Projected Rotational Velocities of 136 Early B-Type Stars in the Outer Galactic Disk

Garmany, C. D.; Glaspey, J. W.; Bragança, Gustavo; Daflon, S.; Fernandes, M. Borges; Oey, M. S.; Bensby, T.; Cunha, Kátia

doi:10.1088/0004-6256/150/2/41

Cited by 18 publications

(21 citation statements)

References 33 publications

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“…The v sin i distribution of Galactic OB-type stars has been investigated in many studies (e.g., Dufton et al 2006;Fraser et al 2010;Bragança et al 2012;Simón-Díaz 2010;Simón-Díaz & Herrero 2014;Garmany et al 2015). These studies often find evidence of a bimodal distribution, showing a low v sin i peak and a group of fast rotators that extends to very high v sin i (e.g., Ramírez-Agudelo et al 2013;Simón-Díaz & Herrero 2014;Garmany et al 2015). A similar result is obtained by Ramachandran et al (2018) for > 200 OB-type stars in the Large Magellanic Cloud (LMC).…”

Section: Angular Momentum Transfer and Projected Rotational Velocitiesmentioning

confidence: 99%

The stellar and wind parameters of six prototypical HMXBs and their evolutionary status

Hainich

Oskinova

Torrejón

et al. 2020

A&A

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Context. High-mass X-ray binaries (HMXBs) are exceptional astrophysical laboratories that offer a rare glimpse into the physical processes that govern accretion on compact objects, massive-star winds, and stellar evolution. In a subset of the HMXBs, the compact objects accrete matter solely from winds of massive donor stars. These so-called wind-fed HMXBs are divided in persistent (classical) HMXBs and supergiant fast X-ray transients (SFXTs) according to their X-ray properties. While it has been suggested that this dichotomy depends on the characteristics of stellar winds, they have been poorly studied. Aims. With this investigation, we aim to remedy this situation by systematically analyzing donor stars of wind-fed HMXBs that are observable in the UV, concentrating on those with neutron star (NS) companions. Methods. We obtained Swift X-ray data, HST UV spectra, and additional optical spectra for all our targets. The spectral analysis of our program stars was carried out with the Potsdam Wolf-Rayet (PoWR) model atmosphere code. Results. Our multi-wavelength approach allows us to provide stellar and wind parameters for six donor stars (four wind-fed systems and two OBe X-ray binaries). The wind properties are in line with the predictions of the line-driven wind theory. Based on the abundances, three of the donor stars are in an advanced evolutionary stage, while for some of the stars, the abundance pattern indicates that processed material might have been accreted. When passing by the NS in its tight orbit, the donor star wind has not yet reached its terminal velocity but it is still significantly slower; its speed is comparable with the orbital velocity of the NS companion. There are no systematic differences between the two types of wind-fed HMXBs (persistent versus transients) with respect to the donor stars. For the SFXTs in our sample, the orbital eccentricity is decisive for their transient X-ray nature. The dichotomy of wind-fed HMXBs studied in this work is primarily a result of the orbital configuration, while in general it is likely that it reflects a complex interplay between the donor-star parameters, the orbital configuration, and the NS properties. Based on the orbital parameters and the further evolution of the donor stars, the investigated HMXBs will presumably form Thorne-Żytkow objects in the future.

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Section: Angular Momentum Transfer and Projected Rotational Velocitiesmentioning

confidence: 99%

The stellar and wind parameters of six prototypical HMXBs and their evolutionary status

Hainich

Oskinova

Torrejón

et al. 2020

A&A

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“…Our T eff -values show reasonable agreement to within ∼10% with respect those effective temperatures that Table 3. Comparison between stellar parameters and abundances from this work (US) and Nieva & Przybilla (2007 Garmany et al (2015), which are based on a photometric calibration for the reddening-free index Q and therefore are expected to be more uncertain. The log g values show differences of up to 0.4 dex (middle plot of Fig.…”

Section: Comparisons With Other Studiesmentioning

confidence: 99%

“…In this work we present stellar parameters (effective temperature, surface gravity and v · sin i, microturbulent and macroturbulent velocities) and oxygen and silicon abundances in non-LTE for a sample of 28 main-sequence OB stars located towards the Galactic anti-center, between galactocentric radii ∼ 9.5 and 15.6 kpc, plus three stars in the solar neighbourhood. The sample analyzed here is part of the larger sample of 136 OB stars in the outer disk analysed by Garmany et al (2015), where multiplicity, photometric effective temperature, and projected rotational velocity (v · sin i) were determined. This paper is structured as follows: Section 2 describes the target selection and the observations; Sect.…”

Section: Introductionmentioning

confidence: 99%

Radial abundance gradients in the outer Galactic disk as traced by main-sequence OB stars

Bragança

Daflon

Lanz

et al. 2019

A&A

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Context. Elemental abundance gradients in galactic disks are important constraints for models of how spiral galaxies form and evolve. However, the abundance structure of the outer disk region of the Milky Way is poorly known, which hampers our understanding of the spiral galaxy that is closest to us and that can be studied in greatest detail. Young OB stars are good tracers of the present-day chemical abundance distribution of a stellar population and because of their high luminosities they can easily be observed at large distances, making them suitable to explore and map the abundance structure and gradients in the outer regions of the Galactic disk. Aims. Using a sample of 31 main-sequence OB stars located between galactocentric distances 8.4 − 15.6 kpc, we aim to probe the present-day radial abundance gradients of the Galactic disk. Methods. The analysis is based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan Clay 6.5-m telescope on Las Campanas. We used a non-NLTE analysis in a self-consistent semi-automatic routine based on TLUSTY and SYNSPEC to determine atmospheric parameters and chemical abundances. Results. Stellar parameters (effective temperature, surface gravity, projected rotational velocity, microturbulence, and macroturbulence) and silicon and oxygen abundances are presented for 28 stars located beyond 9 kpc from the Galactic centre plus three stars in the solar neighborhood. The stars of our sample are mostly on the main-sequence, with effective temperatures between 20 800 − 31 300 K, and surface gravities between 3.23 − 4.45 dex. The radial oxygen and silicon abundance gradients are negative and have slopes of −0.07 dex/kpc and −0.09 dex/kpc, respectively, in the region 8.4 ≤ R G ≤ 15.6 kpc. Conclusions. The obtained gradients are compatible with the present-day oxygen and silicon abundances measured in the solar neighborhood and are consistent with radial metallicity gradients predicted by chemodynamical models of Galaxy Evolution for a subsample of young stars located close to the Galactic plane.

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“…In the blue part, R ∼ 53 000. The spectral reduction was carried out using the Carnegie Observatories python pipeline 2 (Bragança et al 2012;Garmany et al 2015). …”

Section: Sample Observations and Data Reductionmentioning

confidence: 99%

“…To further validate our method, we compared the v sin i for eight stars with those obtained by Bragança et al (2012) and Garmany et al (2015) with a different method based on the full width at half-minimum [FWHM] of He i lines. The results are presented in Table 1: they show a good agreement within errors, although there is some indication of slightly larger values in our case.…”

Section: Rotational Velocitiesmentioning

confidence: 99%

Chemical abundances of fast-rotating massive stars

Cazorla

Morel

Nazé

et al. 2017

A&A

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Aims. Recent observations have challenged our understanding of rotational mixing in massive stars by revealing a population of fastrotating objects with apparently normal surface nitrogen abundances. However, several questions have arisen because of a number of issues, which have rendered a reinvestigation necessary; these issues include the presence of numerous upper limits for the nitrogen abundance, unknown multiplicity status, and a mix of stars with different physical properties, such as their mass and evolutionary state, which are known to control the amount of rotational mixing. Methods. We have carefully selected a large sample of bright, fast-rotating early-type stars of our Galaxy (40 objects with spectral types between B0.5 and O4). Their high-quality, high-resolution optical spectra were then analysed with the stellar atmosphere modelling codes DETAIL/SURFACE or CMFGEN, depending on the temperature of the target. Several internal and external checks were performed to validate our methods; notably, we compared our results with literature data for some well-known objects, studied the effect of gravity darkening, or confronted the results provided by the two codes for stars amenable to both analyses. Furthermore, we studied the radial velocities of the stars to assess their binarity.Results. This first part of our study presents our methods and provides the derived stellar parameters, He, CNO abundances, and the multiplicity status of every star of the sample. It is the first time that He and CNO abundances of such a large number of Galactic massive fast rotators are determined in a homogeneous way.

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Projected Rotational Velocities of 136 Early B-Type Stars in the Outer Galactic Disk

Cited by 18 publications

References 33 publications

The stellar and wind parameters of six prototypical HMXBs and their evolutionary status

The stellar and wind parameters of six prototypical HMXBs and their evolutionary status

Radial abundance gradients in the outer Galactic disk as traced by main-sequence OB stars

Chemical abundances of fast-rotating massive stars

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