Central Bureau for Astronomical Telegrams
IAUC 4633: R CrB; 1987A; EXO 0748-676
The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).
Read IAUC 4634
Circular No. 4633
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
R CORONAE BOREALIS
This variable star is slowly declining in brightness, as
indicated by the following photoelectric and visual photometry.
W. A. Lawson, P. Kilmartin, and A. Gilmore report UBV photometry
obtained at Mount John Observatory with the 0.6-m photometric
reflector: June 14.43 UT, V = 5.83, U-B = +0.14, B-V =
+0.59; 24.44, 5.94, -, +0.59; July 1.38, 5.93, +0.13, +0.58; 12.37,
6.01, +0.33, +0.53; 20.35, 6.43, +0.16, +0.52. Photometry by K.
Krisciunas at Mauna Kea on July 18.36 yields V = 6.33 +/- 0.02,
B-V = +0.54 +/- 0.05. Visual magnitude estimates: July 11.94, 6.2 (J.
Shanklin, Cambridge, England); 12.90, 6.0 (P. Schmeer, Bischmisheim,
W. Germany); 14.20, 6.2 (E. Waagen, Cambridge, MA); 15.16, 6.2 (E.
Mayer, Barberton, OH); 16.16, 6.3 (P. Collins, Scottsdale, AZ);
17.20, 6.4 (C. Scovil, Stamford, CT); 18.91, 6.4 (Shanklin); 19.38,
6.1 (P. Williams, Heathcote, N.S.W.); 19.98, 6.5 (A. Pereira,
Obeceixe, Portugal); 20.93, 6.2 (Pereira); 22.16, 6.5 (Mayer);
22.89, 6.9 (Schmeer); 23.13, 6.7 (D. Levy, Tucson, AZ);
24.10, 6.7 (P. Sventek, Houston, TX); 25.08, 6.8 (R. Browning,
Audubon Park, NJ); 25.10, 7.0 (Sventek); 26.01, 7.1 (Schmeer).
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
D. Allen, W. Couch, and D. Malin, Anglo-Australian Observatory,
write: ''An AAT plate of the light echo taken on July 15 by R.
Sharples shows the outer ring to be appreciably eccentric about the
supernova. The radius ranges from 64" to 68". The greatest
displacement is in the direction of 30 Dor, suggesting that the sheet
of material being illuminated forms a shell centered on that region.
On this assumption, we compute that the supernova is between 10 and
230 pc more distant than 30 Dor, with a best estimate of 140 pc.
The radius of the shell around 30 Dor is 370 pc or 25'."
Visual magnitude estimates by R. H. McNaught, Siding Spring
Observatory: June 21.50 UT, 7.9; 23.80, 8.0; 26.37, 8.0; July 16.73, 8.5.
EXO 0748-676
F. Makino and the Ginga Team telex that the transient eclipsing
x-ray burster EXO 0748-676 (cf. Parmar et al. 1986, Ap.J. 308, 199)
was active on July 21 and 22, as found in the scanned data obtained
with the Large-Area Counter aboard Ginga. The x-ray intensity
varied in the range 5 to 15 mCrab.
1988 July 26 (4633) Daniel W. E. Green
Read IAUC 4634
Our Web policy. Index to the CBAT/MPC/ICQ pages.
