Central Bureau for Astronomical Telegrams
IAUC 2918: S Aps; X-RAY BURSTS FROM GALACTIC CENTER REGION; Cyg X-1; 1975e; V616 Mon
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Read IAUC 2919
Circular No. 2918
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
Western Union: RAPID SATELLITE CAMBMASS
S APODIS
A cablegram from the Carter Observatory reports that O. Hull
had observed this R CrB-type variable to have faded to visual
magnitude 10.7 on Feb. 24.59 UT.
X-RAY BURSTS FROM GALACTIC CENTER REGION
W. H. G. Lewin and the SAS-3 Group, Massachusetts Institute of
Technology, report: "Eleven x-ray bursts were observed from the
galactic center region between Feb. 7.8 and 13.9 UT. The bursts
must have come from at least two sources but probably more. If only two
sources are responsible for the 11 bursts, their positions are: l = -0o.27
+/- 0o.1, b = -0o.22 +/- 0o.1 (R.A. = 17h42m.6, Decl. = -29o16', equinox
1950.0) and l = -0o.72 +/- 0o.15, b = -0o.27 +/- 0o.1 (R.A. = 17h14m.7,
Decl. = -29o40', equinox 1950.0); eight bursts could have come from the
first location, six from the second. Three strong bursts (two of
them reported on IAUC 2911) showed very similar double-peak time
structure; not all bursts show this time structure. If we make the
assumption that only these three bursts come from one source, then
its position is within an area determined by: l = 0o.0, b = -0o.1;
l = -0o.3, b = -0o.2; l = -0o.3, b = -0o.3; l = 0o.0, b = -0o.2. SAS-3
observations of this region are continuing until about Mar. 7.
"On IAUC 2914 we reported a strong x-ray flare, presumably
from 3U 0614+09. In contrast to what the title suggested, we did
not mean to imply that this was an x-ray burst of the kind reported
here and on IAUC 2879, 2907, 2911 and 2915."
CYGNUS X-1
L. J. Kaluzienski, S. S. Holt, E. A. Boldt and P. J.
Serlemitsos, Goddard Space Fliqht Center, report that a significant
decrease (by at least a factor of two) in the 3-6 keV flux from Cyg
X-1 has been detected by the Ariel 5 all-sky monitor. Cyg X-1 has
been in a 'high state' since early Nov. 1975 (cf. IAUC 2863, 2879),
during which the mean intensity on timescales of a few days has
fluctuated between one and two times that of the Crab Nebula. The
decline commenced around Feb. 19.0, and the source remained at or
below this weaker level (0.6 times that of the Crab) until it
disappeared from the instrument's field of view around Feb. 24.5. It
is unclear at present whether the decrease signals a return to the
'low state' prior to Nov. 1975 or merely an extended low level
during the current 'high state'.
PERIODIC COMET SMIRNOVA-CHERNYKH (1975e)
The following precise positions have been reported:
1976 UT R. A. (1950) Decl. m1 Observer
Jan. 8.78278 13 49 50.26 - 4 54 31.3 16 Seki
8.81958 13 49 51.65 - 4 54 39.1 "
Feb. 5.31294 14 05 18.52 - 5 48 12.1 Shao
T. Seki (Kochi Observatory, Geisei Station). From Orient. Astron.
Assoc. Comet Bull. No. 118.
C. Y. Shao (Harvard College Observatory, Agassiz Station).
The following improved orbital elements, by B. G. Marsden, are
from 40 observations 1975 Mar. 4 to 1976 Feb. 5:
T = 1975 Aug. 6.4742 ET Epoch = 1975 Aug. 16.0 ET
Peri. = 90.2195 e = 0.145446
Node = 77.1024 1950.0 a = 4.174405 AU
Incl. = 6.6413 n = 0.1155612
q = 3.567253 AU P = 8.529 years
1976 ET R. A. (1950) Decl. Delta r m2
Apr. 12 13 51.81 - 3 52.7 2.674 3.668 17.8
22 13 45.46 - 3 26.0
May 2 13 39.32 - 3 04.8 2.714 3.684 17.8
12 13 33.96 - 2 51.8
22 13 29.79 - 2 48.5 2.861 3.701 18.0
June 1 13 27.09 - 2 55.4
11 13 26.01 - 3 12.4 3.091 3.718 18.2
21 13 26.55 - 3 39.0
July 1 13 28.68 - 4 14.0 3.373 3.737 18.4
11 13 32.27 - 4 56.4
21 13 37.19 - 5 44.8 3.677 3.756 18.6
31 13 43.31 - 6 38.3
Aug. 10 13 50.49 - 7 35.6 3.978 3.777 18.8
20 13 58.61 - 8 35.8
30 14 07.55 - 9 37.9 4.256 3.797 18.9
Sept. 9 14 17.21 -10 41.1
19 14 27.51 -11 44.6 4.497 3.819 19.1
m2 = 10.0 + 5 log Delta + 10 log r
V616 MONOCEROTIS
J. Bortle, Brooks Observatory, provides further visual magnitude
estimates as follows: Jan. 19.04 UT, 13.4; 29.03, 13.1; Feb.
3.03, 13.2; 8.02, 13.0; 10.09, 13.0; 21.04, 13.1; 29.03, 13.1.
1976 March 1 (2918) Brian G. Marsden
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