Discovery of a brown dwarf companion to the star HIP 64892

We report the discovery of a bright, brown dwarf companion to the star HIP 64892, imaged with VLT/SPHERE during the SHINE exoplanet survey. The host is a B9.5V member of the Lower-Centaurus-Crux subgroup of the Scorpius Centaurus OB association. The measured angular separation of the companion (1.2705 ± 0.0023”) corresponds to a projected distance of 159 ± 12 AU. We observed the target with the dual-band imaging and long-slit spectroscopy modes of the IRDIS imager to obtain its spectral energy distribution (SED) and astrometry. In addition, we reprocessed archival NACO L-band data, from which we also recover the companion. Its SED is consistent with a young (<30 Myr), low surface gravity object with a spectral type of M9γ ± 1. From comparison with the BT-Settl atmospheric models we estimate an effective temperature of Teff = 2600 ± 100 K, and comparison of the companion photometry to the COND evolutionary models yields a mass of ~29−37 MJ at the estimated age of 16−7+15 Myr for the system. The star HIP 64892 is a rare example of an extreme-mass ratio system (q ~ 0.01) and will be useful for testing models relating to the formation and evolution of such low-mass objects.

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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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Comparing galaxy clustering in Horizon-AGN simulated light-cone mocks and VIDEO observations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2946 ◽

2019 ◽

Vol 490 (4) ◽

pp. 5043-5056 ◽

Cited By ~ 1

Author(s):

P W Hatfield ◽

C Laigle ◽

M J Jarvis ◽

J Devriendt ◽

I Davidzon ◽

...

Keyword(s):

Light Cone ◽

Spectral Energy Distribution ◽

Cosmic Time ◽

Stellar Mass ◽

Spectral Energy ◽

Mass Ratio ◽

Distribution Fitting ◽

Low Mass ◽

Stellar Masses ◽

Mass Functions

ABSTRACT Hydrodynamical cosmological simulations have recently made great advances in reproducing galaxy mass assembly over cosmic time – as often quantified from the comparison of their predicted stellar mass functions to observed stellar mass functions from data. In this paper, we compare the clustering of galaxies from the hydrodynamical cosmological simulated light-cone Horizon-AGN to clustering measurements from the VIDEO survey observations. Using mocks built from a VIDEO-like photometry, we first explore the bias introduced into clustering measurements by using stellar masses and redshifts derived from spectral energy distribution fitting, rather than the intrinsic values. The propagation of redshift and mass statistical and systematic uncertainties in the clustering measurements causes us to underestimate the clustering amplitude. We then find that clustering and halo occupation distribution (HOD) modelling results are qualitatively similar in Horizon-AGN and VIDEO. However, at low stellar masses, Horizon-AGN underestimates the observed clustering by up to a factor of ∼3, reflecting the known excess stellar mass to halo mass ratio for Horizon-AGN low-mass haloes, already discussed in previous works. This reinforces the need for stronger regulation of star formation in low-mass haloes in the simulation. Finally, the comparison of the stellar mass to halo mass ratio in the simulated catalogue, inferred from angular clustering, to that directly measured from the simulation validates HOD modelling of clustering as a probe of the galaxy–halo connection.

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CCD photometry and spectroscopy of 14 IRAS sources having far-IR colours similar to Planetary Nebulae

Symposium - International Astronomical Union ◽

10.1017/s0074180900131407 ◽

1997 ◽

Vol 180 ◽

pp. 365-365

Author(s):

B. E. Reddy ◽

M. Parthasarathy

Keyword(s):

Spectral Energy Distribution ◽

Planetary Nebulae ◽

Spectral Energy ◽

Galactic Latitude ◽

Ccd Photometry ◽

Ccd Imaging ◽

Evolved Stars ◽

Molecular Features ◽

Intense Mass ◽

Low Mass

CCD imaging and BVRI photometry of 14 IRAS sources with far-IR colours similar to planetary nebulae and post-AGB stars are presented. Also results of optical and near-IR spectroscopy of 10 of these candidates are given. Based on the spectral energy distribution from 0.4 μm to 100 μm, the sample of program stars are put into two groups. The sources IRAS 08187-1905, IRAS 05238-0626 and IRAS 17086-2403 present similar flux distributions. These three sources have detached cold dust components with dust radii Rd ≈ 1000 R∗. The low infrared variability of theses sources suggests that the intense mass loss has been ceased. All three sources are at high galactic latitude (1>9°) suggesting that these are old low-mass evolved stars. In the IRAS colour-colour diagram of Likkel et al (1991) these sources fall in the region where most of the stars are evolved stars and PNe but without CO detection. This is consistent with at least one source IRAS 17086-2403, in which OH and CO molecular features are not detected. The far-IR excess, non-variability and high latitude of these objects suggest that these are post-AGB supergiants, slowly evolving towards planetary nebula phase.

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Investigating the young solar system analog HD 95086

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732077 ◽

2018 ◽

Vol 617 ◽

pp. A76 ◽

Cited By ~ 18

Author(s):

G. Chauvin ◽

R. Gratton ◽

M. Bonnefoy ◽

A.-M. Lagrange ◽

J. de Boer ◽

...

Keyword(s):

Radial Velocity ◽

Near Infrared ◽

Scattered Light ◽

Spectral Energy Distribution ◽

Giant Planet ◽

Giant Planets ◽

Dual Band ◽

Spectral Energy ◽

Semi Major Axis ◽

Integral Field Spectrograph

Context. HD 95086 (A8V, 17 Myr) hosts a rare planetary system for which a multi-belt debris disk and a giant planet of 4–5 MJup have been directly imaged. Aims. Our study aims to characterize the global architecture of this young system using the combination of radial velocity and direct imaging observations. We want to characterize the physical and orbital properties of HD 95086 b, search for additional planets at short and wide orbits and image the cold outer debris belt in scattered light. Methods. We used HARPS at the ESO 3.6 m telescope to monitor the radial velocity of HD 95086 over two years and investigate the existence of giant planets at less than 3 au orbital distance. With the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE at VLT, we imaged the faint circumstellar environment beyond 10 au at six epochs between 2015 and 2017. Results. We do not detect additional giant planets around HD 95086. We identify the nature (bound companion or background contaminant) of all point-like sources detected in the IRDIS field of view. None of them correspond to the ones recently discovered near the edge of the cold outer belt by ALMA. HD 95086 b is resolved for the first time in J-band with IFS. Its near-infrared spectral energy distribution is well fitted by a few dusty and/or young L7–L9 dwarf spectral templates. The extremely red 1–4 μm spectral distribution is typical of low-gravity objects at the L/T spectral type transition. The planet’s orbital motion is resolved between January 2015 and May 2017. Together with past NaCo measurements properly re-calibrated, our orbital fitting solutions favor a retrograde low to moderate-eccentricity orbit e = 0.2+0.3−0.2, with a semi-major axis ~52 au corresponding to orbital periods of ~288 yr and an inclination that peaks at i = 141°, which is compatible with a planet-disk coplanar configuration. Finally, we report the detection in polarimetric differential imaging of the cold outer debris belt between 100 and 300 au, consistent in radial extent with recent ALMA 1.3 mm resolved observations.

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Broad-band spectral energy distribution of the X-ray transient Swift J1745−26 from outburst to quiescence

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935720 ◽

2020 ◽

Vol 637 ◽

pp. A2

Author(s):

Sylvain Chaty ◽

Francis Fortin ◽

Alicia López-Oramas

Keyword(s):

Energy Distribution ◽

Light Curve ◽

Spectral Energy Distribution ◽

Broad Band ◽

Spectral Energy ◽

X Ray ◽

Upper Limit ◽

Spectral Break ◽

Hard State ◽

Low Mass

Aims. We aim to analyse our study of the X-ray transient Swift J1745−26, using observations obtained from its outburst in September 2012, up to its decay towards quiescence in March 2013. Methods. We obtained optical and infrared observations, through override programme at ESO/VLT with FORS2 and ISAAC instruments, and added archival optical (VLT/VIRCAM), radio and X-ray (Swift) observations, to build the light curve and the broad-band spectral energy distribution (SED) of Swift J1745−26. Results. We show that, during its outburst and also during its decay towards quiescence, Swift J1745−26 SED can be adjusted, from infrared up to X-rays, by the sum of both a viscous irradiated multi-colour black body emitted by an accretion disc, and a synchrotron power law at high energy. In the radio domain, the SED arises from synchrotron emission from the jet. While our SED fitting confirms that the source remained in the low/hard state during its outburst, we determine an X-ray spectral break at frequency 3.1 ≤ νbreak ≤ 3.4 × 1014 Hz, and a radio spectral break at 1012 Hz ≤ νbreak ≤ 1013 Hz. We also show that the system is compatible with an absorption AV of ∼7.69 mag, lies within a distance interval of D ∼ [2.6 − 4.8] kpc with an upper limit of orbital period Porb = 11.3 h, and that the companion star is a late spectral type in the range K0–M0 V, confirming that the system is a low-mass X-ray binary. We finally plot the position of Swift J1745−26 on an optical-infrared – X-ray luminosity diagram: its localisation on this diagram is consistent with the source staying in the low-hard state during outburst and decay phases. Conclusions. By using new observations obtained at ESO/VLT with FORS2 and ISAAC, and adding archival optical (VLT/VIRCAM), radio and X-ray (Swift) observations, we built the light curve and the broad-band SED of Swift J1745−26, and we plotted its position on an optical-infrared – X-ray luminosity diagram. By fitting the SED, we characterized the emission of the source from infrared, via optical, up to X-ray domain, we determined the position of both the radio and X-ray spectral breaks, we confirmed that it remained in the low-hard state during outburst and decay phases, and we derived its absorption, distance interval, orbital period upper limit, and the late-type nature of companion star, confirming Swift J1745−26 is a low-mass X-ray binary.

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Mon-735: a new low-mass pre-main-sequence eclipsing binary in NGC 2264

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1016 ◽

2020 ◽

Vol 495 (2) ◽

pp. 1531-1548

Author(s):

Edward Gillen ◽

Lynne A Hillenbrand ◽

John Stauffer ◽

Suzanne Aigrain ◽

Luisa Rebull ◽

...

Keyword(s):

Main Sequence ◽

Spectral Energy Distribution ◽

Spectral Energy ◽

Centre Of Mass ◽

M Dwarfs ◽

Eclipsing Binary ◽

Star Forming ◽

Low Mass ◽

Effective Temperatures

ABSTRACT We present Mon-735, a detached double-lined eclipsing binary (EB) member of the ∼3 Myr old NGC 2264 star-forming region, detected by Spitzer. We simultaneously model the Spitzer light curves, follow-up Keck/HIRES radial velocities, and the system’s spectral energy distribution to determine self-consistent masses, radii, and effective temperatures for both stars. We find that Mon-735 comprises two pre-main-sequence M dwarfs with component masses of M = 0.2918 ± 0.0099 and 0.2661 ± 0.0095 M⊙, radii of R = 0.762 ± 0.022 and 0.748 ± 0.023 R⊙, and effective temperatures of Teff = 3260 ± 73 and 3213 ± 73 K. The two stars travel on circular orbits around their common centre of mass in P = 1.9751388 ± 0.0000050 d. We compare our results for Mon-735, along with another EB in NGC 2264 (CoRoT 223992193), to the predictions of five stellar evolution models. These suggest that the lower mass EB system Mon-735 is older than CoRoT 223992193 in the mass–radius diagram (MRD) and, to a lesser extent, in the Hertzsprung–Russell diagram (HRD). The MRD ages of Mon-735 and CoRoT 223992193 are ∼7–9 and 4–6 Myr, respectively, with the two components in each EB system possessing consistent ages.

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VVV-WIT-01: highly obscured classical nova or protostellar collision?

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa155 ◽

2020 ◽

Vol 492 (4) ◽

pp. 4847-4857

Author(s):

P W Lucas ◽

D Minniti ◽

A Kamble ◽

D L Kaplan ◽

N Cross ◽

...

Keyword(s):

Spectral Energy Distribution ◽

Spectral Energy ◽

Single Event ◽

Dark Cloud ◽

Continuum Source ◽

Classical Novae ◽

Classical Nova ◽

Low Mass ◽

Compact Array

ABSTRACT A search of the first Data Release of the VISTA Variables in the Via Lactea (VVV) Survey discovered the exceptionally red transient VVV-WIT-01 (H − Ks = 5.2). It peaked before March 2010, then faded by ∼9.5 mag over the following 2 yr. The 1.6–22 μm spectral energy distribution in March 2010 was well fit by a highly obscured blackbody with T ∼ 1000 K and $A_{K_s} \sim 6.6$ mag. The source is projected against the Infrared Dark Cloud (IRDC) SDC G331.062−0.294. The chance projection probability is small for any single event (p ≈ 0.01–0.02), which suggests a physical association, e.g. a collision between low mass protostars. However, blackbody emission at T ∼ 1000 K is common in classical novae (especially CO novae) at the infrared peak in the light curve due to condensation of dust ∼30–60 d after the explosion. Radio follow-up with the Australia Telescope Compact Array detected a fading continuum source with properties consistent with a classical nova but probably inconsistent with colliding protostars. Considering all VVV transients that could have been projected against a catalogued IRDC raises the probability of a chance association to p = 0.13–0.24. After weighing several options, it appears likely that VVV-WIT-01 was a classical nova event located behind an IRDC.

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Brown Dwarf Binaries

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311027086 ◽

2011 ◽

Vol 7 (S282) ◽

pp. 105-110 ◽

Cited By ~ 1

Author(s):

Katelyn N. Allers

Keyword(s):

Brown Dwarfs ◽

Theoretical Models ◽

Solar Neighborhood ◽

Test Model ◽

Brown Dwarf ◽

Fundamental Properties ◽

Model Predictions ◽

Low Mass ◽

Formation And Evolution ◽

Insight Into

AbstractNearly 500 brown dwarfs have been discovered in recent years. The majority of these brown dwarfs exist in the solar neighborhood, yet determining their fundamental properties (mass, age, temperature & metallicity) has proved to be quite difficult, with current estimates relying heavily on theoretical models. Binary brown dwarfs provide a unique opportunity to empirically determine fundamental properties, which can then be used to test model predictions. In addition, the observed binary fractions, separations, mass ratios, & orbital eccentricities can provide insight into the formation mechanism of these low-mass objects. I will review the results of various brown dwarf multiplicity studies, and will discuss what we have learned about the formation and evolution of brown dwarfs by examining their binary properties as a function of age and mass.

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