Search Publications
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…
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…
HST STIS Observations of PG 0946+301: The Highest Quality UV Spectrum of a BALQSO
Pettini, Max; Brandt, W. N.; Laor, Ari +16 more
We describe deep (40 orbits) Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph observations of the broad absorption line (BAL) quasi-stellar object (QSO) PG 0946+301 and make them available to the community. These observations are the major part of a multiwavelength campaign on this object aimed at determining the ionization equili…
The Giant Flare of 1998 August 27 from SGR 1900+14. I. An Interpretive Study of BeppoSAX and Ulysses Observations
Hurley, K.; Feroci, M.; Duncan, R. C. +1 more
The giant flare of 1998 August 27 from SGR 1900+14 was extraordinary in many ways: it was the most intense flux of gamma rays ever detected from a source outside our solar system; it was longer than any previously detected burst from a soft gamma repeater (SGR) in our Galaxy by more than an order of magnitude; and it showed a remarkable four-peake…
On the Origin of Infrared Plateau Features in Proto-Planetary Nebulae
Volk, Kevin; Kwok, Sun; Bernath, Peter
The emission profiles of the 8 and 12 µm plateau features are derived from the Infrared Space Observatory spectra of proto-planetary nebulae. We suggest that these plateau features are primarily the result of alkane and alkene side groups on very large aromatic molecules and small carbonaceous particles. The relationship between the narrow a…
Ultraviolet Line Spectra of Metal-poor Star-forming Galaxies
Pettini, Max; Robert, Carmelle; Heckman, Timothy M. +3 more
We present synthetic ultraviolet spectra of metal-poor star-forming galaxies that were calculated with the Starburst99 package. A new spectral library was generated from Hubble Space Telescope observations of O stars in the Large and Small Magellanic Clouds. The corresponding mean metallicity of the synthetic spectra is approximately 1/4 Zsol…