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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
| The Very Slow Wind from the Pulsating Semiregular Red Giant, L2 Puppis
We have obtained 11.7 and 17.9 μm images at the Keck I telescope ofthe circumstellar dust emission from L2 Pup, which is one ofthe nearest (D=61 pc) mass-losing, pulsating red giants that has asubstantial infrared excess. We propose that the star is losing mass ata rate of ~3×10-7 Msolar yr-1.Given its relatively low luminosity (~1500 Lsolar),relatively high effective temperature (near 3400 K), relatively shortperiod (~140 days), and inferred gas outflow speed of 3.5 kms-1, standard models for dust-driven mass loss do not apply.Instead, the wind may be driven by the stellar pulsations, withradiation pressure on dust being relatively unimportant, as described insome recent calculations. L2 Pup may serve as the prototypeof this phase of stellar evolution, in which a star could lose ~15% ofits initial main-sequence mass.
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| Oxygen-rich semiregular and irregular variables
All the known oxygen-rich semiregulars and irregulars of spectralclasses K and M with the absolute value of B not greater than 30 deg,Delta(m) not less than 0.5 mag, and, for the semiregulars, periods inthe range of 50 to 400 d are compiled. On the basis of theirdistributions on the sky and their brightnesses in the K band at 2.2microns, it is argued that the semiregulars with a period of 300-400 dappear to belong to the same population as the 'thin disk' Miras in thesame period range and have an exponential scale height from the Galacticplane of about 250 pc. The semiregulars with a period range of 200 to300 d belong to the population of the 'thick disk' Miras with anexponential scale height from the Galactic plane of about 500 pc. On thebasis of the similarities of their space distributions and the presenceof Tc in their atmospheres, and using the pulsational mode calculationsby Ostlie and Cox (1986), it is suggested that the semiregulars with aperiod range of 100-150 d are first and second overtone pulsations ofthe same population of AGB stars as the Miras in their fundamentalpulsational mode with periods longer than 300 d.
| 59th Name-List of Variable Stars
Not Available
| On 16 variables discovered at the Bamberg Observatory.
Not Available
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Osservazione e dati astrometrici
| Costellazione: | Acquario |
| Ascensione retta: | 23h04m17.20s |
| Declinazione: | -16°00'35.8" |
| Magnitudine apparente: | 9.377 |
| Moto proprio RA: | 8.2 |
| Moto proprio Dec: | -32 |
| B-T magnitude: | 11.105 |
| V-T magnitude: | 9.52 |
Cataloghi e designazioni:
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