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Line Structure in the Spectrum of FU Orionis
New high-resolution spectra of FU Ori, obtained with the High ResolutionEchelle Spectrometer spectrograph at the Keck I telescope in 2003-2006,make it possible to compare the optical line profiles with thosepredicted by the self-luminous accretion disk model. A dependence ofline width on excitation potential and wavelength, expected for aKeplerian disk, is definitely not present in the optical region, nor isthe line duplicity due to velocity splitting. The absorption linesobserved in the optical region of FU Ori must originate in or near thecentral object, and here their profiles are shown to be those expectedof a rigidly rotating object. They can be fitted by a rapidly rotating(v sin i = 70 km s–1) high-luminosity G-type starhaving a large dark polar spot, with axis inclined toward the line ofsight. Over these years, the radial velocity of FU Ori has remainedconstant to within ±0.3 km s–1, so there is noindication that the star is a spectroscopic binary. These results applyto the optical region (λ < 8800 Å) more distant, coolerregions of the disk contribute in the infrared.
| High-resolution HI and radio continuum observations of the SNR G290.1-0.8
We have observed the supernova remnant (SNR) G290.1-0.8 in the 21-cm HIline and the 20-cm radio continuum using the Australia Telescope CompactArray (ATCA). The HI data were combined with data from the SouthernGalactic Plane Survey to recover the shortest spatial frequencies. Incontrast, HI absorption was analysed by filtering extended HI emission,with spatial frequencies shorter than 1.1kλ. The low-resolutionATCA radio continuum image of the remnant shows considerable internalstructure, resembling a network of filaments across its 13-arcmindiameter. A high-resolution ATCA radio continuum image was alsoconstructed to study the small-scale structure in the SNR. It shows thatthere are no structures smaller than ~17arcsec, except perhaps for abright knot to the south, which is probably an unrelated object. The HIabsorption study shows that the gas distribution and kinematics in frontof SNR G290.1-0.8 are complex. We estimate that the SNR probably lies inthe Carina arm, at a distance 7 (+/-1) kpc. In addition, we have studiednearby sources in the observed field using archival multiwavelength datato determine their characteristics.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought
We use moderate-resolution optical spectrophotometry and the new MARCSstellar atmosphere models to determine the effective temperatures of 74Galactic red supergiants (RSGs). The stars are mostly members of OBassociations or clusters with known distances, allowing a criticalcomparison with modern stellar evolutionary tracks. We find we canachieve excellent matches between the observations and the reddenedmodel fluxes and molecular transitions, although the atomic lines Ca Iλ4226 and Ca II H and K are found to be unrealistically strong inthe models. Our new effective temperature scale is significantly warmerthan those in the literature, with the differences amounting to 400 Kfor the latest type M supergiants (i.e., M5 I). We show that the newlyderived temperatures and bolometric corrections give much betteragreement with stellar evolutionary tracks. This agreement provides acompletely independent verification of our new temperature scale. Thecombination of effective temperature and bolometric luminosities allowsus to calculate stellar radii; the coolest and most luminous stars (KWSgr, Case 75, KY Cyg, HD 206936=μ Cep) have radii of roughly 1500Rsolar (7 AU), in excellent accordance with the largeststellar radii predicted from current evolutionary theory, althoughsmaller than that found by others for the binary VV Cep and for thepeculiar star VY CMa. We find that similar results are obtained for theeffective temperatures and bolometric luminosities using only thedereddened V-K colors, providing a powerful demonstration of theself-consistency of the MARCS models.
| Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable 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/qcat?J/A+A/397/997
| Observational investigation of mass loss of M supergiants
We present the analysis of infrared photometry and millimeterspectroscopy of a sample of 74 late-type supergiants. These observationsare particularly suitable to study the mass loss and the circumstellarenvelopes of evolved massive stars. In particular, we quantify thecircumstellar infrared excess, the relation of mass loss with stellarproperties, using the K-[12] colour index as mass-loss indicator. We donot find any clear correlation between mass loss rate and luminosity. Wealso show that the K-band magnitude is a simple luminosity indicator,because of the relative constancy of the K-band bolometric correction.Based on observations collected at the European Southern Observatory, LaSilla, Chile within program ESO 54.E-0914, and on observations collectedwith the IRAM 30m telescope. Tables A1 to A3 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| The luminosity index for M stars and the distance to the LMC.
Not Available
| Quantitative spectral classification of galactic disc K-M stars from spectrophotometric measurements
New spectral observations for 47 southern galactic red supergiantsobtained with the new RUBIKON spectrophotometer (developed at theAstronomisches Institut der Ruhr-Universitat Bochum) at the Bochum 61-cmtelescope on La Silla are presented. The spectra range from 4800 to 7700A and their resolution is 10 A. The mean error of absolute fluxes is0.028 mag and that of relative fluxes 0.021 mag. The spectra will beavailable at the Strasbourg Stellar Database (CDS). Together with datataken from recently published spectral catalogues, the new observationshave been used to define spectral indices as measures of the strengthsof the following features: Fe i+TiOalpha_1, Mgb+TiOalpha_0,NaD+TiOgamma'_1, TiOgamma'_0 and TiOgamma_1 systems. The indices havebeen checked against errors introduced by reductions, interstellarreddening and different resolutions of different spectral catalogues,and have been found to be very insensitive to all these effects.Therefore, different catalogues may be combined without any loss ofaccuracy and homogeneity. The mean error of a single index has beenfound to be 0.011 mag. For stars from K4 to M7, a strong temperaturedependence is found for all indices. For the Fe i+TiO and especially theMgb+TiO features, a strong dependence on luminosity has also beenobserved. These indices therefore have been combined to form aluminosity index, while the others together form a spectral index. Thecombined indices have been calibrated in terms of MK data using thestepwise linear regression technique, and may be used for quantitativetwo- dimensional spectral classification of late K- and M-type stars.The mean error of the classification is 0.6 of spectral subtype and 0.8of luminosity class, which is much higher than would be expected fromthe uncertainty of the indices alone (which, e.g., for an M4 giantcorrespond to an uncertainty of 0.1 of spectral subtype and 0.3 ofluminosity class). This may be explained by the uncertainty of theoriginal MK classifications and the variability of some programme stars.
| Optical and X-Ray Characteristics of Stars Detected in the Einstein Slew Survey
We detect X-rays for the first time from 63 cool (types AM) stars. Thesestars are part of the 229 total stellar X-ray sources identified to datein the Einstein Slew Survey (hereafter Slew). We also list new X-raydata on one A star that may have a corona, five OB stars, and reportdiscoveries of two new T Tauri stars and two new cataclysmic variables.The stellar content of the Slew high-latitude subset (currently 93%identified for |b_II_| > 20^deg^) is 26%. This agrees well with theEinstein Extended Medium Sensitivity Survey (EMSS) stellar sample, whichonly considered high latitudes. Because of the large solid angle coveredby the Slew, and its shallow limiting flux, the sample will better probethe bright end of the stellar X-ray luminosity function (L_X_ >10^30^ ergs s^-1^). Presently (based on the 221 Slew stars with knownspectral types), the sample is dominated by late-type systems (coolerthan F; 68%). These include dMe's, BY Dra, RS CVn, and FK Comae systems.Based on the limiting magnitudes of catalogs searched to date, the Slewis assessed to be complete for spectral types earlier than K. Hence, Kand M systems will be prominent in the ~50 as yet unidentified stars. Wehave embarked on an extensive program to (1) confirm the X-rayidentifications with the optical counterparts; (2) search for Ca II Hand K and Balmer line emission as activity signatures; and (3) searchfor supporting evidence of magnetic activity by measuring rotationalvelocities and relating them to X-ray luminosity level. Of 64 proposedcoronal systems observed to date, we have confirmed 44 active stars,while in the remaining 20 we have been unable to find definitiveactivity. We have confirmed an additional 19 active stars from stellardatabase searches, and reclassified nine systems as having nonstellaroptical counterparts from optical follow-up identification work andextragalactic database searches. We discuss notable new discoveries.From the sample of single active F7-MS Slew stars with measured ν sini-values, we find a strong (99.9% confidence level) linear correlationof X-ray luminosity with ν sin i and with stellar radius (R).However, L_X_ is uncorrelated with angular rotation speed at the 99%level. For the combined Slew and EMSS single star F7-MS sample, we findthe same 99.9% ν sin i-L_X_ and R-L_X_ correlations. The L_X_-νsin i relation for the combined sample appears to flatten with respectto the quadratic behavior seen for optically selected stellar samples atrotational velocities in excess of ~16 km s^-1^. For the unevolvedsubset of the Slew single star sample, we also find a correlationbetween L_X_ and Rossby number (R_0_; more than 99% confidence). Aleast-squares fit gives L_X_ ~ R_0_^-0.4^, which is similarly flatterthan the quadratic dependence seen in optical samples. Using the stellarsurface X-ray flux F_X_ versus B - V diagram, we interpret these resultsas saturation of the stellar surface by active regions at F_X_/F_bol_ ~10^-3^.
| Stromgren and H-Beta Photometry of OB Associations and Open Clusters - Part Two - TRIANGULUM:16 and CARINA:OB2
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993MNRAS.261..847K&db_key=AST
| Einstein Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars
Results are presented of an extensive X-ray survey of 380 giant andsupergiant stars of spectral types from F to M, carried out with theEinstein Observatory. It was found that the observed F giants orsubgiants (slightly evolved stars with a mass M less than about 2 solarmasses) are X-ray emitters at the same level of main-sequence stars ofsimilar spectral type. The G giants show a range of emissions more than3 orders of magnitude wide; some single G giants exist with X-rayluminosities comparable to RS CVn systems, while some nearby large Ggiants have upper limits on the X-ray emission below typical solarvalues. The K giants have an observed X-ray emission level significantlylower than F and F giants. None of the 29 M giants were detected, exceptfor one spectroscopic binary.
| Infrared circumstellar shells - Origins, and clues to the evolution of massive stars
The infrared fluxes, spatial and spectral characteristics for a sampleof 111 supergiant stars of spectral types F0 through M5 are tabulated,and correlations examined with respect to the nature of theircircumstellar envelopes. One-fourth of these objects were spatialyresolved by IRAS at 60 microns and possess extended circumstellar shellmaterial, with implied expansion ages of about 10 to the 5th yr.Inferences about the production of dust, mass loss, and the relation ofthese characteristics of the evolution of massive stars, are discussed.
| Mass loss from stars : the universal formula for mass loss rate
Not Available
| A unified formula for mass-loss rate of O to M stars
A formula for stellar mass-loss rate has been derived using conservationequations of mass and momentum for coronal and continuumradiation-driven wind. The derived mass-loss rate formula has been foundto be consistent with the observed mass-loss rates for stars from O to Mspectral type. Two constant parameters appearing in the mass-loss rateformula have been found to have values for special group of stars suchas Be-stars, which are different from the majority of stars.
| Far-infrared circumstellar 'debris' shell of red supergiant stars
An examination of IRAS data of red supergiant stars in the field and ingalactic OB star associations indicates the presence of substantialamounts of 60-micron emitting material extending several arcminutesaround many such sources. The characteristics of these large shells arediscussed in terms of remnants of ongoing mass loss, and a simple modeldeveloped for the case of Alpha Orionis, in particular.
| The circumstellar envelopes and chromospheres of cool giants and supergiants
A survey of the circumstellar (CS) envelopes of cool giants andsupergiants shows no correlation between the quantities of CS gas anddust, indicating that radiation pressure on dust grains is not theprincipal mechanism of mass loss. The observed quantity of dust is notsufficient to drive the observed mass loss. Stars with high dust-to-gasratios were also seen to show a high proportion of neutral to ionizedgas and a lack of Ca II H and K emission, and in many cases, Balmeremission, and/or molecular masing. It is argued that shock waves may belinked to dust formation. Mass loss rates were derived for the programstars and found to correlate with K4 absorption width, indicating thatthe mass loss mechanism may be coupled to turbulence.
| Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978ApJS...38..309H&db_key=AST
| Photoelectric two-dimensional spectral classification of M supergiants
A photoelectric system defined by eight narrow bands between 0.7 and 1.1microns has been used to measure nearly all M supergiants that have beenclassified on the MK system. The photometric TiO and CN indicesreproduce the two-dimensional MK classifications to the accuracy of theMK types themselves. Mean fluxes and spectral classifications arepresented for 128 stars.
| Southern search for OH from M supergiants
Results are reported of a search for OH emission from about 50 southernM supergiants, and it is concluded that most optically identified Msupergiants do not have substantial emission at 1612 MHz. Fromexamination of the published OH profiles of unidentified Type II OH/IRstars, it is also concluded that only a small percentage (about 10%) ofthese stars have spectra similar to those of known OH supergiants,suggesting that Type II OH supergiants are an extremely rare class ofobject. A list of unidentified sources which may be supergiants isgiven.
| A velocity separation of stars and gas in Carina
In the Carina spiral feature near galactic longitude of 290 deg, asignificant difference of 10-20 km/sec is observed between the motionsof the young stars and neutral hydrogen gas. The region of theseanomalous motions may extend from 3 to 7 kpc from the sun and is only 2deg wide in longitude. This region may best be described as a narrowsheet, particularly since the extent in latitude is uncertain. Twopossible interpretations of the optical and radio evidence for spiralstructure would place this peculiar region either on the inner side ofthe spiral feature or along the central axis of the optical spiral arm.The observed velocity anomaly has the right sign and a reasonableamplitude for a shock-front effect, and the applicability of Roberts'sshock-wave model of spiral structure to this anomalous region isdiscussed.
| Structure and motions in the CAR spiral feature.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&A....20...29H&db_key=AST
| Spectroscopic and Photometric Observations of M Supergiants in Carina.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972ApJ...172...75H&db_key=AST
| Estrellas Rojas entre Popa y Cruz.
Not Available
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