Search Publications
Ionospheric and dayglow responses to the radiative phase of the Bastille Day flare
Mariska, J. T.; Warren, H. P.; Judge, D. L. +11 more
The Sun's Bastille Day flare on July 14, 2000 produced a variety of geoeffective events. This solar eruption consisted of an X-class flare followed by a coronal mass ejection that produced a major geomagnetic storm. We have undertaken a study of this event beginning with an analysis of the effects of the radiative phase of the flare on the dayglow…
Accurate Stellar Population Studies from Multiband Photometric Observations
Kirshner, Robert P.; Panagia, Nino; Romaniello, Martino +1 more
We present a new technique based on multiband near-ultraviolet and optical photometry to measure both the stellar intrinsic properties, i.e., luminosity and effective temperature, and the interstellar dust extinction along the line of sight to hundreds of stars per square arcminute. The yield is twofold. On the one hand, the resulting reddening ma…
Observations of the Hubble Deep Field South with the Infrared Space Observatory - I. Observations, data reduction and mid-infrared source counts
Oliver, Seb; Elbaz, David; Franceschini, Alberto +14 more
We present results from a deep mid-infrared survey of the Hubble Deep Field South (HDF-S) region performed at 6.7 and 15µm with the ISOCAM instrument on board the Infrared Space Observatory (ISO ). The final map in each band was constructed by the co-addition of four independent rasters, registered using bright sources securely detected in a…
Balmer lines emission region in NGC 3516: Kinematical and physical properties
Jovanović, P.; Popović, L. Č.; Mediavilla, E. G. +1 more
We have studied the Balmer line shapes of NGC 3516 in order to find the structure of central Emission Line Region (ELR) and the physical parameters of the emitting plasma. The shapes of these broad emission lines show evidences of a multicomponent origin and also features which could be identified as the peaks of a rotating disc. We have proposed …
Chemical Evolution of the Circumstellar Envelopes of Carbon-rich Post-Asymptotic Giant Branch Objects
Cernicharo, J.; Goicoechea, J. R.; Herpin, F. +1 more
We have observed, with the 30 m IRAM telescope, the Caltech Submillimeter Observatory telescope, and the Infrared Space Observatory (ISO) satellite,3 the rotational lines of CO at millimeter, submillimeter, and far-IR wavelengths in the direction of carbon-rich stellar objects at different stages of evolution: CRL 2688 (a very young proto-planetar…
The spectroscopic orbits and the geometrical configuration of the symbiotic binary AR Pavonis
Mikołajewska, J.; Quiroga, C.; Brandi, E. +2 more
We analyze optical and near infrared spectra of intermediate and high resolution of the eclipsing symbiotic system AR Pavonis. We have obtained the radial velocity curves for the red and the hot component from the M-giant absorption lines and from the wings of Hα , Hβ and He II lambda 4686 emission profiles, respectively. From the orbital elements…
On the detectability of distant Compton-thick obscured quasars
Fabian, A. C.; Crawford, C. S.; Wilman, R. J.
Chandra and XMM-Newton have resolved the 2-8keV X-ray background (XRB) into point sources. Many of the fainter sources are obscured active galactic nuclei (AGN) with column densities in the range of 1022-1023cm-2, some of which have quasar-like luminosities. According to obscuration models, the XRB above 8keV is do…
Resolving the 47 Tucanae Distance Problem
Salaris, Maurizio; Kilkenny, David; van Wyk, Francois +1 more
We present new B-, V-, and I-band photometry for a sample of 43 local subdwarfs with Hipparcos parallax errors less than 13%, in the metallicity range -1.0<[Fe/H]<-0.3, which we use to perform main-sequence (MS) fitting to the Galactic globular cluster 47 Tuc. This sample is many times larger than those used in previous MS-fitting studies an…
A Study of Saturn's Ring Phase Curves from HST Observations
Poulet, F.; French, R. G.; Dones, L. +1 more
Solar phase curves between 0.3° and 6.0° and color ratios at wavelengths λ=0.336 µm and λ=0.555 µm for Saturn's rings are presented using recent Hubble Space Telescope observations. We test the hypothesis that the phase reddening of the rings is less due to collective properties of the ring particles than to the individual properties o…
Multiple X-ray reflection from ionized slabs
Fabian, A. C.; Ross, R. R.; Ballantyne, D. R.
Multiple reflection of X-rays may be important when an accretion disc and its hot corona have a complicated geometry, or if returning radiation due to gravitational light bending is important, or in emission from a funnel such as proposed in some γ-ray burst models. We simulate the effects of multiple reflection by modifying the boundary condition…