Search Publications
Boron Abundances and Internal Mixing in Stars. I. The Hyades Giants
Pinsonneault, Marc H.; Peterson, Ruth C.; Duncan, Douglas K. +1 more
The boron abundances of two giants and one turnoff star in the Hyades, and the field K0 III giant β Gem, have been measured from spectra obtained with the Hubble Space Telescope in the vicinity of the B I lines near 2500 Å. This provides a test of the dilution of giant envelopes predicted by standard stellar evolutionary models: since B is destroy…
Luminosity Functions for Globular Clusters
D'Antona, Francesca; Ventura, Paolo; Silvestri, Fabio +1 more
We present theoretical mass-luminosity relations and luminosity functions (LFs) for globular cluster stars, from luminosities above the horizontal branch down to the minimum luminosity of hydrogen-burning stars. The LFs are available for metal mass fraction Z from Z = 10-4 to Z = 4 × 10-3, in the Johnson V band and in the Bes…
High-Velocity Lyα Emission from SNR 1987A
Pun, Chun S. J.; Sonneborn, George; Borkowski, Kazimierz J. +2 more
The high-velocity Lyα emission from SN 1987A observed with the Space Telescope Imaging Spectrograph (STIS) evidently comes from a reverse shock formed where the outer envelope of SN 1987A strikes ionized gas inside the inner circumstellar ring. The observations can be explained by a simple kinematic model, in which the Lyα emission comes from hydr…
Monitoring Lyα Emission from the Blazar 3C 279
Urry, C. Megan; Koratkar, Anuradha; Pian, Elena +1 more
The blazar 3C 279 is well studied and shows frequent large continuum flares from radio to γ-ray wavelengths. There have been a number of multiwavelength observations of 3C 279, and hence there are extensive ultraviolet data for this object available in the UV archives. In this paper we present Lyα emission line measurements for 3C 279 using all th…
Coronal C+3 in the Large Magellanic Cloud: Evidence for a Hot Halo
Chu, You-Hua; Wakker, Bart; Points, Sean D. +2 more
Based on the detection of C IV absorption in five Large Magellanic Cloud (LMC) stars observed with the Goddard High-Resolution Spectrograph on the Hubble Space Telescope, we present the first unambiguous evidence that C+3 exists in the LMC away from regions where it could have been locally produced. We can exclude that this C+3
The Acoustic Moat and Thermal Transport in the Neighborhoods of Sunspots
Braun, D. C.; Lindsey, C.
Helioseismic holography of sunspots shows a remarkable acoustic anomaly surrounding the sunspot, which we call an ``acoustic moat.'' We used Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager observations of NOAA Active Region 7973 to render acoustic images of a typical sunspot. These images show a conspicuous halo, 70,000 km in di…
Measurements of Far-UV Emission from Elliptical Galaxies at Z = 0.375
Ferguson, Henry C.; Brown, Thomas M.; Deharveng, Jean-Michel +1 more
The ``UV upturn'' is a sharp rise in spectra of elliptical galaxies shortward of rest-frame 2500 Å. It is a ubiquitous phenomenon in nearby giant elliptical galaxies and is thought to arise primarily from low-mass evolved stars on the extreme horizontal branch and beyond. Models suggest that the UV upturn is a very strong function of age for these…
Mass-Loss Rate and He/H Abundance of the Erupting Component in the Small Magellanic Cloud System HD 5980
Schmutz, W.; Koenigsberger, G.; Peña, M. +1 more
The binary Wolf-Rayet system HD 5980 in the Small Magellanic Cloud underwent a major luminous blue variable-type eruptive event in 1994. It is the first such recorded event in which the apparent precursor transits from WNE to WNL spectral types prior to the eruption. In this paper we analyze the spectrum of the system obtained when the outburst wa…
Atomic Physics with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. IV. Relative Oscillator Strengths for Singly Ionized Nickel
Federman, S. R.; Zsargó, J.
Absorption lines of trace metals like nickel are often used to measure the metallicity and depletion in H I regions within our Galaxy and others. Ultraviolet absorption lines from the dominant ion, Ni II, are generally weak, making them a convenient tool to study metallicity and depletion in these environments. As an aid for studies of dust evolut…
Systematics of RR Lyrae Statistical Parallax. II. Proper Motions and Radial Velocities
Gould, Andrew; Popowski, Piotr
We investigate whether a misestimate of proper motions or radial velocities could have been a source of substantial systematic errors in the statistical parallax determination of the absolute magnitude of RR Lyrae stars. In an earlier paper, we showed that the statistical parallax method is extremely robust and rather insensitive to various system…