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The Bright Optical Companion to the Eclipsing Millisecond Pulsar in NGC 6397
Ferraro, Francesco R.; Sabbi, Elena; Possenti, Andrea +1 more
We report the optical identification of the companion to the eclipsing millisecond pulsar PSR J1740-5340 in the globular cluster NGC 6397. A bright variable star with an anomalous red color and optical variability (~0.2 mag) that nicely correlates to the orbital period of the pulsar (~1.35 days) has been found close to the pulsar position. The pec…
Models for Old, Metal-poor Stars with Enhanced α-Element Abundances. III. Isochrones and Isochrone Population Functions
VandenBerg, Don A.; Bergbusch, Peter A.
An isochrone population function (IPF) gives the relative distribution of stars along an isochrone. IPFs contain the information needed to calculate both luminosity functions and color functions, and they provide a straightforward way of generating synthetic stellar populations. An improved algorithm for interpolating isochrones and IPFs, based on…
Far-Infrared Investigation of Class 0 Sources: Line Cooling
Giannini, Teresa; Nisini, Brunella; Lorenzetti, Dario
We have investigated with the Long Wavelength Spectrometer (LWS) of the Infrared Space Observatory (ISO) the far-infrared spectra (43-197 µm) of a sample of 17 class 0 sources and their associated outflows. In addition to [O I] 63 µm, the pure rotational lines of abundant molecules such as CO, H2O, and OH are frequently obse…
An Evaluation of Coronal Heating Models for Active Regions Based on Yohkoh, SOHO, and TRACE Observations
Aschwanden, Markus J.
Recent soft X-ray and EUV data from space observations with Yohkoh, the Solar and Heliospheric Observatory (SOHO), and the Transition Region and Coronal Explorer (TRACE) established three important observational constraints for coronal heating models: (1) coronal loops in active regions have an overdensity that can be supplied only by upflows of h…
An Abundance Analysis for Four Red Horizontal-Branch Stars in the Extremely Metal-Rich Globular Cluster NGC 6528
Cohen, Judith G.; Carretta, Eugenio; Gratton, Raffaele G. +1 more
We present the results of the first analysis of high-dispersion spectra of four red horizontal-branch stars in the metal-rich globular cluster NGC 6528, located in Baade's window. We find that the mean [Fe/H] for NGC 6528 is +0.07+/-0.01 dex (error of the mean), with a star-to-star scatter of σ=0.02 dex (four stars), although the total error is li…
The Optical-Near-Infrared Spectrum of the M87 Jet fromHubble Space Telescope Observations
Perlman, Eric S.; Sparks, William B.; Macchetto, F. Duccio +2 more
We present 1998 Hubble Space Telescope observations of M87 that yield the first single-epoch optical and radio-optical spectral index image of the jet at 0.15" resolution. We find <αro>~0.67, comparable to previous measurements, and <αo>~0.9 (Fν~ν-α), slightly flatter than previous workers. R…
Evidence for a Sudden Magnetic Field Reconfiguration in Soft Gamma Repeater 1900+14
Hurley, Kevin; Kouveliotou, Chryssa; Göǧüş, Ersin +5 more
We report the detection of large flux changes in the persistent X-ray flux of soft gamma repeater (SGR) 1900+14 during its burst active episode in 1998. Most notably, we find a factor of ~700 increase in the nonburst X-ray flux following the August 27 flare, which decayed in time as a power law. Our measurements indicate that the pulse fraction re…
No Supermassive Black Hole in M33?
Joseph, Charles L.; Ferrarese, Laura; Merritt, David
We observed the nucleus of M33, the third-brightest galaxy in the Local Group, with the Space Telescope Imaging Spectrograph at a resolution at least a factor of 10 higher than previously obtained. Rather than the steep rise expected within the radius of gravitational influence of a supermassive black hole, the random stellar velocities showed a d…
HST/NICMOS2 coronagraphic observations of the circumstellar environment of three old PMS stars: HD 100546, SAO 206462 and MWC 480
Ménard, F.; Mouillet, D.; Augereau, J. C. +1 more
The close environment of four old Pre-Main Sequence stars has been observed thanks to the coronagraphic mode of the HST/NICMOS2 camera at lambda =1.6 mu m. In the course of this program, a circumstellar annulus around HD 141569 was detected and has already been presented in Augereau et al. (\cite{aug99b}b). In this paper, we report the detection o…
FIRBACK: III. Catalog, source counts, and cosmological implications of the 170 mu m ISO
Elbaz, D.; Cesarsky, C.; Bouchet, F. R. +17 more
The FIRBACK (Far Infrared BACKground) survey is one of the deepest imaging surveys carried out at 170 mu m with ISOPHOT onboard ISO, and is aimed at the study of the structure of the Cosmic Far Infrared Background. This paper provides the analysis of resolved sources. After a validated process of data reduction and calibration, we perform intensiv…