Search Publications
The First Detection of Spatially Resolved Mid-Infrared Scattered Light from a Protoplanetary Disk
Duchêne, G.; Ghez, A. M.; McCabe, C.
We report spatially resolved 11.8 µm images, obtained at the W. M. Keck 10 m telescope, of the protoplanetary disk around the pre-main-sequence star HK Tau B. The mid-infrared morphology and astrometry of HK Tau B with respect to HK Tau A indicate that the flux observed in the mid-infrared from HK Tau B has been scattered off the upper surfa…
Far-Ultraviolet Emission from Elliptical Galaxies at z = 0.33
Ferguson, Henry C.; Brown, Thomas M.; Rich, R. Michael +4 more
We present far-UV images of the rich galaxy cluster ZwCl 1358.1+6245, taken with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope (HST). When combined with archival HST observations, our data provide a measurement of the UV-to-optical flux ratio in eight early-type galaxies at z=0.33. Because the UV flux originates in a…
A Far-Ultraviolet Survey of 47 Tucanae. II. The Long-Period Cataclysmic Variable AKO 9
Zurek, David R.; Gilliland, Ronald L.; Shara, Michael M. +2 more
We present time-resolved far-ultraviolet (FUV) spectroscopy and photometry of the 1.1 day eclipsing binary system AKO 9 in the globular cluster 47 Tucanae. The FUV spectrum of AKO 9 is blue and exhibits prominent C IV and H II emission lines. The spectrum broadly resembles that of long-period cataclysmic variables (CVs) in the Galactic field. Comb…
Hubble Space Telescope Observations of Novae in M49
Jordán, Andrés; Côté, Patrick; Ferrarese, Laura
A search for novae in M49 (NGC 4472) has been undertaken with the Hubble Space Telescope. A 55 day observing campaign in F555W (19 epochs) and F814W (five epochs) has led to the discovery of nine novae. We find that M49 may be underabundant in slow, faint novae relative to the Milky Way and M31. Instead, the decline rates of the M49 novae are rema…
Erosion Model for the Sungrazing Comets Observed with the Solar and Heliospheric Observatory
Sekanina, Zdenek
The objectives of this study are to model and interpret quantitatively the brightness variations of 27 Solar and Heliospheric Observatory (SOHO) sungrazers. The light curves, published by Uzzo et al. and by Biesecker et al., are shown to provide information on a proposed erosion process, which consists of continuous, progressive bulk fragmentation…
Tether-cutting Energetics of a Solar Quiet-Region Prominence Eruption
Moore, Ronald L.; Sterling, Alphonse C.
We study the morphology and energetics of a slowly evolving quiet-region solar prominence eruption occurring on 1999 February 8-9 in the solar north polar crown region, using soft X-ray data from the soft X-ray telescope (SXT) on Yohkoh and Fe XV EUV 284 Å data from the EUV Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO). …
Evidence for Grain Growth in the Protostellar Disks of Orion
Bally, John; Throop, Henry; Shuping, R. Y. +1 more
We present a Brα (λ=4.05 µm) image of the largest silhouette proplyd in Orion (114-426) using the facility near-IR spectrometer NIRSPEC at the Keck Observatory. This is the longest wavelength observation of a silhouette disk to date. The diameter of the disk at 4 µm is only marginally smaller than that observed in the optical with the …
A Multiwavelength Approach to the Star Formation Rate Estimation in Galaxies at Intermediate Redshifts
Elbaz, D.; Koo, D. C.; Willmer, C. N. A. +4 more
We use a sample of seven starburst galaxies at intermediate redshifts (z~0.4 and 0.8) with observations ranging from the observed ultraviolet to 1.4 GHz, to compare the star formation rate (SFR) estimators that are used in the different wavelength regimes. We find that extinction-corrected Hα underestimates the SFR, and the degree of this underest…
The Variability of the Solar Coronal Helium Abundance: Polar Coronal Holes Compared to the Quiet Sun
Laming, J. Martin; Feldman, Uri
We report on measurements of the abundance ratio He/H in solar polar coronal holes and neighboring quiet coronal regions, using the SUMER spectrometer on board SOHO. In coronal holes we find He abundances smaller than or equal to the value found in the fast solar wind, 5% by number relative to H, suggesting that the flow speed of He up into the wi…
Protoplanetary Disk Mass Distribution in Young Binaries
Jensen, Eric L. N.; Akeson, Rachel L.
We present millimeter-wave continuum images of four wide (separations 210-800 AU), young stellar binary systems in the Taurus-Auriga star-forming region. For all four sources, the resolution of our observations is sufficient to determine the millimeter emission from each of the components. In all four systems, the primary star's disk has stronger …