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Journal ArticleDOI

The young massive SMC cluster NGC 330 seen by MUSE - II. Multiplicity properties of the massive-star population

TL;DR: In this article, the authors acknowledge support from the FWO_Odysseus program under project G0F8H6N and from the European Space Agency (ESA) and the Belgian Federal Science Policy Office (BELSPO) through the PRODEX Programme.
Abstract: The authors acknowledge support from the FWO_Odysseus program under project G0F8H6N and from the European Space Agency (ESA) and the Belgian Federal Science Policy Office (BELSPO) through the PRODEX Programme. The research leading to these results has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement numbers 772225: MULTIPLES). Parts of the analysis in this project are based on the python code photutils.

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Citations
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Journal ArticleDOI
TL;DR: In this paper, a new generation of PARSEC-colibri stellar isochrones is presented, which include a detailed treatment of the thermally-pulsing asymptotic giant branch (TP-AGB) phase, and covering a wide range of initial metallicities (0.0001
Abstract: We introduce a new generation of PARSEC-COLIBRI stellar isochrones that include a detailed treatment of the thermally-pulsing asymptotic giant branch (TP-AGB) phase, and covering a wide range of initial metallicities (0.0001

159 citations

Journal ArticleDOI
TL;DR: In this article, the Fibre Large Array Multi-element Spectrograph (FLAMES) was used to detect 470 stars in the Small Magellanic Cloud (SMC), NGC 2004 and the N11 region in the Large Magellan Cloud (LMC).
Abstract: We present new observations of 470 stars using the Fibre Large Array Multi-Element Spectrograph (FLAMES) instrument in fields centered on the clusters NGC 330 and NGC 346 in the Small Magellanic Cloud (SMC), and NGC 2004 and the N11 region in the Large Magellanic Cloud (LMC). A further 14 stars were observed in the N11 and NGC 330 fields using the Ultraviolet and Visual Echelle Spectrograph (UVES) for a separate programme. Spectral classifications and stellar radial velocities are given for each target, with careful attention to checks for binarity. In particular we have investigated previously unexplored regions around the central LH9/LH10 complex of N11, finding ~25 new O-type stars from our spectroscopy. We have observed a relatively large number of Be-type stars that display permitted Fe II emission lines. These are primarily not in the cluster cores and appear to be associated with classical Be-type stars, rather than pre main-sequence objects. The presence of the Fe II emission, as compared to the equivalent width of H$\alpha$, is not obviously dependent on metallicity. We have also explored the relative fraction of Be- to normal B-type stars in the field-regions near to NGC 330 and NGC 2004, finding no strong evidence of a trend with metallicity when compared to Galactic results. A consequence of service observations is that we have reasonable time-sampling in three of our FLAMES fields. We find lower limits to the binary fraction of O- and early B-type stars of 23 to 36%. One of our targets (NGC346-013) is especially interesting with a massive, apparently hotter, less luminous secondary component.

146 citations

Journal ArticleDOI
TL;DR: In this paper, the multiplicity properties of B-type stars were investigated in the 30 Doradus region of the Large Magellanic Cloud with multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS).
Abstract: We investigate the multiplicity properties of 408 B-type stars observed in the 30 Doradus region of the Large Magellanic Cloud with multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS). We use a cross-correlation method to estimate relative radial velocities from the helium and metal absorption lines for each of our targets. Objects with significant radial-velocity variations (and with an amplitude larger than 16 km/s) are classified as spectroscopic binaries. We find an observed spectroscopic binary fraction (defined by periods of 0.1) for the B-type stars, f_B(obs) = 0.25 +/- 0.02, which appears constant across the field of view, except for the two older clusters (Hodge 301 and SL 639). These two clusters have significantly lower fractions of 0.08 +/- 0.08 and 0.10 +/- 0.09, respectively. Using synthetic populations and a model of our observed epochs and their potential biases, we constrain the intrinsic multiplicity properties of the dwarf and giant (i.e. relatively unevolved) B-type stars in 30 Dor. We obtain a present-day binary fraction f_B(true) = 0.58 +/- 0.11, with a flat period distribution. Within the uncertainties, the multiplicity properties of the B-type stars agree with those for the O stars in 30 Dor from the VFTS.

17 citations

Journal ArticleDOI
TL;DR: In this paper , the authors studied 32 Galactic O-type stars that were reported as single-lined spectroscopic binaries (SB1s) in the literature and performed spectral disentangling to extract putative signatures of secondary companions from the composite spectra.
Abstract: Context. The quest to detect dormant stellar-mass black holes (BHs) in massive binaries (i.e. OB+BH systems) is challenging; only a few candidates have been claimed to date, all of which must still be confirmed. Aims. To search for these rare objects, we study 32 Galactic O-type stars that were reported as single-lined spectroscopic binaries (SB1s) in the literature. In our sample we include Cyg X-1, which is known to host an accreting stellar-mass BH, and HD 74194, a supergiant fast X-ray transient, in order to validate our methodology. The final goal is to characterise the nature of the unseen companions to determine if they are main-sequence (MS) stars, stripped helium stars, triples, or compact objects such as neutron stars (NSs) or stellar-mass BHs. Methods. After measuring radial velocities and deriving orbital solutions for all the systems in our sample, we performed spectral disentangling to extract putative signatures of faint secondary companions from the composite spectra. We derived stellar parameters for the visible stars and estimated the mass ranges of the secondary stars using the binary mass function. Variability observed in the photometric TESS light curves was also searched for indications of the presence of putative companions, degenerate or not. Results. In 17 of the 32 systems reported as SB1s, we extract secondary signatures, down to mass ratios of ∼0.15. For the 17 newly detected double-lined spectroscopic binaries (SB2s), we derive physical properties of the individual components and discuss why they have not been detected as such before. Among the remaining systems, we identify nine systems with possible NS or low-mass MS companions. For Cyg X-1 and HD 130298, we are not able to extract any signatures for the companions, and the minimum masses of their companions are estimated to be about 7 M . Our simulations show that secondaries with such a mass should be detectable from our dataset, no matter their nature: MS stars, stripped helium stars or even triples. While this is expected for Cyg X-1, confirming our methodology, our simulations also strongly suggest that HD 130298 could be another candidate to host a stellar-mass BH. Conclusions. The quest to detect dormant stellar-mass BHs in massive binaries is far from over, and many more systems need to be scrutinised. Our analysis allows us to detect good candidates, but confirming the BH nature of their companions will require further dedicated monitorings, sophisticated analysis techniques, and multi-wavelength observations.

16 citations

Journal ArticleDOI
TL;DR: In this article , the hidden companions in 51 singlelined spectroscopic (SB1) O-type and evolved B-type binaries identified in the Large Magellanic Cloud (LMC) in the framework of the VLT-FLames Tarantula Survey (VFTS) and its follow-up, the Tarantula Massive Binary Monitoring (TMBM).
Abstract: Context. Massive binaries hosting a black hole (OB + BH) represent a critical phase in the production of BH mergers in the context of binary evolution. In spite of this, such systems have so far largely avoided detection. Single-lined spectroscopic (SB1) O-type binaries are ideal objects to search for elusive BH companions. Moreover, SB1 binaries hosting two main sequence stars probe a regime of more extreme mass ratios and longer periods compared to double-lined binaries (SB2), and they are thus valuable for establishing the natal mass ratio distribution of massive stars. Aims. We characterise the hidden companions in 51 SB1 O-type and evolved B-type binaries identified in the Large Magellanic Cloud (LMC) in the framework of the VLT-FLAMES Tarantula Survey (VFTS) and its follow-up, the Tarantula Massive Binary Monitoring (TMBM). The binaries cover periods between a few days to years (0 < log P < 3[d]). Our goals are to hunt for BHs and sample the low-mass end of the mass-ratio distribution. Methods. To uncover the hidden companions, we implemented the shift-and-add grid disentangling algorithm using 32 epochs of spectroscopy acquired in the framework of TMBM with the FLAMES spectrograph, allowing us to detect companions contributing as little as ≈ 1 − 2% to the visual flux. We further analysed OGLE photometric data for the presence of eclipses or ellipsoidal variations. Results. Out of the 51 SB1 systems, 43 (84%) are found to have non-degenerate stellar companions, of which 28 are confident detections and 15 are less certain (SB1: or SB2:). Of these 43 targets, one is found to be a triple (VFTS 64), and two are found to be quadruples (VFTS 120, 702). Our sample includes a total of eight eclipsing binaries. The remaining eight targets (16%) retain an SB1 classification. We modelled the mass-ratio distribution as f ( q ) ∝ q κ , and derived κ through a Bayesian approach. We used mass-ratio constraints from previously known SB2 binaries, newly uncovered SB2 binaries, and SB1 binaries, while accounting for binary detection bias. We found κ = 0 . 2 ± 0 . 2 for the entire sample and κ = − 0 . 2 ± 0 . 2 when excluding binaries with periods shorter than 10d. In contrast, κ = 1 . 2 ± 0 . 5 was retrieved for tight binaries ( P < 10d), and it is proposed here to be a consequence of binary interactions. Aside from the unambiguous O + BH binary VFTS 243, which was analysed in detail in a separate paper, we identified two additional OB + BH candidates: VFTS 514 and 779. Conclusions. Our study firmly establishes a virtually flat natal mass-ratio distribution ( κ = 0) for O-type stars at LMC metallicity, covering the entire mass-ratio range (0 . 05 < q < 1) and periods in the range 0 < log P < 3[d]. The nature of the OB + BH candidates should be verified through future monitoring, but the frequency of OB + BH candidates is generally in line with recent predictions at LMC metallicity.

9 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the evolutionary significance of the observed luminosity function for main-sequence stars in the solar neighborhood is discussed and it is shown that stars move off the main sequence after burning about 10 per cent of their hydrogen mass and that stars have been created at a uniform rate in a solar neighborhood for the last five billion years.
Abstract: The evolutionary significance of the observed luminosity function for main-sequence stars in the solar neighborhood is discussed. The hypothesis is made that stars move off the main sequence after burning about 10 per cent of their hydrogen mass and that stars have been created at a uniform rate in the solar neighborhood for the last five billion years. Using this hypothesis and the observed luminosity function, the rate of star creation as a function of stellar mass is calculated. The total number and mass of stars which have moved off the main sequence is found to be comparable with the total number of white dwarfs and with the total mass of all fainter main-sequence stars, respectively.

8,607 citations


"The young massive SMC cluster NGC 3..." refers methods in this paper

  • ...For each system, we randomly select the initial mass of the primary M1 from a Salpeter initial mass function (Salpeter 1955) between 4.5 and 8 M ....

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Journal ArticleDOI
TL;DR: In this article, the authors present an updated version of the AESOPUS code used to compute stellar evolutionary tracks in Padova, which is the result of a thorough revision of put physics, together with the inclusion of the pre-main sequence phase.
Abstract: We present the updated version of the code used to compute stellar evolutionary tracks in Padova. It is the result of a thorough revision of the major in put physics, together with the inclusion of the pre‐main sequence phase, not present in our previous releases of stellar models. Another innovative aspect is the possibility of prompt ly generating accurate opacity tables fully consistent with any selected initial chemical composition, by coupling the OPAL opacity data at high temperatures to the molecular opacities computed with our AESOPUS code (Marigo & Aringer 2009). In this work we present extended sets of stellar evolutionary models for various initial chemical compositions, while other set s with different metallicities and/or different distributions of heavy elements are being computed. For the present release of models we adopt the solar distribution of heavy elements from the recent revision by Caffau et al. (2011), corresponding to a Sun’s metallicity Z≃ 0.0152. From all computed sets of stellar tracks, we also derive isochrones in several photometric systems. The aim is to provide the community with the basic tools to model star clusters and galaxies by means of population synthesis techniques.

3,392 citations

Journal ArticleDOI
TL;DR: In this work, extended sets of stellar evolutionary models for various initial chemical compositions are presented, while other set s with different metallicities and/or different distributions of heavy elements are being computed.
Abstract: We present the updated version of the code used to compute stellar evolutionary tracks in Padova. It is the result of a thorough revision of the major input physics, together with the inclusion of the pre-main sequence phase, not present in our previous releases of stellar models. Another innovative aspect is the possibility of promptly generating accurate opacity tables fully consistent with any selected initial chemical composition, by coupling the OPAL opacity data at high temperatures to the molecular opacities computed with our AESOPUS code (Marigo & Aringer 2009). In this work we present extended sets of stellar evolutionary models for various initial chemical compositions, while other sets with different metallicities and/or different distributions of heavy elements are being computed. For the present release of models we adopt the solar distribution of heavy elements from the recent revision by Caffau et al. (2011), corresponding to a Sun's metallicity Z=0.0152. From all computed sets of stellar tracks, we also derive isochrones in several photometric systems. The aim is to provide the community with the basic tools to model star clusters and galaxies by means of population synthesis techniques.

3,175 citations

Journal ArticleDOI
27 Jul 2012-Science
TL;DR: More than 70% of all massive stars will exchange mass with a companion, leading to a binary merger in one-third of the cases, greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations ofmassive stars and their supernovae.
Abstract: The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified the frequency and nature of binary interactions. More than 70% of all massive stars will exchange mass with a companion, leading to a binary merger in one-third of the cases. These numbers greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations of massive stars and their supernovae.

1,779 citations

Journal ArticleDOI
TL;DR: In this paper, the authors acknowledge the support from the ERC Consolidator Grant (CRA 1.05.01.94) and Partial Support Agreement (PSA) for the STARKEY project.
Abstract: We acknowledge the support from the ERC Consolidator Grant funding scheme (project STARKEY, G.A. n. 615604). L.G. and T.S.R. acknowledge partial support from PRIN INAF 2014—CRA 1.05.01.94.05.

843 citations

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