Search Publications

The Subsystem of Open Clusters in the Post-Hipparcos Era: Cluster Structural Parameters and Proper Motions

Piskunov, A. E.; Kharchenko, N. V.; Pakulyak, L. K.

The wide neighborhoods of 401 open clusters are analyzed using the modern, high-precision, homogeneous ASCC-2.5 all-sky catalog. More than 28000 possible cluster members (including about 12500 most probable members) are identified using kinematic and photometric criteria. Star counts with the ASCC-2.5 and USNO-A2.0 catalogs are used to determine t…

Mid-infrared observations of GRS 1915+105 during plateau and flaring states

Fuchs, Y.; Mirabel, I. F.; Claret, A.

We present mid-infrared (4-18 mu m) observations of the microquasar GRS 1915+105 obtained with ISOCAM, the camera on board the Infrared Space Observatory (ISO), in 1996 April and 1997 October. The first observation probably occurred during a flaring event with oscillating synchrotron emission. The 1997 observation occurred a few days before a majo…

Radio-selected Galaxies in Very Rich Clusters at z<=0.25. II. Radio Properties and Analysis

Owen, Frazer N.; Morrison, Glenn E.

We report on the properties of radio-selected galaxies within 30 very rich Abell clusters with z<~0.25. The radio, optical, and X-ray data for these clusters were presented in Paper I. These radio data sample the ultrafaint (L_1.4>=2×10²² W Hz^-1) radio galaxy population with M_R<=-21 using the wel…

Jet-Cloud Interactions in Compact Steep Spectrum Radio Sources

Capetti, A.; Koekemoer, A. M.; Morganti, R. +8 more

We have obtained HST/STIS long slit spectroscopy of the aligned emission line nebulae in three compact steep spectrum (CSS) radio sources - 3C67, 3C277.1, and 3C303.1. We find systematic offsets (~300-500kms) of the emission line velocities on one or both sides of the radio sources. We also see evidence for broad lines (FWHM~500kms) and complex em…

A comparison between model calculations and observations of sunspot oscillations

Cally, P. S.; Rüedi, I.

We investigate the signal which is expected to be produced by magnetic field oscillations in sunspots umbrae due to the combination of the oscillation model, radiative transfer and observing procedure. For this purpose we investigate the signal expected to be produced by theoretical models of sunspot oscillations and compare them with the signal s…

The distance to the LMC cluster NGC 1866; clues from the cluster Cepheid population

Salaris, M.; Groenewegen, M. A. T.

Recent investigations aimed at estimating the distance to the young LMC cluster NGC 1866 have made use of Red Clump stars in the surrounding LMC field, together with empirical and theoretical Main-Sequence fitting methods, and have found significantly different distances for the field and the cluster, the latter being closer by in distance modulus…

Observational Tests of Chromospheric Magnetic Reconnection

Moon, Yong-Jae; Chae, Jongchul; Park, So-Young

Energetic particle acceleration by coronal mass ejections

Kahler, S. W.

The current paradigm for the source of large, gradual solar energetic particle (SEP) events is that theyare accelerated in coronal/interplanetary shocks driven by coronal mass ejections (CMEs). Early studies established that there is a rough correlation between the logs of the CME speed and the logs of the SEP intensities. Here I review two topics…

ISO-SWS calibration and the accurate modelling of cool-star atmospheres. III. A0 to G2 stars

Gustafsson, B.; Decin, L.; Vandenbussche, B. +4 more

Vega, Sirius, beta Leo, alpha Car and alpha Cen A belong to a sample of twenty stellar sources used for the calibration of the detectors of the Short-Wavelength Spectrometer on board the Infrared Space Observatory (ISO-SWS). While general problems with the calibration and with the theoretical modelling of these stars are reported in {Decin} et al.…

Is B1422+231 a ``Golden Lens''?

Raychaudhury, Somak; Saha, Prasenjit; Williams, Liliya L. R.

The object B1422+231 is a quadruply imaged QSO with an exceptionally large lensing contribution from group galaxies other than main lensing galaxy. We have detected diffuse X-rays from the galaxy group in archival Chandra observations; the inferred temperature is consistent with the published velocity dispersion. We explore the range of possible m…