Observations of Star-Forming Regions with the Midcourse Space Experiment
We have imaged seven nearby star-forming regions, the Rosette Nebula,the Orion Nebula, W3, the Pleiades, G300.2-16.8, S263, and G159.6-18.5,with the Spatial Infrared Imaging Telescope on the Midcourse SpaceExperiment (MSX) satellite at 18" resolution at 8.3, 12.1, 14.7, and21.3 μm. The large angular scale of the regions imaged (~7.2-50deg2) makes these data unique in terms of the combination ofsize and resolution. In addition to the star-forming regions, twocirrus-free fields (MSXBG 160 and MSXBG 161) and a field near the southGalactic pole (MSXBG 239) were also imaged. Point sources have beenextracted from each region, resulting in the identification over 500 newsources (i.e., no identified counterparts at other wavelengths), as wellas over 1300 with prior identifications. The extended emission from thestar-forming regions is described, and prominent structures areidentified, particularly in W3 and Orion. The Rosette Nebula isdiscussed in detail. The bulk of the mid-infrared emission is consistentwith that of photon-dominated regions, including the elephant trunkcomplex. The central clump, however, and a line of site toward thenorthern edge of the cavity show significantly redder colors than therest of the Rosette complex.
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Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897
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Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
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Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
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The Angular Momentum of Main Sequence Stars and Its Relation to Stellar Activity
Rotational velocities are reported for intermediate-mass main sequencestars it the field. The measurements are based on new, high S/N CCDspectra from the Coudé Feed Telescope of the Kitt Peak NationalObservatory. We analyze these rotation rates for a dependence on bothmass and age. We compare the average rotation speeds of the field starswith mean velocities for young stars in Orion, the Alpha Persei cluster,the Pleiades, and the Hyades. The average rotation speeds of stars moremassive than $\sim1.6$ \msun\experience little or no change during theevolutionary lifetimes of these stars on the zero age main sequence orwithin the main sequence band. Less massive stars in the range betwee n1.6\msun\ and 1.3\msun\ also show little decline in mean rotation ratewhile they are on the main sequence, and at most a factor of 2 decreasein velocity as they evolve off the main sequence. The {\it e}-foldingtime for the loss of angular momentum b y the latter group of stars isat least 1--2 billion years. This inferred characteristic time scale forspindown is far longer than the established rotational braking time forsolar-type stars with masses below $\sim1.3$ \msun. We conclude from acomparison of the trends in rotation with trends in chromospheric andcoronal activity that the overall decline in mean rotation speed alongthe main sequence, from $\sim2$ \msun\ down to $\sim1.3$ \msun, isimposed during the pre-main sequence phase of evolution, and that thispattern changes little thereafter while the star resides on the mainsequence. The magnetic activity implicated in the rotational spindown ofthe Sun and of similar stars during their main sequence lifetimes mus ttherefore play only a minor role in determining the rotation rates ofthe intermediate mass stars, either because a solar-like dynamo is weakor absent, or else the geometry of the magnetic field is appreciablyless effective in removing angular momentu m from these stars. (SECTION:Stars)
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Photoelectric Observations of X Persei
Not Available
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Hot Inner Disks that Appear and Disappear around Rapidly Rotating A-Type Dwarfs
At any one time, approximately one-quarter of the most rapidly rotatingnormal A-type dwarfs (V sin i >= 200 km s-1) show shell lines of TiII in the near-ultraviolet. Our observations during 22 years show thatthe lines appear and disappear on timescales of decades but do notdisplay significant changes within 1 year. This implies that they arenot remnants of the star formation but rather are probably caused bysporadic mass-loss events. A working hypothesis is that all A-type starsthat are rotating near their limits have these shells, but for onlyone-quarter of the time. Because these lines do not appear in stars withsmaller sin i, the shells must be disks. These are hot inner disks thatmay or may not be related to the cool outer disks seen by Smith andTerrile around beta Pic or through infrared excesses around Vega andother A-type dwarfs. The similar, limited line widths indicate that thedisks are ~7 R* above the stellar surfaces.
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Observations of the recent disc loss in X Persei: photometry and polarimetry.
We present optical and infrared photometric observations of the Be/X-raybinary system X Persei/4U0352+30 during the past decade, covering theentire phase change from Be to OB star and back. Intrinsic colours arederived based on observations during the disk-less phase, givingE(B-V)=0.36+/-0.02, (B-V)_0_=-0.22+/-0.02 and (U-B)_0_=-1.05+/-0.02,suggesting a B0V star at a distance of 900pc+/-300pc and an extinctionof A_v_=1.16+/-0.03. We find evidence for only one variable component,presumed to be the disc. We present measurements of the intrinsicpolarisation, and an estimate of the interstellar polarisation.Polarimetric observations reveal major changes in the degree ofpolarisation, indicating the reformation of a scattering envelope aroundthe star, but these are inconsistent with the predictions of standard Beenvelopes models, possibly as a result of geometrical effects.
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X Persei
Not Available
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The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&db_key=AST
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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.
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Interstellar extinction in the direction of the open cluster IC 348 and the Per OB2 association
The relationship between interstellar extinction and distance in thedirection of dark clouds in the areas around the open cluster IC 348 andthe association Per OB2 is determined using the results of photoelectricphotometry of 189 stars in the Vilnius photometric system. Two absorbinglayers are found. The nearest layer, covering the whole area around IC348, shows the mean extinction A(V) of about 0.7 mag. It begins at thedistance of 160 pc and probably is an extension of the Taurus darkclouds to the northwest. The second absorbing layer has the form of achain of dark condensations named L1468, L1470, and L1471 and is at 260pc distance. This layer has a higher density, its mean extinction beingabout 2.0 mag. The cluster IC 348 is at about the same distance and isphysically related to the dark cloud L1470. The distance of the Per OB2association is found to be 340 pc and the mean extinction of its membersis 0.95 mag. A model of the spatial distribution of the Perseus andTaurus dark clouds based on photometric distance determinations in thisand previous papers is proposed. Six stars in the IC 348 area aresuspected to have emission in the H-alpha line.
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The Atmospheric Parameters of A-Stars and F-Stars - Part One - Comparison of Various Methods
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...271..515S&db_key=AST
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A new calibration of the Geneva photometry in terms of Te, log g, (Fe/H) and mass for main sequence A4 to G5 stars
A new semiempirical calibration of the d, m2, and B2 - V1 parameters ofGeneva photometry is given, which allows Te, log g and (Fe/H) of A4V-III to G5 V stars to be estimated. The calibration is based onKurucz's grid of atmosphere models, corrected by means of fundamentalstars. Recent evolutionary tracks for stars with a metal content Z =0.02 are used to calibrate the d vs. B2 - V1 diagram in terms of massfor solar-composition stars.
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Spectrophotometry of B-A stars (5.6-7.2m) recommended as standard ones.
Not Available
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Two-colour diagrams for differentially rotating stars
Not Available
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Photoelectric Observations of gamma Cas, X Per and BU Tau
Not Available
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Calibration in temperature of photometric parameters
In calibrating photometric parameters in temperature, it is very easy touse a Planck distribution to show that a color index is a temperatureparameter, but it is more difficult to calibrate such a color index interms of temperature because only a few effective temperature values aredetermined. A pioneering work is that of Kuiper (1938), who derived atemperature scale according to spectral type (from A0 to M2 for dwarfsand from G0 to M8 for giants) and a Becker index. The first study givinga relation between effective temperature and a photoelectric color indexis that of Popper (1959) in which Popper derives a relation betweeneffective temperature and B-V for the A and F stars and for G8 to K5(dwarf and giant) stars. Popper has shown the relation betweentemperature parameters of two photometric systems, R-I from thesix-color system of Stebbins and Whitford, and B-V. The intent of thepresent work is to define a set of stars which can be used to determinea calibration of a photometric parameter in terms of effectivetemperature.
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Observed and computed spectral flux distribution of non-supergiant O9-G8 stars. III - Determination of T(eff) for the stars in the Breger Catalogue
The effective temperatures and angular diameters of nonsupergiant O9-G8stars are determined from visible spectrophotometry. The results, whichrefer to 302 stars included in the Breger Catalogue, are derived fromthe comparison between the observed flux distributions and thepredictions of Kurucz's models (1979). The uncertainties to be expectedin individual results are discussed; their sizes are of the order of 5percent in effective temperature and 10 percent in angular diameter.
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Spectrophotometry of peculiar B and A stars. XVI - The derivation of indices by fitting the Balmer and Paschen continua of the normal stars and application to the mercury-manganese stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984A&AS...55..479A&db_key=AST
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X Persei - Optical polarization variation on the 580 day binary-like period
Observations of periodicities in the optical polarization of the weakX-ray source X Persei are reported. Polarization was measured in the Vband 400 times over the course of 356 nights during 1977-1982. The Q andU Stokes parameters derived from the measurements show a definitevariability with a typical amplitude of 0.1%, which is strongest atperiods greater than 100 days. In particular, a strong peak is observedwith a period of 297 days, consistent with the second-harmonic componentof the known 580-day radial velocity cycle. A component with 590-dayperiodicity is not ruled out by the observations, although it was notdetected. Observations imply the 580-day period to be an effect oforbital or rotational processes, with the corotating scattering bodyeither close to the light source or very large in extent, and a systeminclination close to 80 deg.
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Photometry of X Persei in late 1978
X Persei optical intensity has been monitored during seven consecutivenights in late 1978. Observations included the usual UBV broad bands aswell as narrow bands around H-beta and He II 4686. Some activity ofabout 0.05 mag., on a time scale of several hours has been detected,mainly in the U-band. Here, as in previous observations, no clearperiodicity is apparent, including the probable period of 11.2h or 22.4hof the assumed companion 3U0352 + 30. The upper limit of 0.02 mag.coherent modulation of H-beta emission makes these periods unlikely.
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Spectrophotometry of peculiar B and A stars. IV - Secondary standards and the AP stars HD 10783 and CU Virginis
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980AJ.....85..836W&db_key=AST
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Prediction of spectral classification from photometric observations - Application of the UVBY beta photometry and the MK spectra classification. II - General case
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....85...93M&db_key=AST
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Prediction of spectral classification from photometric observations-application to the UVBY beta photometry and the MK spectral classification. I - Prediction assuming a luminosity class
An algorithm based on multiple stepwise and isotonic regressions isdeveloped for the prediction of spectral classification from photometricdata. The prediction assumes a luminosity class with reference touvbybeta photometry and the MK spectral classification. The precisionattained is about 90 percent and 80 percent probability of being withinone spectral subtype respectively for luminosity groups I and V and forluminosity groups III and IV. A list of stars for which discrepanciesappear between photometry and spectral classification is given.
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Spectrophotometry of peculiar B and A stars. III - 21 Persei, 56 Arietis, and 49 CANCRI
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979AJ.....84.1726A&db_key=AST
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Spectrophotometry of peculiar B and A stars. I - On the detection of the lambda 4200 and lambda 5200 broad, continuum features of peculiar A stars
Photometric indices are used to study the broad continuum features thatare present in the energy distributions of many peculiar A stars andthat may be indicators of the atmospheric structure. Indices derivedfrom representative or averages of spectrophotometric scans areconsidered. Values of Maitzen's (1976) delta-a index - a measure of thelambda 5200 feature - are synthetized from spectrophotometric data. Twoother specific indices are calculated from spectrophotometry to measurethe strength of lambda 4200 feature. The details of the photometricvariability are presented with the data. Possible effects of thevariability on the conclusions made are discussed.
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Final catalogue of 229 photometric standards in UBV system near the selected areas 1-115
Not Available
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Spectrophotometry of B, A, and F stars
Energy distributions of 33 normal B, A, and F stars for wavelengths3300-7100 are given that are consistent with the Hayes-Lathamcalibration of Vega. The derived upper limit on the photometric accuracyusing a comparison of observed and synthetic u-b and b-y indices is0.010 mag and 0.008 mag, respectively. Effective temperatures foundusing empirical calibrations agree with those derived using fullyline-blanketed model atmospheres. Effective temperatures are found forselected spectral types.
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UBVRI photometry of X Per
Results are reported for recent standard UBVRI photometric observationsof X Per, which has been tentatively identified as the opticalcounterpart of the X-ray source 3U 0352+30. No variations with periodsof about 11 or 22 hr are found in the data, but evidence of irregularoptical activity from night to night is obtained. It is shown that aslow steady brightening of the star took place over a one-year periodwith different rates in the five colors. An absolute upper limit of 0.01magnitude is placed on any periodic variation in the UBVRI colors withperiods of 5 to 15 min or 10 to 48 hr. It is suggested that the primarystar is well within its Roche lobe for any acceptable value of theprimary/secondary mass ratio, which indicates that the accretion ontothe secondary that is responsible for the X-ray emission cannot be dueto primary Roche-lobe overflow. Alternative accretion mechanismsconsidered include a stellar wind from the primary and passage of thesecondary through a gaseous envelope associated with the primary.
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INHABITED SKY
