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Masses and luminosities of O- and B-type stars and red supergiants
Massive stars are of interest as progenitors of supernovae, i.e.neutron stars and black holes, which can be sources of gravitationalwaves. Recent population synthesis models can predict neutron star andgravitational wave observations but deal with a fixed supernova rate oran assumed initial mass function for the population of massive stars. Here we investigate those massive stars, which are supernovaprogenitors, i.e. with O- and early B-type stars, and also allsupergiants within 3 kpc. We restrict our sample to those massive starsdetected both in 2MASS and observed by Hipparcos, i.e. only those starswith parallax and precise photometry. To determine the luminositieswe calculated the extinctions from published multi-colour photometry,spectral types, luminosity class, all corrected for multiplicity andrecently revised Hipparcos distances. We use luminosities andtemperatures to estimate the masses and ages of these stars usingdifferent models from different authors. Having estimated theluminosities of all our stars within 3 kpc, in particular for all O- andearly B-type stars, we have determined the median and mean luminositiesfor all spectral types for luminosity classes I, III, and V. Ourluminosity values for supergiants deviate from earlier results: Previouswork generally overestimates distances and luminosities compared to ourdata, this is likely due to Hipparcos parallaxes (generally moreaccurate and larger than previous ground-based data) and the fact thatmany massive stars have recently been resolved into multiples of lowermasses and luminosities. From luminosities and effective temperatureswe derived masses and ages using mass tracks and isochrones fromdifferent authors. From masses and ages we estimated lifetimes andderived a lower limit for the supernova rate of ?20 events/Myraveraged over the next 10 Myr within 600 pc from the sun. These data arethen used to search for areas in the sky with higher likelihood for asupernova or gravitational wave event (like OB associations).
| Ultraviolet observations in Puppis with the space telescope 'GLAZAR'
The results of observations of 159 stars at 1640 A in Puppis made withthe space telescope 'Glazar' are presented. It is shown that theobserved stars are members of different groups of stars situated atdistances of about 120, 370, 700, 1250, 2400, and 4000 pc. The last twogroups belong to the Pup OB1 and Pup OB2 stellar associations. There isrelatively little absorption in the observed region. The absorbingmatter is mainly concentrated in small clouds. It is suggested thatthree stars - CP - 27 deg 4197, HD 60479, and HD 61672 - are embedded ina dust envelope and that the star HD 60057 has a hot subdwarf companion.Forty-four of the observed stars are new OB or early A-type stars,spectral types of which were not known.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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Membro dei seguenti gruppi:
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Osservazione e dati astrometrici
| Costellazione: | Poppa |
| Ascensione retta: | 07h28m04.98s |
| Declinazione: | -27°12'55.9" |
| Magnitudine apparente: | 9.761 |
| Moto proprio RA: | -4.7 |
| Moto proprio Dec: | 9.6 |
| B-T magnitude: | 9.76 |
| V-T magnitude: | 9.761 |
Cataloghi e designazioni:
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