy experiment (the 90-percent confidence
upper limit to the bright phase countrate is 1.0 cts/s/half). K.
Beuermann, Max-Planck-Institut fur Extraterrestrische Physik,
Garching; and H.-C. Thomas, Max-Planck-Institut fur Astrophysik,
Garching, report low resolution (2.0 nm FWHM) CCD spectrophotometry
of the only candidate counterpart visible on the POSS plate, using
the ESO/MPI 2.2-m telescope at La Silla on 1987 Oct. 20 and 22.
The optical spectrum was characterized by a variable blue continuum,
very weak Balmer emission lines (equivalent widths of H-alpha and H-beta
were 1.0 and < 0.2 nm, respectively), and pronounced TiO features.
The integrated flux showed recurrent dips which indicate a period
of 126.5 +/- 0.5 min. The x-ray and optical properties of EXO
033319-2554.2 strongly suggest that this source is an AM-Her-type
binary system which was in a low state at the time of the optical
observations. In particular, the nature and position of the 8-min
eclipse-like feature seen in the soft x-ray lightcurve suggests
that this could be the second AM-Her system in which an eclipse by
the companion occurs."
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
M. Hamuy and M. Phillips, Cerro Tololo Interamerican Observatory,
telex: "In agreement with the report on IAUC 4485, we have
not yet observed any significant deviation from a linear decay rate
of the bolometric lightcurve of SN 1987A. Specifically, we do not
confirm the change in slope of the V lightcurve since day 248 as
reported by Meatheringham et al. on IAUC 4482."
1987 November 13 (4486) Daniel W. E. Green
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