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The enigmatic WR46: A binary or a pulsator in disguise. II. The spectroscopy
Crowther, P. A.; van der Hucht, K. A.; van Genderen, A. M. +1 more
We present spectroscopic monitoring of the Wolf-Rayet (WR) star
First orbital elements for the lambda Bootis spectroscopic binary systems HD 84948 and HD 171948. Implications for the origin of the lambda Bootis stars
Kamp, I.; Paunzen, E.; Claret, A. +4 more
We present high-resolution spectroscopic observations of the two lambda Bootis type spectroscopic binary systems HD 84948 and HD 171948. Both systems consist of two true lambda Bootis stars, as has already been proven by a detailed abundance analysis taking into account the binary nature. Nevertheless, we have obtained non-LTE abundances for carbo…
How much of the solar irradiance variations is caused by the magnetic field at the solar surface?
Solanki, S. K.; Fligge, M.
The contribution to total solar irradiance variations by the magnetic field at the solar surface is estimated. Detailed models of the irradiance changes on the basis of magnetograms show that magnetic features at the solar surface account for over 90% of the irradiance variations on a solar rotation time scale and at least 70% on a solar cycle tim…
Observations of Mira stars with the IOTA/FLUOR interferometer and comparison with Mira star models
Beckmann, U.; Weigelt, G.; Hofmann, K. -H. +16 more
We present K'-band observations of five Mira stars with the IOTA interferometer. The interferograms were obtained with the FLUOR fiber optics beam combiner, which provides high-accuracy visibility measurements in spite of time-variable atmospheric conditions. For the M-type Miras X Oph, R Aql, RU Her, R Ser, and the C-type Mira V CrB we derived th…
Aging of Titan's Aerosols
Dimitrov, Vasili; Bar-Nun, Akiva
Titan's haze is composed of aerosols containing long chain polymers of acetylene with some hydrogen cyanide. These polymers have alternating double/single and triple/single bonds, which can open spontaneously or under the action of UV radiation or particle impact. Once opened, they can induce the opening of a double or triple bond in an adjacent c…
A Precise Orbit Determination of χ1 Orionis from Astrometric and Radial Velocity Data
Han, Inwoo; Gatewood, George
We have derived an accurate orbit of χ1 Orionis (HD 39587, HIP 27913, HR 2047) by combining precise astrometric and radial velocity data. The combined orbital analysis yields P=5156.7+/-2.5 days, K1=1.885+/-0.004 km s-1, α1=94.8+/-1.6 mas, e=0.451+/-0.003, and mass ratio (M2/M1) q=0…
Discovery of an Extremely Red Object in the Field of HD 155826
Djorgovski, S. G.; Christian, D. J.; Gorjian, V. +7 more
We have discovered an extremely red object, LSF 1, located 7" southwest (P.A. 217°) of the bright spectroscopic binary system HD 155826. Originally reported by IRAS as one source detected at 12-60 µm, and found as a single 6-25 µm source of similar flux in the Midcourse Space Experiment Galactic plane survey, two bright point sources w…
Fast acceleration of a CME-related X-ray structure in the low solar corona
Nitta, Nariaki V.; Alexander, David; Metcalf, Thomas R.
We report on a unique observation of the early and rapid acceleration of a fast CME in the low solar corona. The coronal disturbance associated with a LASCO CME and concurrent X1.2 flare on 1998 April 23 was well-observed by the Yohkoh Soft X-ray Telescope. The X-ray observations clearly show an accelerating structure, reaching 800-1100 km/s in ~5…
Modeling IR spectra of OH/IR stars at different phases
Suh, Kyung-Won; Kim, H. -Y.
We investigate the spectral energy distributions (SEDs) of OH/IR stars (OH127.8+0.0 and OH26.5+0.6) having thick dust envelopes at different pulsation phases. Using new infrared observational data including the Infrared Space Observatory (ISO) data, we determine the new pulsation parameters. The deep silicate absorption features show significant v…
A Uniform Analysis of the Lyα Forest at z = 0-5. IV. The Clustering and Evolution of Clouds at z <= 1.7
Bechtold, Jill; Dobrzycki, Adam; Scott, Jennifer +1 more
We present results on the evolution and clustering of Lyα lines at low redshift as part of our series ``A Uniform Analysis of the Lyα Forest at z=0-5.'' The sample analyzed in this paper contains 1298 Lyα absorption lines from 165 quasar spectra mined from the archives of the Faint Object Spectrograph on the Hubble Space Telescope (HST). Our sampl…