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IAUC 4027: HT Cas; RZ Leo; PKS 0537-441

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                                                  Circular No. 4027
Central Bureau for Astronomical Telegrams
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

     J. A. Mattei, AAVSO, reports that the dwarf nova HT Cas, not
definitely seen brighter than mag 14.0 since 1980 Mar. 13, is having
a bright outburst.  T. Kinnunen, Turku, Finland, independently
reported the outburst via G. Hurst in England, the latter finding
the star at mv = 11.9 on Jan. 13.80 UT.  AAVSO observations show
the object at mv = 13.2 on Jan. 12.2 UT; during Jan. 13-15, it
varied between mv = 10.8 and 12.6.  This star shows deep eclipses (1
to 2.5 magnitudes) which occur with orbital period 1h47m; eclipses
last 10 min.  The equation for mid-eclipse is: JD (heliocentric) =
2443727.937 +/- 0.07364722 E.  Very frequent (30-s) high-speed
photometry in search of superhumps is strongly urged.

     S. Cristiani, H. W. Duerbeck, and W. C. Seitter, European
Southern Observatory, report that a spectrum of RZ Leo was obtained
on Jan. 11.3 UT with the La Silla 2.2-m telescope.  In the range
380-540 nm, relatively weak and broad (fw 3500 km/s) emission lines
(probably double peaked, with peak separation 1800 km/s) of H beta,
H gamma, and H delta are seen, the latter two surrounded by shallow
absorption troughs (fw 5500 km/s); these are all superimposed on a strong
continuum.  The star was at an estimated magnitude 14.5.  RZ Leo
resembles a dwarf nova in its declining stage; its spectral appearance
and long cycle length make membership in the WZ-Sge sub-group
of dwarf novae likely (cf. IAUC 4026).

     Visual magnitude estimate by C. Scovil, Stamford, CT (provided
via Mattei): Jan. 13.345 UT, 14.0.

PKS 0537-441
     Cristiani also communicates: "The quasar PKS 0537-441 (z =
0.894) is at present in an outburst phase.  It was measured, with a
photoelectric photometer at the ESO 1-m telescope, on 3 occasions
between 1983 Nov. 30 and Dec. 4, providing V = 15.34, U-B = +0.56,
B-V = +0.51, V-R = +0.45, and V-I = +1.07.  CCD photometry on 1985
Jan. 10 gives V = 14.0; several spectra at 0.12-nm resolution show
no trace of the Mg II 279.8-nm line, which at present seems lost in
the continuum.  PKS 0537-441 has apparently turned into a classical
BL Lac object."

1985 January 16                (4027)            Daniel W. E. Green

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