Central Bureau for Astronomical Telegrams
IAUC 7177: N Vel 1999; eta Car
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Circular No. 7177
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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NOVA VELORUM 1999
G. J. Garradd, Loomberah, N.S.W., reports the following
accurate CCD position obtained with a 0.45-m f/5.4 reflector on May
23.358 UT: R.A. = 10h44m48s.39, Decl. = -52o25'30".7 (equinox
2000.0; 6 ACT stars, rms residuals 0".29). He notes a distinct
pale yellow color of the nova visually through the same telescope.
P. Schmeer, Bischmisheim, Germany, notes that there is a blue star
(mag 16.4) listed in the USNO-A2.0 catalogue at position end
figures 48s.416, 31".23. Visual magnitude estimates: May 23.333,
2.6 (D. A. J. Seargent, The Entrance, N.S.W.); 23.508, 2.6 (A.
Pearce, Nedlands, W. Australia).
eta CARINAE
M. F. Corcoran and S. A. Drake, Universities Space Research
Association, Goddard Space Flight Center (GSFC); J. H. Swank and R.
Petre, Laboratory for High Energy Astrophysics, GSFC; K. Ishibashi,
K. Davidson and R. Humphreys, University of Minnesota; A. Damineli,
Instituto Astronomico e Geofisico da University de Sao Paulo; K.
Koyama and Y. Tsuboi, Kyoto University; and R. Viotti, Instituto
Astrofisica Spaziale, CNR, Rome, report: "We compared two x-ray
spectra of the peculiar variable star eta Car obtained by the ASCA
observatory on 1993 Aug. 24 and 1999 Feb. 2. These spectra were
both obtained near phase 0.20, where phase is calculated according
to the epoch and period of Damineli et al. (1997, New Astron. 2,
107). We find that the absorbed 2-10-keV x-ray flux in 1999 is
(6.4 +/- 0.05) x 10E-11 erg cmE-2 sE-1, while that in 1993 was (5.8
+/- 0.09) x 10E-11 erg cmE-2 sE-1. Our RXTE monitoring of the 2-
10-keV x-ray flux for +/- 20 days around the ASCA observation (1999
Jan. 20-Mar. 1) shows a steady decline in this energy band (from 23
to 18 PCU counts/s), with no sign of any x-ray flaring activity.
Thus the observed change in the ASCA spectra suggests that the 2-
10-keV x-ray flux has undergone a long-term brightening of about 10
percent that is independent of the Damineli cycle. The x-ray
variation may be related to a long-term increase in the optical
brightness of the star (cf. van Genderen et al. 1999, A.Ap. 343,
847) and/or the recent brightening at optical and infrared
wavelengths (IAUC 7146). The x-ray brightening we report is not
the result of a change in circumstellar absorption, since
circumstellar absorption is negligible at energies above 2 keV.
Our preliminary analysis suggests that the flux increase is
primarily due to an increase in the emission measure of the x-ray
emitting region during the interval 1993-1999."
(C) Copyright 1999 CBAT
1999 May 23 (7177) Daniel W. E. Green
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