Discovery of a Possible Early-T Thick-disk Subdwarf from the AllWISE2 Motion Survey*

Kellogg, Kendra; Kirkpatrick, J. Davy; Metchev, Stanimir; Gagné, Jonathan; Faherty, Jacqueline K.

doi:10.3847/1538-3881/aaa3f2

Cited by 5 publications

(3 citation statements)

References 57 publications

(98 reference statements)

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“…Classification of these sources as bona fide subdwarfs has been challenging. For example, the spectra of two early sdT candidates WISE J071121.36−573634.2 and WISE J210529.08−623558.7, which show thick-disk-like kinematics, possess weak or ambiguous signs of low-metallicity, which may be attributable to multiplicity effects (Luhman & Sheppard 2014;Kellogg et al 2018). Even the tangential velocity estimates of these sources, estimated from spectral type-absolute magnitude relations, may be inaccurate for subdwarf types, depending on the band used.…”

Section: Introductionmentioning

confidence: 99%

WISEA J041451.67–585456.7 and WISEA J181006.18–101000.5: The First Extreme T-type Subdwarfs?

Schneider

Burgasser²,

Gerasimov³

et al. 2020

ApJ

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We present the discoveries of WISEA J041451.67−585456.7 and WISEA J181006.18−101000.5, two lowtemperature (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]  −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.

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Section: Introductionmentioning

confidence: 99%

WISEA J041451.67–585456.7 and WISEA J181006.18–101000.5: The First Extreme T-type Subdwarfs?

Schneider

Burgasser²,

Gerasimov³

et al. 2020

ApJ

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“…Note this is expected for mildly metal-poor T subdwarfs as we have discussed in Section 5. WISE J071121.36−573634.2 (WI0711; Kellogg et al 2018) has a relative high tangential velocity that consistent with the thick disc. However, its subdwarf nature is not quite clear based on its poor quality NIR spectra.…”

Section: T Subdwarfs In the Literaturementioning

confidence: 86%

Primeval very low-mass stars and brown dwarfs - VI. Population properties of metal-poor degenerate brown dwarfs

Zhang,

Burgasser,

Galvez-Ortiz

et al. 2019

Preprint

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We presented 15 new T dwarfs that were selected from UKIRT Infrared Deep Sky Survey, Visible and Infrared Survey Telescope for Astronomy, and Wide-field Infrared Survey Explorer surveys, and confirmed with optical to near infrared spectra obtained with the Very Large Telescope and the Gran Telescopio Canarias. One of these new T dwarfs is mildly metal-poor with slightly suppressed K-band flux. We presented a new X-shooter spectrum of a known benchmark sdT5.5 subdwarf, HIP 73786B. To better understand observational properties of brown dwarfs, we discussed transition zones (mass ranges) with low-rate hydrogen, lithium, and deuterium burning in brown dwarf population. The hydrogen burning transition zone is also the substellar transition zone that separates very low-mass stars, transitional, and degenerate brown dwarfs. Transitional brown dwarfs have been discussed in previous works of the Primeval series. Degenerate brown dwarfs without hydrogen fusion are the majority of brown dwarfs. Metal-poor degenerate brown dwarfs of the Galactic thick disc and halo have become T5+ subdwarfs. We selected 41 T5+ subdwarfs from the literature by their suppressed K-band flux. We studied the spectral-type-colour correlations, spectral-type-absolute magnitude correlations, colour-colour plots, and HR diagrams of T5+ subdwarfs, in comparison to these of L-T dwarfs and L subdwarfs. We discussed the T5+ subdwarf discovery capability of deep sky surveys in the 2020s.

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“…If confirmed, these three objects would more than double the number of known early-type T subdwarfs. To date, only two early-type T subdwarfs are known: the sdT0 WISE 071121.36−573634.2 discovered by Kellogg et al (2018) as part of the follow-up for the AllWISE2 motion survey (Kirkpatrick et al 2016); and the sdT1.5 WISE 210529.08−623558.7, discovered by Luhman & Sheppard (2014) as part of an analysis of high proper motion objects from the WISE survey. In addition, there are three published late-type T subdwarfs: the sdT5.5 HIP73786B, a common proper motion companion to the metal-poor K-star HIP73786 discovered by Murray et al (2011) using data from the United Kingdom InfraRed Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS); the sdT6.5 ULAS J131610.28+075553.0 discovered by Burningham et al (2014) in the UKIDSS Large Area Survey; and the sdT8 WISE J200520.38+542433.9, a companion to the sdM1.5 Wolf 1130, discovered by Mace et al (2013) using photometry from 2MASS, WISE, and other telescopes.…”

Section: Subdwarfsmentioning

confidence: 99%

Spectroscopic Follow-up of Discoveries from the NEOWISE Proper Motion Survey

Greco

Schneider

Cushing

et al. 2019

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We present low-resolution near-infrared spectra of discoveries from an all-sky proper motion search conducted using multi-epoch data from the Wide-field Infrared Survey Explorer. Using the data from NEOWISE, along with the AllWISE catalog, Schneider et al. (2016) conducted an all-sky proper motion survey to search for nearby objects with high proper motions. Here, we present a follow-up spectroscopic survey of 65 of their discoveries, which focused primarily on potentially nearby objects (d < 25 pc), candidate late-type brown dwarfs (≥L7), and subdwarf candidates. We found 31 new M dwarfs, 18 new L dwarfs, and 11 new T dwarfs. Of these, 13 are subdwarfs, including one new sdL1 and two new sdL7s. Eleven of these discovereies, with spectral types ranging from M7 to T7 (including one subdwarf) are predicted to be within 25 pc, adding to the number of known objects in the solar neighborhood. We also discovered three new early-type T subdwarf candidates, one sdT1, one sdT2, and one sdT3, which would increase the number of known early-type T subdwarfs from two to five.

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Discovery of a Possible Early-T Thick-disk Subdwarf from the AllWISE2 Motion Survey*

Cited by 5 publications

References 57 publications

WISEA J041451.67–585456.7 and WISEA J181006.18–101000.5: The First Extreme T-type Subdwarfs?

WISEA J041451.67–585456.7 and WISEA J181006.18–101000.5: The First Extreme T-type Subdwarfs?

Primeval very low-mass stars and brown dwarfs - VI. Population properties of metal-poor degenerate brown dwarfs

Spectroscopic Follow-up of Discoveries from the NEOWISE Proper Motion Survey

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