WISEA J041451.67-585456.7 and WISEA J181006.18-101000.5: The First Extreme T-type Subdwarfs? (original) (raw)
ADS
;
- Burgasser, Adam J. ;
- Gerasimov, Roman ;
- Marocco, Federico ;
- Gagné, Jonathan ;
- Goodman, Sam ;
- Beaulieu, Paul ;
- Pendrill, William ;
- Rothermich, Austin ;
- Sainio, Arttu ;
- Kuchner, Marc J. ;
- Caselden, Dan ;
- Meisner, Aaron M. ;
- Faherty, Jacqueline K. ;
- Mamajek, Eric E. ;
- Hsu, Chih-Chun ;
- Greco, Jennifer J. ;
- Cushing, Michael C. ;
- Kirkpatrick, J. Davy ;
- Bardalez-Gagliuffi, Daniella ;
- Logsdon, Sarah E. ;
- Allers, Katelyn ;
- Debes, John H. ;
- Backyard Worlds: Planet 9 Collaboration
Abstract
We present the discoveries of WISEA J041451.67-585456.7 and WISEA J181006.18-101000.5, two low-temperature (1200-1400 K), high proper motion T-type subdwarfs. Both objects were discovered via their high proper motion (>0"5 yr-1); WISEA J181006.18-101000.5 as part of the NEOWISE proper motion survey and WISEA J041451.67-585456.7 as part of the citizen science project Backyard Worlds; Planet 9. We have confirmed both as brown dwarfs with follow-up near-infrared spectroscopy. Their spectra and near-infrared colors are unique among known brown dwarfs, with some colors consistent with L-type brown dwarfs and other colors resembling those of the latest-type T dwarfs. While no forward model consistently reproduces the features seen in their near-infrared spectra, the closest matches suggest very low metallicities ([Fe/H] leqslant\leqslant leqslant -1), making these objects likely the first examples of extreme subdwarfs of the T spectral class (esdT). WISEA J041451.67-585456.7 and WISEA J181006.18-101000.5 are found to be part of a small population of objects that occupy the "substellar transition zone," and have the lowest masses and effective temperatures of all objects in this group.
Publication:
The Astrophysical Journal
Pub Date:
July 2020
DOI:
arXiv:
Bibcode:
Keywords:
- T subdwarfs;
- Brown dwarfs;
- Subdwarf stars;
- T dwarfs;
- 1680;
- 185;
- 2054;
- 1679;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Astrophysics of Galaxies
E-Print:
Accepted for publication in the Astrophysical Journal