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The Homunculus reflection nebula around η Carinae provides a rare opportunity to observe the spectrum of a star from more than one direction. In the case of η Car, the nebula's geometry is known well enough to infer how line profiles vary with latitude. We present STIS spectra of several positions in the Homunculus, showing directly that η Car has an aspherical stellar wind. P Cygni absorption in Balmer lines depends on latitude, with relatively high velocities and strong absorption near the polar axis. Stronger absorption at high latitudes is surprising, and it suggests higher mass flux toward the poles, perhaps resulting from radiative driving with equatorial gravity darkening on a rotating star. Reflected profiles of He i lines are more puzzling, offering clues to the wind geometry and ionization structure. During η Car's high-excitation state in March 2000, the wind was fast and dense at the poles, with higher ionization at low latitudes.Older STIS data obtained since 1998 reveal that this global stellar-wind geometry changes during η Car's 5.5 year cycle, and may suggest that this star's spectroscopic events are shell ejections. Whether or not a companion star triggers these outbursts remains ambiguous. The most dramatic changes in the wind occur at low latitudes, while the dense polar wind remains relatively undisturbed during an event. The apparent stability of the polar wind also supports the inferred bipolar geometry. The wind geometry and its variability have critical implications for understanding the 5.5 year cycle and long-term variability, but do not provide a clear alternative to the binary hypothesis for generating η Car's X-rays.

Using The Hubble Space Telescope's Space Telescope Imaging Spectrograph (HST's STIS ), observations of the [O III] emission from the narrow-line region (NLR) of NGC 4151 were obtained and radial velocities determined. Five orbits of HST time were used to obtain spectra at five parallel slit configurations, at a position angle of 58 o , with spatial resolution 0 ′′ .2 across and 0 ′′ .1 along each slit. A spectral resolving power (∆λ/λ) of ∼9,000 with the G430M grating gave velocity measurements accurate to ∼34 km s −1 . A kinematic model was generated to match the radial velocities, for comparison to previous kinematic models of biconical radial outflow developed for low-dispersion spectra at two slit positions. The new high-resolution spectra permit the measurement of accurate velocity dispersions for each radial-velocity component. The full-width at half-maximum (FWHM) reaches a maximum of 1000 km s −1 near the nucleus, and generally decreases with increasing distance to about 100 km s −1 in the Based on observations made with the NASA/ESA Hubble Space Telescope. STScI is operated bt the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with proposal GTO-8473

We present Hubble Space Telescope (HST ) spectroscopy of the nucleus of M31 obtained with the Space Telescope Imaging Spectrograph (STIS). Spectra that include the Ca ii infrared triplet (k ' 8500 8) see only the red giant stars in the double brightness peaks P1 and P2. In contrast, spectra taken at k ' 3600 5100 8 are sensitive to the tiny blue nucleus embedded in P2, the lower surface brightness nucleus of the galaxy. P2 has a K-type spectrum, but we find that the blue nucleus has an A-type spectrum: it shows strong Balmer absorption lines. Hence, the blue nucleus is blue not because of AGN light but rather because it is dominated by hot stars. We show that the spectrum is well described by A0 giant stars, A0 dwarf stars, or a 200 Myr old, single-burst stellar population. White dwarfs, in contrast, cannot fit the blue nucleus spectrum. Given the small likelihood for stellar collisions, recent star formation appears to be the most plausible origin of the blue nucleus. In stellar population, size, and velocity dispersion, the blue nucleus is so different from P1 and P2 that we call it P3 and refer to the nucleus of M31 as triple.Because P2 and P3 have very different spectra, we can make a clean decomposition of the red and blue stars and hence measure the light distribution and kinematics of each uncontaminated by the other. The line-of-sight velocity distributions of the red stars near P2 strengthen the support for Tremaine's eccentric disk model. Their wings indicate the presence of stars with velocities of up to 1000 km s À1 on the anti-P1 side of P2.The kinematics of P3 are consistent with a circular stellar disk in Keplerian rotation around a supermassive black hole. If the P3 disk is perfectly thin, then the inclination angle i ' 55 is identical within the errors to the inclination of the eccentric disk models for P1+P2 by Peiris & Tremaine and by Salow & Statler. Both disks rotate in the same sense and are almost coplanar. The observed velocity dispersion of P3 is largely caused by blurred rotation and has a maximum value of ¼ 1183 AE 201 km s À1 . This is much larger than the dispersion ' 250 km s À1 of the red stars along the same line of sight and is the largest integrated velocity dispersion observed in any galaxy. The rotation curve of P3 is symmetric around its center. It reaches an observed velocity of V ¼ 618 AE 81 km s À1 at radius 0B05 ¼ 0:19 pc, where the observed velocity dispersion is ¼ 674 AE 95 km s À1 . The corresponding circular rotation velocity at this radius is $1700 km s À1 . We therefore confirm earlier suggestions that the central dark object interpreted as a supermassive black hole is located in P3.Thin-disk and Schwarzschild models with intrinsic axial ratios b/a P 0:26 corresponding to inclinations between 55 and 58 match the P3 observations very well. Among these models, the best fit and the lowest black hole mass are obtained for a thin-disk model with M ¼ 1:4 ; 10 8 M . Allowing P3 to have some intrinsic thickness and considering possible systematic errors, the 1 confi...