A photometric study of the ORI OB1 association. II. Photometric analysis.

Warren, W. H.; Hesser, J. E.

doi:10.1086/190447

Cited by 38 publications

(25 citation statements)

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“…These subgroups were largely analyzed in later studies (e.g., Warren & Hesser 1977a, 1977bGenzel & Stutzki 1989;Brown et al 1994). In particular, Brown et al (1994) determined ages (1a: 11:4 AE 1:9 Myr; 1b: 1:7 AE 1:1 Myr; 1c: 4:6 AE 2:0 Myr) and distances (1a: 380 AE 90 pc, 1b: 360 AE 70 pc; 1c: 400 AE 90 pc) on the basis of the photometric properties of each subgroup.…”

Section: Orion Ob1 Samplementioning

confidence: 99%

“…The dashed lines are the limits of the subassociation from Warren & Hesser (1977a) for 1a (triangles), 1b (circles inside the dashed box) and 1c (circles outside the dashed box). A subset of stars in the region defined for Ori OB1a ( Warren & Hesser 1977a) (triangles surrounded by circles), is spatially associated with molecular gas and dust; this subset is more likely related to the younger subassociation Ori OB1c.…”

Section: Orion Ob1 Samplementioning

confidence: 99%

“…Figure 1 shows stars in the Orion OB1 association overlaid on a map of integrated 13 CO emissivity from Bally et al (1987) (gray scale) and isocontours of Galactic extinction for A V ¼ 1, 2, 3, and 4, from Schlegel et al (1998). We plot the boundaries from Warren & Hesser (1977a) between the subgroups 1a, 1b, and 1c. Because of the similarities in the ages and distances of the subassociations OB1b and OB1c, we have joined these subassociations into one (labeled ''OB1bc'').…”

Section: Orion Ob1 Samplementioning

confidence: 99%

“…As discussed in x 2.2, we have combined the associations Ori OB1b and Ori OB1c as defined by Warren & Hesser (1977a) into one. These authors reported ages of 5.1 and 3.7 Myr for Ori OB1b and Ori OB1c, respectively.…”

Section: Orion Ob1bcmentioning

confidence: 99%

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Herbig Ae/Be Stars in nearby OB Associations

Hernández¹,

Calvet²,

Hartmann³

et al. 2005

221

274

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We have carried out a study of the early-type stars in nearby OB associations spanning an age range of $3-16 Myr, with the aim of determining 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) OB associations Upper Scorpius, Perseus OB2, Lacerta OB1, and Orion OB1, with membership determined from Hipparcos data. We also included in our study the early-type stars in the Trumpler 37 cluster, part of the Cep OB2 association. We obtained spectra for 440 Hipparcos stars in these associations, from which we determined accurate spectral types, visual extinctions, effective temperatures, luminosities and masses, using Hipparcos photometry. Using colors corrected for reddening, we find that the Herbig Ae/Be stars and the classical Be (CBe) stars occupy clearly different regions in the JHK diagram. Thus, we use the location on the JHK diagram, as well as the presence of emission lines and of strong 12 m flux relative to the visual, to identify the Herbig Ae/ Be stars in the associations. We find that the Herbig Ae/Be stars constitute a small fraction of the early-type stellar population even in the younger associations. Comparing the data from associations with different ages and assuming that the near-infrared excess in the Herbig Ae/Be stars arises from optically thick dusty inner disks, we determined the evolution of the inner disk frequency with age. We find that the inner disk frequency in the age range 3-10 Myr in intermediate-mass stars is lower than that in the low-mass stars (<1 M ); in particular, it is a factor of $10 lower at $3 Myr. This indicates that the timescales for disk evolution are much shorter in the intermediate-mass stars, which could be a consequence of more efficient mechanisms of inner disk dispersal (viscous evolution, dust growth, and settling toward the midplane).

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Section: Orion Ob1 Samplementioning

confidence: 99%

Section: Orion Ob1 Samplementioning

confidence: 99%

Section: Orion Ob1 Samplementioning

confidence: 99%

Section: Orion Ob1bcmentioning

confidence: 99%

See 2 more Smart Citations

Herbig Ae/Be Stars in nearby OB Associations

Hernández¹,

Calvet²,

Hartmann³

et al. 2005

221

274

View full text Add to dashboard Cite

show abstract

“…These Strömgren values are transformed into the UBV Johnson system by using the transformation equations of Warren & Hesser (1977) to transform the Strömgren b−y and u−b colour indices to Johnson B − V and U − B colour indices. As the "y" standard magnitude obtained using the "y" Strömgren filter is equivalent to the "V " magnitude of the "V " Johnson filter, knowing the B − V and U − B colour indices, the B and U magnitudes are calculated directly.…”

Section: Photometrymentioning

confidence: 99%