Central Bureau for Astronomical Telegrams
IAUC 5523: N Cyg 1992
The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).
Read IAUC 5524
Circular No. 5523
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 CYGNI 1992
S. N. Shore, Goddard High Resolution Spectrograph, Computer
Sciences Corporation; S. G. Starrfield and S. J. Austin, Arizona
State University; R. Gonzales-Riestra, International Ultraviolet
Explorer (IUE) Observatory, European Space Agency, Madrid; G.
Sonneborn, Goddard Space Flight Center; and R. M. Wagner, Ohio
State University, report: "Observations with the IUE satellite
show that the ultraviolet spectrum of Nova Cyg 1992 has exhibited
considerable evolution since our last report (IAUC 5461). We have
obtained both low- and high-dispersion spectra on, at least, weekly
intervals since discovery and find that the 120- to 200-nm flux
maximum occurred between Apr. 5 and 20. This is about 6 weeks after
maximum light occurred in the optical. The blanketing produced
by the overlapping iron-peak lines has disappeared. Our May 9.8 UT
spectrum (120-200 nm) displays resonance transition P Cyg lines of
N V 124.0 nm, Si IV 140.0 nm, C IV 155.0 nm, and emission lines
from inter-combination transitions, especially O III] 166.0 nm, N
III] 175.0 nm (the strongest line in the spectrum), and C III]
191.0 nm. Si III] 189.5 nm, N IV] 148.7 nm, O I 130.0 nm, O V
137.1 nm, and He II 164.0 nm are also present and very broad. Ly-
alpha is seen in emission with a strong interstellar absorption
feature and possibly a P-Cyg profile. The 200-340 nm spectrum is
dominated by Mg II 280.0 nm. The FWHM of this line is 2400 km/s,
as are the short wavelength inter-combination lines, while the
terminal velocity of the P-Cyg absorption troughs is about 4600 km/s.
There is no evidence for the O III Bowen fluorescence lines at
313.3 nm. The integrated ultraviolet and optical flux (120-900 nm)
is 2.4 x 10E-8 erg cmE-2 sE-1. The ultraviolet spectrum of Nova
Cyg now closely resembles post-maximum spectra of ONeMg novae such
as Nova LMC 1990 No. 1 and Nova Her 1991 and, therefore, we identify
this nova as a probable ONeMg nova. The flux ratio of He II
164.0 nm to He II 468.6 nm (obtained using the OSU CCD spectrograph
on the Perkins 1.8-m telescope at the Lowell Observatory: see IAUC
5522) is 1.6, indicating a reddening E(B-V) = 0.2-0.4 (Case B
recombination) and implying an H I column density of order 10E21
cmE-2. Assuming that at maximum the nova reached the Eddington
luminosity for a 1-solar-mass white dwarf, its distance is from 1
to 2 kpc, making it the closest ONeMg nova. Regular monitoring
with IUE is continuing."
1992 May 16 (5523) Daniel W. E. Green
Read IAUC 5524
Our Web policy. Index to the CBAT/MPC/ICQ pages.
