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IAUC 5934: A0535+26; N Cas 1993

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                                                  Circular No. 5934
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)


A0535+26
     M. H. Finger, Computer Sciences Corporation; and R. B. Wilson
and B. A. Harmon, NASA/Marshall Space Flight Center, report for the
BATSE/Compton GRO Observatory team: "The hard x-ray flux currently
being observed from the x-ray binary pulsar A0535+26 (IAUC 5931, 5933)
has significant aperiodic variability in addition to coherent pulsations.
Power spectra contain the pulsed component and an underlying continuum
with a significant bump between approximately 20 and 80 mHz, in both
the 20-50 and 50-100 keV energy bands.  The continuum in the 20-50 keV
power spectra on Feb. 9 and 12 has been fitted with a sum of power-law
and gaussian components.  On both days the power-law component has an
index of near 1.0 and a fractional RMS (10-500 mHz) near 20 percent.
On Feb. 9 the bump was centered at 50 +/- 1 mHz, had an FWHM of
28 +/- 3 mHz and a fractional RMS of 14.1 +/- 0.5 percent.  On Feb. 12
the bump was centered at 65 +/- 1 mHz, had a FWHM of 37 +/- 3 mHz and a
fractional RMS of 11.6 +/- 0.4 percent.  The 20-40 keV flux increased
from 3.1 +/- 0.2 Crab on Feb. 9 to 5.6 +/- 0.2 Crab on Feb. 12.  The
shift in center frequency is therefore consistent with the luminosity
dependence predicted by the beat-frequency QPO model (Alpar and Shaham
1985, Nature 316, 239).  Both the total and pulsed flux have continued
to increase.  On Feb. 14 the 20-40 keV total flux was 6.2 +/- 0.1 Crab,
and the phase-averaged pulsed flux was 1.6 +/- 0.1 Crab (total)."


NOVA CASSIOPEIAE 1993
     Recent visual magnitude estimates indicate that the nova is
now fading rapidly: Feb. 1.13 UT, 8.0 (J. Pleszka, Cracow, Poland);
2.12, 8.3 (C. E. Spratt, Victoria, BC); 3.09, 8.4 (J. D. Shanklin,
Cambridge, England); 4.72, 8.5 (A. Lauvstad, Levanger, Norway);
5.86, 8.3 (P. Rapavy, Rimavska Sobota, Slovakia); 6.76, 8.2
(M. Verdenet, Bourbon-Lancy, France); 8.02, 8.2 (G. W. Kronk, Troy,
IL); 9.11, 8.1 (R. Royer, Lakewood, CA); 10.23, 8.3 (P. Schmeer,
Bischmisheim, Germany); 12.03, 8.5 (R. Hays, Worth, IL); 12.80,
8.4 (B. H. Granslo, Fjellhamar, Norway); 13.10, 8.6 (Royer);
13.73, 9.0 (Granslo); 14.76, 9.0 (Schmeer); 15.06, 9.2 (W. G.
Dillon, Missouri City, TX); 15.78, 9.6 (Granslo); 16.04, 9.9 (Hays);
16.78, 10.1 (Schmeer); 17.06, 10.1 (Dillon); 17.77, 10.5 (T. Vanmunster,
Landen, Belgium).


1994 February 17               (5934)              Brian G. Marsden

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