Banyan. Viii. New Low-Mass Stars and Brown Dwarfs With Candidate Circumstellar Disks

Boucher, Anne; Lafrenière, David; Gagné, Jonathan; Malo, Lison; Faherty, Jacqueline K.; Doyon, René; Chen, Christine

doi:10.3847/0004-637x/832/1/50

Cited by 39 publications

(46 citation statements)

References 111 publications

(136 reference statements)

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“…In low-mass stars (0.1-1  M ), the transition from primordial disks to debris disks occur at about 10 Myr, and debris disks peak at the age of 10-30 Myr. In contrast, brown dwarf disks are still in the primordial stage at 10 Myr, and their debris disks seem to largely disappear by the age of 40-50 Myr (Riaz & Kennedy 2014), with rare exceptions (Boucher et al 2016). Thus, it is possible that LSR J1835 still has a disk.…”

Section: Discussionmentioning

confidence: 99%

First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved

Berdyugina¹,

Harrington²,

Kuzmychov³

et al. 2017

ApJ

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We report the first direct detection of a strong, 5 kG magnetic field on the surface of an active brown dwarf. LSR J1835+3259 is an M8.5 dwarf exhibiting transient radio and optical emission bursts modulated by fast rotation. We have detected the surface magnetic field as circularly polarized signatures in the 819 nm sodium lines when an active emission region faced the Earth. Modeling Stokes profiles of these lines reveals the effective temperature of 2800 K and log gravity acceleration of 4.5. These parameters place LSR J1835+3259 on evolutionary tracks as a young brown dwarf with the mass of  M 55 4 J and age of 22±4 Myr. Its magnetic field is at least 5.1 kG and covers at least 11% of the visible hemisphere. The active region topology recovered using line profile inversions comprises hot plasma loops with a vertical stratification of optical and radio emission sources. These loops rotate with the dwarf in and out of view causing periodic emission bursts. The magnetic field is detected at the base of the loops. This is the first time that we can quantitatively associate brown dwarf non-thermal bursts with a strong, 5 kG surface magnetic field and solve the puzzle of their driving mechanism. This is also the coolest known dwarf with such a strong surface magnetic field. The young age of LSR J1835+3259 implies that it may still maintain a disk, which may facilitate bursts via magnetospheric accretion, like in higher-mass T Tau-type stars. Our results pave a path toward magnetic studies of brown dwarfs and hot Jupiters.

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Section: Discussionmentioning

confidence: 99%

First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved

Berdyugina¹,

Harrington²,

Kuzmychov³

et al. 2017

ApJ

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“…Within the uncertainties, the measured radial velocities are consistent with membership in their assigned moving groups. Figure 3 depicts the spectra for our four targets around the lithium feature at 6707.8Å, along with the spectrum of J0501 (adopted from Boucher et al 2016), degraded to the resolution and rebinned to the dispersion of our data. As seen in Figure 3, we do not detect clear evidence of lithium in our data, deriving upper limits of 0.11-0.25Å.…”

Section: Age Estimates and Radial Velocity Measurementsmentioning

confidence: 99%

“…Additionally, both J0808 and J0501, another Peter Pan disk candidate in the Columba system (Boucher et al 2016), were observed at two-minute cadence from 2018 October 18-November 15 by the Transiting Exoplanet Survey Satellite (TESS; Ricker et al 2014) during Cycle 1, Sector 4, as part of TESS GI Program G011148 (PI Kuchner). J0808 appeared in CCD 4 of Camera 4, while J0501 appeared in CCD 4 of Camera 3.…”

Section: High-cadence Optical Imagingmentioning

confidence: 99%

Peter Pan Disks: Long-lived Accretion Disks Around Young M Stars

Silverberg

Wisniewski

Kuchner

et al. 2020

ApJ

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WISEA J080822.18-644357.3, an M star in the Carina association, exhibits extreme infrared excess and accretion activity at an age greater than the expected accretion disk lifetime. We consider J0808 as the prototypical example of a class of M star accretion disks at ages 20 Myr, which we call "Peter Pan" disks, since they apparently refuse to grow up. We present four new Peter Pan disk candidates identified via the Disk Detective citizen science project, coupled with Gaia astrometry. We find that WISEA J044634.16-262756.1 and WISEA J094900.65-713803.1 both exhibit significant infrared excess after accounting for nearby stars within the 2MASS beams. The J0446 system has > 95% likelihood of Columba membership. The J0949 system shows > 95% likelihood of Carina membership. We present new GMOS optical spectra of all four objects, showing possible accretion signatures on all four stars. We present ground-based and TESS lightcurves of J0808 and 2MASS J0501-4337, including a large flare and aperiodic dipping activity on J0808, and strong periodicity on J0501. We find Paβ and Brγ emission indicating ongoing accretion in near-IR spectroscopy of J0808. Using observed characteristics of these systems, we discuss mechanisms that lead to accretion disks at ages 20 Myr, and find that these objects most plausibly represent long-lived CO-poor primordial disks, or "hybrid" disks, exhibiting both debris-and primordial-disk features. The question remains: why have gas-rich disks persisted so long around these particular stars?

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“…Its W 1 − W 4 color (0.93±0.23) is not red enough to respect the W 1−W 4 > 1.0 criterion of Schneider et al (2012b) for infrared excess (see also Schneider et al 2012a), and a comparison with predictions from BT-Settl models places the infrared excess of this source at a significance below 3σ in these two photometric bands (see Boucher et al 2016). …”

Section: Mass J11112820-2655027mentioning

confidence: 99%

BANYAN. IX. The Initial Mass Function and Planetary-mass Object Space Density of the TW HYA Association

Gagné

Faherty

Mamajek

et al. 2017

ApJS

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103

106

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A determination of the initial mass function (IMF) of the current, incomplete census of the 10 Myrold TW Hya association (TWA) is presented. This census is built from a literature compilation supplemented with new spectra and 17 new radial velocities from on-going membership surveys, as well as a re-analysis of Hipparcos data that confirmed HR 4334 (A2 Vn) as a member. Though the dominant uncertainty in the IMF remains census incompleteness, a detailed statistical treatment is carried out to make the IMF determination independent of binning, while accounting for small number statistics. The currently known high-likelihood members are fitted by a log-normal distribution with a central mass of 0.21−0.06 M and a characteristic width of 0.8 +0.2 −0.1 dex in the 12 M Jup -2 M range, whereas a Salpeter power law with α = 2.2 +1.1 −0.5 best describes the IMF slope in the 0.1-2 M range. This characteristic width is higher than other young associations, which may be due to incompleteness in the current census of low-mass TWA stars. A tentative overpopulation of isolated planetary-mass members similar to 2MASS J11472421-2040204 and 2MASS J11193254-1137466 is identified: this indicates that there might be as many as 10 +13 −5 similar members of TWA with hot-start modeldependent masses estimated at ∼ 5-7 M Jup , most of which would be too faint to be detected in 2MASS . Our new radial velocity measurements corroborate the membership of 2MASS J11472421-2040204, and secure TWA 28 (M8.5 γ), TWA 29 (M9.5 γ) and TWA 33 (M4.5 e) as members. The discovery of 2MASS J09553336-0208403, a young L7-type interloper unrelated to TWA, is also presented.

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Banyan. Viii. New Low-Mass Stars and Brown Dwarfs With Candidate Circumstellar Disks

Cited by 39 publications

References 111 publications

First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved

First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved

Peter Pan Disks: Long-lived Accretion Disks Around Young M Stars

BANYAN. IX. The Initial Mass Function and Planetary-mass Object Space Density of the TW HYA Association

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