All-sky Co-moving Recovery Of Nearby Young Members (ACRONYM). II. The β Pictoris Moving Group^∗

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 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 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.

Spectroscopic Orbits of Subsystems in Multiple Stars. III.

“…The period of A,B is estimated as ∼20 kyr. According to Shkolnik et al (2017) and to some other authors, the system is a member of the β Pictoris moving group; lithium lines were found in the spectrum of B (spectral type K7V). The component A, of K2V spectral type, is a chromospherically active star V390 Pav.…”

Calibrating the metallicity of M dwarfs in wide physical binaries with F-, G-, and K-primaries – I: High-resolution spectroscopy with HERMES: stellar parameters, abundances, and kinematics★

“…All of them except HD 98736 had been later assigned to SKGs linked to the LA, which supports our classification: Hercules-Lyra (V538 Aur and V382 Ser, by Fuhrmann 2004;DX Leo and HH Leo, by Eisenbeiss et al 2013), AB Doradus (V577 Per, by Riedel et al 2017), and Columba (V368 Cep, with BANYAN Σ). The eighth known LA star candidate is HD 82939, which proper-motion companion MCC 549 has been subject of debate: Schlieder et al (2012) proposed it to be a member in the β Pictoris In the top left panel, the dashed grey line confines the young disc population as defined by Eggen (1984Eggen ( , 1989 moving group, also linked to the LA, but this statement was later denied by Malo et al (2014) and Shkolnik et al (2017). There is no trail of lithium in our HERMES spectrum of HD 82939 (G5 V), which supports the Malo et al (2014) conclusion.…”

A Search for Variability in Exoplanet Analogues and Low-Gravity Brown Dwarfs

“…The full survey sample is shown in Table 3. We consider the following young moving groups in this paper: TW Hydra (TWA, 10 ± 3 Myr; Bell et al 2015), β Pictoris (β Pic, 22 ± 6 Myr; Shkolnik et al 2017), Columba (Col, Myr; Bell et al 2015), Tucana-Horologium (THA, 45 ± 4 Myr; Bell et al 2015), Carina (Car, Myr; Bell et al 2015), Argus (Arg, 30−50 Myr;Torres et al 2008), AB Doradus (AB Dor, 110−150 Myr; Barenfeld et al 2013;Luhman et al 2007) and Carina-Near (CarN, 200±50 Myr;Zuckerman et al 2006). Our targets show signs of low-gravity in their spectra and/or are candidate members of nearby young moving groups.…”