Search Publications
Analytic Light Curves for Planetary Transit Searches
Agol, Eric; Mandel, Kaisey
We present exact analytic formulae for the eclipse of a star described by quadratic or nonlinear limb darkening. In the limit that the planet radius is less than a tenth of the stellar radius, we show that the exact light curve can be well approximated by assuming the region of the star blocked by the planet has constant surface brightness. We app…
Detection of an Extrasolar Planet Atmosphere
Gilliland, Ronald L.; Charbonneau, David; Brown, Timothy M. +1 more
We report high-precision spectrophotometric observations of four planetary transits of HD 209458, in the region of the sodium resonance doublet at 589.3 nm. We find that the photometric dimming during transit in a bandpass centered on the sodium feature is deeper by (2.32+/-0.57)×10-4 relative to simultaneous observations of the transit…
The Rest-Frame Extreme-Ultraviolet Spectral Properties of Quasi-stellar Objects
Kriss, Gerard A.; Zheng, Wei; Davidsen, Arthur F. +1 more
We use a sample of 332 Hubble Space Telescope spectra of 184 quasi-stellar objects (QSOs) with z>0.33 to study the typical ultraviolet spectral properties of QSOs, with emphasis on the ionizing continuum. Our sample is nearly twice as large as that from previous work by W. Zheng and colleagues and provides much better spectral coverage in the e…
The Metal Content of Dwarf Starburst Winds: Results from Chandra Observations of NGC 1569
Kobulnicky, Henry A.; Martin, Crystal L.; Heckman, Timothy M.
We present deep Chandra spectral imaging of the dwarf starburst galaxy NGC 1569. The unprecedented spatial resolution allows us to spatially identify the components of the integrated X-ray spectrum. Fitted spectral models require an intrinsic absorption component and higher metal abundances than previous studies indicated. Our results provide the …
Measured Mass-Loss Rates of Solar-like Stars as a Function of Age and Activity
Zank, Gary P.; Wood, Brian E.; Linsky, Jeffrey L. +1 more
Collisions between the winds of solar-like stars and the local interstellar medium result in a population of hot hydrogen gas surrounding these stars. Absorption from this hot H I can be detected in high-resolution Lyα spectra of these stars from the Hubble Space Telescope. The amount of absorption can be used as a diagnostic for the stellar mass-…
On the Relationship between Radio Emission and Black Hole Mass in Galactic Nuclei
Ho, Luis C.
We use a comprehensive database of black hole masses (MBH) and nuclear luminosities to investigate the relationship between radio emission and MBH. Our sample covers a wide range of nuclear activity, from nearby inactive nuclei to classical Seyfert 1 nuclei and luminous quasars. Contrary to some previous studies, we find that…
A Redshift z=6.56 Galaxy behind the Cluster Abell 370
Kneib, J. -P.; Motohara, K.; Capak, P. +5 more
We report the discovery of a redshift z=6.56 galaxy lying behind the cluster Abell 370. The object HCM 6A was found in a narrowband imaging survey using a 118 Å bandpass filter centered at 9152 Å in the Low-Resolution Imaging Spectrograph (LRIS) camera on the 10 m Keck II telescope. Candidate Lyα emitters were identified by the equivalent width of…
Nested and Single Bars in Seyfert and Non-Seyfert Galaxies
Peletier, Reynier F.; Laine, Seppo; Knapen, Johan H. +1 more
We analyze the observed properties of nested and single stellar bar systems in disk galaxies. The 112 galaxies in our sample comprise the largest matched Seyfert versus non-Seyfert galaxy sample of nearby galaxies with complete near-infrared or optical imaging sensitive to length scales ranging from tens of parsecs to tens of kiloparsecs. The pres…
Massive Stars in the Arches Cluster
Gilmore, Diane; Teplitz, Harry I.; Graham, James R. +9 more
We present and use new spectra and narrowband images, along with previously published broadband images, of stars in the Arches cluster to extract photometry, astrometry, equivalent width, and velocity information. The data are interpreted with a wind/atmosphere code to determine stellar temperatures, luminosities, mass-loss rates, and abundances. …
The Chemical Composition and Age of the Metal-poor Halo Star BD +17°3248
Beers, Timothy C.; Truran, James W.; Burles, Scott +8 more
We have combined new high-resolution spectra obtained with the Hubble Space Telescope (HST) and ground-based facilities to make a comprehensive new abundance analysis of the metal-poor, halo star BD +17°3248. We have detected the third r-process peak elements osmium, platinum, and (for the first time in a metal-poor star) gold, elements whose abun…