A Search for L/T Transition Dwarfs with Pan-STARRS1 and WISE. III. Young L Dwarf Discoveries and Proper Motion Catalogs in Taurus and Scorpius–Centaurus

Best, W.M.J.; Liu, M.C.; Magnier, E.A.; Bowler, B.P.; Aller, K.M.; Zhang, Z.; Kotson, M.C.; Burgett, W.S.; Chambers, K.C.; Draper, P.W.; Flewelling, H.; Hodapp, K.W.; Kaiser, N.; Metcalfe, N.; Wainscoat, R.J.; Waters, C.

Abstract

We present the discovery of eight young M7–L2 dwarfs in the Taurus star-forming region and the Scorpius–Centaurus OB Association, serendipitously found during a wide-field search for L/T transition dwarfs using Pan-STARRS1 (optical) and WISE (mid-infrared) photometry. We identify PSO J060.3200+25.9644 (near-infrared spectral type L1) and PSO J077.1033+24.3809 (L2) as new members of Taurus based on their vl-g gravity classifications, the consistency of their photometry and proper motions with previously known Taurus objects, and the low probability of contamination by field objects. PSO J077.1033+24.3809 is the coolest substellar member of Taurus found to date. Both Taurus objects are among the lowest-mass free-floating objects ever discovered, with estimated masses ≈6 ${M}_{\mathrm{Jup}}$, and provide further evidence that isolated planetary-mass objects can form as part of normal star formation processes. PSO J060.3200+25.9644 (a.k.a. DANCe J040116.80+255752.2) was previously identified as a likely member of the Pleiades (age $\approx \,125\,\mathrm{Myr}$) based on photometry and astrometry, but its vl-g gravity classification and near-infrared photometry imply a much younger age and thus point to Taurus membership. We have also discovered six M7–L1 dwarfs in outlying regions of Scorpius–Centaurus with photometry, proper motions, and low-gravity spectral signatures consistent with membership. These objects have estimated masses ≈15–36 ${M}_{\mathrm{Jup}}$. The M7 dwarf, PSO J237.1470−23.1489, shows excess mid-infrared flux implying the presence of a circumstellar disk. Finally, we present catalogs of Pan-STARRS1 proper motions for low-mass members of Taurus and Upper Scorpius with median precisions of ≈3 mas yr−1, including 67 objects with no previous proper motion and 359 measurements that improve on literature values.

Citation

Best, W., Liu, M., Magnier, E., Bowler, B., Aller, K., Zhang, Z., …Waters, C. (2017). A Search for L/T Transition Dwarfs with Pan-STARRS1 and WISE. III. Young L Dwarf Discoveries and Proper Motion Catalogs in Taurus and Scorpius–Centaurus. Astrophysical Journal, 837(1), Article 95. https://doi.org/10.3847/1538-4357/aa5df0

• Journal Article Type: Article
• Acceptance Date: Jan 31, 2017
• Online Publication Date: Mar 7, 2017
• Publication Date: Mar 7, 2017
• Deposit Date: Mar 30, 2017
• Publicly Available Date: Mar 31, 2017
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 837
• Issue: 1
• Article Number: 95
• DOI: https://doi.org/10.3847/1538-4357/aa5df0
• Public URL: https://durham-repository.worktribe.com/output/1381840