Search Publications
Technique for Detecting Warm-Hot Intergalactic Gas in Quasar Ultraviolet Spectra
Binette, Luc; Rodríguez-Martínez, Mario; Haro-Corzo, Sinhue +1 more
The ionizing spectral energy distribution of quasars exhibits a steepening of the distribution shortward of ~1200 Å. The change of the power-law index from approximately -1 (near-UV) to -2 (far-UV) has so far been interpreted as being intrinsic to quasars. We consider the possibility that the steepening may result from a tenuous absorption compone…
Comparison of Total Solar Irradiance with NASA/National Solar Observatory Spectromagnetograph Data in Solar Cycles 22 and 23
Jones, Patricia B.; Jones, Harrison P.; Branston, Detrick D. +1 more
NASA/National Solar Observatory Spectromagnetograph (SPM) data are compared with spacecraft measurements of total solar irradiance (TSI) variations for 8 yr beginning with the declining phase of solar cycle 22 and extending into the maximum of cycle 23. Previously reported conclusions based on a similar comparison for a shorter time period appear …
Hubble Space Telescope Observations of Three Very Young Star Clusters in the Small Magellanic Cloud
Mutchler, Max; Villaver, Eva; Shaw, Richard A. +1 more
We present Space Telescope Imaging Spectrograph (STIS) broadband imagery and optical slitless spectroscopy of three young star clusters in the Small Magellanic Cloud (SMC). MA 1796 and MG 2 were previously known as planetary nebulae and were observed as such in our Hubble Space Telescope (HST) survey. With the HST spatial resolution, we show that …
XMM-Newton Observation of Fe Kα Emission from a Broad Absorption Line Quasar: Markarian 231
Turner, T. J.; Kraemer, S. B.
We present results from a 20 ks XMM-Newton observation of Mrk 231. The European Photon Imaging Camera (EPIC) spectral data reveal strong line emission due to Fe Kα, which has rarely been detected in this class, as broad absorption line quasars (BAL QSOs) are very faint in the X-ray band. The line energy is consistent with an origin in neutral Fe. …
Optimal Masks for Solar g-Mode Detection
Kosovichev, A. G.; Scherrer, P. H.; Schou, J. +1 more
The detection of gravity (g) modes of solar oscillations is important for probing the physical conditions in the Sun's energy-generating core. We have developed a new method of spatial masks optimized to reveal solar g-modes of angular degree l=1-3 and applied it to Michelson Doppler Imager data in the frequency range of 50-500 µHz. These ma…
Atomic Data and Spectral Line Intensities for Si VII
Bhatia, A. K.; Landi, E.
Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for the Si VII configurations 2s22p4, 2s2p5, 2p6, 2s22p33s, 2s22p33p, and 2s22p33d, giving rise to 86 fine-struc…
ι Cassiopeiae: Orbit, Masses, and Photometry from Adaptive Optics Imaging in the I and H Bands
Roberts, Lewis C., Jr.; Drummond, Jack; Milster, Scott +1 more
The multiple-star system ι Cas was observed as a calibration for our adaptive optics observations in 2001 July with the Advanced Electro-Optical System (AEOS) 3.63 m telescope in Maui, Hawaii, and the first ever image of the faint astrometric component Aa (along with A and B) was obtained at the H-band wavelength. Another image was obtained in 200…
Nonthermal Mass Motions within the High-Temperature Plasmas above a Complex Solar Active Region
Curdt, W.; Landi, E.; Feldman, U.
We report on mass motions in high-temperature plasmas at radial distances of 1.06-1.20 Rsolar corresponding to 3.3×104-1.3×105 km above the west solar limb. The observations were conducted over a 53 hr time period while a complex active region moved across the west solar limb. We found that the nonthermal mass moti…
Predictions for the Counts of Faint, High-Redshift Galaxies in the Mid-Infrared
Spergel, David N.; Turner, Edwin L.; Haiman, Zoltán
Deep mid-infrared (MIR) observations could reveal a population of faint, high-redshift (z>3), dusty starburst galaxies that are the progenitors of present-day spheroids or bulges and are beyond the reach of current instruments. We utilize a semianalytic galaxy formation scheme to find a range of models for the MIR galaxy counts, down to a flux …
Using Optical and Near-Infrared Photometry to Test MACHO Lens Candidates
Sarajedini, Ata; von Hippel, Ted; Ruiz, Maria Teresa
We obtained new VLT/ISAAC H-band observations for five MACHO LMC source stars and adjacent LMC field regions. After combining our near-IR photometry with Hubble Space Telescope/PC BVRI optical photometry, we compared the MACHO objects to the adjacent field stars in a variety of color-magnitude and color-color diagrams. These diagnostic diagrams we…