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51.
L. Kaderhandt A. Barr Domínguez R. Chini M. Hackstein M. Haas F. Pozo Nuez M. Murphy 《Astronomische Nachrichten》2015,336(7):677-681
We present a first overview of variable stars in the Bochum Galactic Disk Survey (GDS) with emphasis on eclipsing binaries (EBs). This ongoing survey is performed by a robotic twin refractor at the Universitätssternwarte Bochum located near Cerro Armazones in Chile. It comprises a mosaic of 268 fields in a stripe of Δb = ±3° along the Galactic plane observed once per month simultaneously in the Sloan r and i filters with a detection limit of rs ∼ 16 mag and is ∼ 15 mag. The data from the first three years until the end of February 2014 yields a total of 41718 variable stars with variability amplitudes between 0.1–6 mag. A cross‐match with SIMBAD identified 11 465 of these variables unambiguously, while 2184 had multiple matches; most of the remaining stars could be matched with 2MASS objects. Among the SIMBAD‐listed objects with single matches, only 1982 turned out as known variables while a further 256 are suspected of variability. That leaves a total of 39480 potentially new variables. The group of known variables comprises 419 stars (21 %) that are classified as EBs while 443 (22%) are of other types; for the remaining 1120 catalogued variables (57 %) the type is unknown. Investigating variability as a function of spectral type, we find that SIMBAD provides spectral types for 2811 (25 %) of the identified stars. Spectral classes B (26 %), A (20 %), and M (25%) contain the most numerous variables, while all other classes contribute less than 10% each. More than half of the B (55 %) and A (56%) stars are designated as EBs, suggesting that hundreds of new B‐ and A‐type EBs may be contained in the GDS archive. In contrast, among the numerous M stars no EBs are known. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
52.
Hugh Cameron 《大气与海洋》2013,51(1):17-20
PHYSICS IN CANADA ‐ SURVEY AND OUTLOOK ‐ PREPARED BY A STUDY GROUP OF THE CANADIAN ASSOCIATION OF PHYSICISTS HEADED BY DR. D.C. ROSE, AND PUBLISHED IN MAY, 1967. 相似文献
53.
Paul D. Allen Simon P. Driver Alister W. Graham Ewan Cameron Jochen Liske Roberto De Propris 《Monthly notices of the Royal Astronomical Society》2006,371(1):2-18
We present near-infrared (NIR) adaptive optics-assisted spectroscopic observations of the CO (Δμ= 2) absorption bands towards the centre of the giant elliptical galaxy NGC 1399. The observations were made with NAOS-CONICA (on the European Southern Observatory's Very Large Telescope) and have a full width at half-maximum resolution of 0.15 arcsec (14 pc). Kinematic analysis of the observations reveals a decoupled core and strongly non-Gaussian line-of-sight velocity profiles in the central 0.2 arcsec (19 pc). NIR imaging also indicates an asymmetric elongation of the central isophotes in the same region.
We use spherical orbit-superposition models to interpret the kinematics, using a set of orthogonal 'eigen-velocity profiles' that allow us to fit models directly to spectra. The models require a central black hole of mass 1.2+0.5 −0.6 × 109 M⊙ , with a strongly tangentially biased orbit distribution in the inner 40 pc. 相似文献
We use spherical orbit-superposition models to interpret the kinematics, using a set of orthogonal 'eigen-velocity profiles' that allow us to fit models directly to spectra. The models require a central black hole of mass 1.2
54.
Stephen R. Kane T. A. Lister rew Collier Cameron Keith Horne David James Don L. Pollacco Rachel A. Street Yiannis Tsapras 《Monthly notices of the Royal Astronomical Society》2005,362(1):117-126
Recent wide field photometric surveys, which target a specific field for long durations, are ideal for studying both long- and short-period stellar variability. Here, we report on 75 variable stars detected during the observations of a field in Pegasus using the Wide Angle Search for Planets Prototype (WASP0) instrument, 73 of which are new discoveries. The variables detected include 16 δ Scuti stars, 34 eclipsing binaries, 3 BY Draconis stars and 4 RR Lyraes. We estimate that the fraction of stars in the field brighter than V ∼ 13.5 exhibiting variable behaviour with an amplitude greater than 0.6 per cent rms is ∼0.4 per cent. These results are compared with other wide field stellar variability surveys, and implications for detecting transits due to extra-solar planets are discussed. 相似文献
55.
L. Kaper N.R. Trams P. Barr J.Th. Van Loon L.B.F.M. Waters 《Astrophysics and Space Science》1997,255(1-2):199-204
We present the first results of our ISO program on High-Mass X-ray Binaries (HMXBs). Infrared photometry, obtained at different
aspect angles of the systems, is used to investigate the massive star's disrupted stellar wind and the accretion flow towards
the compact X-ray source.
Scenarios for massive binary evolution predict that HMXBs receive a large kick velocity during the supernova explosion of
the compact star's progenitor. One might, therefore, expect to observe wind bow shocks around these systems such as observed
around many OB-runaway stars. Such a wind bow shock has recently been discovered around the system Vela X-1.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
56.
S.P.S. Eyres A. Evans A. Salama P. Barr J. Clavel N. Jenkins K. Leech M. Kessler T. Lim L. Metcalfe B. Schulz 《Astrophysics and Space Science》1997,255(1-2):361-366
A number of symbiotic stars have been observed with ISO. In addition to a number of emission lines, SWS observations of the
symbiotic novae RR Tel and V1016 Cyg reveal prominent, broad 10 & 18 μm silicate dust features. The 10 μm features are similar
to the crystalline silicate profiles seen in classical novae. There is some evidence that the silicate brightness in V1016
Cyg varies with Mira-component phase. However, the silicate feature in RR Tel also showed some variation even though observations
were made at very similar Mira-component phases. PHT observations of S-type symbiotic stars show the IR emission to be dominated
by the red-giant component. However, an excess in the PHT-P filters from 10 to 15 μm is evident in all the stars, and there
may be a broad 3.2 μm absorption feature or a broad 3.8 μm emission feature. At this time we have no adequate physical explanations
for any of these features.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
57.
J. R. Barnes Travis S. Barman L. Prato D. Segransan H. R. A. Jones C. J. Leigh A. Collier Cameron D. J. Pinfield 《Monthly notices of the Royal Astronomical Society》2007,382(1):473-480
We obtained 238 spectra of the close-orbiting extrasolar giant planet HD 189733b with resolution R ∼ 15 000 during one night of observations with the Near-Infrared High-Resolution Spectrograph (NIRSPEC), at the Keck II Telescope. We have searched for planetary absorption signatures in the 2.0–2.4 μm region where H2 O and CO are expected to be the dominant atmospheric opacities. We employ a phase-dependent orbital model and tomographic techniques to search for the planetary absorption signatures in the combined stellar and planetary spectra. Because potential absorption signatures are hidden in the noise of each single exposure, we use a model list of lines to apply a spectral deconvolution. The resulting mean profile possesses a signal-to-noise ratio (S/N) that is 20 times greater than that found in individual lines. Our spectral time series thus yields spectral signatures with a mean S/N = 2720. We are unable to detect a planetary signature at a contrast ratio of log10 ( F p / F * ) =−3.40 , with 63.8 per cent confidence. Our findings are not consistent with model predictions which nevertheless give a good fit to mid-infrared observations of HD 189733b. The 1σ result is a factor of 1.7 times less than the predicted 2.185-μm planet/star flux ratio of log10 ( F p / F * ) ∼−3.16 . 相似文献
58.
59.
A.G.W. Cameron 《Icarus》1985,62(2):319-327
According to the single-impact hypothesis for forming the Moon, the angular momentum needed for the present Earth-Moon system can be imparted to the proto-Earth by a collision with a body having one-tenth of the mass or more. The collision must vaporize a large amount of rock which must stay in the form of vapor after expanding in density by a factor of several, so that pressure gradients can accelerate significant amounts of the matter into orbital motion about the proto-Earth. A successful theory must put considerably more than a lunar mass into orbit, having considerably more angular momentum than is needed to assemble a lunar mass in orbit at 3 Earth radii. Such a collision has been simulated by a particular form of a particle-in-cell representation of hydrodynamics and 78 cases have been run representing variations in a variety of parameters. A significant fraction of the cases were successful in creating a satisfactory prelunar accretion disk. A fairly common characteristic of these cases was the presence of an excess velocity in the collision (above that of a parabolic orbit), implying that the projectile involved in the collision existed in an Earth-crossing orbit of significant ellipticity. A majority of the mass of the prelunar accretion disk is contributed by the projectile. 相似文献
60.