Masses of Astrometrically-Discovered and Imaged Binaries: G 78-28AB and GJ 231.1BC

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dc.creatorPravdo, Steven H.
dc.creatorShaklan, Stuart B.
dc.creatorWiktorowicz, Sloane J.
dc.creatorKulkarni, Shri
dc.creatorLloyd, James P.
dc.creatorMartinache, Frantz
dc.creatorTuthill, Peter G.
dc.creatorIreland, Michael J.
dc.date2006-05-11
dc.date.accessioned2026-07-07T10:38:59Z
dc.date.available2026-07-07T10:38:59Z
dc.descriptionThe Stellar Planet Survey (STEPS) is an ongoing astrometric search for giant planets and brown dwarfs around a sample of ~30 M-dwarfs. We have discovered several low-mass companions by measuring the motion of our target stars relative to their reference frames. The highest mass discovery thus far is G 78-28B, a companion to the M-dwarf G 78-28A. The orbital period is 4.18 +/- 0.03 y, the system mass is 0.565 +/- 0.055 Msolar, and the semi-major axis is 2.19 +/- 0.10 AU. Imaging observations with the Keck laser guide star adaptive optics (LGSAO) and the Palomar AO instruments resolved the system and also yielded JHK-band delta magnitudes. We use the orbital solution, light ratios, and mass-luminosity relationships to derive component masses of MA = 0.370 +/- 0.034 Msolar and MB = 0.195 +/- 0.021 Msolar. G 78-28B is of type M4 V based upon its colors and mass. We also discovered GJ 231.1C, a companion to GJ 231.1B, with STEPS and imaged the companion with LGSAO and Palomar AO, but the orbital period is longer than our observing baseline; thus the system parameters are less constrained. In GJ 231.1BC the masses are MB = 0.25 +/- 0.06 Msolar and MC =0.12 +/- 0.02 Msolar. The inferred spectral type of GJ 231.1C is M5 V. We demonstrate the results of the current state of mass estimation techniques with our data.
dc.description25 pages, 8 figures, accepted for ApJ
dc.identifierhttps://arxiv.org/abs/astro-ph/0605306
dc.identifierhttp://arxiv.org/abs/astro-ph/0605306
dc.identifierAstrophys.J.649:389-398,2006
dc.identifierdoi:10.1086/506192
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/180878
dc.subjectAstrophysics
dc.titleMasses of Astrometrically-Discovered and Imaged Binaries: G 78-28AB and GJ 231.1BC
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