Massive stars in the young cluster VVV CL074

Abstract

Context. The evolution of massive stars is not fully constrained. Studies of young massive clusters hosting various populations of massive stars can help refine our understanding of the life and fate of massive stars. Aims. In this context, our goal is to study the massive stellar content of the young massive cluster VVV CL074. Methods. We obtained K-band spectroscopy of the brightest cluster members in order to identify the massive star population. We also determined the stellar properties of the cluster's massive stars to better quantify the evolutionary sequences linking different types of massive stars. We collected integral field spectroscopy of selected fields in the cluster VVV CL074 with SINFONI on the ESO/VLT. We performed a spectral classification based on the K-band spectra and comparison to infrared spectral atlases. We determined the stellar parameters of the massive stars from analysis with atmosphere models computed with the code CMFGEN. Results. We uncover a population of 25 early-type (OB and Wolf-Rayet) stars, 19 being newly discovered by our observations out of which 15 are likely cluster members. The cluster's spectrophotometric distance is 10.2±1.6 kpc, placing it close to the intersection of the galactic bar and the Norma arm, beyond the galactic center. This makes VVV CL074 one the farthest young massive clusters identified so far. Among the massive stars population, three objects are Wolf-Rayet stars, the remaining are O and B stars. From the Hertzsprung-Russell diagram we find that most stars have an age between 3 and 6 Myr according to the Geneva evolutionary tracks. WN8 and WC8-9 stars are the descendants of stars with initial masses between 40 and 60 M ⊙ . The massive star population of VVV CL074 is very similar to that of the cluster DBS2003-179 and to a lesser extent to that of the Quintuplet cluster, indicating the same age. The central cluster of the Galaxy is ∼3 Myr older. From the comparison of the massive stars populations in these four clusters, one concludes that galactic stars with an initial mass in the range 40 to 60 M ⊙ likely go through a WN8-9 phase. ⋆ Based on observations conducted at ESO on the Very Large Telescope under program 099.D-0161(B).

Upper mass-loss limits and clumping in the intermediate and outer wind regions of OB stars

“…CMFGEN, Hillier & Miller 1998; FAST-WIND, Santolaya-Rey et al 1997 andPuls et al 2005; POWR, Gräfener et al 2002) 1 , it is possible to derive both physical stellar and wind parameters by means of quantitative spectroscopy (e.g. Najarro 1995;Puls et al 1996;Herrero et al 2002;Urbaneja et al 2003;Puls et al 2005;Berlanas et al 2018;Sander et al 2014;Martins et al 2019). However, despite the initial success of theoretical predictions based on stationary outflows (Vink et al 2000;Kudritzki 2002;Puls et al 2003), it is well established A&A 658, A61 (2022) nowadays that stellar winds from massive stars are timedependent and structured in velocity and density, displaying small-scale inhomogeneities (see review by Puls et al 2008;Hamann et al 2008;Sander 2017).…”

Recipes for bolometric corrections and Gaia luminosities of B-type stars: application to an asteroseismic sample

“…Here, we focus on this problem for early-type stars with effective temperatures T eff ≥ 10 4 K. For such stars, the problem is often circumvented by working with spectroscopic luminosities Lspec, which are an approximation of the actual luminosities and are calculated directly from the spectroscopic effective temperatures T eff and surface gravities log g (Lspec ≡ T 4 eff / log g, Langer & Kudritzki 2014;Simón-Díaz et al 2017;Castro et al 2018). Bolometric luminosities can also be obtained by converting measured apparent magnitudes to absolute bolometric magnitudes using distance measurements and bolometric corrections, as previously done for stars with effective temperatures above 10000 K by, e.g., Humphreys (1979); Underhill (1980); Schonberner & Drilling (1984); Stahl et al (1984); Singh & Chaubey (1987); Massey et al (1989a,b); Parker & Garmany (1993); Hubrig et al (2000); Hunter et al (2007); Fossati et al (2014); Camacho et al (2016); Martins et al (2019); Dufton et al (2019Dufton et al ( , 2020; Balona et al (2019); Balona & Ozuyar (2020).…”

Recipes for bolometric corrections and Gaia luminosities of B-type stars: Application to an asteroseismic sample

“…Here, we focus on this problem for early-type stars with effective temperatures T eff ≥ 10 4 K. For such stars, the problem is often circumvented by working with spectroscopic luminosities Lspec, which are an approximation of the actual luminosities and are calculated directly from the spectroscopic effective temperatures T eff and surface gravities log g (Lspec ≡ T 4 eff / log g, Langer & Kudritzki 2014;Simón-Díaz et al 2017;Castro et al 2018). Bolometric luminosities can also be obtained by converting measured apparent magnitudes to absolute bolometric magnitudes using distance measurements and bolometric corrections, as previously done for stars with effective temperatures above 10000 K by, e.g., Humphreys (1979); E-mail: maygade.pedersen@kuleuven.be Underhill (1980); Schonberner & Drilling (1984); Stahl et al (1984); Singh & Chaubey (1987); Massey et al (1989a,b); Parker & Garmany (1993); Hubrig et al (2000); Hunter et al (2007); Fossati et al (2014); Camacho et al (2016); Martins et al (2019); Dufton et al (2019Dufton et al ( , 2020; Balona et al (2019); Balona & Ozuyar (2020).…”