The Solar Neighborhood. XLII. Parallax Results from the CTIOPI 0.9 m Program—Identifying New Nearby Subdwarfs Using Tangential Velocities and Locations on the H–R Diagram

Jao, Wei-Chun; Henry, Todd J.; Winters, Jennifer G.; Subasavage, John P.; Riedel, Adric R.; Silverstein, Michele L.; Ianna, P. A.

doi:10.3847/1538-3881/aa8b64

Cited by 15 publications

(13 citation statements)

References 103 publications

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“…The position of the subdwarfs in the color-magnitude diagram is also consistent with other work on metal-poor M dwarfs (see for e.g. Lepine et al 2007;Jao et al 2008Jao et al , 2017.…”

Section: Gaia Dr2 Color Magnitude Diagramssupporting

confidence: 90%

“…With Gaia DR2 we were able to calculate precise tangential velocities for 22, 373 M and L dwarfs in the MLSDSS-GaiaDR2 sample. To explore the disk and halo popu-lations of stars in our catalog, we studied the correlation between tangential velocity (v tan ) and color-magnitude diagram position for the MLSDSS-GaiaDR2 sample (Figure 21) as done by previous work (Lepine et al 2007;Gizis & Reid 1999;Jao et al 2017).…”

Section: Tangential Velocitymentioning

confidence: 99%

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Exploring the Age-dependent Properties of M and L Dwarfs Using Gaia and SDSS

et al. 2019

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We present a sample of 74, 216 M and L dwarfs a) constructed from two existing catalogs of cool dwarfs spectroscopically identified in the Sloan Digital Sky Survey (SDSS). We cross-matched the SDSS catalog with Gaia DR2 to obtain parallaxes and proper motions and modified the quality cuts suggested by the Gaia Collaboration to make them suitable for late-M and L dwarfs. We also provide relations between Gaia colors and absolute magnitudes with spectral type and conclude that (G − G RP ) has the tightest relation to spectral type for M and L dwarfs. In addition, we study magnetic activity as a function of position on the color-magnitude diagram, finding that Hα magnetically active stars have, on average, redder colors and/or brighter magnitudes than inactive stars. This effect cannot be explained by youth alone and might indicate that active stars are magnetically inflated, binaries and/or high metallicity. Moreover, we find that vertical velocity and vertical action dispersion are correlated with Hα emission, confirming that these two parameters are age indicators. We also find that stars below the main sequence have high tangential velocity which is consistent with a low metallicity and old population of stars that belong to the halo or thick disk.

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“…The position of the subdwarfs in the color-magnitude diagram is also consistent with other work on metal-poor M dwarfs (see for e.g. Lepine et al 2007;Jao et al 2008Jao et al , 2017.…”

Section: Gaia Dr2 Color Magnitude Diagramssupporting

confidence: 90%

Section: Tangential Velocitymentioning

confidence: 99%

Exploring the Age-dependent Properties of M and L Dwarfs Using Gaia and SDSS

et al. 2019

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“…We use the estimated mass of LHS 1678 and the mass-rotation relation of 3) imply that the star has a metallicity less than zero. The lack of characteristically large CaHn (n=1-3) and TiO5 band strengths in our RC Spec spectrum (Figure 1) suggests that LHS 1678 is not a cool subdwarf (Gizis 1997), in agreement with its position within the main sequence and its low tangential velocity (Jao et al 2017). These findings are consistent with our assessments of galactic kinematics and low magnetic activity.…”

Section: Stellar Agesupporting

confidence: 87%

“…Sixteen years (2004-2020) of ground-based astrometry from the RECONS program at the CTIO/SMARTS 0.9m telescope in Chile show compelling evidence that LHS 1678 hosts a low-mass stellar or substellar companion with an orbital period longer than the timespan defined by the dataset. As initially reported by Jao et al (2017), there is residual motion in the position of the LHS 1678 photocenter after solving for parallax and proper motion. Images of the field were acquired through the V J (henceforth simply V ) filter at air-masses < 1.1, meaning that corrections required for differential color refraction were minimal.…”

Section: Astrometric Detection Of a Stellar Or Substellar Companionmentioning

confidence: 51%

The LHS 1678 System: Two Earth-Sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc

Silverstein,

Schlieder,

Barclay

et al. 2021

Preprint

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We present the TESS discovery of the LHS 1678 (TOI-696) exoplanet system, comprised of two approximately Earth-sized transiting planets and a likely astrometric brown dwarf orbiting a bright (V J =12.5, K s =8.3) M2 dwarf at 19.9 pc. The two TESS-detected planets are of radius 0.70±0.04 R ⊕ and 0.98±0.06 R ⊕ in 0.86-day and 3.69-day orbits, respectively. Both planets are validated and characterized via ground-based follow-up observations. HARPS RV monitoring yields 97.7 percentile mass upper limits of 0.35 M ⊕ and 1.4 M ⊕ for planets b and c, respectively. The astrometric companion detected by the CTIO/SMARTS 0.9m has an orbital period on the order of decades and is undetected by other means. Additional ground-based observations constrain the companion to being a high-mass brown dwarf or smaller. Each planet is of unique interest; the inner planet has an ultra-short period, and the outer planet is in the Venus zone. Both are promising targets for atmospheric characterization with the JWST and mass measurements via extreme-precision radial velocity. A third planet candidate of radius 0.9±0.1 R ⊕ in a 4.97-day orbit is also identified in multi-Cycle TESS data for validation in future work. The host star is associated with an observed gap in the lower main sequence of the Hertzsprung-Russell diagram. This gap is tied to the transition from partially-to fully-convective interiors in M dwarfs, and the effect of the associated stellar astrophysics on exoplanet evolution is currently unknown. The culmination of these system properties makes LHS 1678 a unique, compelling playground for comparative exoplanet science and understanding the formation and evolution of small, short-period exoplanets orbiting low-mass stars.

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“…Then it was classified as an M subdwarf (Kuiper 1940) after the discovery of the HRD and definition of cool subdwarfs (Kuiper 1939). To date, thousands of M subdwarfs (Zhang et al 2013;Savcheva et al 2014;Zhong et al 2015;Jao et al 2017;Zhang et al 2019a), hundreds of late-type M subdwarfs (Lépine et al 2003b;Burgasser et al 2007;Lépine & Scholz 2008;Lodieu et al 2012Lodieu et al , 2017Kirkpatrick et al 2016), and about 66 L subdwarfs (Burgasser et al 2003;Kirkpatrick et al 2014;Zhang et al 2017a, hereafter Primeval I; Primeval III; Zhang et al 2018b, hereafter Primeval IV) have been discovered with modern sky surveys. About 41 T subdwarfs have also been discovered (e.g., Burgasser et al 2002;Pinfield et al 2012;Mace et al 2013;Burningham et al 2014) and studied in the literature (Zhang et al 2019b, hereafter Primeval VI).…”

Section: Introductionmentioning

confidence: 99%

Primeval very low-mass stars and brown dwarfs -- VII. The discovery of the first wide M + L extreme subdwarf binary

Zhang

2019

Preprint

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I present the discovery of the first wide M + L extreme subdwarf binary system Gaia J0452−36AB. The binary is located at a distance of 137.27 +0.68 −0.67 pc with a projected separation of 15828±78 au. I classified Gaia J0452−36AB as esdM1 and esdL0 subdwarfs, respectively. Gaia J0452−36AB have typical halo kinematics, metallicity of [Fe/H] ≈ −1.4, and temperature of ∼ 3550 and 2600 K, respectively. Gaia J0452−36AB is a pair of very low-mass stars with masses of 0.151 +0.029 −0.019 and 0.0855 +0.0014 −0.0010 M , and is a gravitationally bound system. I tested the metallicity consistency of existing M subdwarf classification schemes with Gaia J0452−36AB and a sample of M and L subdwarfs with known metallicity. I found that the metallicity of each M subclass defined by the the metallicity index ζ CaH/TiO is not consistent from mid-to-late M subtypes. Because late-type M and L subdwarfs have dusty atmospheres and high surface gravity which have significant impacts on CaH and TiO indices that used in the classification. The metallicity scale of late-type M subdwarfs would be overestimated by the ζ CaH/TiO index. I discussed the mass range of M subdwarfs, and explained the lack of late-type M extreme and ultra subdwarfs, and decreasing binary fraction from sdM, to esdM, and usdM subclasses. The four M subclasses have different mass ranges. The comparison between M subclasses is between populations in different mass ranges. I also present the discovery of Ruiz 440-469B, an M8 dwarf wide companion to a cool DA white dwarf, Ruiz 440-469.

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The Solar Neighborhood. XLII. Parallax Results from the CTIOPI 0.9 m Program—Identifying New Nearby Subdwarfs Using Tangential Velocities and Locations on the H–R Diagram

Cited by 15 publications

References 103 publications

Exploring the Age-dependent Properties of M and L Dwarfs Using Gaia and SDSS

Exploring the Age-dependent Properties of M and L Dwarfs Using Gaia and SDSS

The LHS 1678 System: Two Earth-Sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc

Primeval very low-mass stars and brown dwarfs -- VII. The discovery of the first wide M + L extreme subdwarf binary

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