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  • 1
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    Online Resource
    The McDonald Accelerating Stars Survey (MASS): Discovery of a Long-period Substellar Companion Orbiting the Old Solar Analog HD 47127
    American Astronomical Society ; 2021
    In:  The Astrophysical Journal Letters Vol. 913, No. 2 ( 2021-06-01), p. L26-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 913, No. 2 ( 2021-06-01), p. L26-
    Abstract: Brown dwarfs with well-determined ages, luminosities, and masses provide rare but valuable tests of low-temperature atmospheric and evolutionary models. We present the discovery and dynamical mass measurement of a substellar companion to HD 47127, an old (≈7–10 Gyr) G5 main-sequence star with a mass similar to the Sun. Radial velocities of the host star with the Harlan J. Smith Telescope uncovered a low-amplitude acceleration of 1.93 ± 0.08 m s −1 yr −1 based on 20 years of monitoring. We subsequently recovered a faint (Δ H = 13.14 ± 0.15 mag) comoving companion at 1.″95 (52 au) with follow-up Keck/NIRC2 adaptive optics imaging. The radial acceleration of HD 47127 together with its tangential acceleration from Hipparcos and Gaia EDR3 astrometry provide a direct measurement of the three-dimensional acceleration vector of the host star, enabling a dynamical mass constraint for HD 47127 B (67.5–177 M Jup at 95% confidence) despite the small fractional orbital coverage of the observations. The absolute H -band magnitude of HD 47127 B is fainter than the benchmark T dwarfs HD 19467 B and Gl 229 B but brighter than Gl 758 B and HD 4113 C, suggesting a late-T spectral type. Altogether the mass limits for HD 47127 B from its dynamical mass and the substellar boundary imply a range of 67–78 M Jup assuming it is single, although a preference for high masses of ≈100 M Jup from dynamical constraints hints at the possibility that HD 47127 B could itself be a binary pair of brown dwarfs or that another massive companion resides closer in. Regardless, HD 47127 B will be an excellent target for more refined orbital and atmospheric characterization in the future.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/abfec8
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2021
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 2
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    Online Resource
    SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star *
    American Astronomical Society ; 2020
    In:  The Astrophysical Journal Letters Vol. 904, No. 2 ( 2020-12-01), p. L25-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 904, No. 2 ( 2020-12-01), p. L25-
    Abstract: We present the direct imaging discovery of a substellar companion to the nearby Sun-like star, HD 33632 Aa, at a projected separation of ∼20 au, obtained with SCExAO/CHARIS integral field spectroscopy complemented by Keck/NIRC2 thermal infrared imaging. The companion, HD 33632 Ab, induces a 10.5 σ astrometric acceleration on the star as detected with the Gaia and Hipparcos satellites. SCExAO/CHARIS JHK (1.1–2.4 μ m) spectra and Keck/NIRC2 L p (3.78 μ m) photometry are best matched by a field L/T transition object: an older, higher-gravity, and less dusty counterpart to HR 8799 cde. Combining our astrometry with Gaia/Hipparcos data and archival Lick Observatory radial velocities, we measure a dynamical mass of 46.4 ± 8 M J and an eccentricity of e 〈 0.46 at 95% confidence. HD 33632 Ab’s mass and mass ratio (4.0% ± 0.7%) are comparable to the low-mass brown dwarf GJ 758 B and intermediate between the more massive brown dwarf HD 19467 B and the (near-)planet-mass companions to HR 2562 and GJ 504. Using Gaia to select for direct imaging observations with the newest extreme adaptive optics systems can reveal substellar or even planet-mass companions on solar system–like scales at an increased frequency compared to blind surveys.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/abc631
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2020
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 3
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    Online Resource
    orvara: An Efficient Code to Fit Orbits Using Radial Velocity, Absolute, and/or Relative Astrometry
    American Astronomical Society ; 2021
    In:  The Astronomical Journal Vol. 162, No. 5 ( 2021-11-01), p. 186-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 162, No. 5 ( 2021-11-01), p. 186-
    Type of Medium: Online Resource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.3847/1538-3881/ac042e
    RVK:
    US 1090
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2021
    detail.hit.zdb_id: 2207625-6
    detail.hit.zdb_id: 2003104-X
    SSG: 16,12
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  • 4
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    Dynamical Mass of the Young Substellar Companion HD 984 B
    American Astronomical Society ; 2022
    In:  The Astronomical Journal Vol. 163, No. 2 ( 2022-02-01), p. 50-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 163, No. 2 ( 2022-02-01), p. 50-
    Abstract: Model-independent masses of substellar companions are critical tools to validate models of planet and brown dwarf cooling, test their input physics, and determine the formation and evolution of these objects. In this work, we measure the dynamical mass and orbit of the young substellar companion HD 984 B. We obtained new high-contrast imaging of the HD 984 system with Keck/NIRC2 that expands the baseline of relative astrometry from 3 to 8 yr. We also present new radial velocities of the host star with the Habitable-Zone Planet Finder spectrograph at the Hobby-Eberly Telescope. Furthermore, HD 984 exhibits a significant proper motion difference between Hipparcos and Gaia EDR3. Our joint orbit fit of the relative astrometry, proper motions, and radial velocities yields a dynamical mass of 61 ± 4 M Jup for HD 984 B, placing the companion firmly in the brown dwarf regime. The new fit also reveals a higher eccentricity for the companion ( e = 0.76 ± 0.05) compared to previous orbit fits. Given the broad age constraint for HD 984, this mass is consistent with predictions from evolutionary models. HD 984 B’s dynamical mass places it among a small but growing list of giant planet and brown dwarf companions with direct mass measurements.
    Type of Medium: Online Resource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.3847/1538-3881/ac35e8
    RVK:
    US 1090
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2022
    detail.hit.zdb_id: 2207625-6
    detail.hit.zdb_id: 2003104-X
    SSG: 16,12
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  • 5
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    Online Resource
    Precise Dynamical Masses of ε Indi Ba and Bb: Evidence of Slowed Cooling at the L/T Transition
    American Astronomical Society ; 2022
    In:  The Astronomical Journal Vol. 163, No. 6 ( 2022-06-01), p. 288-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 163, No. 6 ( 2022-06-01), p. 288-
    Abstract: We report individual dynamical masses of 66.92 ± 0.36 M Jup and 53.25 ± 0.29 M Jup for the binary brown dwarfs ε Indi Ba and Bb, measured from long-term (≈10 yr) relative orbit monitoring and absolute astrometry monitoring data on the Very Large Telescope (VLT). Relative astrometry with NACO fully constrains the Keplerian orbit of the binary pair, while absolute astrometry with FORS2 measures the system’s parallax and mass ratio. We find a parallax consistent with the Hipparcos and Gaia values for ε Indi A, and a mass ratio for ε Indi Ba to Bb precise to better than 0.2%. ε Indi Ba and Bb have spectral types T1-1.5 and T6, respectively. With an age of 3.5 − 1.0 + 0.8 Gyr from ε Indi A’s activity, these brown dwarfs provide some of the most precise benchmarks for substellar cooling models. Assuming coevality, the very different luminosities of the two brown dwarfs and our moderate mass ratio imply a steep mass–luminosity relationship ( L ∝ M 5.37 ± 0.08 ) that can be explained by a slowed cooling rate in the L/T transition, as previously observed for other L/T binaries. Finally, we present a periodogram analysis of the near-infrared photometric data, but find no definitive evidence of periodic signals with a coherent phase.
    Type of Medium: Online Resource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.3847/1538-3881/ac66d2
    RVK:
    US 1090
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2022
    detail.hit.zdb_id: 2207625-6
    detail.hit.zdb_id: 2003104-X
    SSG: 16,12
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  • 6
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    Surveying nearby brown dwarfs with HGCA: direct imaging discovery of a faint, high-mass brown dwarf orbiting HD 176535 A
    Oxford University Press (OUP) ; 2023
    In:  Monthly Notices of the Royal Astronomical Society Vol. 522, No. 4 ( 2023-05-11), p. 5622-5637
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 522, No. 4 ( 2023-05-11), p. 5622-5637
    Abstract: Brown dwarfs with well-measured masses, ages, and luminosities provide direct benchmark tests of substellar formation and evolutionary models. We report the first results from a direct imaging survey aiming to find and characterize substellar companions to nearby accelerating stars with the assistance of the Hipparcos–Gaia Catalog of Accelerations (HGCA). In this paper, we present a joint high-contrast imaging and astrometric discovery of a substellar companion to HD 176535 A, a K3.5V main-sequence star aged approximately $3.59_{-1.15}^{+0.87}$ Gyr at a distance of 36.99 ± 0.03 pc. In advance of our high-contrast imaging observations, we combined precision High Accuracy Radial velocity Planet Searcher (HARPS) Radial Velocities (RVs) and HGCA astrometry to predict the potential companion’s location and mass. We thereafter acquired two nights of KeckAO/NIRC2 direct imaging observations in the L′ band, which revealed a companion with a contrast of $\Delta L^{\prime }_p = 9.20\pm 0.06$ mag at a projected separation of ≈0.35 arcsec (≈13 au) from the host star. We revise our orbital fit by incorporating our dual-epoch relative astrometry using the open-source Markov chain Monte Carlo orbit fitting code orvara. We obtain a dynamical mass of $65.9_{-1.7}^{+2.0} M_{\rm Jup}$ that places HD 176535 B firmly in the brown dwarf regime. HD 176535 B is a new benchmark dwarf useful for constraining the evolutionary and atmospheric models of high-mass brown dwarfs. We found a luminosity of $\rm log(\mathit{ L}_{bol}/L_{\odot }) = -5.26\pm 0.07$ and a model-dependent effective temperature of 980 ± 35 K for HD 176535 B. We infer HD 176535 B to be a T dwarf from its mass, age, and luminosity. Our dynamical mass suggests that some substellar evolutionary models may be underestimating luminosity for high-mass T dwarfs. Given its angular separation and luminosity, HD 176535 B would make a promising candidate for Aperture Masking Interferometry with JWST and GRAVITY/Keck Planet Imager and Characterizer, and further spectroscopic characterization with instruments like the CHARIS/SCExAO/Subaru integral field spectrograph.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stad1315
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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  • 7
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    Precise Dynamical Masses and Orbital Fits for β Pic b and β Pic c
    American Astronomical Society ; 2021
    In:  The Astronomical Journal Vol. 161, No. 4 ( 2021-04-01), p. 179-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 161, No. 4 ( 2021-04-01), p. 179-
    Abstract: We present a comprehensive orbital analysis to the exoplanets β Pictoris b and c that resolves previously reported tensions between the dynamical and evolutionary mass constraints on β Pic b. We use the Markov Chain Monte Carlo orbit code orvara to fit 15 years of radial velocities and relative astrometry (including recent GRAVITY measurements), absolute astrometry from Hipparcos and Gaia, and a single relative radial velocity measurement between β Pic A and b. We measure model-independent masses of M Jup for β Pic b and 8.3 ± 1.0 M Jup for β Pic c. These masses are robust to modest changes to the input data selection. We find a well-constrained eccentricity of 0.119 ± 0.008 for β Pic b, and an eccentricity of for β Pic c, with the two orbital planes aligned to within ∼05. Both planets’ masses are within ∼1 σ of the predictions of hot-start evolutionary models and exclude cold starts. We validate our approach on N -body synthetic data integrated using REBOUND . We show that orvara can account for three-body effects in the β Pic system down to a level ∼5 times smaller than the GRAVITY uncertainties. Systematics in the masses and orbital parameters from orvara ’s approximate treatment of multiplanet orbits are a factor of ∼5 smaller than the uncertainties we derive here. Future GRAVITY observations will improve the constraints on β Pic c’s mass and (especially) eccentricity, but improved constraints on the mass of β Pic b will likely require years of additional radial velocity monitoring and improved precision from future Gaia data releases.
    Type of Medium: Online Resource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.3847/1538-3881/abdc2e
    RVK:
    US 1090
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2021
    detail.hit.zdb_id: 2207625-6
    detail.hit.zdb_id: 2003104-X
    SSG: 16,12
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  • 8
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    Online Resource
    Improved Dynamical Masses for Six Brown Dwarf Companions Using Hipparcos and Gaia EDR3
    American Astronomical Society ; 2021
    In:  The Astronomical Journal Vol. 162, No. 6 ( 2021-12-01), p. 301-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 162, No. 6 ( 2021-12-01), p. 301-
    Abstract: We present comprehensive orbital analyses and dynamical masses for the substellar companions Gl 229 B, Gl 758 B, HD 13724 B, HD 19467 B, HD 33632 Ab, and HD 72946 B. Our dynamical fits incorporate radial velocities, relative astrometry, and, most importantly, calibrated Hipparcos-Gaia EDR3 accelerations. For HD 33632 A and HD 72946 we perform three-body fits that account for their outer stellar companions. We present new relative astrometry of Gl 229 B with Keck/NIRC2, extending its observed baseline to 25 yr. We obtain a 〈 1% mass measurement of 71.4 ± 0.6 M Jup for the first T dwarf Gl 229 B and a 1.2% mass measurement of its host star (0.579 ± 0.007 M ⊙ ) that agrees with the high-mass end of the M-dwarf mass–luminosity relation. We perform a homogeneous analysis of the host stars’ ages and use them, along with the companions’ measured masses and luminosities, to test substellar evolutionary models. Gl 229 B is the most discrepant, as models predict that an object this massive cannot cool to such a low luminosity within a Hubble time, implying that it may be an unresolved binary. The other companions are generally consistent with models, except for HD 13724 B, which has a host star activity age 3.8 σ older than its substellar cooling age. Examining our results in context with other mass–age–luminosity benchmarks, we find no trend with spectral type but instead note that younger or lower-mass brown dwarfs are overluminous compared to models, while older or higher-mass brown dwarfs are underluminous. The presented mass measurements for some companions are so precise that the stellar host ages, not the masses, limit the analysis.
    Type of Medium: Online Resource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.3847/1538-3881/ac273e
    RVK:
    US 1090
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2021
    detail.hit.zdb_id: 2207625-6
    detail.hit.zdb_id: 2003104-X
    SSG: 16,12
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  • 9
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    htof: A New Open-source Tool for Analyzing Hipparcos, Gaia, and Future Astrometric Missions
    American Astronomical Society ; 2021
    In:  The Astronomical Journal Vol. 162, No. 6 ( 2021-12-01), p. 230-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 162, No. 6 ( 2021-12-01), p. 230-
    Abstract: We present htof , an open-source tool for interpreting and fitting the intermediate astrometric data (IAD) from both the 1997 and 2007 reductions of Hipparcos, the scanning law of Gaia, and future missions such as the Nancy Grace Roman Space Telescope (NGRST). htof solves the astrometric parameters of any system for any arbitrary combination of absolute astrometric missions. In preparation for later Gaia data releases, htof supports arbitrarily high-order astrometric solutions (e.g., five-, seven-, and nine-parameter fits). Using htof , we find that the IAD of 6617 sources in Hipparcos 2007 might have been affected by a data corruption issue. htof integrates an ad hoc correction that reconciles the IAD of these sources with their published catalog solutions. We developed htof to study masses and orbital parameters of substellar companions, and we outline its implementation in one orbit fitting code ( orvara ). We use htof to predict a range of hypothetical additional planets in the β Pic system, which could be detected by coupling NGRST astrometry with Gaia and Hipparcos. htof is pip installable and available at https://github.com/gmbrandt/htof .
    Type of Medium: Online Resource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.3847/1538-3881/ac12d0
    RVK:
    US 1090
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2021
    detail.hit.zdb_id: 2207625-6
    detail.hit.zdb_id: 2003104-X
    SSG: 16,12
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  • 10
    Online Resource
    Online Resource
    Precise Masses and Orbits for Nine Radial-velocity Exoplanets
    American Astronomical Society ; 2021
    In:  The Astronomical Journal Vol. 162, No. 6 ( 2021-12-01), p. 266-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 162, No. 6 ( 2021-12-01), p. 266-
    Abstract: Radial-velocity (RV) surveys have discovered hundreds of exoplanetary systems but suffer from a fundamental degeneracy between planet mass M p and orbital inclination i . In this paper, we resolve this degeneracy by combining RVs with complementary absolute astrometry taken from the Gaia EDR3 version of the cross calibrated Hipparcos–Gaia Catalog of Accelerations (HGCA). We use the Markov Chain Monte Carlo orbit code orvara to simultaneously fit literature RVs and absolute astrometry from the HGCA. We constrain the orbits, masses, and inclinations of nine single and massive RV companions orbiting nearby G and K stars. We confirm the planetary nature of six companions: HD 29021 b ( 4.47 − 0.65 + 0.67 M Jup ), HD 81040 b ( 7.24 − 0.37 + 1.0 M Jup ), HD 87883 b ( 6.31 − 0.32 + 0.31 M Jup ), HD 98649 b ( 9.7 − 1.9 + 2.3 M Jup ), HD 106252 b ( 10.00 − 0.73 + 0.78 M Jup ), and HD 171238 b ( 8.8 − 1.3 + 3.6 M Jup ). We place one companion, HD 196067 b ( 12.5 − 1.8 + 2.5 M Jup ) on the planet–brown dwarf boundary and two companions in the low-mass brown dwarf regime: HD 106515 Ab ( 18.9 − 1.4 + 1.5 M Jup ), and HD 221420 b ( 20.6 − 1.6 + 2.0 M Jup ). The brown dwarf HD 221420 b, with a semimajor axis of 9.99 − 0.70 + 0.74 au, a period of 27.7 − 2.5 + 3.0 yr, and an eccentricity of 0.162 − 0.030 + 0.035 represents a promising target for high-contrast imaging. The RV orbits of HD 87883 b, HD 98649 b, HD 171238 b, and HD 196067 b are not fully constrained yet because of insufficient RV data. We find two possible inclinations for each of these orbits due to difficulty in separating prograde from retrograde orbits, but we expect this will change decisively with future Gaia data releases.
    Type of Medium: Online Resource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.3847/1538-3881/ac27ab
    RVK:
    US 1090
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2021
    detail.hit.zdb_id: 2207625-6
    detail.hit.zdb_id: 2003104-X
    SSG: 16,12
    Location Call Number Limitation Availability
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