Central Bureau for Astronomical Telegrams
IAUC 7677: WZ Sge; V2274 Cyg
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Circular No. 7677
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)
WZ SAGITTAE
P. J. Wheatley, University of Leicester; E. Kuulkers, Space
Research Organization Netherlands (SRON) and Utrecht University;
J. J. Drake, Smithsonian Astrophysical Observatory; J. S. Kaastra,
SRON; C. W. Mauche, Lawrence Livermore National Laboratory; S. G.
Starrfield, Arizona State University; and R. M. Wagner, University
of Arizona; together with a team from the Chandra X-ray Center,
report: "The Chandra X-ray Observatory made a 20000-s low-energy-
transmission-grating (LETG) observation of WZ Sge beginning on July
27.11 UT, three and a half days into outburst (IAUC 7669, 7670).
The mean zeroth-order count rate was 4.5 counts/s, and this is
modulated on the orbital period of WZ Sge with a double-peaked
profile. The dispersed spectrum extends from 0.2 to 17.5 nm and
has a mean count rate of 20 counts/s. Longward of 6.5 nm, the
spectrum is dominated by a forest of broad (FWHM between 800 and
1200 km/s) emission lines of such species as O V-VI, Ne V-VIII, Mg
V-VII, and Fe VII-IX. Shortward of 6.5 nm, weaker lines of highly
ionized ions are seen, with O VIII (1.89 nm) the strongest. The
long-wavelength LETG spectrum is very similar to the EUVE spectrum
of OY Car in superoutburst (Mauche and Raymond 2001, Ap.J. 541,
924) and appears to be formed by the same mechanism -- scattering
of boundary-layer radiation in the system's accretion-disk wind. A
second Chandra observation of WZ Sge was made with the ACIS-S CCD
detector beginning July 29.70 and lasting 5000 s. The source is
detected at x-ray energies up to 7 keV, and the x-ray spectrum is
dominated also by strong emission lines. Most features can be
accounted for with a multi-temperature thermal plasma model with
the exception of an anomalously strong emission line at 2.4 keV,
probably S XV (He-like). Five additional Chandra observations of
WZ Sge are planned, the first on Aug. 6 and the last in the week
beginning Sept. 17."
V2274 CYGNI
J. C. Wilson, Cornell University; and R. J. Rudy and D. K.
Lynch, The Aerospace Corporation, report 0.8-2.5-micron
spectrophotometry of V2274 Cyg (= N Cyg 2001) using the Palomar
1.5-m telescope (+ CorMASS) on July 31.3 UT, when the nova was in
early decline: "The spectrum showed narrow, low-excitation lines
that were typical of the early emission stage. The H I Paschen and
Brackett lines were present, along with He I 1.0831-microns, which
was weak. Also present were the Lyman-beta-fluoresced O I lines
and possibly permitted lines of C I and N I."
(C) Copyright 2001 CBAT
2001 August 2 (7677) Daniel W. E. Green
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