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IAUC 3541: TT Ari; Cyg X-1

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IAUC number 

                                                  Circular No. 3541
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 617-864-5758


TT ARIETIS
     J. E. Bortle, Stormville, New York, reports that a visual
observation of this novalike variable (R.A. = 2h04m10s, Decl. = +15o02'.6,
equinox 1950.0) on Nov. 17.030 UT found the star at mv > 14; W. M.
Lowder, Tuckahoe, New York, confirmed this finding.  Bortle last
had observed TT Ari in 1980 Apr. at mv ~ 11.5.

     E. Waagen, American Association of Variable Star Observers,
informs us that AAVSO observations during the last 10 years and data
reported by H. Huth (1960, Mitteilungen uber Verinderliche Sterne
No. 454, Sonneberg) dating back to 1929 show that TT Ari has
remained in the visual magnitude range 10.2-11.8, indicating that
this apparent decrease in brightness is highly atypical of the
star.

     J. Krautter, Landessternwarte, Heidelberg, telexes that he;
G. Klare and B. Wolf, Landessternwarte, Heidelberg; N. Vogt, European
Southern Observatory; and J. Rahe and W. Wargau, Remeis-Sternwarte,
Bamberg, observed TT Ari with the International Ultraviolet
Explorer at the European Space Agency Ground Station in Villafranca,
Spain, on Nov. 17.  Measurements with the fine error sensor show
the star to be extraordinarily faint at mv = 14.5, an observation
confirmed photographically by Klare at the Landessternwarte, Heidelberg.
An IUE swp-spectrum in the 120.0-200.0-nm region shows a
strong ultraviolet continuum, with strong C IV emission and weak
emission of C II, Si IV, N IV, Si II and Al III.  The character of
the line spectrum has changed radically from that of earlier
ultraviolet observations made when TT Ari was brighter (mv ~ 11).  The
spectrum now is similar to that of a dwarf nova.


CYGNUS X-1
     N. Oda and the Hakucho Team, Institute of Space and Aeronautical
Science, University of Tokyo, communicate: "Hakucho observed a
short transition from low to high state between Nov. 8.12 and 10.00
UT of what is probably Cyg X-1.  The peak intensity was ~ 2 times
the Crab over the range 1-12 keV on Nov. 10.  The intensity declined
to ~ 1 Crab on Nov. 11 and recovered to low level on Nov. 12.
The last transition of Cyg X-1 to its high state occurred between
1980 May and June, and it then returned to low state in mid-July
(cf. IAUC 3491 and 3502)."


1980 November 19               (3541)              Daniel W. E. Green

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