Search Publications
Quasar Candidates in the Hubble Deep Field
Martini, Paul; Conti, Alberto; Kennefick, Julia D. +1 more
The Hubble Deep Field (HDF) gives us an unprecedented view of our universe and an opportunity to study a wide range of questions in galaxy evolution and cosmology. Here we focus on the search for unresolved faint quasars and active galactic nuclei (AGNs) in the crude combine images using a multicolor imaging analysis that has proved very successfu…
Coronal Hole Boundaries and their Interactions with Adjacent Regions
Schwadron, N. A.; Zurbuchen, T. H.; Fisk, L. A.
Coronal hole boundaries are the interfaces between regions where the coronal magnetic field contains a significant component which is open into the heliosphere and regions where the field is primarily closed. It is pointed out that there are constraints on the magnetic field which opens into the heliosphere that must be satisfied in the corona: it…
Detection of the 62 Micron Crystalline H2O Ice Feature in Emission toward HH 7 with the Infrared Space Observatory Long-Wavelength Spectrometer
Ceccarelli, Cecilia; Giannini, Teresa; Nisini, Brunella +4 more
We report the detection of the 62 µm feature of crystalline water ice in emission toward the bow-shaped Herbig-Haro object HH 7. Significant amounts of far-infrared continuum emission are also detected between 10 and 200 µm, so that Herbig-Haro objects cease to be pure emission-line objects at far-infrared wavelengths. The formation of…
Large Craters on Small Objects: Occurrence, Morphology, and Effects
Thomas, P. C.
Spacecraft imaging data allow an accounting of the occurrence and characteristics of the largest craters on small asteroids and satellites. Data covering Phobos, Deimos, Gaspra, Ida, Mathilde, Vesta, Amalthea, Thebe, Janus, Epimetheus, Hyperion, and Proteus show that ∼50% of rocky objects support craters with diameters of 1 object mean radius (R <…
The absolute magnitudes of RR Lyrae stars from BT HIPPARCOS parallaxes parallaxes
Salaris, M.; Groenewegen, M. A. T.
Using the method of ``reduced parallaxes'' for the Halo RR Lyrae stars in the hipparcos catalogue we derive a zero point of 0.77 +/- 0.26 mag for an assumed slope of 0.18 in the M_V-[Fe/H] relation. This is 0.28 magnitude brighter than the value Fernley et al. (1998a) derived by employing the method of statistical parallax for the identical sample…
The kinematics of the planetary nebula BD+30 deg3639
Bryce, Myfanwy; Mellema, Garrelt
In this paper we describe the results of the first optical kinematic study of the planetary nebula BD+30 deg3639. This system has a central star of the Wolf-Rayet type and is believed to be fairly young. Emission-line spectra were obtained at high spectral and spatial resolution using the Utrecht echelle spectrometer at the William Herschel Telesc…
Infrared Space Observatory Observations of Far-Infrared Rotational Emission Lines of Water Vapor toward the Supergiant Star VY Canis Majoris
Feuchtgruber, Helmut; Neufeld, David A.; Melnick, Gary J. +1 more
We report the detection of numerous far-infrared emission lines of water vapor toward the supergiant star VY Canis Majoris. A 29.5-45 µm grating scan of VY CMa, obtained using the Short-Wavelength Spectrometer (SWS) of the Infrared Space Observatory at a spectral resolving power λ/Δλ of ~2000, reveals at least 41 spectral features due to wat…
EUV Observations Above Polar Coronal Holes
Del Zanna, G.; Fludra, A.; Bromage, B. J. I.
We derive electron temperature and density as a function of height up to 0.2 R⊙ above the limb in polar coronal holes, using five EUV data sets recorded by the SOHO Coronal Diagnostic Spectrometer between July 1997 and February 1998. Radial T and N distributions, averaged in a 2° to 10° range of position angles, are the same above the N…
Magnetic braking of the present Sun
Li, Jianke
Magnetic braking is essential for angular momentum transport in late-type stars which have convective envelopes. The mechanism may be entirely responsible for the slow rotation of the present Sun, on which a braking model is normally calibrated. Recent or current satellite missions such as Helios and Ulysses have jointly revealed a more complete p…
On the Nuclear Rotation Curve of M31
Statler, Thomas S.
The currently favored model for the double nucleus of M31 consists of an eccentric disk with an off-center density concentration caused by stars lingering at the apocenters of their orbits about the central black hole. If such a disk is to be in equilibrium, the requirement that it precess uniformly because of self-gravity imposes a characteristic…