Central Bureau for Astronomical Telegrams
IAUC 6328: NOVALIKE Var IN Sgr; C/1996 B2
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Circular No. 6328
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)
NOVALIKE VARIABLE IN SAGITTARIUS
H. W. Duerbeck, European Southern Observatory, reports: "A
10-min direct CCD image of Sakurai's object (cf. IAUC 6322, 6323,
6325), taken on Feb. 29.4 UT with the 0.91-m Dutch telescope at La
Silla through an H-alpha filter, shows that the star is surrounded
by an almost-circular nebula of diameter 30"; the strongest
emission originates in the northwest quadrant. An exposure through
a filter centered at 665 nm does not show any nebulosity, excluding
the possibility that the shell is composed of illuminated dust.
Thus Sakurai's object is surrounded by a faint planetary nebula, a
finding that is expected for an object undergoing a final helium
flash (cf. IAUC 6325)."
D. Pollacco, Royal Greenwich Observatory, communicates:
"Observations of this object by F. Verbunt, G. Geertsema, and M.
van den Berg, using the 4.2-m William Herschel Telescope (+ ISIS
spectrograph) on Feb. 29.25 UT, show it to be the central star of a
limb-brightened planetary nebula (dimensions at least 45" north-
south). The spectrum is typical of old, low-moderate excitation
planetary nebulae with the [O III] 500.7-nm/H-beta ratio about 5
(very similar to the planetary nebula A58 surrounding the only
other observed shell flash object, V605 Aql, in 1919). In view of
the rareness of these events -- this is the first one that can be
studied with modern equipment -- observers are strongly encouraged
to monitor this object at both optical and infrared wavelengths.
Spectroscopy over the coming months (years?) will be especially
important as the material ejected during the shell flash is
shocked/photoionized by the rapidly evolving star. Photometry may
indicate massive dust ejection episodes, causing optical variations
similar to those observed in R CrB stars. Infrared spectroscopy
will first reveal the exposed Wolf-Rayet core."
COMET C/1996 B2 (HYAKUTAKE)
Total (visual) magnitude and coma-diameter estimates: Feb.
24.46 UT, 6.6, 18' (C. S. Morris, Lockwood Valley, CA, 10x50
binoculars; 30' tail in p.a. 278 deg); 25.52, 6.9, 12' (R. Keen, Mt.
Thorodin, CO, 7x50 binoculars); 27.15, 6.7, about 22' (H. Mikuz,
Ljubljana, Slovenia, 0.20-m reflector + CCD + V filter; faint,
diffuse tail about 1 deg long in p.a. about 290 deg); 28.18, 6.4,
-- (J. D. Shanklin, Minera, Wales, 7x50 binoculars; 1.8 deg tail in
p.a. 305 deg); 29.37, 6.1, 15' (G. W. Kronk, Troy, IL, 20x80
binoculars).
(C) Copyright 1996 CBAT
1996 February 29 (6328) Daniel W. E. Green
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