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Observational Evidence for the Effect of Amplification Bias in Gravitational Microlensing Experiments
Han, Cheongho; Kim, Ho-Il; Jeong, Youngjin
Recently Alard, Mao, & Guibert and Alard proposed to detect the shift of a star's image centroid, δx, as a method to identify the lensed source among blended stars. Goldberg & Woźniak actually applied this method to the OGLE-1 database and found that seven of 15 events showed significant centroid shifts of δx >~ 0.2". The amount of cent…
Absolute magnitudes and kinematics of CP stars from HIPPARCOS data
Luri, X.; Figueras, F.; Torra, J. +5 more
The position in the HR diagram and the kinematic characteristics of different kinds of CP stars of the upper main sequence are obtained using the LM method of Luri et al. Most of the CP stars are main sequence stars occupying the whole width of the sequence. From a kinematic point of view, they belong to the young disk population (ages < 1.5 Gy…
Jovian radio “bullseyes” observed by Ulysses
MacDowall, R. J.; Kaiser, M. L.
We report the observation of extremely rare semi-bullseye or target-like features in the dynamic spectra of Jupiter obtained in 1991-1994 by the Ulysses Unified Radio and Plasma wave instrument. The emissions lie in the 20-50 kHz band and consist of narrow band (∼1-2 kHz) semi-concentric wisps on frequency-time dynamic spectra. The individual wisp…
ISO observations of the radio-loud BALQSO 1556+3517
Clavel, J.
To date, the quasar 1556+3517 is the only radio loud Broad Absorption Line QSO (BALQSO; Becker et al. 1997). This prompted narrow band filter imaging observations in the range 4-15 mu with the ISO satellite. The source is clearly detected in all filters and appears point-like and isolated at the resolution of ISO. The overall Spectral Energy Distr…
A HgMn companion to the Cepheid SU Cyg.
Wahlgren, G. M.; Evans, N. R.
We report here the discovery of a chemically peculiar star of the HgMn type as a companion to the classical Cepheid variable SU Cyg. This is the first investigation of a HgMn star in a binary system in which a star of a more advanced evolutionary stage is the primary. The age of the Cepheid provides an estimate to the age of the chemical peculiari…
ISO-SWS Observations of the Time Variability of Oxygen-righ Mira Variables
Izumiura, H.; Onaka, T.; Tanabé, T. +3 more
We present the first observation of variation of the infrared spectrum of circumstellar dust emission around an oxygen-rich Mira variable star, Z Cyg, over an entire light variation cycle, based on the periodic SWS01 observations. The 10 µm and 20 µm ‘silicate features’ become stronger relative to the photospheric emission at maximum that at minim…
The Pleiades and alpha Persei Clusters
Eggen, Olin J.
The upper-main-sequence members of the Pleiades and alpha Persei clusters, considered as members of the Local Association, yield mean parallaxes that are only 4% larger than the mean values from Hipparcos observations. The (log T_eff, M_V) diagram reveals that in the temperature range from 6000 to 8000 K, the Hyades and alpha Persei main-sequence …
Search for cool circumstellar matter in the Ursae Majoris group with ISO
Henning, Thomas; Abraham, Peter; Lemke, Dietrich +2 more
We observed the mid- and far-infrared spectral energy distributions of 9 A-type stars from the 300 Myrs old Ursae Majoris group using the ISO satellite and the UKIRT telescope. We found that only 1 out of the 9 stars shows clear signature of circumstellar dust, and we derived an upper limit of 0.05 Mmoon for the dust mass around the oth…
PZ Mon - An Active Evolved Star
Saar, Steven H.
An Hipparcos parallax and new high-resolution spectra show that PZ Mon, long considered a spotted UV Ceti flare star, is actually a distant active giant (K1III+?), probably an RS CVn, with km s
Broad band X-ray spectrum of Cygnus X-1
Rao, A. R.; Chitnis, V. R.; Agrawal, P. C.
We present the hard X-ray (20 - 100 keV) observations of Cygnus X-1 obtained using a large area balloon-borne Xenon filled Multi-anode Proportional Counter (XMPC) telescope. The observations were carried out during the gamma_2 state of the source and we obtain a power law photon index of 1.62+/-0.07. To constrain the spectral shape of the source, …