Central Bureau for Astronomical Telegrams
IAUC 5572: N Sgr 1992 No. 2; AG Car
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Circular No. 5572
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 SAGITTARII 1992 No. 2
L. V. Morrison, Royal Greenwich Observatory, reports the
following accurate position, obtained with the Carlsberg Automatic
Meridian Circle on La Palma: R.A. = 18h23m26s.946, Decl. =
-28 21'59".57 (equinox J2000.0, FK5 reference frame; epoch 1992.53;
accuracy +/- 0s.007 in R.A., +/- 0".12 in Decl.); the corresponding
B1950.0 position is R.A. = 18h20m17s.226, Decl. = -28 23'35".05.
Johnson V magnitudes (+/- 0.05) obtained with the same instrument:
July 19.92 UT, 9.31; 23.92, 9.39; 27.92, 9.58; 29.92, 9.98; 31.92,
10.14.
AG CARINAE
C. Leitherer, Space Telescope Science Institute (STScI); R.
Allen, University of Arizona; B. Altner, ARC, Landover; A. Damineli,
Instituto Astronomico e Geofisico, Universidade de Sao Paulo (IAG);
L. Drissen, STScI; R. Gruenwald, IAG; O. Lupie, A. Nota, F. Paresce,
and C. Robert, STScI; W. Schmutz (ETH, Zurich), and S. N. Shore,
Goddard Space Flight Center, communicate: "We report the detection
of ultraviolet line depolarization in the luminous blue variable AG
Car (= HD 94910 = CD -59 3430). AG Car is currently brightening
from its minimum magnitude of V about 8.5 (cf. IAUC 5307). On 1992
May 4, we measured V = 6.79 and B-V = +0.66 at Porto Alegre Observatory.
Ultraviolet spectropolarimetry of AG Car has been obtained
with the Faint Object Spectrograph onboard the Hubble Space
Telescope. The data have a spectral resolution of about 0.2 nm, and
cover the wavelength region 230-330 nm. Observing dates were 1991
Nov. 19, 1992 May 15, and July 15. Simultaneous ultraviolet
spectroscopy obtained with the IUE satellite in its high-dispersion
mode shows numerous metallic lines around 260 nm, many of them
displaying P-Cyg profiles. The resonance lines of Fe II multiplet 1
and Mg II multiplet 1 are particularly strong. The continuum
polarization of AG Car between 290 and 330 nm is 1.0 +/- 0.2 percent.
The polarization is lower around 280 nm and decreases to 0.3 +/-
0.3 percent shortward of 270 nm. This suggests significant
depolarization due to many absorption lines in this spectral region.
The depolarization may indicate an asymmetric outflow of material
from the star. Pronounced time-variable stellar-wind characteristics
are also apparent from optical spectroscopy obtained by us
during the last 12 months. Continuous monitoring of the current
activity cycle of AG Car in all accessible wavelength bands is
highly desirable."
1992 August 3 (5572) Daniel W. E. Green
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