내용
사진
사진 업로드
DSS Images Other Images
관련 글
Few Skewed Disks Found in First Closure-Phase Survey of Herbig Ae/Be Stars
Using the three-telescope IOTA interferometer on Mount Hopkins, wereport results from the first near-infrared (λ=1.65 μm)closure-phase survey of young stellar objects (YSOs). These closurephases allow us to unambiguously detect departures from centrosymmetry(i.e., skew) in the emission pattern from YSO disks on the scale of ~4mas, expected from generic ``flared disk'' models. Six of 14 targetsshowed small, yet statistically significant nonzero closure phases, withlargest values from the young binary system MWC 361-A and the(pre-main-sequence?) Be star HD 45677. Our observations are quitesensitive to the vertical structure of the inner disk, and we confrontthe predictions of the ``puffed-up inner wall'' models of Dullemond,Dominik, & Natta (DDN). Our data support disk models with curvedinner rims because the expected emission appears symmetricallydistributed around the star over a wide range of inclination angles. Incontrast, our results are incompatible with the models possessingvertical inner walls because they predict extreme skewness (i.e., largeclosure phases) from the near-IR disk emission that is not seen in ourdata. In addition, we also present the discovery of mysterious H-band``halos'' (~5%-10% of light on scales 0.01"-0.50") around a few objects,a preliminary ``parametric imaging'' study for HD 45677, and the firstastrometric orbit for the young binary MWC 361-A.
| Dust Emission Features in NGC 7023 between 0.35 and 2.5 Microns: Extended Red Emission (0.7 Microns) and Two New Emission Features (1.15 and 1.5 Microns)
We present 0.35-2.5 μm spectra of the south and northwest filamentsin the reflection nebula NGC 7023. These spectra were used to test thetheory of Seahra & Duley that carbon nanoparticles are responsiblefor extended red emission (ERE). Our spectra fail to show theirpredicted second emission band at 1.0 μm even though both filamentsexhibit strong emission in the familiar 0.7 μm ERE band. Thenorthwest filament spectrum does show one, and possibly two, new dustemission features in the near-infrared. We clearly detect a strongemission band at 1.5 μm which we tentatively attribute toβ-FeSi2 grains. We tentatively detect a weaker emissionband at 1.15 μm which coincides with the location expected fortransitions from the conduction band to midgap defect states of siliconnanoparticles. This is added evidence that silicon nanoparticles areresponsible for ERE as they already can explain the observed behavior ofthe main visible ERE band.
| H2 Line Ratios to Discriminate Dense Photodissociation Regions from Shocks: Application to NGC 2023 and NGC 7023
We measured the distribution of H2 line ratios, 2-1 S(1)/1-0S(1) and 4-2 S(1)/3-1 S(1), in typical dense photodissociation regions(PDRs) associated with the reflection nebulae, NGC 2023 and NGC 7023.The line images were obtained with a recently developed wide-field(3.9′x3.9′) Fabry-Perot imager, MUSE. In both objects, the2-1 S(1)/1-0 S(1) ratio varies spatially between 0.2 and 0.6 as a resultof the variation of gas density (n~105-106cm-3) and UV intensity(G0~103-104) in PDRs. On the otherhand, the 4-2 S(1)/3-1 S(1) ratio is nearly constant (~1) in bothobjects. This constancy of the 4-2 S(1)/3-1 S(1) ratio agrees with modelpredictions. Since the observed 4-2 S(1)/3-1 S(1) ratio is significantlylarger than the expected ratio for shock excitation, the 4-2 S(1)/3-1S(1) ratio is expected to discriminate both dense and diffuse PDRs fromshocks.
| A catalog of rotational and radial velocities for evolved stars
Rotational and radial velocities have been measured for about 2000evolved stars of luminosity classes IV, III, II and Ib covering thespectral region F, G and K. The survey was carried out with the CORAVELspectrometer. The precision for the radial velocities is better than0.30 km s-1, whereas for the rotational velocity measurementsthe uncertainties are typically 1.0 km s-1 for subgiants andgiants and 2.0 km s-1 for class II giants and Ib supergiants.These data will add constraints to studies of the rotational behaviourof evolved stars as well as solid informations concerning the presenceof external rotational brakes, tidal interactions in evolved binarysystems and on the link between rotation, chemical abundance and stellaractivity. In this paper we present the rotational velocity v sin i andthe mean radial velocity for the stars of luminosity classes IV, III andII. Based on observations collected at the Haute--Provence Observatory,Saint--Michel, France and at the European Southern Observatory, LaSilla, Chile. Table \ref{tab5} also available in electronic form at CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| UBV photometry of stars whose positions are accurately known. VI
Results are presented from UBV photometric observations of 1000 stars ofthe Bright Star Catalogue and the faint extension of the FK5.Observations were carried out between July 1987 and December 1990 withthe 40-cm Cassegrain telescope of the Kvistaberg Observatory.
| Photometric Data for the Bright Stars
Not Available
| Luminosity Function and Space Motions of G8-K1 Stars Derived from Spectroscopic Parallaxes.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955ApJ...122..222H&db_key=AST
|
새 글 등록
관련 링크
새 링크 등록
다음 그룹에 속해있음:
|
관측 및 측정 데이터
천체목록:
|
INHABITED SKY
