Home     Evrende yaþayabilmek için    
Services
    Niçin Edinmelisiniz     En fazla Destek olanlar     Gökyüzü görüntüsü     Koleksiyon     Forum     Blog New!     SSS     Giriþ  
→ Adopt this star  

HD 244459


Ýçindekiler

Görüntüler

Resim Yükleyin

DSS Images   Other Images


Ýlgili Makaleler

Herbig Ae/Be Stars in nearby OB Associations
We have carried out a study of the early-type stars in nearby OBassociations spanning an age range of ~3-16 Myr, with the aim ofdetermining the fraction of stars that belong to the Herbig Ae/Be class.We studied the B, A, and F stars in the nearby (<=500 pc) OBassociations Upper Scorpius, Perseus OB2, Lacerta OB1, and Orion OB1,with membership determined from Hipparcos data. We also included in ourstudy the early-type stars in the Trumpler 37 cluster, part of the CepOB2 association. We obtained spectra for 440 Hipparcos stars in theseassociations, from which we determined accurate spectral types, visualextinctions, effective temperatures, luminosities and masses, usingHipparcos photometry. Using colors corrected for reddening, we find thatthe Herbig Ae/Be stars and the classical Be (CBe) stars occupy clearlydifferent regions in the JHK diagram. Thus, we use the location on theJHK diagram, as well as the presence of emission lines and of strong 12μm flux relative to the visual, to identify the Herbig Ae/Be stars inthe associations. We find that the Herbig Ae/Be stars constitute a smallfraction of the early-type stellar population even in the youngerassociations. Comparing the data from associations with different agesand assuming that the near-infrared excess in the Herbig Ae/Be starsarises from optically thick dusty inner disks, we determined theevolution of the inner disk frequency with age. We find that the innerdisk frequency in the age range 3-10 Myr in intermediate-mass stars islower than that in the low-mass stars (<1 Msolar) inparticular, it is a factor of ~10 lower at ~3 Myr. This indicates thatthe timescales for disk evolution are much shorter in theintermediate-mass stars, which could be a consequence of more efficientmechanisms of inner disk dispersal (viscous evolution, dust growth, andsettling toward the midplane).

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.

Yeni bir Makale Öner


Ýlgili Baðlantýlar

  • - Baðlantý Bulunamadý -
Yeni Bir Baðlantý Öner


sonraki gruplarýn üyesi:


Gözlemler ve gökölçümü verileri

Takýmyýldýz:Avci
Sað Açýklýk:05h30m53.34s
Yükselim:+05°41'34.2"
Görünürdeki Parlaklýk:10.16
özdevim Sað Açýklýk:-4.2
özdevim Yükselim:-0.4
B-T magnitude:10.53
V-T magnitude:10.191

Kataloglar ve belirtme:
Özgün isimleri
HD 1989HD 244459
TYCHO-2 2000TYC 126-1332-1
USNO-A2.0USNO-A2 0900-01711932
HIPHIP 25831

→ VizieR 'den daha fazla katalog ve tanýmlama isteyin