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 Hipparcos 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 $\approx$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.

Research Note accepted for publication in Astronomy and Astrophysics, 8 pages (incl. Appendices and 3 figures)

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• A low-mass triple system with a wide L/T transition brown dwarf component: NLTT 51469AB/SDSS 2131-0119