Central Bureau for Astronomical Telegrams
IAUC 4172: EXO 020528+1454.8; VERY BLUE Var IN Ori
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Circular No. 4172
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
EXO 020528+1454.8
R. Hudec, Ondrejov Observatory; and W. Wenzel, Sonneberg
Observatory, telex: "A new, soft x-ray source, EXO 020528+1454.8 (R.A. =
2h05m28s2, Decl. = +14deg54'49"2, equinox 1950.0; error radius 15" ),
was observed by the EXOSAT low-energy experiment during 1985 Aug. 20.7
21.1 UT. The source, which lies only 21' from the observed target
TT Ari, had an intensity of ~ 1 mCrab and was found on exposures
taken both with thin Lexan (0.013 +/- 0.001 cts/s) and Al/parylene
filters (0.01 +/- 0.002 cts/s). The x-ray lightcurve shows some
hints of variability, but there is no obvious orbital modulation.
No source was observed by K. Beuermann (private communication) at
this position, to a limit of a few thin-Lexan mcts/s, on 1983 Dec.
2 and 6 and 1985 Jan. 18, suggesting that it is either transient
or highly variable. The error box contains a reddish possible
optical counterpart that seems to vary over B = 15.3-16.0 (on plates
taken by B. Fuhrmann, W. Gotz, G. Hacke, A. Mrkos and G. A. Richter),
but without obvious relation to the x-ray activity. Sonneberg
Schmidt plates taken by Gotz show that this object is a close
pair. No other candidates were seen down to mag 16 on plates
taken at the time of the x-ray observations."
VERY BLUE VARIABLE IN ORION
J. Maza, University of Chile, write: "H. Hamuy and I report
the discovery of a very blue variable star, located near the Seyfert
1 galaxy Arakelian 120, at R.A. = 5h13m53s16, Decl. = -0deg15'28"5
(equinox 1950.0). Fourteen UBVRI photometric observations made
during 1985 Feb.-1986 Jan. at Cerro Tololo Interamerican Observatory
show mean V = 14.08 and mean colors U-B = -0.82, B-V = +0.05,
V-R = +0.08, R-I = +0.11. V varies between 13.95 and 14.28, U-B
between -0.70 and -0.93, and the other colors show smaller variations.
Differential UBV photometry carried out at 5-min intervals
over the course of two hours on 1986 Jan. 13 shows rapid variations
of 0.1 in V, even between consecutive observations; U-B shows rapid
variations of as much as 0.2. It appears that the star gets bluer
when it brightens. A spectrogram (range 400-700 nm) obtained on
1985 Apr. 26 by M. T. Ruiz and myself with the CTIO 1.5-m telescope
and SIT-vidicon shows a featureless blue continuum; it is rather
noisy, and neither emission nor absorption lines can be inferred."
1986 January 31 (4172) Brian G. Marsden
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