The discovery of a shell-like event in the O-type star HD 120678

Gamen, R.; Arias, J. I.; Barbá, R. H.; Morrell, N.; Walborn, N. R.; Sota, A.; Apellániz, J. Maíz; Alfaro, E. J.

doi:10.1051/0004-6361/201118725

Cited by 13 publications

(20 citation statements)

References 38 publications

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“…They suggested that these sources could be a wind-colliding binary system. Gamen et al (2012) showed that stars can change their spectra within months.…”

Section: Appendix A: Spectral Classification Of Emission-line Starsmentioning

confidence: 99%

KMOS view of the Galactic centre

Feldmeier-Krause

Neumayer

Schödel

et al. 2015

A&A

106

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Context. The Galactic centre hosts a crowded, dense nuclear star cluster with a half-light radius of 4 pc. Most of the stars in the Galactic centre are cool late-type stars, but there are also > ∼ 100 hot early-type stars in the central parsec of the Milky Way. These stars are only 3−8 Myr old. Aims. Our knowledge of the number and distribution of early-type stars in the Galactic centre is incomplete. Only a few spectroscopic observations have been made beyond a projected distance of 0.5 pc of the Galactic centre. The distribution and kinematics of earlytype stars are essential to understand the formation and growth of the nuclear star cluster. Methods. We cover the central >4 pc 2 (0.75 sq. arcmin) of the Galactic centre using the integral-field spectrograph KMOS (VLT). We extracted more than 1000 spectra from individual stars and identified early-type stars based on their spectra. Results. Our data set contains 114 bright early-type stars: 6 have narrow emission lines, 23 are Wolf-Rayet stars, 9 stars have featureless spectra, and 76 are O/B type stars. Our wide-field spectroscopic data confirm that the distribution of young stars is compact, with 90% of the young stars identified within 0.5 pc of the nucleus. We identify 24 new O/B stars primarily at large radii. We estimate photometric masses of the O/B stars and show that the total mass in the young population is > ∼ 12 000 M . The O/B stars all appear to be bound to the Milky Way nuclear star cluster, while less than 30% belong to the clockwise rotating disk. We add one new star to the sample of stars affiliated with this disk. Conclusions. The central concentration of the early-type stars is a strong argument that they have formed in situ. An alternative scenario, in which the stars formed outside the Galactic centre in a cluster that migrated to the centre, is refuted. A large part of the young O/B stars is not on the disk, which either means that the early-type stars did not all form on the same disk or that the disk is dissolving rapidly.

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“…They suggested that these sources could be a wind-colliding binary system. Gamen et al (2012) showed that stars can change their spectra within months.…”

Section: Appendix A: Spectral Classification Of Emission-line Starsmentioning

confidence: 99%

KMOS view of the Galactic centre

Feldmeier-Krause

Neumayer

Schödel

et al. 2015

A&A

106

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“…Gamen et al (2008) revised the classification of the main-sequence O5 to O5III(f) and mentioned that it is actually a binary with a 5.9 d period and minimum masses of 31 and 15 M .…”

Section: Hm1mentioning

confidence: 99%

“…VB10 (XID 7) was classified as O5V by Massey et al (2001), but its nature was recently revised: it is a binary of type O5III(f)+OB, with a period of 5.9d, and minimum masses of 31 + 15 M (Gamen et al 2008). Amongst the three X-ray bright O-stars, VB10 is the hardest and brightest (log [L X /L BOL ] = −7.0).…”

Section: Detected O-starsmentioning

confidence: 99%

X-ray properties of the young open clusters HM1 and IC 2944/2948

Nazé

Rauw

Sana

et al. 2013

A&A

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Using XMM-Newton data, we study for the first time the X-ray emission of HM1 and IC 2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both clusters display the usual high-energy properties of that type of objects, though with log [L X /L BOL ] apparently lower in HM1 than in IC 2944/2948. Compared with studies of other clusters, it seems that a low signal-to-noise ratio at soft energies, due to the high extinction, may be the main cause of this difference. In HM1, the two Wolf-Rayet stars show contrasting behaviors: WR89 is extremely bright, but much softer than WR87. It remains to be seen whether wind-wind collisions or magnetically confined winds can explain these emissions. In IC 2944/2948, the X-ray sources concentrate around HD 101205; a group of massive stars to the north of this object is isolated, suggesting that there exist two subclusters in the field-of-view.

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“…The project will include further high-angular resolution imaging, multiple-epoch R ∼ 40 000 optical spectroscopy (Gamen et al 2008), a recalibration of the intrinsic colors for hot stars and the extinction law , and a combination of spectroscopic and trigonometric parallaxes . Regarding high-resolution imaging, the goal is to eventually observe ∼500 massive stars with AstraLux and, if a similar instrument becomes available in the Southern hemisphere, to observe another ∼500 stars from there, in all cases using the Galactic O-Star Catalog (Maíz Apellániz et al 2004;Sota et al 2008) to select the sample.…”

Section: Overall Strategymentioning

confidence: 99%

High-resolution imaging of Galactic massive stars with AstraLux

Apellániz¹

2010

A&A

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Context. Massive stars have high-multiplicity fractions, and many of them have still undetected components, thus hampering the study of their properties. Aims. I study a sample of massive stars with high angular resolution to better characterize their multiplicity. Methods. I observed 138 fields that include at least one massive star with AstraLux, a lucky imaging camera at the 2.2 m Calar Alto telescope. I also used observations of 3 of those fields with ACS/HRC on HST to obtain complementary information and to calibrate the AstraLux data. The results were compared with existing information from the Washington Double Star Catalog, Tycho-2, 2MASS, and other literature results. Results. I discover 16 new optical companions of massive stars, the majority of which are likely to be physically bound to their primaries. I also improve the accuracy for the separation and magnitude difference of many previously known systems. In a few cases the orbital motion is detected when comparing the new data with existing ones and constraints on the orbits are provided. Conclusions. The analysis indicate that the majority of the AstraLux detections are bound pairs. For a range of separations of 0. 1-14 and magnitude differences lower than 8, I find that the multiplicity fraction for massive stars is close to 50%. When objects outside those ranges are included, the multiplicity fraction should be considerably higher.

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The discovery of a shell-like event in the O-type star HD 120678

Cited by 13 publications

References 38 publications

KMOS view of the Galactic centre

KMOS view of the Galactic centre

X-ray properties of the young open clusters HM1 and IC 2944/2948

High-resolution imaging of Galactic massive stars with AstraLux

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