Search Publications
Lyman-alpha observations of comet 46 P/Wirtanen with swan on SOHO: H2O production rate near 1997 perihelion
Schmidt, W.; Bertaux, J. L.; Lallement, R. +4 more
The SWAN instrument on board SOHO is a Lyman-α photometer able to map the sky intensity with a resolution of 1°, primarily devoted to the study of the large scale distribution of solar wind from its imprints on the interplanetary sky background. In addition SWAN was extensively used to map the Lyman α emission of several comets since launch in Dec…
First Direct Measurement of Acceleration in the Outflow of a Nova: U Scorpii (1999)
Livio, Mario; Lépine, Sébastien; Shara, Michael M. +1 more
We report the first direct measurement of acceleration in the outflow of a nova, U Sco, observed 5 days after the start of an outburst. Spectroscopic time series of the intense Hα emission line, obtained with the Space Telescope Imaging Spectrograph camera on board the Hubble Space Telescope, shows a bright emission component moving across the spe…
The Twin Astrographic Catalog on the HIPPARCOS System
Zacharias, N.; Zacharias, M. I.
The Twin Astrographic Catalog (TAC) is an astrometric, photographic catalog covering most of the sky between declinations +90 deg and -18 deg to an average limiting magnitude of about V=11 and B=12. This release 2 is based on the same 4912 plates as release 1, which were taken with the US Naval Observatory Twin Astrograph (blue and yellow lens) be…
Hubble Space Telescope Imaging Polarimetry of eta Carinae
Hillier, D. J.; Nota, A.; Clampin, M. +3 more
Linear polarization measurements have been a key to our understanding of the massive star system eta Carinae and its surrounding Homunculus nebula. We here present the results of (linear) polarimetric imaging of eta Carinae in the V band (F555W) with the Hubble Space Telescope's Wide Field Planetary Camera 2 (HST/WFPC2). The data agree well with p…
Near-Infrared Observations of Hot Spots in the Circumnuclear Rings of NGC 2997 and NGC 6951
Elmegreen, Debra Meloy; Chromey, Frederick R.; Sawyer, Jessica E. +1 more
Near-infrared observations of NGC 2997 and NGC 6951 reveal complete rings of symmetrically placed hot spots, which are star-forming complexes. The masses of the complexes range from a few times 10^4 to a few times 10^5 M_solar in both galaxies. The regular hot-spot spacings of about 200 pc in a ring 55 pc thick in NGC 2997 and 380 pc in a ring 150…
In Search of Emerging Magnetic Flux underneath the Solar Surface with Acoustic Imaging
Chang, Hsiang-Kuang; Chou, Dean-Yi; Sun, Ming-Tsung
With the method of acoustic imaging in helioseismology, we study an emerging flux region, NOAA 7978, using data taken with instruments of the Taiwan Oscillation Network (TON) and the Michelson Doppler Imager (MDI). Phase-shift maps of NOAA 7978 focusing at different depths are constructed, which show the evolution of emerging magnetic flux. Althou…
Corotating Interaction Regions at High Latitudes
Simnett, G. M.; Tsurutani, B. T.; Horbury, T. S. +16 more
Ulysses observed a stable strong CIR from early 1992 through 1994 during its first journey into the southern hemisphere. After the rapid latitude scan in early 1995, Ulysses observed a weaker CIR from early 1996 to mid-1997 in the northern hemisphere as it traveled back to the ecliptic at the orbit of Jupiter. These two CIRs are the observational …
The 10-200 MU M spectral energy distribution of the prototype narrow-line X-ray galaxy NGC 7582
Lemke, D.; Radovich, M.; Acosta-Pulido, J. +1 more
We present the spectral energy distribution (SED) between 10 and 200 mu m obtained for the prototype narrow-line X-ray galaxy NGC 7582 with ISOPHOT, the photometer on board the Infrared Space Observatory. The emission is spatially extended and we separated for the first time the nuclear and extranuclear infrared SEDs. The nuclear luminosity (L_IR …
Structure and Dynamics of Interconnecting Loops and Coronal Holes in Active Longitudes
Kosovichev, A. G.; Scherrer, P. H.; Benevolenskaya, Elena E.
Using SOHO/MDI and SOHO/EIT data we study properties and dynamics of interconnected active regions, and the relations between the photospheric magnetic fields and coronal structures in active longitudes during the beginning of solar cycle 23. The emergence of new magnetic flux results in appearance of new interconnecting loops. The existence of st…
The iron abundance in hot central stars of planetary nebulae derived from IUE spectra
Rauch, T.; Werner, K.; Dreizler, S. +1 more
We present the first attempt to determine the iron abundance in hot central stars of planetary nebulae. We perform an analysis with fully metal-line blanketed NLTE model atmospheres for a sample of ten stars (T_eff >~ 70 000 K) for which high-resolution UV spectra are available from the IUE archive. In all cases lines of Fe Vi or Fe Vii can be …