Overlooked wide companions of nearby F stars

Abstract

Aims. We checked a sample of 545 F stars within 50 pc for wide companions using existing near-infrared and optical sky surveys. Methods. Applying the common proper motion (CPM) criterion, we detected wide companion candidates with 6-120 arcsec angular separations by visual inspection of multi-epoch finder charts and by searching in proper motion catalogues. Final proper motions were measured by involving positional measurements from up to eleven surveys. Spectral types of red CPM companions were estimated from their absolute J-band magnitudes based on the H distances of the primaries.Results. In addition to about 100 known CPM objects, we found 19 new CPM companions and confirmed 31 previously known candidates. A few CPM objects are still considered as candidates according to their level of proper motion agreement. Among the new objects there are nine M0-M4, eight M5-M6, one ≈L3.5 dwarf (HD 3861B), and one white dwarf (WD) (HD 2726B), whereas we confirmed two K, 19 M0-M4, six M5-M6, two early-L dwarfs, and two DA WDs as CPM companions. In a few cases, previous spectral types were available that all agree well with our estimates. Two companions (HD 22879B and HD 49933B) are associated with moderately metal-poor Gaia benchmark stars. One doubtful CPM companion, spectroscopically classified as WD but found to be very bright (J = 11.1) by others, should either be a very nearby foreground WD or a different kind of object associated with HD 165670.Key words. proper motions -stars: abundances -binaries: general -stars: low-mass -white dwarfs -solar neighborhood IntroductionStellar binaries and multiple systems appear to be the main product of star formation if the primaries of these systems are at least as massive as the Sun. The solar neighbourhood, representing the average Galactic disk population of stellar systems that typically have existed for several Gyrs, is naturally one of the best-investigated regions with respect to multiplicity. The Research Consortium on Nearby Stars (RECONS) 1 states a multiplicity rate, i.e. the probability that a given system has more than one component, of 29% for their 10 pc sample. However, this overall "low rate is because M-type dwarfs dominate the solar neighbourhood (a full 73% of the stellar sample ... are M-type dwarfs), and do not have companions as often as their more massive stellar cousins". Among the 100 nearest RECONS systems (with a horizon of about 6.5 pc), there are 70 where M dwarfs are the most-massive component, of which only 18 (26%) are known to have companions. On the other hand, there are 22 AFGK primaries, of which 12 (55%) are in known multiple systems. The RECONS 10 pc census shows a strong increase from 2000 to 2012 both in the number of M dwarfs (+25%) and in the number of stellar and LT-type companions (+26%).The multiplicity of F-and G-type stars in a wider solar neighbourhood was the focus of investigations by Fuhrmann & Chini (2012, 2015, Chini et al. (2014), Tokovinin (2011, 2014), and Tokovinin & Lépine (2012. To distinguish between T...

Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2

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“…Mason et al (2001),Deacon et al (2014),De Rosa et al (2014),Dhital et al (2015),Gauza et al (2015),Smith et al (2015),Scholz (2016),Kirkpatrick et al (2016), Gálvez-…”