Search Publications
Differential Microlensing of the Continuum and Broad Emission Lines in SDSS J0924+0219, the Most Anomalous Lensed Quasar
Keeton, Charles R.; Schechter, Paul L.; Burles, Scott +1 more
SDSS J092455.87+021924.9 is the most glaring example of a gravitational lens with anomalous flux ratios; optical broadband photometry shows image D to be a factor of 12 fainter than expected for smooth lens potentials. We report spectroscopy showing that the anomaly is present in the broad emission line flux ratios as well. There are differences b…
The Statistical Relationship between the Photospheric Magnetic Parameters and the Flare Productivity of Active Regions
Jing, Ju; Wang, Haimin; Song, Hui +2 more
Using line-of-sight Michelson Doppler Imager (MDI) magnetograms of 89 active regions and Solar Geophysical Data (SGD) flare reports, we explored, for the first time, the magnitude scaling correlations between three parameters of magnetic fields and the flare productivity of solar active regions. These parameters are (1) the mean value of spatial m…
2MASS J22521073-1730134: A Resolved L/T Binary at 14 Parsecs
Burgasser, Adam J.; Reid, I. Neill; Cruz, K. L. +1 more
NICMOS images of the nearby late-type L dwarf 2MASS J22521073-1730134 (DENIS-P J225210.73-173013.4) show that it is a close double, separation 0.13". The companion is 1.0 mag fainter than the primary in the F110W passband and 1.55 mag fainter in the F170M images. The latter passband is centered on the 1.6 µm methane band. The small separatio…
Spectral State Transitions of the Ultraluminous X-Ray Sources X-1 and X-2 in NGC 1313
Feng, Hua; Kaaret, Philip
X-ray spectral state transitions are a key signature of black hole X-ray binaries and follow a well-defined pattern. We examined 12 XMM-Newton observations of the nearby spiral galaxy NGC 1313, which harbors two compact ultraluminous X-ray sources (ULXs), X-1 and X-2, in order to determine if the state transitions in ULXs follow the same pattern. …
C II Abundances in Early-Type Stars: Solution to a Notorious Non-LTE Problem
Przybilla, N.; Nieva, M. F.
We address a long-standing discrepancy between non-LTE analyses of the prominent C II 4267 and 6578/82 Å multiplets in early-type stars. A comprehensive non-LTE model atom of C II is constructed based on critically selected atomic data. This model atom is used for an abundance study of six apparently slow-rotating main-sequence and giant early B-t…
Chandra ACIS Spectroscopy of N157B: A Young Composite Supernova Remnant in a Superbubble
Gotthelf, E. V.; Chu, You-Hua; Wang, Q. Daniel +3 more
We present a Chandra ACIS observations of N157B, a young supernova remnant (SNR) located in the 30 Doradus star formation region of the Large Magellanic Cloud. This remnant contains the most energetic pulsar known (PSR J053747.39-691020.2 E˙=4.8×1038 ergs s-1), which is surrounded by a X-ray-bright nonthermal nebula that like…
The Fundamental Plane for z = 0.8-0.9 Cluster Galaxies
Jørgensen, Inger; Chiboucas, Kristin; Barr, Jordi +3 more
We present the fundamental plane (FP) for 38 early-type galaxies in the two rich galaxy clusters RX J0152.7-1357 (z=0.83) and RX J1226.9+3332 (z=0.89), reaching a limiting magnitude of MB=-19.8 in the rest frame of the clusters. While the zero-point offset of the FP for these high-redshift clusters relative to our low-redshift sample is…
The Low-z Intergalactic Medium. II. Lyβ, O VI, and C III Forest
Shull, J. Michael; Danforth, Charles W.; Stocke, John T. +1 more
We present the results of a large survey of H I, O VI, and C III absorption lines in the low-redshift (z<0.3) intergalactic medium (IGM). We begin with 171 strong Lyα absorption lines (Wλ>=80 mÅ) in 31 AGN sight lines studied with the Hubble Space Telescope and measure corresponding absorption from higher order Lyman lines with FU…
Measuring M Dwarf Winds with DAZ White Dwarfs
Debes, John H.
Hydrogen atmosphere white dwarfs with metal lines, so-called DAZs, show evidence for ongoing accretion of material onto their surfaces. Some DAZs are known to have unresolved M dwarf companions, which could account for the observed accretion through a stellar wind. I combine observed Ca abundances of the DAZs with information on the orbital separa…
The Araucaria Project: The Distance to the Local Group Galaxy IC 1613 from Near-Infrared Photometry of Cepheid Variables
Soszyński, Igor; Dall'Ora, Massimo; Bono, Giuseppe +5 more
We have measured accurate near-infrared magnitudes in the J and K bands of 39 Cepheid variables in the irregular Local Group galaxy IC 1613 with well-determined periods and optical VI light curves. Using the template light curve approach of Soszyński, Gieren, & Pietrzyński, accurate mean magnitudes were obtained from these data, which allowed …