Blue Giants in the Neighborhood of NGC 6231.

Morgan, W. W.; González, Graciela; González, Guillermina

doi:10.1086/145755

Cited by 4 publications

(5 citation statements)

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“…Its major axis is approximately parallel to the Galactic plane (Morgan et al 1953a). A sparser group, Tr 24, is to be found near IC 4628 while two other clusters, NGC 6242 and NGC 6268, lie slightly north of the association.…”

Section: Ngc 6231 and Thementioning

confidence: 93%

“…2 • long by 1 • wide, it extends from the gaseous nebula IC 4628 on its northern end to the young open cluster NGC 6231 towards its southern end. Its major axis is approximately parallel to the Galactic plane (Morgan et al 1953a). A sparser group, Tr 24, is to be found near IC 4628 while two other clusters, NGC 6242 and NGC 6268, lie slightly north of the association.…”

Section: Introductionmentioning

confidence: 93%

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An XMM-Newtonview of the young open cluster NGC 6231

Sana

Gosset

Rauw

et al. 2006

A&A

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This paper is the first of a series dedicated to the X-ray properties of the young open cluster NGC 6231. Our data set relies on an XMM-Newton campaign of a nominal duration of 180 ks and reveals that NGC 6231 is very rich in the X-ray domain too. Indeed, 610 X-ray sources are detected in the present field of view, centered on the cluster core. The limiting sensitivity of our survey is approximately 6 × 10 −15 erg cm −2 s −1 but clearly depends on the location in the field of view and on the source spectrum. Using different existing catalogues, over 85% of the X-ray sources could be associated with at least one optical and/or infrared counterpart within a limited cross-correlation radius of 3 at maximum. The surface density distribution of the X-ray sources presents a slight N-S elongation. Once corrected for the spatial sensitivity variation of the EPIC instruments, the radial profile of the source surface density is well described by a King profile with a central density of about 8 sources per arcmin 2 and a core radius close to 3.1 arcmin. The distribution of the X-ray sources seems closely related to the optical source distribution. The expected number of foreground and background sources should represent about 9% of the detected sources, thus strongly suggesting that most of the observed X-ray emitters are physically belonging to NGC 6231. Finally, beside a few bright but soft objects -corresponding to the early-type stars of the cluster -most of the sources are relatively faint (∼5 × 10 −15 erg cm −2 s −1 ) with an energy distribution peaked around 1.0-2.0 keV.

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Section: Ngc 6231 and Thementioning

confidence: 93%

Section: Introductionmentioning

confidence: 93%

An XMM-Newtonview of the young open cluster NGC 6231

Sana

Gosset

Rauw

et al. 2006

A&A

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“…HDE 326 329 = CPD −41 7735. This star was not included in Maíz Apellániz et al (2004) but was classified as O type by Morgan et al (1953a). The WDS lists a dim companion 7.…”

Section: Normal Samplementioning

confidence: 99%

The Galactic O-Star Spectroscopic Survey (Gosss). Ii. Bright Southern Stars

Sota

Apellániz

Morrell

et al. 2014

ApJS

515

481

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We present the second installment of GOSSS, a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R ∼ 2500 digital observations from both hemispheres selected from the Galactic O-Star Catalog (GOSC). In this paper we include bright stars and other objects drawn mostly from the first version of GOSC, all of them south of δ = −20 • , for a total number of 258 O stars. We also revise the northern sample of Paper I to provide the full list of spectroscopically classified Galactic O stars complete to B = 8, bringing the total number of published GOSSS stars to 448. Extensive sequences of exceptional objects are given, including the early Of/WN, O Iafpe, Ofc, ON/OC, Onfp, Of?p, and Oe types, as well as double/triple-lined spectroscopic binaries. The new spectral subtype O9.2 is also discussed. The magnitude and spatial distributions of the observed sample are analyzed. We also present new results from OWN, a multi-epoch high-resolution spectroscopic survey coordinated with GOSSS that is assembling the largest sample of Galactic spectroscopic massive binaries ever attained. The OWN data combined with additional information on spectroscopic and visual binaries from the literature indicate that only a very small fraction (if any) of the stars with masses above 15-20 M¯are born as single systems. In the future we will publish the rest of the GOSSS survey, which is expected to include over 1000 Galactic O stars.

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“…Though with some uncertainty on the RV measurements, they reported to have detected the signature of a blueshifted secondary component on the first spectrum of their series, thus suggesting variability on a time‐scale of days. The spectral types quoted in the literature are O8.5 III (Levato & Malaroda 1980), O9 III (Schild, Hiltner & Sanduleak 1969; PHYB90) or O9 V (Morgan, González & González 1953a). The remark by RCB97 that the object's colour is changing with time could also indicate a slight change in its spectral type.…”

Section: The O‐type Star Population In Ngc 6231mentioning

confidence: 99%

“…We adopt in the following V = 8.471 (Sung, private communication) which is close to previous determinations of V = 8.5 (PHYB90), 8.48 (PHC91), 8.47 (Schild et al 1969), 8.50 (Feinstein & Ferrer 1968), 8.46 (Bok, Bok & Graham 1966) or 8.48 (Heske & Wendker 1984). Quoted spectral types are in the range B0 V (Morgan, González & González 1953a; Morgan, Whitford & Code 1953b) – B0/1 III (Schild et al 1969; Houk 1978). A couple of RV measurements were also performed by Struve (1944), Wilson (1953) and PHYB90 who obtained a Ca K ‐corrected RV of about −25 to −30 km s −1 .…”

Section: The O‐type Star Population In Ngc 6231mentioning

confidence: 99%

The massive star binary fraction in young open clusters – I. NGC 6231 revisited

Sana

Gosset

Nazé

et al. 2008

Monthly Notices of the Royal Astronomical Society

133

155

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We present the results of a long‐term high‐resolution spectroscopy campaign on the O‐type stars in NGC 6231. We revise the spectral classification and multiplicity of these objects and we constrain the fundamental properties of the O‐star population. Almost three quarters of the O‐type stars in the cluster are members of a binary system. The minimum binary fraction is 0.63, with half the O‐type binaries having an orbital period of the order of a few days. The eccentricities of all the short‐period binaries are revised downward, and henceforth match a normal period–eccentricity distribution. The mass ratio distribution shows a large preference for O + OB binaries, ruling out the possibility that, in NGC 6231, the companion of an O‐type star is randomly drawn from a standard initial mass function. Obtained from a complete and homogeneous population of O‐type stars, our conclusions provide interesting observational constraints to be confronted with the formation and early evolution theories of O‐stars.

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Blue Giants in the Neighborhood of NGC 6231.

Cited by 4 publications

References 0 publications

An XMM-Newtonview of the young open cluster NGC 6231

An XMM-Newtonview of the young open cluster NGC 6231

The Galactic O-Star Spectroscopic Survey (Gosss). Ii. Bright Southern Stars

The massive star binary fraction in young open clusters – I. NGC 6231 revisited

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