All-sky co-moving recovery of nearby young members (ACRONYM). II. the β Pictoris Moving Group

Evgenya Shkolnik, Katelyn N. Allers, Adam L. Kraus, Michael C. Liu, Laura Flagg

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

Abstract

We confirm 66 low-mass stellar and brown dwarf systems (K7-M9) plus 19 visual or spectroscopic companions of the β Pictoris moving group (BPMG). Of these, 41 are new discoveries, increasing the known low-mass members by 45%. We also add four objects to the 14 known with masses predicted to be less than . Our efficient photometric + kinematic selection process identified 104 low-mass candidates, which we observed with ground-based spectroscopy. We collected infrared observations of the latest spectral types (>M5) to search for low-gravity objects. These and all <M5 candidates were observed with high-resolution optical spectrographs to measure the radial velocities and youth indicators, such as lithium absorption and Hα emission, needed to confirm BPMG membership, achieving a 63% confirmation rate. We also compiled the most complete census of BPMG membership, with which we tested the efficiency and false-membership assignments using our selection and confirmation criteria. Using the new census, we assess a group age of 226 Myr, consistent with past estimates. With the now-densely sampled lithium depletion boundary, we resolve the broadening of the boundary by either an age spread or astrophysical influences on lithium-burning rates. We find that 69% of the now-known members with AFGKM primaries are M stars, nearing the expected value of 75%. However, the new initial mass function for the BPMG shows a deficit of 0.2-0.3 stars by a factor of ∼2. We expect that the AFGK census of the BPMG is also incomplete, probably due to biases of searches toward the nearest stars.

Original languageEnglish (US)
Article number69
JournalAstronomical Journal
Volume154
Issue number2
DOIs
StatePublished - Aug 2017

Keywords

  • activity stars
  • binaries
  • individual: (β Pictoris Moving Group) stars
  • kinematics and dynamics stars
  • low-mass stars
  • pre-main sequence
  • spectroscopic open clusters and associations

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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