Dynamical Mass of the Young Substellar Companion HD 984 B

Abstract Model-independent masses of substellar companions are critical tools to validate models of planet and brown dwarf cooling, test their input physics, and determine the formation and evolution of these objects. In this work, we measure the dynamical mass and orbit of the young substellar companion HD 984 B. We obtained new high-contrast imaging of the HD 984 system with Keck/NIRC2 that expands the baseline of relative astrometry from 3 to 8 yr. We also present new radial velocities of the host star with the Habitable-Zone Planet Finder spectrograph at the Hobby-Eberly Telescope. Furthermore, HD 984 exhibits a significant proper motion difference between Hipparcos and Gaia EDR3. Our joint orbit fit of the relative astrometry, proper motions, and radial velocities yields a dynamical mass of 61 ± 4 M Jup for HD 984 B, placing the companion firmly in the brown dwarf regime. The new fit also reveals a higher eccentricity for the companion (e = 0.76 ± 0.05) compared to previous orbit fits. Given the broad age constraint for HD 984, this mass is consistent with predictions from evolutionary models. HD 984 B’s dynamical mass places it among a small but growing list of giant planet and brown dwarf companions with direct mass measurements.

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Direct imaging of an ultracool substellar companion to the exoplanet host star HD 4113 A

Astronomy and Astrophysics ◽

10.1051/0004-6361/201630136 ◽

2018 ◽

Vol 614 ◽

pp. A16 ◽

Cited By ~ 16

Author(s):

A. Cheetham ◽

D. Ségransan ◽

S. Peretti ◽

J.-B. Delisle ◽

J. Hagelberg ◽

...

Keyword(s):

Giant Planet ◽

Radial Velocities ◽

Physical Parameters ◽

Imaging Data ◽

Brown Dwarf ◽

Contrast Imaging ◽

Direct Imaging ◽

Dynamical Mass ◽

Methane Absorption ◽

Mass Estimate

Using high-contrast imaging with the SPHERE instrument at the Very Large Telescope (VLT), we report the first images of a cold brown dwarf companion to the exoplanet host star HD 4113A. The brown dwarf HD 4113C is part of a complex dynamical system consisting of a giant planet, a stellar host, and a known wide M-dwarf companion. Its separation of 535 ± 3 mas and H-band contrast of 13.35 ± 0.10 mag correspond to a projected separation of 22 AU and an isochronal mass estimate of 36 ± 5 MJ based on COND models. The companion shows strong methane absorption, and through fitting an atmosphere model, we estimate a surface gravity of logg = 5 and an effective temperature of ~500–600 K. A comparison of its spectrum with observed T dwarfs indicates a late-T spectral type, with a T9 object providing the best match. By combining the observed astrometry from the imaging data with 27 years of radial velocities, we use orbital fitting to constrain its orbital and physical parameters, as well as update those of the planet HD 4113A b, discovered by previous radial velocity measurements. The data suggest a dynamical mass of 66−4+5 MJ and moderate eccentricity of 0.44−0.07+0.08 for the brown dwarf. This mass estimate appears to contradict the isochronal estimate and that of objects with similar temperatures, which may be caused by the newly detected object being an unresolved binary brown dwarf system or the presence of an additional object in the system. Through dynamical simulations, we show that the planet may undergo strong Lidov-Kozai cycles, raising the possibility that it formed on a quasi-circular orbit and gained its currently observed high eccentricity (e ~ 0.9) through interactions with the brown dwarf. Follow-up observations combining radial velocities, direct imaging, and Gaia astrometry will be crucial to precisely constrain the dynamical mass of the brown dwarf and allow for an in-depth comparison with evolutionary and atmosphere models.

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Constraining the properties of HD 206893 B

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935044 ◽

2019 ◽

Vol 627 ◽

pp. L9 ◽

Cited By ~ 8

Author(s):

A. Grandjean ◽

A.-M. Lagrange ◽

H. Beust ◽

L. Rodet ◽

J. Milli ◽

...

Keyword(s):

Radial Velocity ◽

Semimajor Axis ◽

High Contrast ◽

Brown Dwarf ◽

Contrast Imaging ◽

Dynamical Mass ◽

Orbital Parameters ◽

High Contrast Imaging ◽

Very Large Telescope ◽

Astrometric Data

Context. High contrast imaging enables the determination of orbital parameters for substellar companions (planets, brown dwarfs) from the observed relative astrometry and the estimation of model and age-dependent masses from their observed magnitudes or spectra. Combining astrometric positions with radial velocity gives direct constraints on the orbit and on the dynamical masses of companions. A brown dwarf was discovered with the VLT/SPHERE instrument at the Very Large Telescope (VLT) in 2017, which orbits at ∼11 au around HD 206893. Its mass was estimated between 12 and 50 MJ from evolutionary models and its photometry. However, given the significant uncertainty on the age of the system and the peculiar spectrophotometric properties of the companion, this mass is not well constrained. Aims. We aim at constraining the orbit and dynamical mass of HD 206893 B. Methods. We combined radial velocity data obtained with HARPS spectra and astrometric data obtained with the high contrast imaging VLT/SPHERE and VLT/NaCo instruments, with a time baseline less than three years. We then combined those data with astrometry data obtained by HIPPARCOS and Gaia with a time baseline of 24 yr. We used a Markov chain Monte Carlo approach to estimate the orbital parameters and dynamical mass of the brown dwarf from those data. Results. We infer a period between 21 and 33 yr and an inclination in the range 20−41° from pole-on from HD 206893 B relative astrometry. The RV data show a significant RV drift over 1.6 yr. We show that HD 206893 B cannot be the source of this observed RV drift as it would lead to a dynamical mass inconsistent with its photometry and spectra and with HIPPARCOS and Gaia data. An additional inner (semimajor axis in the range 1.4–2.6 au) and massive (∼15 MJ) companion is needed to explain the RV drift, which is compatible with the available astrometric data of the star, as well as with the VLT/SPHERE and VLT/NaCo nondetection.

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A dusty benchmark brown dwarf near the ice line of HD 72946

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937134 ◽

2019 ◽

Vol 633 ◽

pp. L2 ◽

Cited By ~ 4

Author(s):

A.-L. Maire ◽

J.-L. Baudino ◽

S. Desidera ◽

S. Messina ◽

W. Brandner ◽

...

Keyword(s):

Proper Motion ◽

Major Axis ◽

High Contrast ◽

Brown Dwarf ◽

Contrast Imaging ◽

Semi Major Axis ◽

Dynamical Mass ◽

High Contrast Imaging ◽

Solar Type ◽

Solar Type Star

Context. HD 72946 is a bright and nearby solar-type star hosting a low-mass companion at long period (P ∼ 16 yr) detected with the radial velocity (RV) method. The companion has a minimum mass of 60.4 ± 2.2 MJ and might be a brown dwarf. Its expected semi-major axis of ∼243 mas makes it a suitable target for further characterization with high-contrast imaging, in particular to measure its inclination, mass, and spectrum and thus definitely establish its substellar nature. Aims. We aim to further characterize the orbit, atmosphere, and physical nature of HD 72946B. Methods. We present high-contrast imaging data in the near-infrared with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. We also use proper motion measurements of the star from HIPPARCOS and Gaia. Results. The SPHERE data reveal a point source with a contrast of ∼9 mag at a projected separation of ∼235 mas. No other point sources are detected in the field of view. By jointly fitting the RV, imaging, and proper motion data, we constrain all the orbital parameters of HD 72946B and assess a dynamical mass of 72.4 ± 1.6 MJ and a semi-major axis of 6.456.45+0.08−0.07 au. Empirical comparison of its SPHERE spectrum to template dwarfs indicates a spectral type of L5.0 ± 1.5. The J–H3 color is close to the expectations of the DUSTY models and suggests a cloudy atmosphere. Comparison with atmospheric models of the spectrophotometry suggests an effective temperature of ∼1700 K. The bolometric luminosity (log(L/L⊙) = −4.11 ± 0.10 dex) and dynamical mass of HD 72946B are more compatible with evolutionary models for an age range of ∼0.9−3 Gyr. The formation mechanism of the companion is currently unclear as the object appears slightly away from the bulk of model predictions. HD 72946B is currently the closest benchmark brown dwarf companion to a solar-type star with imaging, RV, and proper motion measurements.

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Spectral and atmospheric characterisation of a new benchmark brown dwarf HD 13724 B

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037524 ◽

2020 ◽

Vol 635 ◽

pp. A203 ◽

Cited By ~ 3

Author(s):

E. L. Rickman ◽

D. Ségransan ◽

J. Hagelberg ◽

J.-L. Beuzit ◽

A. Cheetham ◽

...

Keyword(s):

Radial Velocity ◽

High Contrast ◽

Imaging Data ◽

Brown Dwarf ◽

Low Resolution ◽

Contrast Imaging ◽

Echelle Spectrograph ◽

Dynamical Mass ◽

High Contrast Imaging ◽

Mass Estimate

Context. HD 13724 is a nearby solar-type star at 43.48 ± 0.06 pc hosting a long-period low-mass brown dwarf detected with the CORALIE echelle spectrograph as part of the historical CORALIE radial-velocity search for extra-solar planets. The companion has a minimum mass of 26.77−2.2+4.4 MJup and an expected semi-major axis of ~240 mas making it a suitable target for further characterisation with high-contrast imaging, in particular to measure its inclination, mass, and spectrum and thus establish its substellar nature. Aims. Using high-contrast imaging with the SPHERE instrument on the Very Large Telescope (VLT), we are able to directly image a brown dwarf companion to HD 13724 and obtain a low-resolution spectrum. Methods. We combine the radial-velocity measurements of CORALIE and HARPS taken over two decades and high-contrast imaging from SPHERE to obtain a dynamical mass estimate. From the SPHERE data we obtain a low-resolution spectrum of the companion from Y to J band, as well as photometric measurements from IRDIS in the J, H, and K bands. Results. Using high-contrast imaging with the SPHERE instrument at the VLT, we report the first images of a brown dwarf companion orbiting the host star HD 13724. It has an angular separation of 175.6 ± 4.5 mas and an H-band contrast of 10.61 ± 0.16 mag, and using the age estimate of the star to be ~1 Gyr gives an isochronal mass estimate of ~44 MJup. By combining radial-velocity and imaging data we also obtain a dynamical mass of 50.5−3.5+3.3 MJup. Through fitting an atmospheric model, we estimate a surface gravity of logg = 5.5 and an effective temperature of 1000 K. A comparison of its spectrum with observed T dwarfs estimates a spectral type of T4 or T4.5, with a T4 object providing the best fit.

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How many suns are in the sky? Multiplicity surveys of exoplanet host stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319001595 ◽

2018 ◽

Vol 14 (S345) ◽

pp. 316-317 ◽

Cited By ~ 1

Author(s):

M. Mugrauer ◽

C. Ginski ◽

N. Vogt ◽

R. Neuhäuser ◽

C. Adam

Keyword(s):

Milky Way ◽

Planet Formation ◽

High Contrast ◽

Contrast Imaging ◽

Direct Imaging ◽

High Contrast Imaging ◽

Multiple Stars ◽

First Results ◽

Formation And Evolution ◽

Host Stars

AbstractIn order to determine the true impact of stellar multiplicity on the formation and evolution of planets, we initiated direct imaging surveys to search for (sub)stellar companions of exoplanet host stars on close orbits, as their gravitational impact on the planet bearing disk at first and on formed planets afterwards is expected to be maximal. According to theory these are the most challenging environments for planet formation and evolution but might occur quite frequently in the milky way, due to the large number of multiple stars within our galaxy. On this poster we showed results, obtained so far in the course of our AO and Lucky-imaging campaigns of exoplanet host stars, conducted with NACO/ESO-VLT for southern and with AstraLux/CAHA2.2m for northern targets, respectively. In addition, we introduced our new high contrast imaging survey with SPHERE/ESO-VLT to search for close companions of southern exoplanet host stars, and presented some first results.

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Orbital and spectral characterization of the benchmark T-type brown dwarf HD 19467B

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037984 ◽

2020 ◽

Vol 639 ◽

pp. A47

Author(s):

A.-L. Maire ◽

K. Molaverdikhani ◽

S. Desidera ◽

T. Trifonov ◽

P. Mollière ◽

...

Keyword(s):

High Surface ◽

Formation Mechanisms ◽

Evolutionary Models ◽

Imaging Data ◽

Brown Dwarf ◽

Contrast Imaging ◽

Nearby Star ◽

Dynamical Mass ◽

Orbital Parameters ◽

Bolometric Luminosity

Context. Detecting and characterizing substellar companions for which the luminosity, mass, and age can be determined independently is of utter importance to test and calibrate the evolutionary models due to uncertainties in their formation mechanisms. HD 19467 is a bright and nearby star hosting a cool brown dwarf companion detected with radial velocities and imaging, making it a valuable object for such studies. Aims. We aim to further characterize the orbital, spectral, and physical properties of the HD 19467 system. Methods. We present new high-contrast imaging data with the SPHERE and NaCo instruments. We also analyze archival data from the instruments HARPS, NaCo, HIRES, UVES, and ASAS. Furthermore, we use proper motion data of the star from HIPPARCOS and Gaia. Results. We refined the properties of the host star and derived an age of 8.0+2.0−1.0 Gyr based on isochrones, gyrochronology, and chemical and kinematic arguments. This age estimate is slightly younger than previous age estimates of ~9–11 Gyr based on isochrones. No orbital curvature is seen in the current imaging, radial velocity, and astrometric data. From a joint fit of the data, we refined the orbital parameters for HD 19467B, including: a period of 398+95−93 yr, an inclination of 129.8+8.1−5.1 deg, an eccentricity of 0.56 ± 0.09, a longitude of the ascending node of 134.8 ± 4.5 deg, and an argument of the periastron of 64.2+5.5−6.3 deg. We assess a dynamical mass of 74+12−9 MJ. The fit with atmospheric models of the spectrophotometric data of the companion indicates an atmosphere without clouds or with very thin clouds, an effective temperature of 1042+77−71 K, and a high surface gravity of 5.34+0.8−0.9 dex. The comparison to model predictions of the bolometric luminosity and dynamical mass of HD 19467B, assuming our system age estimate, indicates a better agreement with the Burrows et al. (1997, ApJ, 491, 856) models; whereas, the other evolutionary models used tend to underestimate its cooling rate.

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The likelihood of detecting young giant planets with high-contrast imaging and interferometry

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2600 ◽

2019 ◽

Vol 490 (1) ◽

pp. 502-512 ◽

Cited By ~ 1

Author(s):

A L Wallace ◽

M J Ireland

Keyword(s):

Radial Velocity ◽

Near Infrared ◽

Giant Planet ◽

Giant Planets ◽

Contrast Imaging ◽

Distribution Models ◽

High Contrast Imaging ◽

Solar Type ◽

Infrared Wavelengths ◽

Core Accretion

ABSTRACT Giant planets are expected to form at orbital radii that are relatively large compared to transit and radial velocity detections (>1 au). As a result, giant planet formation is best observed through direct imaging. By simulating the formation of giant (0.3–5MJ) planets by core accretion, we predict planet magnitude in the near-infrared (2–4 μm) and demonstrate that, once a planet reaches the runaway accretion phase, it is self-luminous and is bright enough to be detected in near-infrared wavelengths. Using planet distribution models consistent with existing radial velocity and imaging constraints, we simulate a large sample of systems with the same stellar and disc properties to determine how many planets can be detected. We find that current large (8–10 m) telescopes have at most a 0.2 per cent chance of detecting a core-accretion giant planet in the L’ band and 2 per cent in the K band for a typical solar-type star. Future instruments such as METIS and VIKiNG have higher sensitivity and are expected to detect exoplanets at a maximum rate of 2 and 8 per cent, respectively.

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SPHERE+, Imaging young planets down to the snow line

10.5194/epsc2021-24 ◽

2021 ◽

Author(s):

Anthony Boccaletti ◽

Keyword(s):

Adaptive Optics ◽

Near Infrared ◽

Imaging Spectroscopy ◽

Giant Planet ◽

High Spectral Resolution ◽

Contrast Imaging ◽

High Contrast Imaging ◽

Orbital Periods ◽

Complementary Techniques ◽

Technical Solutions

SPHERE, the high contrast imaging facility at the VLT has contributed significantly to the exploration of planetary systems, by revealing many details in proto-planetary and debris disks, by measuring the atmospheric properties of young giant planets and by deriving constraints on the giant planet population in long orbital periods. Such achievements allow us to provide a better understanding of planetary formation and evolution. The versatility of SPHERE also enables various secondary and sometimes unexpected science cases owing to a large spectral coverage from the visible to the near IR, and the availability of several observing modes as imaging, spectroscopy and polarimetry. Yet the access to the region where planets are expected to form, is not complete and still represents a challenge. To overcome this limitation larger contrasts at shorter separations are definitely required.&#160; The SPHERE+ concept precisely aims to provide the capabilities to primarily access the bulk of the young giant planet population down to the snowline&#160; in order to bridge the gap with complementary techniques. As a second objective, SPHERE+ should be able to observe an increased sample of targets, fainter and redder than those observed in the first survey. Finally, SPHERE+ will provide a higher level of characterization of planet&#8217;s atmospheres. To achieve these goals, SPHERE should be upgraded with a faster Adaptive Optics system to reach&#160; high contrasts at closer angular separations, together with a more sensitive wavefront sensor in the infrared to observe redder targets. Medium and high spectral resolution in the near infrared will be brought by a dedicated IFU spectrograph or taking advantage of the HiRISE project to combined SPHERE and CRIRES+. We will present the science cases and the technical solutions that are foreseen to reach the appropriate performances, and provide potential ways for such an upgrade. &#160;

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The Gemini NICI Planet-Finding Campaign: The Frequency of Giant Planets around Young B and A Stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313007874 ◽

2013 ◽

Vol 8 (S299) ◽

pp. 60-61

Author(s):

Eric L. Nielsen ◽

Michael C. Liu ◽

Zahed Wahhaj ◽

Beth A. Biller ◽

Thomas L. Hayward ◽

...

Keyword(s):

Brown Dwarfs ◽

Giant Planets ◽

High Mass ◽

High Contrast ◽

Brown Dwarf ◽

Contrast Imaging ◽

High Contrast Imaging ◽

Null Result ◽

Upper Limits

AbstractWe have carried out high contrast imaging of 70 young, nearby B and A stars to search for brown dwarf and planetary companions as part of the Gemini NICI Planet-Finding Campaign. Our survey represents the largest, deepest survey for planets around high-mass stars (≈1.5–2.5 M⊙) conducted to date and includes the planet hosts β Pic and Fomalhaut. Despite detecting two new brown dwarfs, our observations did not detect new planets around our target stars, and we present upper limits on the fraction of high-mass stars that can host giant planets that are consistent with our null result.

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Direct Imaging of Exoplanets Living an Exciting Life

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315006560 ◽

2015 ◽

Vol 10 (S314) ◽

pp. 213-219

Author(s):

G. Chauvin

Keyword(s):

Physical Properties ◽

Imaging Techniques ◽

Formation Mechanisms ◽

Contrast Imaging ◽

The Past ◽

High Contrast Imaging ◽

Nearby Stars ◽

Formation And Evolution ◽

Observing Techniques

AbstractWith the development of high contrast imaging techniques and instruments, vast efforts have been devoted during the past decades to detect and characterize lighter, cooler and closer companions to nearby stars, and ultimately image new planetary systems. Complementary to other planet-hunting techniques, this approach has opened a new astrophysical window to study the physical properties and the formation mechanisms of brown dwarfs and planets. In this review, I will briefly describe the different observing techniques and strategies used, the main samples of targeted nearby stars, finally the main results obtained so far about exoplanet discoveries characterization of their physical properties, and study of their occurrence and possible formation and evolution mechanisms.

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