Near-infrared Spectra of the Inflated Post-common Envelope Brown Dwarf NLTT 5306 B

Buzard, Cam; Casewell, Sarah L.; Lothringer, Joshua D.; Blake, Geoffrey A.

doi:10.3847/1538-3881/ac6508

“…The kinematics of the system suggest it belongs to the Galactic thick disc, which implies the system is most likely older than 5 Gyr. There are also signs of accretion onto the WD from a wind (Longstaff et al 2019) and the BD seems to be inflated (Casewell et al 2020b;Buzard et al 2022).…”

Section: Non-eclipsing Systemsmentioning

confidence: 99%

Close detached white dwarf + brown dwarf binaries: further evidence for low values of the common envelope efficiency

Zorotovic,

Schreiber

2022

Preprint

1

0

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Common envelope evolution is a fundamental ingredient in our understanding of the formation of close binary stars containing compact objects which includes the progenitors of type Ia supernovae, short gamma ray bursts and most stellar gravitational wave sources. To predict the outcome of common envelope evolution we still rely to a large degree on a simplified energy conservation equation. Unfortunately, this equation contains a theoretically rather poorly constrained efficiency parameter (α CE ) and, even worse, it is unclear if energy sources in addition to orbital energy (such as recombination energy) contribute to the envelope ejection process. In previous works we reconstructed the evolution of observed populations of post common envelope binaries (PCEBs) consisting of white dwarfs with main sequence star companions and found indications that the efficiency is rather small (α CE ≃ 0.2 − 0.3) and that extra energy sources are only required in very few cases. Here we used the same reconstruction tool to investigate the evolutionary history of a sample of observed PCEBs with brown dwarf companions. In contrast to previous works, we found that the evolution of observationally well characterized PCEBs with brown dwarf companions can be understood assuming a low common envelope efficiency (α CE = 0.24 − 0.41), similar to that required to understand PCEBs with main sequence star companions, and that contributions from recombination energy are not required. We conclude that the vast majority of PCEBs form from common envelope evolution that can be parameterized with a small efficiency and without taking into account additional energy sources.

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“…From the lack of any eclipse in the NLTT5306 system, Buzard et al (2022) constrained the inclination to be below i = 78°.7 ± 0°.4 (where 90°is edge-on). Buzard et al (2022) also fit models to 44 epochs of NIR spectra from Keck +NIRSPEC (McLean et al 1998;Martin et al 2018), as well as two subsets that separated the day and night side of NLTT5306B. Their results showed a minimal difference between day and night sides for effective temperature.…”

Section: Brown Dwarf-white Dwarf Binary System Nltt5306mentioning

confidence: 99%

“…The precise orbital inclination is unknown; however, we were able to narrow down the possible range of values based on observational constraints. For example, due to a lack of any observed transit in the phase curve, Buzard et al (2022) previously estimated an upper limit of i 78°.7 ± 0°. 4 with the following equation:…”

Section: System Parametersmentioning

confidence: 99%

Hotter than Expected: Hubble Space Telescope (HST)/WFC3 Phase-resolved Spectroscopy of a Rare Irradiated Brown Dwarf with Strong Internal Heat Flux

Amaro

¹

,

Apai

²

,

Zhou

³

et al. 2023

ApJ

Self Cite

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With infrared flux contrasts larger than typically seen in hot Jupiter, tidally locked white dwarf–brown dwarf binaries offer a superior opportunity to investigate atmospheric processes in irradiated atmospheres. NLTT5306 is such a system, with a M BD = 52 ± 3 M Jup brown dwarf, orbiting a T eff = 7756 ± 35 K white dwarf with an ultra-short period of ∼102 minutes. We present Hubble Space Telescope/Wide Field Camera 3 spectroscopic phase curves of NLTT5306, consisting of 47 spectra from 1.1 to 1.7 μm with an average signal-to-noise ratio ∼ 65 per wavelength. We extracted the phase-resolved spectra of the brown dwarf NLTT5306B, finding a small <100 K day–night temperature difference (∼5% of the average day-side temperature). Our best-fit model phase curves revealed a complex wavelength-dependence on amplitudes and relative phase offsets, suggesting longitudinal–vertical atmospheric structure. The night-side spectrum was well fit by a cloudy, nonirradiated atmospheric model while the day side was best matched by a cloudy, weakly irradiated model. Additionally, we created a simple radiative energy redistribution model of the atmosphere and found evidence for efficient day-to-night heat redistribution and a moderately high Bond albedo. We also discovered an internal heat flux much higher than expected given the published system age, leading to an age reassessment that resulted in NLTT5306B most likely being much younger. We find that NLTT5306B is the only known significantly irradiated brown dwarf where the global temperature structure is not dominated by external irradiation, but rather its own internal heat. Our study provides an essential insight into the drivers of global circulation and day-to-night heat transport as a function of irradiation, rotation rate, and internal heat.

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The Brown Dwarf Kinematics Project (BDKP). VI. Ultracool Dwarf Radial and Rotational Velocities from SDSS/APOGEE High-resolution Spectroscopy

Hsu,

Burgasser,

Theissen

et al. 2024

ApJS

1

0

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We present precise measurements of radial (RV) and projected rotational ( v sin i ) velocities of a sample of 258 M6 to L2 dwarfs with multiepoch, high-resolution (λ/Δλ = 22,500), near-infrared (1.514–1.696 μm) spectroscopic observations reported in the Apache Point Observatory Galactic Evolution Experiment Data Release 17. The spectra were modeled using a Markov Chain Monte Carlo forward-modeling method, which achieved median precisions of σ RV = 0.4 km s−1 and σ v sin i = 1.1 km s−1. One-half of our sample (138 sources) are previously known members of nearby young clusters and moving groups, and we identified three new kinematic members of the Argus or Carina Near moving groups, 2MASS J05402570+2448090, 2MASS J14093200+4138080, and 2MASS J21272531+5553150. Excluding these sources, we find that the majority of our sample have kinematics consistent with the Galactic thin disk, and 11 sources are associated with the intermediate thin/thick disk. The field sample has a velocity dispersion of 38.2 ± 0.3 km s−1, equivalent to an age of 3.30 ± 0.19 Gyr based on empirical age–velocity dispersion relations, and a median v sin i of 17 km s−1. For 172 sources with multiepoch observations, we identified 37 as having significant RV variations, and determined preliminary orbit parameters for 26 sources with four or more epochs, nine of which are short-period binary candidates. For 40 sources with photometric variability periods from the literature less than 5 days and v sin i > 20 km s−1, we find a decline in projected radii ( R sin i ) with age congruent with evolutionary models. Finally, we also present multiepoch RV and v sin i measurements for additional 444 candidate ultracool dwarfs.

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Near-infrared Spectra of the Inflated Post-common Envelope Brown Dwarf NLTT 5306 B

Cited by 3 publications

References 50 publications

Close detached white dwarf + brown dwarf binaries: further evidence for low values of the common envelope efficiency

Close detached white dwarf + brown dwarf binaries: further evidence for low values of the common envelope efficiency

Hotter than Expected: Hubble Space Telescope (HST)/WFC3 Phase-resolved Spectroscopy of a Rare Irradiated Brown Dwarf with Strong Internal Heat Flux

The Brown Dwarf Kinematics Project (BDKP). VI. Ultracool Dwarf Radial and Rotational Velocities from SDSS/APOGEE High-resolution Spectroscopy

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