Search Publications
On the Spatial Dependence of Low-Degree Solar p-Mode Frequency Shifts from Full-Disk and Resolved-Sun Observations
Korzennik, S. G.; Jiménez-Reyes, S. J.; García, R. A. +1 more
We have analyzed low angular degree (low-l) solar p-mode frequency shifts extracted from two types of observations, both made by instruments on board the ESA/NASA Solar and Heliospheric Observatory satellite during a period that covers the rising phase of activity, cycle 23 (1995-2002). The first are full-disk (Sun-as-a-star) averages made in Dopp…
Galactic Center Extinction: Evidence of Metallic Needles in the General Interstellar Medium
Dwek, Eli
The extinction curve derived from Infrared Space Observatory mid-infrared observations of the Galactic center (GC) exhibits a surprisingly flat behavior in the ~3-8 µm region, contrary to the deep minimum expected from standard interstellar dust models consisting of bare silicate and graphite dust particles. We show that this extinction is l…
On the Nature of the Bright Short-Period X-Ray Source in the Circinus Galaxy Field
Wu, Kinwah; Weisskopf, Martin C.; Tennant, Allyn F. +2 more
The spectrum and light curve of the bright X-ray source CG X-1 in the field of the Circinus galaxy are reexamined. Previous analyses have concluded that the source is an accreting black hole of mass >~50 Msolar, although it has been noted that the light curve resembles that of an AM Herculis system. Here we show that the short period…
Hydrogen Lyα Intensity Oscillations Observed by the Solar and Heliospheric Observatory Ultraviolet Coronagraph Spectrometer
Li, X.; Morgan, H.; Habbal, S. Rifai
We report on a search for significant oscillations in different coronal structures by applying a wavelet analysis to Solar and Heliospheric Observatory UVCS observations of the hydrogen Lyα 1216 Å line intensity taken between 1.5 and 2.2 Rsolar. Significant periodic oscillations, unlikely to be a result of instrumental effects, are show…
First Evidence of Circumstellar Disks around Blue Straggler Stars
De Marco, Orsola; Shara, Michael M.; Zurek, David +2 more
We present an analysis of optical Hubble Space Telescope Space Telescope Imaging Spectrograph and Faint Object Spectrograph spectroscopy of six blue stragglers found in the globular clusters M3, NGC 6752, and NGC 6397. These stars are a subsample of a set of ~50 blue stragglers and stars above the main-sequence turnoff in four globular clusters th…
Impulsive and Gradual Nonthermal Emissions in an X-Class Flare
Qiu, Jiong; Gary, Dale E.; Lee, Jeongwoo
In this paper we present a comprehensive case study of an X-class flare observed on 2001 April 6. The flare consists of two episodes, the first characterized by impulsive spiky bursts and the second by gradual smooth emission at hard X-ray and microwave wavelengths. Emissions in the two episodes are regarded as the impulsive and gradual components…
Ulysses Observations of the Magnetic Connectivity between Coronal Mass Ejections and the Sun
Crooker, N. U.; Riley, Pete; Gosling, J. T.
We have investigated the magnetic connectivity of coronal mass ejections (CMEs) to the Sun using Ulysses observations of suprathermal electrons at various distances between 1 and 5.2 AU. Drawing on ideas concerning the eruption and evolution of CMEs, we had anticipated that there might be a tendency for CMEs to contain progressively more open fiel…
XMM-Newton Spectroscopy of Four Bright Ultraluminous X-Ray Sources in the Antennae Galaxies (NGC 4038/4039)
Zezas, A.; Miller, J. M.; Fabbiano, G. +1 more
We report the results of spectral fits to four bright ultraluminous X-ray sources (ULXs) in the Antennae galaxies (NGC 4038/4039) observed for 41 ks with XMM-Newton. Although emission regions are not resolved as well as in prior Chandra observations, at least four ULXs (X-11, X-16, X-37, and X-44 in the Zezas and Fabbiano scheme) are sufficiently …
Astrometric Discovery of GJ 164B
Henry, Todd; Benedict, G. Fritz; Pravdo, Steven H. +1 more
We discovered a low-mass companion to the M dwarf GJ 164 with the CCD-based imaging system of the Stellar Planet Survey astrometric program. The existence of GJ 164B was confirmed with Hubble Space Telescope NICMOS imaging observations. A high-dispersion spectral observation in V sets a lower limit of Δm>2.2 mag between the two components of th…
12C/13C Ratio in Planetary Nebulae from the IUE Archives
Ferland, G. J.; Rubin, R. H.; Chollet, E. E. +1 more
We investigated the abundance ratio of 12C/13C in planetary nebulae by examining emission lines arising from C III 2s2p3Po2,1,0-->2s21S0. Spectra were retrieved from the International Ultraviolet Explorer archives, and multiple spectra of the same object wer…