Hα Emission Stars and Herbig-Haro Objects in the Vicinity of Bright-rimmed Clouds

Ogura, K.; Sugitani, Koji; Pickles, Andrew

doi:10.1086/339976

Cited by 110 publications

(218 citation statements)

References 40 publications

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“…"), while the stars with several hundred Myears are noted as "PMS?". We also use indications about the nature of the stars from previous studies of Walker (1961), Tucholke et al (1986), Ogura et al (2002), Indebetouw et al (2007). All the non-ELS considered here as PMS objects have masses lower than 8 M , in agreement with the masses expected for this kind of object (M < 15 M Iben 1965).…”

Section: Non-elssupporting

confidence: 66%

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Early-type objects in NGC 6611 and the Eagle Nebula

Martayan

Floquet

Hubert

et al. 2008

A&A

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Aims. An important question about Be stars is whether they are born as such or whether they have become Be stars during their evolution. It is necessary to observe young clusters to answer this question. Methods. To this end, observations of stars in NGC 6611 and the star-formation region of Eagle Nebula were carried out with the ESO-WFI in slitless spectroscopic mode and at the VLT-GIRAFFE (R 6400-17 000). The targets for the GIRAFFE observations were pre-selected from the literature and our catalogue of emission-line stars based on the WFI study. GIRAFFE observations allowed us to study the population of the early-type stars accurately both with and without emission lines. For this study, we determined the fundamental parameters of OBA stars thanks to the GIRFIT code. We also studied the status of the objects (main sequence or pre-main sequence stars) by using IR data, membership probabilities, and location in HR diagrams. Results. The nature of the early-type stars with emission-line stars in NGC 6611 and its surrounding environment is derived. The slitless observations with the WFI clearly indicate a small number of emission-line stars in M16. We observed with GIRAFFE 101 OBA stars, among them 9 are emission-line stars with circumstellar emission in Hα. We found that W080 could be a new He-strong star, like W601. W301 is a possible classical Be star, W503 is a mass-transfer eclipsing binary with an accretion disk, and the other ones are possible Herbig Ae/Be stars. We also found that the rotational velocities of main sequence B stars are 18% lower than those of pre-main sequence B stars, in good agreement with theory about the evolution of rotational velocities. Combining adaptive optics, IR data, spectroscopy, and radial velocity indications, we found that 27% of the B-type stars are binaries. We also redetermined the age of NGC 6611 found equal to 1.2-1.8 Myears, in good agreement with the most recent determinations.

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Section: Non-elssupporting

confidence: 66%

“…These targets are not B-type objects, but T Tauri stars as explained by Ogura et al (2002) and Herbig & Dahm (2001). However, we concentrate our study only on the stars with V magnitude up to 15 for our purpose.…”

Section: Eso-wfi In Spectroscopic Modementioning

confidence: 99%

Early-type objects in NGC 6611 and the Eagle Nebula

Martayan

Floquet

Hubert

et al. 2008

A&A

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“…In the case of BRC 11NE and BRC 37, however, only a few Hα stars are available. But, as one sees in figures 1f and 1p of Ogura, Sugitani, Pickles (2002), a relatively clear aggregate of stars can be noticed that appears to be associated with the BRCs; these aggregates show up more prominently in the 2MASS images. We, therefore, have added the stars having 2MASS counterparts from the aggregates, and they are indicated with "A" (additional stars) in the finding charts, figure 1.…”

Section: Star Selection and Reddening Correctionmentioning

confidence: 74%

“…BRCs 11NE, 12 and 14 belong to the H II region IC 1848 and BRC 37 to IC 1396. For each BRC the Hα emission stars of Ogura, Sugitani, Pickles (2002) have been selected as the member stars. In the case of BRC 11NE and BRC 37, however, only a few Hα stars are available.…”

Section: Star Selection and Reddening Correctionmentioning

confidence: 99%

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Age Sequence in Small Clusters Associated with Bright-Rimmed Clouds

Ogura

Chauhan

Pandey

et al. 2007

Publications of the Astronomical Society of Japan

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Bright-rimmed clouds (BRCs) found in H II regions are probable sites of triggered star formation due to compression by ionization/shock fronts, and it is hypothesized that star formation proceeds from the exciting star(s) side outward of the H II region ("small-scale sequential star formation"). In order to quantitatively testify this hypothesis we undertook BVI c photometry of four BRC aggregates. The amounts of interstellar extinction and reddening for each star have been estimated by using the JHK s photometry. Then we constructed reddening-corrected V/V-I c color-magnitude diagrams, where the age of each star has been derived. All the stars turned out to be a few tenths to a few Myr old. Although the scatters are large and the numbers of the sample stars are small, we found a clear trend that the stars inside or in the immediate vicinity of the bright rim are younger than those outside it in all the four aggregates, confirming the hypothesis in question.

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