Search Publications
On the Inference of Differential Emission Measures Using Diagnostic Line Ratios
McIntosh, Scott W.
Spectroscopic diagnosis of hot optically thin plasmas can be used to infer valuable information about the temperature structure of the emitting plasma volume, through the emission measure differential (DEM) in Te, DEM(Te). However, the uncertainties in atomic parameters (required to model the plasma emission) make such infere…
A New Observational Search for Vulcanoids in SOHO/LASCO Coronagraph Images
Parker, Joel Wm.; Stern, S. Alan; Levison, Harold F. +3 more
We examined SOHO/LASCO (Solar and Heliospheric Observatory/Large Angle Spectroscopic Coronagraph) C3 coronagraph images to search for the long-suspected population of small bodies, the vulcanoids, in heliocentric orbits interior to Mercury. We searched the entire vulcanoid region from 0.07-0.21 AU by visually blinking daily image averages co-regis…
Luminosity function and mass segregation in M92
Marconi, G.; Buonanno, R.; Iannicola, G. +2 more
We present WFPC2-HST observations of the lower main sequence of the galactic globular cluster M92 (NGC6341), extending down to V ~= 27. Our data, which cover a region of the cluster extending from the very center out to r ~= 380 arcsec, show that the slope of the luminosity function becomes flatter going towards the center of the cluster, as expec…
A wind accretion wake in RW Hydrae?
Schmutz, W.; Nussbaumer, H.; Schild, H. +3 more
RW Hydrae is an eclipsing detached binary star system, consisting of a mass losing M-giant and a hot white dwarf on circular orbits. We analyze UV observations of RW Hydrae. Approximately at phi = 0.78, clearly unrelated to the primary eclipse, we detect in the UV light curve an event with significantly reduced UV flux. The spectral characteristic…
Comparisons of the Tycho-2 Catalogue Proper Motions with HIPPARCOS and ACT
Makarov, V. V.; Urban, S. E.; Wycoff, G. L.
The recently released Tycho-2 Catalogue is expected to supersede the currently used catalogs based on the Tycho data, specifically, the ACT Reference Catalog and the Tycho Reference Catalogue. Here the proper motions of the newly released Tycho-2 Catalogue are compared with those of the Hipparcos Catalogue and the ACT Reference Catalog. Tycho-2 is…
Hercules X-1: Empirical Models of Ultraviolet Emission Lines
Raymond, John; Bautista, Manuel; Boroson, Bram +4 more
The UV emission lines of Hercules X-1, resolved with the Hubble Space Telescope (HST) Goddard High Resolution Spectrograph and Space Telescope Imaging Spectrograph, can be divided into broad (FWHM~750 km s-1) and narrow (FWHM~150 km s-1) components. The broad lines can be unambiguously identified with emission from an accreti…
Variable Galaxies in the Hubble Deep Field
Phillips, M. M.; Gilliland, Ronald L.; Sarajedini, Vicki L.
We present results from a study to detect variable galaxies in the Hubble Deep Field North (HDF-N). The goal of this project is to investigate the number density of active galactic nuclei (AGNs) at z~=1 through the detection of variable galaxy nuclei. The advantage of the Hubble Space Telescope is its ability to do accurate photometry within small…
Mode Identification of BPM 37093 with the HST
Kepler, S. O.; Montgomery, M. H.; Winget, D. E. +3 more
Theoretical calculations indicate that the massive pulsating white dwarf BPM 37093 has a crystallized interior (Winget et al. 1997, Kanaan 1996, Montgomery 1998). Crystallization was predicted theoretically about 40 years ago (Abrisokov 1961, Kirshnitz 1960; Salpeter 1961), but in spite of its importance in astrophysics, there is no direct observa…
The Vela pulsar (PSR B0833-45) proper motion revisited with HST astrometry
Caraveo, P. A.; De Luca, A.; Mignani, R. P.
Using all the HST WFC/WFPC2 images of the field collected so far, we have performed an accurate relative astrometry analysis to re-assess the value of the Vela pulsar proper motion. Although covering a much shorter time span, our measurement clearly confirms the previous result obtained by Nasuti et al. (1997) using ground-based optical data and n…
Far-infrared-loud quasars - I. Disturbed and quiescent quasars in the PG survey
Clements, D. L.
We use host galaxy imaging studies of the PG quasar survey to compare the far-infrared (FIR) properties of quasars with disturbed and undisturbed host galaxies. By using survival analysis, we show that the quasars with disturbed host galaxies, with morphologies classified from a homogeneous data set, have a 60-µm luminosity distribution that…