Discovery of Two T Dwarf Companions with the Spitzer Space Telescope

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dc.creatorLuhman, K. L.
dc.creatorPatten, B. M.
dc.creatorMarengo, M.
dc.creatorSchuster, M. T.
dc.creatorHora, J. L.
dc.creatorEllis, R. G.
dc.creatorStauffer, J. R.
dc.creatorSonnett, S. M.
dc.creatorWinston, E.
dc.creatorGutermuth, R. A.
dc.creatorMegeath, S. T.
dc.creatorBackman, D. E.
dc.creatorHenry, T. J.
dc.creatorWerner, M. W.
dc.creatorFazio, G. G.
dc.date2006-09-16
dc.date.accessioned2026-07-07T10:23:38Z
dc.date.available2026-07-07T10:23:38Z
dc.descriptionWe report the discovery of T dwarf companions to the nearby stars HN Peg (G0V, 18.4 pc, ~0.3 Gyr) and HD 3651 (K0V, 11.1 pc, ~7 Gyr). During an ongoing survey of 5'x5' fields surrounding stars in the solar neighborhood with IRAC aboard the Spitzer Space Telescope, we identified these companions as candidate T dwarfs based on their mid-IR colors. Using near-IR spectra obtained with SpeX at the NASA IRTF, we confirm the presence of methane absorption that characterizes T dwarfs and measure spectral types of T2.5+/-0.5 and T7.5+/-0.5 for HN Peg B and HD 3651 B, respectively. By comparing our Spitzer data to images from 2MASS obtained several years earlier, we find that the proper motions of HN Peg B and HD 3651 B are consistent with those of the primaries, confirming their companionship. HN Peg B and HD 3651 B have angular separations of 43.2" and 42.9" from their primaries, which correspond to projected physical separations of 795 and 476 AU, respectively. A comparison of their luminosities to the values predicted by theoretical evolutionary models implies masses of 0.021+/-0.009 and 0.051+/-0.014 Msun for HN Peg B and HD 3651 B. In addition, the models imply an effective temperature for HN Peg B that is significantly lower than the values derived for other T dwarfs at similar spectral types, which is the same behavior reported by Metchev & Hillenbrand for the young late-L dwarf HD 203030 B. Thus, the temperature of the L/T transition appears to depend on surface gravity. Meanwhile, HD 3651 B is the first substellar companion directly imaged around a star that is known to harbor a close-in planet from RV surveys. The discovery of this companion supports the notion that the high eccentricities of close-in planets like the one near HD 3651 may be the result of perturbations by low-mass companions at wide separations.
dc.descriptionAstrophysical Journal, in press
dc.identifierhttps://arxiv.org/abs/astro-ph/0609464
dc.identifierhttp://arxiv.org/abs/astro-ph/0609464
dc.identifierAstrophys.J.654:570-579,2006
dc.identifierdoi:10.1086/509073
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/175900
dc.subjectAstrophysics
dc.titleDiscovery of Two T Dwarf Companions with the Spitzer Space Telescope
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