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Candidate Pre-Main-Sequence F Stars with Circumstellar Dust Identified Using Combined 2MASS and uvby Data
We propose a method that uses near-infrared plus uvby photometry toidentify potentially extensive circumstellar dusty environments around Fand A stars. The method has been applied to a sample of ~900 metal-richreddened F stars with 2 Micron All Sky Survey and uvby data, suggestingthe presence of circumstellar dust emitting in the near-infrared for ~70stars. The logTe-MV diagram suggests that most, ifnot all, are likely pre-main-sequence (PMS) stars. They seem to be acontinuation of the class of Herbig Ae/Be PMS stars in the spectral typeF. Their number drops sharply downward of logTe~3.84(spectral types later than ~F5), which may provide new clues to the PMSevolution of 1-2 Msolar stars. We present a list of 21 of themost conspicuous candidate stars with circumstellar dust. About half ofthem are associated with the extended star-forming region around ρOphiuchi. The brightest of these 21 stars, with V<~7.5, turn out tobe IRAS sources, suggesting the presence of heated dust emitting in thefar-infrared. Also in this list, HD 81270 is reported as a very unusualstar moving away from the Galactic plane at a projected speed of 70 kms-1.
| 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.
| The interstellar reddening in front of globular clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975PASP...87...65C&db_key=AST
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Osservazione e dati astrometrici
| Costellazione: | Sagittario |
| Ascensione retta: | 18h01m23.21s |
| Declinazione: | -31°44'54.2" |
| Magnitudine apparente: | 8.398 |
| Distanza: | 190.84 parsec |
| Moto proprio RA: | 7.1 |
| Moto proprio Dec: | -21.8 |
| B-T magnitude: | 8.913 |
| V-T magnitude: | 8.441 |
Cataloghi e designazioni:
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