Central Bureau for Astronomical Telegrams
IAUC 5716: alpha Ori; NO X-RAY PULSAR IN N63A
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Circular No. 5716
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
alpha ORIONIS
S. L. S. Yang, A. M. Larson, and A. W. Irwin, University of
Victoria; and G. A. H. Walker and A. R. Walker, University of
British Columbia, report: "Precise measurements of the relative
radial velocities of alpha Ori, made at the Dominion Astrophysical
Observatory using the hydrogen-fluoride absorption cell, confirm
the rapid increase reported by Hatzes and Cochran on IAUC 5713.
Between 1992 Oct. 26 and 1993 Jan. 19, the radial velocity increased
by almost 2.8 km/s. During the same period, there is also
a small 'filling in' of the Ca II triplet line at 866 nm. The
stellar surface temperature, as inferred from the changing equivalent
widths of lines, has also decreased by 565 +/- 170 K, which is
consistent with the about 0.45 mag drop in the brightness as
reported by Guinan et al. on IAUC 5708."
A. K. Dupree, Center for Astrophysics; E. Guinan, Villanova
University; and M. Smith, Computer Sciences Corporation and IUE
Observatory, report: "Our monitoring program of alpha Ori with
spectroscopy, photometry, and radial velocity measures indicates that
the current deep light minimum and radial velocity changes (see
IAUC 5708, 5713, and above) resemble the star's behavior during
1988/1989. Fading of alpha Ori in the visual and ultraviolet was
accompanied by local changes in the radial velocity of 6-7 km/s over
a 3 to 5-month time period. The current behavior of the supergiant
seems typical of variations observed with periods of about
400 days since the intensive monitoring began in 1984. Photospheric
radial velocity variations of about 6 km/s in 5 months are not
uncommon (see Smith et al. 1989, A.J. 98, 2233; Dupree et al. 1991,
ASP Conf. Ser. 11, 468)."
NO X-RAY PULSAR IN N63A
K. Dennerl and M. Kurster withdraw their claim of a pulsar in
N63A (cf. IAUC 5714), noting that "the pulsed emission was caused
by an instrumental effect, specifically that the observed modulation
is related to the spacecraft wobble. By coincidence, the center
of the N63A image was periodically covered by the wire intersections
within the PSPC support grid (a mesh of wires spaced by
2'.9) during the wobble motion, resulting in a maximum of shading,
while no such obscurations of the comparison source occurred. We
conclude that our previous interpretation that a pulsar is reponsible
for the variability can no longer be sustained. We apologize
for the inconvenience."
1993 March 1 (5716) Daniel W. E. Green
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