Central Bureau for Astronomical Telegrams
IAUC 4617: PSR 1957+20; V482 Cyg; MARS
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Circular No. 4617
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
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
PSR 1957+20
A. S. Fruchter, J. E. Gunn, S. G. Djorgovski, S. R. Kulkarni and
A. Dressler communicate: "We wish to report the detection of an
optical counterpart to the eclipsing millisecond pulsar, PSR 1957+20.
Using the Palomar 1.5-m reflector on the night of May 8, and the 5-m
reflector on the nights of May 9-11, we found a variable star of
maximum apparent visual mag 20.5 at the position R.A. = 19h57m25s.0,
Decl. = +20D39'59" (equinox 1950.0), which is consistent with the
pulsar VLA position obtained by M. Goss. The optical counterpart
varies by at least a factor of five in intensity over the course of
the 9.16-hour pulsar orbit, with minimum light occurring during pulsar
eclipse. The inaccuracy in the estimate of the variation is caused by
the presence of a comparably bright background star less than 1" away.
The color temperature of the object, about 4500 K (uncorrected for
reddening), does not vary appreciably during the orbit. A short
spectrum showed no evidence of strong emission lines."
V482 CYGNI
G. M. Hurst, Basingstoke, England; and G. Poyner, Birmingham,
England, independently report a sudden fading of this R CrB-type star,
the second in six months (cf. IAUC 4511). Visual magnitude estimates:
Feb. 21.19 UT, 12.9 (P. Schmeer, Bischmisheim, West Germany); Mar.
28.2, 11.9 (A. Mizser, Budapest, Hungary); Apr. 11.11, 12.4 (Schmeer);
19.08, 11.9 (Schmeer); May 22.05, 11.6 (M. Verdenet, Bourbon-Lancy,
France); June 14.94, 11.3 (Poyner); 15.94, 11.7 (Hurst); 18.99, 11.5
(Poyner); 22.95, 12.6 (Hurst); 23.00, 12.9 (Poyner).
MARS
Reports have been received of a major dust storm over the Martian
southern hemisphere, much in accord with the prediction by J. D. Beish
and D. C. Parker (1988, Sky Telescope 75, 370) for the onset of
activity near Hellas in early June. K. Rhea, Paragould, AR, noted a
small yellow patch in the northwest quadrant of Hellas as early as
June 7, and by the 13th it had expanded to Yaonis. On June 14 Beish
and Parker, Miami, FL, independently detected the feature, which
extended up to 7500 km by 2500 km during June 17-21; by the 23rd it
had become more diffused. On June 18 R. Schmude, Jr., College
Station, TX, reported the storm as centered at longitude 260 deg
latitude -50 deg, extending about 60 deg in longitude and 30 deg in
latitude; on the 19th the feature extended more than 90 deg.
1988 June 23 (4617) Brian G. Marsden
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