Project 1640 Observations of Brown Dwarf GJ 758 B: Near-infrared Spectrum and Atmospheric Modeling

Nilsson, Ricky; Veicht, A.; Godfrey, Paige A. Giorla; Rice, Emily L.; Aguilar, Jonathan; Pueyo, Laurent; Roberts, Lewis C.; Oppenheimer, Ben R.; Brenner, Douglas; Luszcz‐Cook, Statia; Bacchus, E.; Beichman, Charles; Burruss, Rick; Cady, Eric; Dekany, Richard; Fergus, Rob; Hillenbrand, Lynne A.; Hinkley, Sasha; King, David L.; Lockhart, Thomas; Parry, Ian; Sivaramakrishnan, Anand; Soummer, Rémi; Vasisht, Gautam; Zhai, Chengxing; Zimmerman, Neil

doi:10.3847/1538-4357/aa643c

Cited by 10 publications

(11 citation statements)

References 53 publications

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“…this is in good agreement with the inferred effective temperatures of 600-750 K for Gl 758 B from multi-band imaging and spectroscopy (Vigan et al 2016;Nilsson et al 2017). Based on this consistency and the fact that the companion's orbital period must be much longer than the time baseline of the RV observations (?20 years), we conclude that Gl 758 B is likely the source of the acceleration.…”

Section: Is the Acceleration Caused By Gl 758 B?supporting

confidence: 82%

“…Although Gl 758 B has only completed a small fraction of its orbit, the most likely orbital solutions relying solely on astrometry suggest it is eccentric with a semimajor axis between about 20 and 60 au. Nilsson et al (2017) propose that the acceleration induced by Gl 758 B should be measurable on the host star, but no evidence of a trend was observed by Vigan et al (2016) using RVs from the ELODIE spectrograph and Lick Observatory, most likely due to the relatively large uncertainties of these data sets.…”

Section: Overview Of the Gl 758 Systemmentioning

confidence: 88%

“…We first anchor the 1.0-1.75μm spectrum of Gl 758 B from Nilsson et al (2017) by flux calibrating the P1640 observations to the H-band apparent magnitude from Thalmann et al (2009). To this we add the photometry from Vigan et al (2016) and Janson et al (2011) to directly account for the comparably high K-band flux from this object.…”

Section: Bolometric Luminosity Of Gl 758 Bmentioning

confidence: 99%

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Orbit and Dynamical Mass of the Late-T Dwarf GL 758 B*

Bowler

Dupuy

Endl

et al. 2018

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Gl758B is a late-T dwarf orbiting a metal-rich Sun-like star at a projected separation of ρ≈1 6 (25 au). We present four epochs of astrometry of this system with NIRC2 at Keck Observatory spanning 2010 to 2017 together with 630 radial velocities (RVs) of the host star acquired over the past two decades from McDonald Observatory, Keck Observatory, and the Automated Planet Finder at Lick Observatory. The RVs reveal that Gl758 is accelerating with an evolving rate that varies between 2 and 5 m s −1 yr −1 , consistent with the expected influence of the imaged companion Gl758B. A joint fit of the RVs and astrometry yields a dynamical mass of -+ 42 719 M Jup for the companion with a robust lower limit of 30.5M Jup at the 4-σ level. Gl758B is on an eccentric orbit (e = 0.26-0.67 at 95% confidence) with a semimajor axis of a= -+ 21.1 1.3 2.7 au and an orbital period of P= -+ 96 9 21 yr, which takes it within ≈9au from its host star at periastron passage. Substellar evolutionary models generally underpredict the mass of Gl758B for nominal ages of 1-6Gyr that have previously been adopted for the host star. This discrepancy can be reconciled if the system is older-which is consistent with activity indicators and recent isochrone fitting of the host star-or alternatively if the models are systematically overluminous by ≈0.1-0.2dex. Gl758B is currently the lowest-mass directly imaged companion inducing a measured acceleration on its host star. In the future, bridging RVs and high-contrast imaging with the next generation of extremely large telescopes and space-based facilities will open the door to the first dynamical mass measurements of imaged exoplanets.

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Section: Is the Acceleration Caused By Gl 758 B?supporting

confidence: 82%

Section: Overview Of the Gl 758 Systemmentioning

confidence: 88%

Section: Bolometric Luminosity Of Gl 758 Bmentioning

confidence: 99%

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Orbit and Dynamical Mass of the Late-T Dwarf GL 758 B*

Bowler

Dupuy

Endl

et al. 2018

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“…Depending on the adopted age of the system, evolutionary models predict masses for the com-Article number, page 1 of 5 arXiv:1806.07899v1 [astro-ph.SR] 20 Jun 2018 A&A proofs: manuscript no. 33309corr panion of between 10 and 40 M Jup (Janson et al 2011;Nilsson et al 2017;Bowler et al 2018). However, evolutionary models are highly uncertain at these low masses.…”

Section: Introductionmentioning

confidence: 98%

Improving dynamical mass constraints for intermediate-period substellar companions using Gaia DR2

Calissendorff

Janson

2018

A&A

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The relationship between luminosity and mass is of fundamental importance for direct imaging studies of brown dwarf and planetary companions to stars. In principle this can be inferred from theoretical mass-luminosity models; however, these relations have not yet been thoroughly calibrated, since there is a lack of substellar companions for which both the brightness and mass have been directly measured. One notable exception is GJ 758 B, a brown dwarf companion in a ∼20 AU orbit around a nearby Sun-like star, which has been both directly imaged and dynamically detected through a radial velocity trend in the primary. This has enabled a mass constraint for GJ 758 B of 42 +19 −7 M Jup . Here, we note that Gaia is ideally suited for further constraining the mass of intermediate-separation companions such as GJ 758 B. A study of the differential proper motion, ∆µ, with regards to HIPPARCOS is particularly useful in this context, as it provides a long time baseline for orbital curvature to occur. By exploiting already determined orbital parameters, we show that the dynamical mass can be further constrained to 42.4 +5.6−5.0 M Jup through the Gaia-HIPPARCOS ∆µ motion. We compare the new dynamical mass estimate with substellar evolutionary models and confirm previous indications that there is significant tension between the isochronal ages of the star and companion, with a preferred stellar age of ≤ 5 Gyr while the companion is only consistent with very old ages of ≥ 8 Gyr.

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“…GJ 758b is a T dwarf companion separated by 30 AU from a Solar type star with an age of 5-9 Gyr (Thalmann et al 2009;Janson et al 2011). This object has been characterized before, however, previous work has demonstrated that its photometry is difficult to fit with at-mospheric models or spectra of analog objects (Vigan et al 2016;Nilsson et al 2017).…”

Section: Introductionmentioning

confidence: 99%

A new statistical method for characterizing the atmospheres of extrasolar planets

Henderson¹,

Skemer²,

Morley³

et al. 2017

Monthly Notices of the Royal Astronomical Society

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By detecting light from extrasolar planets, we can measure their compositions and bulk physical properties. The technologies used to make these measurements are still in their infancy, and a lack of self-consistency suggests that previous observations have underestimated their systemic errors. We demonstrate a statistical method, newly applied to exoplanet characterization, which uses a Bayesian formalism to account for underestimated errorbars. We use this method to compare photometry of a substellar companion, GJ 758b, with custom atmospheric models. Our method produces a probability distribution of atmospheric model parameters including temperature, gravity, cloud model (f sed ), and chemical abundance for GJ 758b. This distribution is less sensitive to highly variant data, and appropriately reflects a greater uncertainty on parameter fits.

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Project 1640 Observations of Brown Dwarf GJ 758 B: Near-infrared Spectrum and Atmospheric Modeling

Cited by 10 publications

References 53 publications

Orbit and Dynamical Mass of the Late-T Dwarf GL 758 B*

Orbit and Dynamical Mass of the Late-T Dwarf GL 758 B*

Improving dynamical mass constraints for intermediate-period substellar companions using Gaia DR2

A new statistical method for characterizing the atmospheres of extrasolar planets

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