Astron. J., 154, 69-69 (2017/August-0)
All-sky Co-moving Recovery Of Nearby Young Members (ACRONYM). II. The β Pictoris Moving Group.
SHKOLNIK E.L., ALLERS K.N., KRAUS A.L., LIU M.C. and FLAGG L.
Abstract (from CDS):
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 0.07 M☉. 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 22 ± 6 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 M☉ 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.
© 2017. The American Astronomical Society. All rights reserved.
binaries: spectroscopic - open clusters and associations: individual: β Pictoris Moving Group - stars: activity - stars: kinematics and dynamics - stars: low-mass - stars: pre-main sequence - stars: pre-main sequence
VizieR on-line data:
<Available at CDS (J/AJ/154/69): table1.dat table2.dat table3.dat table4.dat>
Table 4: TYC 9703-0762 is a misprint for TYC 9073-0762-1.
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