The Villafranca catalog of Galactic OB groups

Abstract

Context. This is the second paper of a series on Galactic OB groups that uses astrometric and photometric data from Gaia and spectral classifications from the Galactic O-Star Spectroscopic Survey (GOSSS) and the Library of Libraries of Massive-star high-Resolution spectra (LiLiMaRlin). The previous paper was based on the second Gaia data release (DR2). Since then, the early third Gaia data release (EDR3) has appeared with new astrometry and photometry. Aims. The two aims of this paper are to revise the results for the sample from paper I using Gaia EDR3 data and to expand the sample of analyzed stellar groups to 26, from Villafranca O-001 to Villafranca O-026. Methods. We used GOSSS to select Galactic stellar groups with O stars and an updated version of the method in paper 0 of this series, combining Gaia EDR3 G + G BP + G RP photometry, positions, proper motions, and parallaxes to assign memberships and measure distances. We present 99 spectra from GOSSS and 32 from LiLiMaRlin for stars in the analyzed groups or in their foreground.Results. We derived distances to the 26 stellar groups with unprecedented precision and accuracy, with total (random plus systematic) uncertainties lower than 1% for distances within 1 kpc and of ∼3% around 3 kpc, which are values almost four times better than for Gaia DR2. We provide homogeneous spectral types for 110 stars and correct a number of errors in the literature, especially for objects in Villafranca O-023 (Orion nebula cluster). For each group, we discuss its membership and present possible runaway and walkaway stars. At least two of the studied groups, Villafranca O-O12 S in NGC 2467 and Villafranca O-014 NW in the North America nebula, are orphan clusters in which the most massive stars have been ejected by dynamical interactions, leaving objects with a capped mass function. The existence of such clusters has important consequences for the study of the initial mass function (IMF), the distribution of supernova explosions across the Galaxy, and the population and dynamics of isolated compact objects. We fit pre-main-sequence (PMS) isochrones to the color-magnitude diagrams (CMDs) of four clusters to derive ages of 2.0±0.5 Ma for Villafranca O-026 (σ Orionis cluster), 4±2 Ma for Villafranca O-016 (NGC 2264), 5.0±0.5 Ma for Villafranca O-021 (NGC 2362), and 8±2 Ma for Villafranca O-024 (γ Velorum cluster).

The outer orbit of the high-mass stellar triple system Herschel 36 determined with the VLTI

“…With the new estimate of a Aa−Ab =3.49±1.13 mas and the total mass derived from the orbital solution (see Table 3), we estimated a distance to the target of d = 1.33 ± 0.32 kpc. This value is consistent within 1-σ with the estimates reported by Campillay et al (2019), Maíz Apellániz et al (2022 and with the GAIA EDR3 parallax of Herschel 36 being 0.775 + / − 0.024 mas. More precise constraints on the distance to the system could be obtained by refining the orbital estimation with better astrometric VLTI observations obtained through beamcombiners like GRAVITY.…”

“…The target of this study is Herschel 36 A, an intriguing hierarchical triple system with a combined luminosity that matches the theoretical luminosity of three ZAMS stars (Arias et al 2010), suggesting that the system is in a very early evolutionary stage with an age of the order of ∼1 Ma. The source is located at 1234±16 pc (Maíz Apellániz et al 2022) and it is responsible for the ionization of the central part of the M8 nebula. Herschel 36 A consists of three known components.…”

Probing the low-mass end of the companion mass function for O-type stars

“…It appears to be roughly coeval with other components and it can be fitted best with a 0.9 M star in the age range of 1.8−4.5 Myr -BD −13 • 4929 it is part of NGC 6611 and it is found to be a SB3 by (Sana et al 2009). The triple system is composed by an O8 V and two B0.5: V+B0.5: V SpT stars (Maíz Apellániz et al 2022). We detected two companions in IFS, which are also confirmed by the IRDIS images.…”

“…-HD 64 568 has been associated with an O3 V((f*))z SpT (Sota et al 2014). It has recently been classified as runaway from the southern component of NGC 2467 by Maíz Apellániz et al (2020Apellániz et al ( , 2022. We did not find close companions in the IFS field nor in the IRDIS larger FOV.…”

Escape from the Bermuda cluster: Orphanization by multiple stellar ejections

“…spectroscopy from the Galactic O-Star Spectroscopic Survey (GOSSS, Maíz Apellániz et al 2011) and the Library of Libraries of Massive-star high-Resolution spectra (LiLi-MaRlin, Maíz Apellániz et al 2019a) to study the properties of Galactic stellar groups with OB stars. In Villafranca I (Maíz Apellániz et al 2020a) we analyzed 16 OB groups using Gaia Data Release 2 (DR2) data and in Villafranca II (Maíz Apellániz et al 2022) we added another ten and reanalyzed the 26 objects with Gaia Early Data Release 3 (EDR3) data. In Villafranca I we discussed the case of Villafranca O-014, the OB group associated with the North America and Pelican nebulae.…”