Revealing the Vertical Cloud Structure of a Young Low-mass Brown Dwarf, an Analog to the β-Pictoris b Directly Imaged Exoplanet, through Keck I/MOSFIRE Spectrophotometric Variability

Context. A low-mass brown dwarf has recently been imaged around HR 2562 (HD 50571), a star hosting a debris disk resolved in the far infrared. Interestingly, the companion location is compatible with an orbit coplanar with the disk and interior to the debris belt. This feature makes the system a valuable laboratory to analyze the formation of substellar companions in a circumstellar disk and potential disk-companion dynamical interactions. Aims. We aim to further characterize the orbital motion of HR 2562 B and its interactions with the host star debris disk. Methods. We performed a monitoring of the system over ~10 months in 2016 and 2017 with the VLT/SPHERE exoplanet imager. Results. We confirm that the companion is comoving with the star and detect for the first time an orbital motion at high significance, with a current orbital motion projected in the plane of the sky of 25 mas (~0.85 au) per year. No orbital curvature is seen in the measurements. An orbital fit of the SPHERE and literature astrometry of the companion without priors on the orbital plane clearly indicates that its orbit is (quasi-)coplanar with the disk. To further constrain the other orbital parameters, we used empirical laws for a companion chaotic zone validated by N-body simulations to test the orbital solutions that are compatible with the estimated disk cavity size. Non-zero eccentricities (>0.15) are allowed for orbital periods shorter than 100 yr, while only moderate eccentricities up to ~0.3 for orbital periods longer than 200 yr are compatible with the disk observations. A comparison of synthetic Herschel images to the real data does not allow us to constrain the upper eccentricity of the companion.

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The search for very low mass (brown dwarf) stars as wide binaries

Cool Stars, Stellar Systems, and the Sun - Lecture Notes in Physics ◽

10.1007/3-540-18653-0_192 ◽

2008 ◽

pp. 525-527

Author(s):

Ian D. Hepburn

Keyword(s):

Brown Dwarf ◽

Dwarf Stars ◽

Low Mass

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X-Ray Detection of Brown Dwarfs with Chandra

Symposium - International Astronomical Union ◽

10.1017/s0074180900211108 ◽

2003 ◽

Vol 211 ◽

pp. 447-450 ◽

Cited By ~ 1

Author(s):

Scott J. Wolk

Keyword(s):

Brown Dwarfs ◽

Stellar Clusters ◽

Brown Dwarf ◽

Low Mass Stars ◽

X Ray ◽

Low Mass ◽

Vast Range

I review recent observations of brown dwarfs by the Chandra X-ray Observatory. These observations fall in 2 categories, young stellar clusters which contain brown dwarfs and brown dwarf candidates and directed pointings at brown dwarfs and very low mass stars. Surprisingly, there are already over 60 published detections of brown dwarfs by Chandra. A review of the X–ray characteristics shows these objects are subject to flaring and their temperatures and luminosities have a vast range which is related to age.

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Deep Near-Infrared Surveys and Young Brown Dwarf Populations in Star-Forming Regions

Symposium - International Astronomical Union ◽

10.1017/s0074180900210346 ◽

2003 ◽

Vol 211 ◽

pp. 87-90

Author(s):

M. Tamura ◽

T. Naoi ◽

Y. Oasa ◽

Y. Nakajima ◽

C. Nagashima ◽

...

Keyword(s):

High Resolution ◽

Adaptive Optics ◽

Near Infrared ◽

Brown Dwarf ◽

Ir Camera ◽

Star Forming ◽

Star Forming Regions ◽

New Instrument ◽

Infrared Surveys ◽

Low Mass

We are currently conducting three kinds of IR surveys of star forming regions (SFRs) in order to seek for very low-mass young stellar populations. First is a deep JHKs-bands (simultaneous) survey with the SIRIUS camera on the IRSF 1.4m or the UH 2.2m telescopes. Second is a very deep JHKs survey with the CISCO IR camera on the Subaru 8.2m telescope. Third is a high resolution companion search around nearby YSOs with the CIAO adaptive optics coronagraph IR camera on the Subaru. In this contribution, we describe our SIRIUS camera and present preliminary results of the ongoing surveys with this new instrument.

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Hunting for brown dwarfs in the globular cluster M4: second epoch HST NIR observations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz996 ◽

2019 ◽

Vol 486 (2) ◽

pp. 2254-2264 ◽

Cited By ~ 3

Author(s):

A Dieball ◽

L R Bedin ◽

C Knigge ◽

M Geffert ◽

R M Rich ◽

...

Keyword(s):

Globular Cluster ◽

White Dwarf ◽

Near Infrared ◽

Magnitude Estimate ◽

Cluster Member ◽

Imaging Data ◽

Brown Dwarf ◽

Data Set ◽

Bona Fide ◽

Low Mass

ABSTRACT We present an analysis of the second epoch Hubble Space TelescopeWide Field Camera 3 F110W near-infrared (NIR) imaging data of the globular cluster M 4. The new data set suggests that one of the previously suggested four brown dwarf candidates in this cluster is indeed a high-probability cluster member. The position of this object in the NIR colour–magnitude diagrams (CMDs) is in the white dwarf/brown dwarf area. The source is too faint to be a low-mass main-sequence (MS) star, but, according to theoretical considerations, also most likely somewhat too bright to be a bona-fide brown dwarf. Since we know that the source is a cluster member, we determined a new optical magnitude estimate at the position the source should have in the optical image. This new estimate places the source closer to the white dwarf sequence in the optical–NIR CMD and suggests that it might be a very cool (Teff ≤ 4500 K) white dwarf at the bottom of the white dwarf cooling sequence in M 4, or a white dwarf/brown dwarf binary. We cannot entirely exclude the possibility that the source is a very massive, bright brown dwarf, or a very low-mass MS star, however, we conclude that we still have not convincingly detected a brown dwarf in a globular cluster, but we expect to be very close to the start of the brown dwarf cooling sequence in this cluster. We also note that the MS ends at F110W ≈ 22.5 mag in the proper-motion cleaned CMDs, where completeness is still high.

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Two new free-floating or wide-orbit planets from microlensing

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834557 ◽

2019 ◽

Vol 622 ◽

pp. A201 ◽

Cited By ~ 18

Author(s):

Przemek Mróz ◽

Andrzej Udalski ◽

David P. Bennett ◽

Yoon-Hyun Ryu ◽

Takahiro Sumi ◽

...

Keyword(s):

Gravitational Lensing ◽

Milky Way ◽

Planet Formation ◽

Physical Mechanism ◽

Galactic Disk ◽

Galactic Bulge ◽

Brown Dwarf ◽

Low Mass ◽

Rule Out

Planet formation theories predict the existence of free-floating planets that have been ejected from their parent systems. Although they emit little or no light, they can be detected during gravitational microlensing events. Microlensing events caused by rogue planets are characterized by very short timescales tE (typically below two days) and small angular Einstein radii θE (up to several μas). Here we present the discovery and characterization of two ultra-short microlensing events identified in data from the Optical Gravitational Lensing Experiment (OGLE) survey, which may have been caused by free-floating or wide-orbit planets. OGLE-2012-BLG-1323 is one of the shortest events discovered thus far (tE = 0.155 ± 0.005 d, θE = 2.37 ± 0.10μas) and was caused by an Earth-mass object in the Galactic disk or a Neptune-mass planet in the Galactic bulge. OGLE-2017-BLG-0560 (tE = 0.905 ± 0.005 d, θE = 38.7 ± 1.6μas) was caused by a Jupiter-mass planet in the Galactic disk or a brown dwarf in the bulge. We rule out stellar companions up to a distance of 6.0 and 3.9 au, respectively. We suggest that the lensing objects, whether located on very wide orbits or free-floating, may originate from the same physical mechanism. Although the sample of ultrashort microlensing events is small, these detections are consistent with low-mass wide-orbit or unbound planets being more common than stars in the Milky Way.

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Sporadic and intense accretion in a 1 Myr-old brown dwarf candidate

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936810 ◽

2020 ◽

Vol 634 ◽

pp. A128

Author(s):

D. Nguyen-Thanh ◽

N. Phan-Bao ◽

S. J. Murphy ◽

M. S. Bessell

Keyword(s):

Spectral Energy Distribution ◽

Brown Dwarfs ◽

Photometric Data ◽

Spectral Energy ◽

Brown Dwarf ◽

M Dwarfs ◽

Trigonometric Parallax ◽

Accretion Process ◽

Accretion Rates ◽

Low Mass

Context. Studying the accretion process in very low-mass objects has important implications for understanding their formation mechanism. Many nearby late-M dwarfs that have previously been identified in the field are in fact young brown dwarf members of nearby young associations. Some of them are still accreting. They are therefore excellent targets for further studies of the accretion process in the very low-mass regime at different stages. Aims. We aim to search for accreting young brown dwarf candidates in a sample of 85 nearby late-M dwarfs. Methods. Using photometric data from DENIS, 2MASS, and WISE, we constructed the spectral energy distribution of the late- M dwarfs based on BT-Settl models to detect infrared excesses. We then searched for lithium and Hα emission in candidates that exhibit infrared excesses to confirm their youth and the presence of accretion. Results. Among the 85 late-M dwarfs, only DENIS-P J1538317−103850 (M5.5) shows strong infrared excesses in WISE bands. The detection of lithium absorption in the M5.5 dwarf and its Gaia trigonometric parallax indicate an age of ~1 Myr and a mass of 47 MJ. The Hα emission line in the brown dwarf shows significant variability that indicates sporadic accretion. This 1 Myr-old brown dwarf also exhibits intense accretion bursts with accretion rates of up to 10−7.9 M⊙ yr−1. Conclusions. Our detection of sporadic accretion in one of the youngest brown dwarfs might imply that sporadic accretion at early stages could play an important role in the formation of brown dwarfs. Very low-mass cores would not be able to accrete enough material to become stars, and thus they end up as brown dwarfs.

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