Near-Infrared Integral Field Spectroscopy and Mid-Infrared Spectroscopy of the Starburst Galaxy M82
We present new infrared observations of the central regions of thestarburst galaxy M82. The observations consist of near-infrared integralfield spectroscopy in the H and K bands obtained with the MPE 3Dinstrument and of λ=2.4-45 μm spectroscopy from the ShortWavelength Spectrometer (SWS) onboard the Infrared Space Observatory.These measurements are used, together with data from the literature, to(1) reexamine the controversial issue of extinction, (2) determine thephysical conditions of the interstellar medium (ISM) within thestar-forming regions, and (3) characterize the composition of thestellar populations. Our results provide a set of constraints fordetailed starburst modeling, which we present in a companion paper. Wefind that purely foreground extinction cannot reproduce the globalrelative intensities of H recombination lines from optical to radiowavelengths. A good fit is provided by a homogeneous mixture of dust andsources, and with a visual extinction of AV=52 mag. The SWSdata provide evidence for deviations from commonly assumed extinctionlaws between 3 and 10 μm. The fine-structure lines of Ne, Ar, and Sdetected with SWS imply an electron density of ~300 cm-3, andabundance ratios Ne/H and Ar/H nearly solar and S/H about one-fourthsolar. The excitation of the ionized gas indicates an average effectivetemperature for the OB stars of 37,400 K, with little spatial variationacross the starburst regions. We find that a random distribution ofclosely packed gas clouds and ionizing clusters and an ionizationparameter of ~10-2.3 represent well the star-forming regionson spatial scales ranging from a few tens to a few hundreds of parsecs.From detailed population synthesis and the mass-to-K-light ratio, weconclude that the near-infrared continuum emission across the starburstregions is dominated by red supergiants with average effectivetemperatures ranging from 3600 to 4500 K and roughly solar metallicity.Our data rule out significant contributions from older, metal-richgiants in the central few tens of parsecs of M82. Based on observationswith ISO, an ESA project with instruments funded by ESA Member States(especially the PI countries: France, Germany, Netherlands, and theUnited Kingdom) and with the participation of ISAS and NASA. The SWS isa joint project of SRON and MPE.
|
Statistical analysis of intrinsic polarization, IR excess and projected rotational velocity distributions of classical Be stars
We present the results of statistical analyses of a sample of 627 Bestars. The parameters of intrinsic polarization (p*),projected rotational velocity (v sin i), and near IR excesses have beeninvestigated. The values of p* have been estimated for a muchlarger and more representative sample of Be stars (~490 objects) thanpreviously. We have confirmed that most Be stars of early spectral typehave statistically larger values of polarization and IR excesses incomparison with the late spectral type stars. It is found that thedistributions of p* diverge considerably for the differentspectral subgroups. In contrast to late spectral types (B5-B9.5), thedistribution of p* for B0-B2 stars does not peak at the valuep*=0%. Statistically significant differences in the meanprojected rotational velocities (/line{vsin i}) are found for differentspectral subgroups of Be stars in the sense that late spectral typestars (V luminosity class) generally rotate faster than early types, inagreement with previously published results. This behaviour is, however,not obvious for the III-IV luminosity class stars. Nevertheless, thecalculated values of the ratio vt/vc of the truerotational velocity, vt, to the critical velocity forbreak-up, vc, is larger for late spectral type stars of allluminosity classes. Thus, late spectral type stars appear to rotatecloser to their break-up rotational velocity. The distribution of nearIR excesses for early spectral subgroups is bi-modal, the position ofthe second peak displaying a maximum value E(V-L)~ 1 . m 3for O-B1.5 stars, decreasing to E(V-L)~0. m8 for intermediatespectral types (B3-B5). It is shown that bi-modality disappears for latespectral types (B6-B9.5). No correlations were found betweenp* and near IR excesses and between E(V-L) and vsin i for thedifferent subgroups of Be stars. In contrast to near IR excesses, arelation between p* and far IR excesses at 12 mu m is clearlyseen. A clear relation between p* and vsin i (as well asbetween p* and /line{vsin i}/vc) is found by thefact that plots of these parameters are bounded by a ``triangular"distribution of p*: vsin i, with a decrease of p*towards very small and very large vsin i (and /line{vsini}/vc) values. The latter behaviour can be understood in thecontext of a larger oblateness of circumstellar disks for the stars witha rapid rotation. From the analysis of correlations between differentobservational parameters we conclude that circumstellar envelopes forthe majority of Be stars are optically thin disks with the range of thehalf-opening angle of 10degr
|
Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
|
The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
|
Optical images of MCLD123.5+24.9: a cloud illuminated by the North star?
We present B R I images of a 1degr {x}1degr field centered on themolecular cloud (MCLD123.5+24.9) located in the large infrared cirrusknown as the Polaris Flare. The optical images are compared with IRASimages and an extinction map derived from stellar reddenings. We analysethe possibility for the North star (HD8890), only 1degr North of thefield, to be the source of MCLD123.5+24.9 optical emission. For widelyaccepted values of the dust albedo (omega = 0.6) and the assymetryparameter of the Henyey Greenstein phase function (0.7
|
The Stromvil System: an Effective Combination of Two Medium-Band Photometric Systems
It is shown that the addition to the Stromgren four-color photometricsystem of three passbands at 374, 516 and 656 nm from the Vilniusphotometric system makes the combined system more universal. This newsystem, called the Stromvil system, makes it possible to classify starsof all spectral types, even in the presence of interstellar reddening.This property of the system is especially important in CCD photometry,allowing the photometric classification of very faint stars. Apreliminary calibration of the system in terms of spectral andluminosity classes, temperatures and surface gravities is available. Alist of preliminary standards for the Stromvil system in the regions ofCygnus, Aquila and near the North Celestial Pole is given.
|
On the normal energy distribution in stellar spectra: Main-sequence B stars
Not Available
|
The Distribution of Dust Clouds in the Interstellar Medium
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...457..764D&db_key=AST
|
The ROSAT all-sky survey catalogue of optically bright OB-type stars.
For the detailed statistical analysis of the X-ray emission of hot starswe selected all stars of spectral type O and B listed in the Yale BrightStar Catalogue and searched for them in the ROSAT All-Sky Survey. Inthis paper we describe the selection and preparation of the data andpresent a compilation of the derived X-ray data for a complete sample ofbright OB stars.
|
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.
|
New Bright Be-Stars and the Be-Star Frequency
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...274..870C&db_key=AST
|
SAO stars with infrared excess in the IRAS Point Source Catalog
We have undertaken a search for SAO stars with infrared excess in theIRAS Point Source Catalog. In contrast to previous searches, the entireIRAS (12)-(25)-(60) color-color diagram was used. This selection yieldeda sample of 462 stars, of which a significant number are stars withcircumstellar material. The stars selected can be identified aspre-main-sequence stars, Be stars, protoplanetary systems, post-AGBstars, etc. A number of objects are (visual) binary stars.Characteristic temperatures and IR excesses are calculated and theirrelations to spectral type are investigated.
|
A survey of Be stars in the infrared. II - Determination of envelope dimensions
Plate material concerning 34 Be stars in the 8309-8791-A region wasobtained at the Observatoire de Haute Provence at 33 A/mm dispersion. Itis found that emissions are frequent in all Be stars, but are moreconcentrated in early-type stars. The same phenomenon is found for theCa II emissions, where a positive correlation of Ca II emission andlarge IR excesses measured with the IRAS satellite is demonstrated.
|
Photoelectric photometry of bright stars in the vicinity of the North Celestial Pole
Not Available
|
Catalogue of i and w/w crit values for rotating early type stars
Not Available
|
A. de Sitter's photographic polar photometry revisited; some remarks on photographic photometry with objective gratings
Not Available
|
Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
|
Effects of stellar rotation on the Geneva photometric system
The effects of stellar rotation on colors and parameters of the Genevaphotometric system are considered, using homogeneous material. Attentionis focused on these parameters useful for deriving physical propertiesof B- and A-type stars. Two major photometric planes in this respect,the (X, Y) plane and the (d, Delta) plane, are not discernibly affectedby rotation. The temperature parameter, B(2) - V(1) is reddened byrotation to an extent that is in agreement with model calculations foruniformly rotating stars.
|
Connection between nonradial pulsations and stellar winds in massive stars. VI - Variability in H alpha, polarization, and magnetic fields in early-type stars
The early-type stars whose spectra show Balmer emission lines areconsidered, taking into account the division of these stars into twogroups, including the OB supergiants and the Be stars. In the case ofthe Be stars, recent observations at H-alpha, H-beta, and H-gamma withbest S/N approximately 500 and resolution approximately 0.1 A haverevealed a previously unsuspected 'winebottle', or two-tier, structureto the symmetric emission profile in several Be stars. For many Bestars, the circumstellar material has an apparent two-componentstructure. Attention is given to H-alpha variations in four typical Bestars, linear polarization, and magnetic fields.
|
Catalog of O-B stars observed with Tokyo Meridian Circle
A catalog of the O-B stars, selected from 'Blaauw-Parenago' list andRubin's catalog, has been compiled on the FK4 system by the observationsmade with Gautier 8-inch Meridian Circle at the Tokyo AstronomicalObservatory during the period, 1971 to 1979. It contains 1059 stars andwas compiled for the future establishment of high precision propermotions of O-B stars.
|
A catalog of ultraviolet interstellar extinction excesses for 1415 stars
Ultraviolet interstellar extinction excesses are presented for 1415stars with spectral types B7 and earlier. The excesses with respect to Vare derived from Astronomical Netherlands Satellite (ANS) 5-channel UVphotometry at central wavelengths of approximately 1550, 1800, 2500, and3300 A. A measure of the excess extinction in the 2200-A extinction bumpis also given. The data are valuable for investigating the systematicsof peculiar interstellar extinction and for studying the character of UVinterstellar extinction in the general direction of stars for which theextinction-curve shape is unknown.
|
Catalogue of the energy distribution data in spectra of stars in the uniform spectrophotometric system.
Not Available
|
The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
|
The chemical composition of the globular cluster M55
The chemical composition of five giant stars in the globular cluster M55has been determined from the analysis of high-resolution echellespectrograms in both the red and the blue spectral regions. The overalliron-peak abundances are m/H = 1.3 + or - 0.1. The abundances of thevery heavy elements follow a pattern similar to the solar composition.Carbon in these giants is deficient relative to the iron-peak elementsby about a factor of 4.
|
Be stars in binaries
The known companions to 80 Be stars and 355 B stars listed in the BrightStar Catalogue in the range B1-B7 III-V and north of delta = -30 deg areconsidered. The known near-absence of Be binaries with periods less than1/10 yr is confirmed. For longer periods up to the limit of 10,000 AU ofthis survey, the Be and B stars do not differ in binary frequencies.This result implies that during pre-main-sequence contraction, the tidalbraking in binaries wider than 0.5 AU was inadequate to prevent theformation of stars with nearly the break-up rotational velocities. Thefraction of Be and B stars that have companions is higher in clustersand associations (38 percent) than among field stars (25 percent),confirming that escapees from clusters tend to be single stars. There issome evidence that the companions of Be stars that occur in the sameluminosity range tend also to be Be stars; that result was expectedbecause in visual binaries there is a known tendency for rapidlyrotating primaries to have rapidly rotating secondaries.
|
Active Be stars
Intensifier director scanner H-alpha profiles are presented of thebright northern Be stars, which have recently developed significantemission line variability. These stars are candidates for intensivespectroscopic, photometric, and polarimetric observations during thecurrent season.
|
Far ultraviolet colors of B and Be stars
A far-UV color index, G, which is free of interstellar reddening effectsis applied to TD-1 satellite observations of B and Be stars listed inthe catalogs of Jamar et al. (1976) and Macau-Hercot et al. (1978). Theexpressions defining G(in terms of the wavelengths 146, 235, and 274 nm)and the S70 index of spectral type are set forth. Tables of mean andindividual-star G and S70 indices and plots of G versus S70, Delta-Gversus spectral type, Delta-G versus H-alpha and H-beta intensity, and Gversus V(sin i) are presented and discussed. The Be stars are classifiedas strong if they show strong Balmer emission, some Paschen and Fe IIemission, and IR excess; otherwise they are 'weak'. Weak Be stars arefound to have G similar to that of B stars, while G in strong Be starsis either much more negative or much less negative than in the B stars.No correlation is found between G and V(sin i) for either B or Be stars.
|
Spectral types and rotational velocities of the brighter Be stars and A-F type shell stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982ApJS...50...55S&db_key=AST
|
Refined Data for Parallax Stars
Not Available
|
Vertical-circle observations of the aberration of stellar light of different spectral types
Measurements of 9 stars of high declination generally confirm Becker'srelation between the constant of aberration and the spectral type of thestars. The right ascensions and the declinations of the 9 stars are alsodetermined. The relation between aberration and spectral type cannot beexplained by atmospheric dispersion. The relation does not affectmeasurements of trigonometric parallaxes.
|
