The star formation history and accretion-disc fraction among the K-type members of the Scorpius–Centaurus OB association

By M. Pecaut, Eric Mamajek. 2016

273 citations recorded by the source corpus.

We present results of a spectroscopic survey for new K- and M-type members of Scorpius-Centaurus (Sco-Cen), the nearest OB Association (~100-200 pc). Using an X-ray, proper motion and color-magnitude selected sample, we obtained spectra for 361 stars, for which we report spectral classifications and Li and Halpha equivalent widths. We identified 156 new members of Sco-Cen, and recovered 51 previously published members. We have combined these with previously known members to form a sample of 493 solar-mass (~0.7-1.3 Msun) members of Sco-Cen. We investigated the star-formation history of this sample, and re-assessed the ages of the massive main-sequence turn-off and the G-type members in all three subgroups. We performed a census for circumstellar disks in our sample using WISE infrared data and find a protoplanetary disk fraction for K-type stars of 4.4$^{+1.6}_{-0.9}$% for Upper Centaurus-Lupus and Lower Centaurus-Crux at ~16 Myr and 9.0$^{+4.0}_{-2.2}$% for Upper Scorpius at ~10 Myr. These data are consistent with a protoplanetary disk e-folding timescale of ~4-5 Myr for ~1 Msun stars, twice that previously quoted (Mamajek 2009), but consistent with the Bell et al. revised age scale of young clusters. Finally, we construct an age map of Scorpius-Centaurus which clearly reveals substructure consisting of concentrations of younger and older stars. We find evidence for strong age gradients within all three subgroups. None of the subgroups are consistent with being simple, coeval populations which formed in single bursts, but likely represents a multitude of smaller star formation episodes of hundreds to tens of stars each.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/530a5b6223a158cf85694ed6ea4f1973b5fb7bbc

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Citations in the corpus

• Discovery of a warm, dusty giant planet around HIP 65426 (2017, methodology): “This is fully consistent with the Sco-Cen age map by Pecaut & Mamajek (2016), that yields an age of 14 Myr at the position of HIP 65426 using a complementary approach (much larger number of stars extending to fainter magnitude but relying on kinematic parallaxes, while we used the Gaia…”
• Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70 (2018, methodology): “Using low-resolution optical spectra, Pecaut & Mamajek (2016) derived a stellar temperature of 3972 K, corresponding to a K7 spectral type.”
• BANYAN. XI. The BANYAN Σ Multivariate Bayesian Algorithm to Identify Members of Young Associations with 150 pc (2018, methodology): “…2014; (5) Gen- naro et al. 2012; (6) Murphy et al. 2013; (7) Brandt & Huang 2015; (8) Barrado y Navascués et al. 2004; (9) Dobbie et al. 2010; (10) Pecaut & Mamajek 2016; (11) Murphy & Lawson 2015; (12) Platais et al. 1998; (13) Dahm 2015; (14) Wilking et al. 2008; (15) Kenyon & Hartmann…”
• The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics from 10 to 100 au (2019, methodology): “…(1989), (27) Houk (1978), (28) Lépine et al. (2013), (29) Davison et al. (2015), (30) Abt (2009), (31) Corbally (1984), (32) Kirkpatrick et al. (1991), (33) Pecaut & Mamajek (2016b), (34) Sreedhar Rao & Abhyankar (1991), (35) Paunzen et al. (2001), (36) Levenhagen & Leister (2006), (37)…”
• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (2016, background): “We assume that protoplanetary disks around dwarfs such as Proxima dissipate after between t0 = 3 Myr and 10 Myr (Pascucci et al. 2009; Pfalzner et al. 2014; Pecaut & Mamajek 2016).”
• Magellan Adaptive Optics Imaging of PDS 70: Measuring the Mass Accretion Rate of a Young Giant Planet within a Gapped Disk (2018, background): “PDS 70 is a K7 pre-main sequence T Tauri type star in the Upper Centuarus Lupus association (Riaud et al. 2006, Pecaut & Mamajek 2016).”
• Orbital and atmospheric characterization of the planet within the gap of the PDS 70 transition disk (2018, methodology): “We note that the derived stellar age of PDS 70 is significantly younger than the median age derived for UCL with 16±2 Myr and an age spread of 7 Myr by Pecaut & Mamajek (2016).”
• Water loss from terrestrial planets orbiting ultracool dwarfs: implications for the planets of TRAPPIST-1 (2016, background): “We first assume that protoplanetary disks around UCDs dissipate after 3 Myr (Pascucci et al. 2009; Pecaut & Mamajek 2016) ; this is our “time zero”.”
• Kinematics in Young Star Clusters and Associations with Gaia DR2 (2018, result): “This size is quite similar to the size of Upper Scorpius in the Scorpius-Centaurus Association, which is ∼75–100 pc long along its longest axis (Galli et al. 2018) and has an age of ∼10 Myr (Pecaut & Mamajek 2016).”