Central Bureau for Astronomical Telegrams
IAUC 3078: X-RAY SOURCES; AR Lac
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Read IAUC 3079
Circular No. 3078
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Cable Address: SATELLITES, NEWYORK Telex: 921428
Telephone: (617) 864-5758
X-RAY SOURCES
The SAS-3 Group, Massachusetts Institute of Technology, will
continuously observe x-ray burst sources during June 7-24, July 8-24
and July 27-30 simultaneously with ground-based observatories.
A preliminary observing schedule (eight sources), along with source
positions and logistic details, have been sent to all participants
currently known (30 observatories). Those interested who have not
yet contacted M.I.T. should telephone (617) 253-4282 (alternative
numbers, the first digits identical, are -7525, -5842, -3182 and
-3184), or they can telex to W. H. G. Lewin, Room 37-627, Telex No.
921473 (answerback code MIT CAM), Cambridge, Mass., U.S.A.
G. Ricker and F. Primini, M.I.T. SAS-3 Group, report a strong
recurrence of the transient x-ray source A0535+26. During the interval
May 20.25-21.25 UT the source brightness (2-20 keV) ranged
from < 0.2 Crab to ~ 0.5 Crab. The source was not detected (< 0.2
Crab) during the period May 12.7-15.5 UT
M. G. Watson and J. P. Pye, Ariel 5 Group, University of
Leicester, report that the ssi light curve of 3U 1538-52 shows a
clear eclipse-like modulation with zero phase on 1976 Nov. 12.13 +/-
0.15 UT and a period of 3.73 +/- 0.01 days, confirming the result by
Becker et al. (IAUC 3039, 3054). P. J. N. Davison, Mullard Space
Science Laboratory, adds that combination of Ariel 5 Experiment C
data (spanning Apr. 23-25) with the Ariel 5 ssi and OSO-8 observations
yields an improved period of 3.730 +/- 0.002 days. The change
in center-of-mass pulsation period between Aug. 1976 and Apr. 1977
is +0.36 +/- 0.39 seconds.
AR LACERTAE
B. W. Bopp and M. Schmitz, University of Toledo, write: "Image-tube
spectrograms (dispersion 40 A/mm) of the H-alpha region of AR Lac
were obtained at Ritter Observatory on May 13.4 UT, immediately
following the giant radio outburst reported to us by P. A. Feldman,
Herzberg Institute of Astrophysics. The H-alpha profile at this phase
(~ 0.7) is broad and diffuse, with absorption components from both
the hotter and cooler stars barely resolved. There is no convincing
evidence for emission on our spectra, but the H-alpha absorption feature
from the cooler K0 star appears weak and possibly filled in."
1977 May 24 (3078) Brian G. Marsden
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