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Solving the Discrepancy between the Extreme-Ultraviolet and Microwave Observations of the Quiet Sun
Landi, E.; Chiuderi Drago, F.
The aim of the present work is to understand the origin of the long-standing discrepancy between the EUV/UV-based predictions of the quiet-Sun microwave spectrum and the observed one. We compare accurate measurements of the quiet-Sun microwave brightness temperature (Tb) with theoretical calculations obtained by using the differential e…
Hα, Extreme-Ultraviolet, and Microwave Observations of the 2000 March 22 Solar Flare and Spontaneous Magnetic Reconnection
Gallagher, Peter T.; Choe, G. S.; Nita, Gelu M. +4 more
The evolution of a GOES class X1.1 solar flare, which occurred in NOAA Active Region 8910 on 2000 March 22, is discussed using observations from the Owens Valley Solar Array (OVSA), Big Bear Solar observatory (BBSO), Transition Region and Coronal Explorer (TRACE), and the Michelson Doppler Imager (MDI) on board Solar and Heliospheric Observatory (…
The Pulsar/White Dwarf/Planet System in M4: Improved Astrometry
Richer, Harvey B.; Ibata, Rodrigo; Fahlman, Gregory G. +1 more
A young and undermassive white dwarf has been identified as the possible companion to the millisecond pulsar PSR B1620-26 in M4. This association is important since it then helps constrain the mass of the third body in the system to be of order a few times that of Jupiter. The presence of this planet in M4 has critical implications for planetary f…
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 (L1.4>=2×1022 W Hz-1) radio galaxy population with MR<=-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