共查询到20条相似文献，搜索用时 62 毫秒
1.
A. Thoul R. Scuflaire B. Vatovez A. Noels P. Magain M. Briquet M.-A. Dupret 《Astrophysics and Space Science》2003,284(1):241-244
Models of Cen A & B have been computed using the masses determinedby Pourbaix et al. (2002) and the data derived from the spectroscopicanalysis of Neuforge and Magain (1997). The seismological dataobtained by Bouchy and Carrier (2001, 2002) do help improveour knowledge of the evolutionary status of the system. All the constraintsare satisfied with a model which gives an age of about 6 Gyr for the binary. 相似文献
2.
We present the first results of a survey of Blue Compact Galaxies with a 10 m array. Blue Compact Galaxies (BCGs) are dwarf galaxies experiencing an intense burst of star formation. As dwarf systems, their main characteristics is a low heavy-elements abundance. Although dust is thought to be less abundant in these galaxies than in normal spirals, the presence of a compact starburst region favors a detection in the infrared, and 10 m imaging is perfectly suited to star formation studies in BCGs since it focuses on the hottest dust inside the star-forming regions. 相似文献
3.
Maxim Voronkov Andrej Sobolev Simon Ellingsen Andrei Ostrovskii Alexei Alakoz 《Astrophysics and Space Science》2005,295(1-2):217-223
We report the detection with the ATCA of 6.7 GHz methanol emission towards OMC-1. The source has a size between 40 and 90, is located to the south-east of Ori-KL and may coincide in position with the 25 GHz masers. The source may be an example of an interesting case recently predicted in theory where the transitions of traditionally different methanol maser classes show maser activity simultaneously. In addition, results of recent search for methanol masers from the 25 and 104.3 GHz transitions are reported. 相似文献
4.
Ramon D. Wolstencroft S. M. Scarrott T. M. Gledhill 《Astrophysics and Space Science》1995,224(1-2):395-398
The asymmetries in the brightness structure and levels of polarization between the two sides of the Pic disc are discussed. The possibility of these differences being caused by a planet, or planets, within the circumstellar disc is investigated. 相似文献
5.
Present Observational Status of the Intermediate Mass Stars: δ Sct Stars, γ Dor Stars and roAp Stars
D.W. Kurtz 《Astrophysics and Space Science》2003,284(1):29-36
The present observational status of the Sct stars, Dor stars and roAp stars is discussed. The Sct stars are the most intensively observed of the three groups, but it has become clear that there are severe problems in extracting asteroseismic information from them. Dozens of frequencies are observed, but hundreds of frequencies are predicted from the models; unique matches of observation and theory still elude us. The Sct stars are observationally complex – some recent `best case' campaigns are discussed. It is possible that substantial observational advances for Sct stars may need to await upcoming satellite missions. New Dor stars are beingdiscovered frequently, and new behaviour is being found for them. They constitutean observationally young field. Their pulsational frequency range is being expanded, their position in the HR diagram is becoming better known (but is yet to be fully constrained), and the possibility exists of hybrid Dor – Sct stars that have greatasteroseismic promise, although it is clear such stars are rare, if they do exist. It has been observationally challenging to extract more than a fewfrequencies for any Dor star so far. Exciting spectroscopic discoveries of new behaviour in roAp stars promise unprecedented information about the structure of the peculiar atmospheres ofthose stars – pulsation amplitude and phase in 3D, magnetic field structurein 3D, abundance stratification in 3D, realistic T- for the most peculiarstars – as well as entirely new information about the interaction of pulsation,rotation and magnetic fields. Recent theoretical work has led to new understandingof the previously inexplicable frequency spacing of HR 1217 with new Whole Earth Telescope observations supporting this theory. An `improved oblique pulsator model' has been developed in which the pulsationaxis is not the magnetic axis; this model has passed several observationaltests and new ones are being devised to examine it further. 相似文献
6.
We have started a program of high-resolution (0.4/pixel) 10m imaging of bipolar outflow sources using the 10m camera CAMIRAS. We present recent results obtained at the Canada France Hawaii Telescope which reveal extended emission or IR companions in several luminous objects. The extended emission we detected probably arises from transiently heated very small grains, while the newly discovered companions could contribute significantly to the outflow activity and extended far-IR emission usually attributed to the main optical source. 相似文献
7.
8.
J. Puls A. Feldmeier U. W. E. Springmann S. P. Owocki A. W. Fullerton 《Astrophysics and Space Science》1994,221(1-2):409-426
On the basis of a a careful analysis of resonance line formation (both for singlets and doublets) in structured winds, presenttime dependent models of the line driven winds of hot stars (Owocki et al., this volume; Feldmeier, this volume) are shown to be able to explain a number of observational features with respect to variability and structure: they are (in principle) able to reproduce theblack andbroad troughs (without any artificial turbulence velocity) and the blue edge variability observed in saturated resonance lines; they might explain the long lived narrow absorption components often observed in unsaturated lines at high velocities; they predict a relation between the edge velocity of UV-lines and the radiation temperature of the observed X-ray emission.As a first example of the extent to which theoretical models can be constrained by comparisons between observations and profiles calculated by spectrum synthesis from structured winds, we show here that models with deep-seated onset of structure formation ( 1.1R
*
) produce resonance lines which agreequalitatively with observational findings; in contrast, the here presented models with structure formation only well out in the wind ( 1.6R
*
) fail in this respect. 相似文献
9.
S. I. Plachinda 《Astrophysics》2005,48(1):9-19
Multiyear high precision measurements of the longitudinal component of the magnetic field (Be) of four supergiants are reported: Aqr (G0 Ib), Aqr (G2 Ib), Gem (G8 Ib), and Peg (K2 Ib). The best measurement accuracy, =0.8 G, was achieved for Peg. A Monte Carlo method was used to test the reliability of the derived measurement errors. The differences between the observational errors and the calculated Monte Carlo errors were 3.2%. For Aqr and Aqr no statistically significant value of the magnetic field was recorded when averaged over a night. For eGem the following overnight average values of the magnetic field were recorded on five nights: 11.1±2.7 G, 9.8±2.5 G, –10.5±3.0 G, 38.1±7.4 G, and 5.3±1.5 G. For Peg the magnetic field recorded over two nights was –5.3±0.9 G and – 2.7±0.8 G.Translated from Astrofizika, Vol. 48, No. 1, pp. 15–28 (February 2005). 相似文献
10.
We have used the ESO 10 m camera, TIMMI, to image with a very high angular resolution (PFoV: 0.3; FWHM:0.9) several main-sequence star disk candidates. Information on the -Pictoris dust disk has been obtained in a region largely inaccessible to previous observations: 0–80 AU, with a resolution of about 5 AU after deconvolution. Another promising target for 10 m imaging, 51 Ophiuchi, appears point-like.based on data collected at the European Southern Observatory (ESO), La Silla, Chile 相似文献
11.
P. O. Lagage G. Oloffson S. Cabrit C. Cesarsky L. Nordh J. M. Rodriguez Espinosa 《Experimental Astronomy》1994,3(1-4):163-164
The region around the Herbig Ae/Be star LkH198 was imaged at 10m with the CAMIRAS camera at the Canada-France-Hawaii Telescope and the Nordic Optical Telescope. We discovered a deeply embedded companion 6 north of LkH198, which may be responsible for most of the far-infrared emission in the region and for driving the molecular flow. LkH198 appears point-like at our resolution (FWHM 1.3), excluding an extended envelope of transiently heated small grains as the dominant origin of the mid-infrared excess in that star. 相似文献
12.
Vincenzo Ripepi 《Astrophysics and Space Science》2003,284(1):69-72
We present time series observations of the intermediate mass Pre-Main Sequence star H254 belonging to the young star cluster IC 348 and of the Herbig Ae star V351 Ori.Both these stars present light variation on short time scale (a few hours) typical of the Scuti pulsation. The new data are briefly described together with the plan for future observational campaigns on PMS Scuti stars. 相似文献
14.
We have investigated ROSAT X-ray data of OB stars to search for evidence of time variability in the X-ray emission from early-type stars. As an example for such studies we present a detailed variability analysis for our two program stars Ori and Ori which have been multiply observed with ROSAT. The long-term analysis of both stars now covers a time range of 2.5 years and includes six pointed PSPC observations, an additional pointed HRI observation of Ori and the ROSAT all-sky survey data of both stars. Over a long time range the X-ray light curves of Ori and Ori show no evidence for variability. In the case of Ori we detected a moderate increase in X-ray count rate during a period of 2 days which can be explained as a strong shock propagating in the wind of an O-type star. 相似文献
16.
One of the major goals in VHE--ray astronomy is to open the energy range below 100 GeV with earthbound detectors. This paper demonstrates a new method for analyzing erenkov light of a shower in a erenkov telescope array. This method is successful for showers in this low energy regime where previous techniques (e.g. alpha analysis) are not applicable. A Monte Carlo simulation is applied to a system of 19 Whipple type [3, Cawley 1990] Imaging Atmospheric erenkov telescopes (IAT), each built as a 10 m diameter reflector and equipped with a 109 photomultiplier tube camera. The energy threshold for a single detector of this type is given [5, Kerrick et al. 1995] as 250 GeV. Analysis of simulated coincident events of the system for those events not having enough light to apply a standard imaging analysis [4, Hillas 1985], leads to a considerably lower threshold of 85 GeV. With a new analysis method of these events it is shown that it should be possible to distinguish between -ray induced and proton induced showers. The improvement of sensitivity (Q = figure of merit) of this analysis method is found to be Q=2.9. 相似文献
17.
Stephan R. McCandliss Bruce Bohannan Carmelle Robert Anthony F. J. Moffat 《Astrophysics and Space Science》1994,221(1-2):155-167
The original temporal analysis of a 12 night spectral timeseries of WR-134 has been found to be flawed and a re-analysis shows that the line profile variations are indeed periodic. When combined with a 4 night timeseries taken 45 days earlier, a period near 2.27 d is found in periodograms of the Heii 5412 line centroid,rms line width, and line skew variations. When the emission line residuals are ordered as a function of phase, a sinuous feature appears to snake about the line center with an amplitude of ± 500 km s–1. This is 20 larger than the line centroid amplitude; the calculation of which is heavily weighted by static portions of the line profile. In addition to the snake, emission residuals appear that move away from line center on unbound trajectories and are thought to result from the interaction of a periodic driver with the unstable flow of the radiation driven wind. The nature of the periodic driver is a topic for discussion. 相似文献