Central Bureau for Astronomical Telegrams
IAUC 5938: N Cas 1993; PSR 0329+54
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Circular No. 5938
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)
NOVA CASSIOPEIAE 1993
S. N. Shore, Indiana University, South Bend; S. Starrfield
and P. Hauschildt, Arizona State University; R. Gonzalez-Riestra,
IUE Observatory, Vilspa; and G. Sonneborn, NASA/Goddard Space Flight
Center, report: "Observations of Nova Cas 1993 with the IUE Satellite
have confirmed the formation of dust (IAUC 5925, 5936) in the nova
ejecta during the deep optical decline that is now underway (IAUC
5934). Spectra obtained on Feb. 18.1 and 19.5 UT show that the
120-200-nm portion of the spectrum has declined by more than a factor
of ten since Feb. 11.2 UT with virtually no change in the absorption
line opacity; the entire wavelength interval has been uniformly
depressed. The longer-wavelength portion of the spectrum, 220-340 nm,
exhibits depression by more than a factor of 20 in comparison
to Feb. 11.5, with a broad peak in the extinction near Mg II 280 nm.
The Feb. 18.3 long-wavelength spectra now show the C II 232-nm
multiplet in emission, one of the few changes in the line spectrum
during the past two weeks. There is no evidence for either enhanced
absorption near 220 nm or for a steep short-wavelength rise.
Therefore, the observed extinction, from the circumstellar dust
that has just formed in the nova ejecta, does not resemble typical
interstellar dust. The most likely explanation is that these grains
are larger than normal interstellar dust. If the drop in the emitted
radiation in the ultraviolet and optical is compensated by an increase
in the infrared radiation as expected (cf. Gehrz 1988, Ann. Rev.
Astron. Astrophys. 26, 377), the integrated infrared flux longward
of 1 micron should reach of order 8*10**-8 erg cm-2 s-1 (based on the
ultraviolet flux depression). We have used E(B-V) = 0.5 to correct for the
interstellar (not circumstellar) extinction. Before the decline began,
the 120-340-nm continuum contained the bulk of the luminosity. The
bolometric luminosity of the nova has been constant to within about 10
percent from 1993 Dec. 15 to 1994 Feb. 11. It likely still is, except
that it is now hidden by the enhanced extinction produced by the
increasingly opaque circumstellar dust."
PSR 0329+54
In the item by Dagkesamansky and Shitov on IAUC 5930, it
should have been made clear that the possibility of a 1110-day periodicity has
been studied earlier (Demiansky and Proszynski 1979, Nature 282, 383;
Cordes and Downs 1985, Ap.J. Suppl. 59, 343; Bailes, Lyne and Shemar
1993, ASP Conf. Ser. 36, 19).
1994 February 21 (5938) Brian G. Marsden
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