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IAUC 3208: A0535+26; MXB1730-335; AR AND HK Lac; HD 165590

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IAUC number

                                                  Circular No. 3208
Central Bureau for Astronomical Telegrams
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

     G. Clark and M. Chartres, Massachusetts Institute of Technology,
report that SAS 3 has recorded a flare-up of the recurrent
transient pulsating x-ray source A0535+26.  The flare-up began
about Apr. 10d07h UT, and the flux reached 0.4 Crab by Apr. 12d12h.
Optical observations of the probable optical counterpart HDE
245770 during this x-ray outburst are desirable.

     H. Marshall and W. Lewin, Massachusetts Institute of Technology,
have continued to observe the Rapid Burster (cf. IAUC 3204)
with SAS 3 for ~ 35 seconds every ~ 94 min (i.e., for a total of
500 seconds daily).  The number of bursts detected on consecutive
days from Mar. 30 to Apr. 11 was 6, 8, 8, 9, 14, 8, 5, 1?, 2, 1?,
0, 0 and 0.  It may well be that the burst activity has stopped.
The observations are continuing.

     F. Walter, P. Charles and S. Bowyer, Space Sciences Laboratory,
University of California at Berkeley, report the detection of soft
x-rays from the RS CVn systems AR Lac and HK Lac using the low-energy
detectors of the A2 experiment aboard HEAO 1.  The observations
occurred between 1977 Dec. 19 and 22 inclusive.  The sources
are slightly confused because of their 1o.5 separation.  Assuming
distances of 50 and 150 pc, respectively, source luminosities (0.15-2.8 keV)
were derived to be (10 +/- 3) x 10**30 erg/s for AR Lac and (8
+/- 3) x 10**31 erg/s for HK Lac.  These are consistent with the
luminosities observed from other active RS CVn systems (cf. IAUC 3173).

HD 165590
     C. L. Morbey, A. H. Batten and J. M. Fletcher, Dominion
Astrophysical Observatory, report that recent observations of this
high-e visual binary (cf. IAUC 3088) show that periastron will occur
later than indicated by Van Biesbroeck's (1954, Publ. Yerkes Obs. 8,
317) elements.  A change of 14 km/s in the usually constant radial
velocity component has been observed over the past year.

1978 April 13                  (3208)              Brian G. Marsden

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