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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
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| Moderate-Resolution Near-Infrared Spectroscopy of Cool Stars: A New K-Band Library
I present an atlas of near-infrared K-band spectra of 31 late-typegiants and supergiants and two carbon stars. The spectra were obtainedat resolving powers of 830 and 2000, and have a signal-to-noise ratio>~100. These data are complemented with results from similar existinglibraries in both K and H band, and they are used to identify varioustools useful for stellar population studies at moderate resolution. Ifocus on several of the most prominent absorption features and (1)investigate the effects of spectral resolution on measurements of theirequivalent width (EW), (2) examine the variations with stellarparameters of the EWs, and (3) construct composite indices as indicatorsof stellar parameters and of the contribution from excess continuumsources commonly found in star-forming and AGN galaxies. Among thefeatures considered, the 12CO (2,0) and 12CO (6,3)bandheads together with the Si I 1.59 μm feature, first proposed byOliva, Origlia, and coworkers, constitute the best diagnostic set forstellar spectral classification and for constraining the excesscontinuum emission. The Ca I 2.26 μm and Mg I 2.28 μm featuresoffer alternatives in the K band to the 12CO (6,3) bandheadand Si I feature.
| Spectral classification of the cool giants in symbiotic systems
We derive the spectral types of the cool giants in about 100 symbioticsystems. Our classification is mainly based on near IR spectra in orderto avoid the contamination of the spectrum by the nebula and the hotcomponent in the visual region. The accuracy of our spectral types isapproximately one spectral subclass, similar to previous near IRclassification work, and much better than visual spectral typeestimates. Strong, intrinsic spectral type variations (>2 spectralsubtypes) are only seen in systems containing pulsating mira variables.We present a catalogue of spectral types for cool giants in symbioticsystems which also includes determinations taken from the literature.The catalogue gives spectral types for the cool giants in about 170systems which is nearly the full set of confirmed symbiotics. Based onour classifications we discuss the distribution of spectral types of thecool giants in galactic symbiotic binaries. We find that the spectraltypes cluster strongly between M3 and M6, with a peak at M5. Thedistribution of systems with a mira variable component peaks even later,at spectral types M6 and M7. This is a strong bias towards late spectraltypes when compared to red giants in the solar neighbourhood. Also thefrequency of mira variables is much larger among symbiotic giants. Thispredominance of very late M-giants in symbiotic systems seems toindicate that large mass loss is a key ingredient for triggeringsymbiotic activity on a white dwarf companion. Further we find forsymbiotic systems a strong correlation between the spectral type of thecool giant and the orbital period. In particular we find a tightrelation for the minimum orbital period for symbiotic systems with redgiants of a given spectral type. This limiting line in the spectral type- orbital period diagram seems to be equivalent with the relationR<=l_1/2, where R is the radius of the red giant and l_1 the distancefrom the center of the giant to the inner Lagrangian point L_1. Thiscorrelation possibly discloses that symbiotic stars are - with probablyonly one exception in our sample - well detached binary systems. Basedon observations obtained with the 1.52~m and 3.6~m telescopes of theEuropean Southern Observatory (ESO), the 1.93~m telescope of theObservatoire de Haute-Provence (OHP), the 2.3~m telescope of theAustralian National University (ANU) at Siding Spring, and the WilliamHerschel Telescope (WHT) at La Palma. This research has made use of theAFOEV database, operated at CDS, France.
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| High resolution spectroscopy of symbiotic stars I. SY Muscae: orbital elements, M giant radius, distance
We have obtained a series of high resolution optical spectra of theeclipsing symbiotic system SY Mus. We measured the radial velocity curveof the M star component, and determined its rotation velocity. Assumingco-rotation we obtain for its radius 86Rsun_. We determineM4.5 for the spectral type, i.e. its temperature is 3500K. The resultingluminosity is 1000Lsun_. The cool component is thus a giantstar with a luminosity slightly larger than average. Comparison withevolutionary tracks yield an actual mass of 1.30Msun_. Fromthe binary mass function we obtain 0.43Msun_ for the hotcompanion. The separation of the stellar components is 1.72AU and thedistance from the center of the red giant to the inner Lagrange pointL_1_ is 1.05AU. The red giant extends to less than 40% of the distanceto L_1_ and therefore, the SY Mus binary system is well detached. Wepresent line profiles of Hα and the Raman scattered line atλ6825 at various orbital phases. The Hα profile is oftendouble-peaked and shows rapid intensity variations near quadrature. Thisindicates that the bulk of the Hα emission is produced in a smallhigh density region close to the red star's surface facing the hotcompanion. The non-variability of the Raman scattered line atλ6825 indicates that the Raman scattering zone is large comparedto the size of the red giant. We do not observe any change in theabsorption spectrum of the red giant as a function of phase, i.e. thereis no observable irradiation effect.
| The Perkins catalog of revised MK types for the cooler stars
A catalog is presented listing the spectral types of the G, K, M, and Sstars that have been classified at the Perkins Observatory in therevised MK system. Extensive comparisons have been made to ensureconsistency between the MK spectral types of stars in the Northern andSouthern Hemispheres. Different classification spectrograms have beengradually improved in spite of some inherent limitations. In thecatalog, the full subclasses used are the following: G0, G5, G8, K0, K1,K2, K3, K4, K5, M0, M1, M2, M3, M4, M5, M6, M7, and M8. Theirregularities are the price paid for keeping the general scheme of theoriginal Henry Draper classification.
| A list of MK standard stars
Not Available
| 1988 Revised MK Spectral Standards for Stars GO and Later
Not Available
| 1985 revised MK spectral standards : stars GO and later
Not Available
| Revised MK Spectral Standard Stars Later than G0
Not Available
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Dades d'Observació i Astrometria
| Constel·lació: | Pyxis |
| Ascensió Recta: | 09h18m43.63s |
| Declinació: | -34°05'45.3" |
| Magnitud Aparent: | 7.55 |
| Distancia: | 970.874 parsecs |
| Moviment propi RA: | -4.2 |
| Moviment propi Dec: | 1.5 |
| B-T magnitude: | 9.541 |
| V-T magnitude: | 7.715 |
Catàlegs i designacions:
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