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HS0507+0434: a double DA degenerate with a ZZCeti component
Reimers, D.; Dreizler, S.; Heber, U. +6 more
HS0507+0434 and HS2240+1234 are two new common proper motion pairs of DA white dwarfs, discovered by the Hamburg Quasar Survey. Our model atmosphere analysis shows that HS0507+0434A has an effective temperature of 20000K and is remarkably young (tau_cool < 1Gyr) compared to the average cooling time of all known wide double degenerates (~ 3Gyr).…
Infrared lasers in the circumstellar disk of MWC 349
Quirrenbach, A.; Martin-Pintado, J.; Thum, C. +1 more
Observations of hydrogen recombination lines were made with the Infrared Space Observatory (ISO) towards the star MWC349, where the alpha -transitions at short millimeter and submillimeter wavelengths have been found to be masers. All alpha -line s in the ISO wavelength range from 2.4 to 190mu m (quantum numbers n=4 to 15) were detected. We find t…
A new determination of the local distribution of interstellar NaI
Crifo, F.; Lallement, R.; Welsh, B. Y.
We present galactic maps of the distribution of neutral sodium absorption column density using the newly determined Hipparcos satellite distances for a total of 290 stars lying within 250pc of the Sun. These maps now replace those originally presented in Welsh {et al./} (1994). The Local Bubble is now seen to be a neutral gas-free cavity (nH<…
NGC 2264 IRS: Evidence for Triggered Star Formation
Schneider, Glenn; Thompson, Rodger I.; Corbin, Michael R. +1 more
As part of its commissioning process the Near-Infrared Camera and Multiobject Spectrometer (NICMOS) obtained images of the infrared source NGC 2264 IRS, also known as Allen's source, in three colors . In addition to the completely overexposed image of IRS there are six point objects, never previously observed, at projected separations of 2.6" to 4…
Cloning Hubble Deep Fields. II. Models for Evolution by Bright Galaxy Image Transformation
Broadhurst, Tom; Bouwens, Rychard; Silk, Joseph
In a companion paper, we outlined a methodology for generating parameter-free, model-independent ``no-evolution'' fields of faint galaxy images, demonstrating the need for significant evolution in the Hubble Deep Field (HDF) at faint magnitudes. Here we incorporate evolution into our procedure, by transforming the input bright galaxy images with r…
The Physical Characteristics of the Small-Scale Interstellar Structure toward µ Crucis
Meyer, David M.; Blades, J. C.; Lauroesch, J. T. +1 more
We present Hubble Space Telescope Goddard High Resolution Spectrograph echelle observations of multiple interstellar lines of C I, Mg I, Cr II, and Zn II toward both stars in the µ Crucis binary system. Despite large differences in the profiles of the neutral species, no significant variations between the stars are seen in the Cr II and Zn I…
Pulsation in lambda Bootis stars
Strassmeier, K. G.; Handler, G.; Garrido, R. +7 more
In this paper we present a further step in applying asteroseismic techniques to the group of lambda Bootis stars which can be characterized as nonmagnetic A to F-type Population I dwarfs with significant (surface) underabundances of Fe-peak elements. Since no conclusive theory explaining the origin of the observed abundance anomalies exists, an ex…
Hubble Space Telescope Imaging of the Mass-losing Supergiant VY Canis Majoris
Kastner, Joel H.; Weintraub, David A.
The highly luminous M supergiant VY CMa is a massive star that appears to be in its final death throes, losing mass at high rate en route to exploding as a supernova. Subarcsecond-resolution optical images of VY CMa, obtained with the Faint Object Camera (FOC) aboard the Hubble Space Telescope, vividly demonstrate that mass loss from VY CMa is hig…
Ultraviolet Spectroscopy of the Quasar Pair LB 9605, LB 9612 with the Hubble Space Telescope: Evolution in the Size of the Lyα Absorbers?
Weymann, Ray J.; Foltz, Craig B.; Impey, Chris D. +1 more
Ultraviolet spectroscopy has been obtained with the faint object spectrograph of the Hubble Space Telescope in the Lyα forest of the quasar pair, LB 9605 (zem = 1.834) and LB 9612 (zem = 1.898), in order to measure the size of the Lyα absorbers. The quasars are separated by 1.65 arcmin on the sky corresponding to a proper sep…
On the determination of absolute magnitude zero-points from HIPPARCOS parallaxes
Koen, Chris; Laney, Dave
The period-luminosity (PL) relation zero-point determination from Hipparcos trigonometric parallaxes of Cepheids is contentious. It is shown that the method used by Feast & Catchpole is equivalent to a standard minimization of sum of squares, and that it is free of Lutz-Kelker bias. The same technique is applied to RR Lyrae and field HB star d…