Spectral and orbital characterisation of the directly imaged giant planet HIP 65426 b

HIP 65426 b is a recently discovered exoplanet imaged during the course of the SPHERE-SHINE survey. Here we present new L′ and M′ observations of the planet from the NACO instrument at the VLT from the NACO-ISPY survey, as well as a new Y –H spectrum and K-band photometry from SPHERE-SHINE. Using these data, we confirm the nature of the companion as a warm, dusty planet with a mid-L spectral type. From comparison of its SED with the BT-Settl atmospheric models, we derive a best-fit effective temperature of Teff = 1618 ± 7 K, surface gravity log g = 3.78−0.03+0.04 and radius R = 1.17 ± 0.04RJ (statistical uncertainties only). Using the DUSTY and COND isochrones we estimate a mass of 8 ± 1MJ. Combining the astrometric measurements from our new datasets and from the literature, we show the first indications of orbital motion of the companion (2.6σ significance)and derive preliminary orbital constraints. We find a highly inclined orbit (i = 1.07−10+13 deg) with an orbital period of 800−400+1200 yr. We also report SPHERE sparse aperture masking observations that investigate the possibility that HIP 65426 b was scattered onto its current orbit by an additional companion at a smaller orbital separation. From this data we rule out the presence of brown dwarf companions with masses greater than 16 MJ at separations larger than 3 AU, significantly narrowing the parameter space for such a companion.

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Two bodies with high eccentricity around the cataclysmic variable QS Vir

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311020941 ◽

2010 ◽

Vol 6 (S276) ◽

pp. 495-496 ◽

Cited By ~ 5

Author(s):

Leonardo A. Almeida ◽

Francisco Jablonski

Keyword(s):

Orbital Period ◽

Giant Planet ◽

Cataclysmic Variable ◽

Brown Dwarf ◽

Period Variations ◽

Angular Momentum Loss ◽

Best Fitting ◽

Orbital Periods ◽

The Masses ◽

Two Bodies

AbstractQS Vir is an eclipsing cataclysmic variable with 3.618 hrs orbital period. This system has the interesting characteristics that it does not show mass transfer between the components through the L1 Lagrangian point and shows a complex orbital period variation history. Qian et al. (2010) associated the orbital period variations to the presence of a giant planet in the system plus angular momentum loss via magnetic braking. Parsons et al. (2010) obtained new eclipse timings and observed that the orbital period variations associated to a hypothetical giant planet disagree with their measurements and concluded that the decrease in orbital period is part of a cyclic variation with period ~16 yrs. In this work, we present 28 new eclipse timings of QS Vir and suggest that the orbital period variations can be explained by a model with two circumbinary bodies. The best fitting gives the lower limit to the masses M1 sin(i) ~ 0.0086 M⊙ and M2 sin(i) ~ 0.054 M⊙; orbital periods P1 ~ 14.4 yrs and P2 ~ 16.99 yrs, and eccentricities e1 ~ 0.62 and e2~0.92 for the two external bodies. Under the assumption of coplanarity among the two external bodies and the inner binary, we obtain a giant planet with ~0.009 M⊙ and a brown dwarf with ~ 0.056 M⊙ around the eclipsing binary QS Vir.

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Search for intermittent X-ray pulsations from neutron stars in low-mass X-ray binaries

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2021.6 ◽

2021 ◽

Vol 38 ◽

Author(s):

Yunus Emre Bahar ◽

Manoneeta Chakraborty ◽

Ersin Göğüş

Keyword(s):

Neutron Stars ◽

Orbital Period ◽

Oscillation Frequency ◽

Orbital Motion ◽

X Rays ◽

X Ray ◽

Second Stage ◽

Corrected Data ◽

Low Mass ◽

X Ray Binaries

Abstract We present the results of our extensive binary orbital motion corrected pulsation search for 13 low-mass X-ray binaries. These selected sources exhibit burst oscillations in X-rays with frequencies ranging from 45 to 1 122 Hz and have a binary orbital period varying from 2.1 to 18.9 h. We first determined episodes that contain weak pulsations around the burst oscillation frequency by searching all archival Rossi X-ray Timing Explorer data of these sources. Then, we applied Doppler corrections to these pulsation episodes to discard the smearing effect of the binary orbital motion and searched for recovered pulsations at the second stage. Here we report 75 pulsation episodes that contain weak but coherent pulsations around the burst oscillation frequency. Furthermore, we report eight new episodes that show relatively strong pulsations in the binary orbital motion corrected data.

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3D spectroscopic analysis of helium-line white dwarfs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3684 ◽

2020 ◽

Author(s):

Elena Cukanovaite ◽

Pier-Emmanuel Tremblay ◽

Pierre Bergeron ◽

Bernd Freytag ◽

Hans-Günter Ludwig ◽

...

Keyword(s):

Effective Temperature ◽

White Dwarfs ◽

Energy Transport ◽

3D Models ◽

Spectroscopic Technique ◽

Surface Gravity ◽

Atmospheric Models ◽

Physical Treatment ◽

Spectroscopic Parameters ◽

1D Model

Abstract In this paper, we present corrections to the spectroscopic parameters of DB and DBA white dwarfs with −10.0 ≤ log (H/He) ≤−2.0, 7.5 ≤ log g ≤9.0 and 12 000 K ≲ Teff ≲ 34 000 K, based on 282 3D atmospheric models calculated with the CO5BOLD radiation-hydrodynamics code. These corrections arise due to a better physical treatment of convective energy transport in 3D models when compared to the previously available 1D model atmospheres. By applying the corrections to an existing SDSS sample of DB and DBA white dwarfs, we find significant corrections both for effective temperature and surface gravity. The 3D log g corrections are most significant for Teff ≲ 18, 000 K, reaching up to −0.20 dex at log g = 8.0. However, in this low effective temperature range, the surface gravity determined from the spectroscopic technique, can also be significantly affected by the treatment of the neutral van der Waals line broadening of helium and by non-ideal effects due to the perturbation of helium by neutral atoms. Thus, by removing uncertainties due to 1D convection, our work showcases the need for improved description of microphysics for DB and DBA model atmospheres. Overall, we find that our 3D spectroscopic parameters for the SDSS sample are generally in agreement with Gaia DR2 absolute fluxes within 1-3σ for individual white dwarfs. By comparing our results to DA white dwarfs, we determine that the precision and accuracy of DB/DBA atmospheric models are similar. For ease of user application of the correction functions, we provide an example Python code.

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VLT/SPHERE astrometric confirmation and orbital analysis of the brown dwarf companion HR 2562 B

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732476 ◽

2018 ◽

Vol 615 ◽

pp. A177 ◽

Cited By ~ 3

Author(s):

A.-L. Maire ◽

L. Rodet ◽

C. Lazzoni ◽

A. Boccaletti ◽

W. Brandner ◽

...

Keyword(s):

Orbital Motion ◽

Orbital Plane ◽

Real Data ◽

Far Infrared ◽

Brown Dwarf ◽

Orbital Parameters ◽

System A ◽

Low Mass ◽

Debris Disk ◽

Orbital Periods

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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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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Model Atmospheres for X-ray Bursting Neutron Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900160875 ◽

1987 ◽

Vol 125 ◽

pp. 251-251

Author(s):

Richard A. London ◽

Ronald E. Taam ◽

W. Michael Howard

Keyword(s):

Neutron Stars ◽

Electron Scattering ◽

Effective Temperature ◽

Radiation Spectrum ◽

Temperature Structure ◽

Atmospheric Models ◽

Low Frequencies ◽

X Ray ◽

Initial Rise ◽

Improper Use

Self consistent neutron star atmospheric models have been constructed which include the effects of Comptonization, free-free and bound-free absorption. It has been demonstrated that for parameters relevant to x-ray bursting neutron stars the atmosphere does not radiate like a blackbody during any phase of an x-ray burst. In particular, during the initial rise and final decline of the burst the temperature structure of the atmosphere is affected by backwarming associated with the high opacity due to free-free processes at low frequencies to an extent that the radiation spectrum is shifted to higher energies than a blackbody of the same effective temperature. On the other hand, near the peak of the burst, the opacity is more gray-like as the electron scattering opacity dominates; however, in this case thermalizaton of the radiation field occurs at such large optical depths (τ ∼ 5) that the spectral temperature is higher than the effective temperature. This result is found despite the importance of Comptonization in the thermalization process. Thus, the super Eddington fluxes implied by the spectral data alone are misleading and result from the improper use of the spectral temperature for the effective temperature. For neutron stars characterized by a soft equation of state and radiating near the Eddington effective temperature, fluxes obtained in this way could be overestimated by a factor of about 5.

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Dynamical masses for the nearest brown dwarf binary: ε Indi Ba,b

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310011452 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 761-761

Author(s):

C. V. Cardoso ◽

M. J. McCaughrean ◽

R. R. King ◽

L. M. Close ◽

R.-D. Scholz ◽

...

Keyword(s):

Main Sequence ◽

Brown Dwarfs ◽

Evolutionary Models ◽

Atmospheric Models ◽

Brown Dwarf ◽

Near Ir ◽

The Earth ◽

Benchmark System ◽

Model Independent ◽

Dynamical Masses

Binary brown dwarfs are important because their dynamical masses can be determined in a model-independent way. If a main sequence star is also involved, the age and metallicity for the system can be determined, making it possible to break the sub-stellar mass-age degeneracy. The most suitable benchmark system for intermediate age T dwarfs is ε Indi Ba,b, two T dwarfs (spectral types T1 and T6; McCaughrean et al. (2004)) orbiting a K4.5V star, ε Indi A, at a projected separation of 1460AU. At a distance of 3.6224pc (HIPPARCOS distance to ε Indi A; van Leeuwen (2007)), these are the closest brown dwarfs to the Earth, and thus both components are bright and the system is well-resolved. The system has been monitored astrometrically with NACO and FORS2 on the VLT since June 2004 and August 2005, respectively, in order to determine the system and individual masses independent of evolutionary models. We have obtained a preliminary system mass of 121±1MJup. We have also analysed optical/near-IR spectra (0.6-5.0μm at a resolution up to R~5000; King et al. (2009)) allowing us to determine bolometric luminosities, compare and calibrate evolutionary and atmospheric models of T dwarfs at an age of 4-8Gyr.

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What Do Young Brown Dwarfs Tell Us About Exoplanets?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315006225 ◽

2015 ◽

Vol 10 (S314) ◽

pp. 226-231

Author(s):

Katelyn N. Allers ◽

Michael C. Liu ◽

Trent J. Dupuy

Keyword(s):

Effective Temperature ◽

Brown Dwarfs ◽

Evolutionary Models ◽

Atmospheric Models ◽

Sky Surveys ◽

Fundamental Properties ◽

Dust Clouds ◽

Planetary Mass ◽

Substellar Objects ◽

Successes And Challenges

AbstractIn recent years, all-sky surveys have uncovered a new and interesting population of young (≈10–200 Myr), nearby substellar objects. Many of these objects have inferred masses and temperatures that overlap those of directly imaged exoplanets. These young brown dwarfs provide valuable analogs to young, dusty exoplanets in a context where detailed spectroscopic observations across a broad range of wavelengths and at high S/N are possible. How do the temperatures inferred by atmospheric models and evolutionary models compare? Can we determine the formation mechanism of a young planetary-mass object? How well do we understand the role that disequilibrium chemistry and dust clouds play in the atmospheres of these objects? We review the successes and challenges in determining the fundamental properties (mass, log(g), effective temperature) of young substellar objects, both brown dwarfs and gas-giant exoplanets.

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Proxima’s orbit around α Centauri

Astronomy and Astrophysics ◽

10.1051/0004-6361/201629930 ◽

2017 ◽

Vol 598 ◽

pp. L7 ◽

Cited By ~ 53

Author(s):

P. Kervella ◽

F. Thévenin ◽

C. Lovis

Keyword(s):

Radial Velocity ◽

High Precision ◽

Orbital Period ◽

Triple System ◽

Orbital Motion ◽

The Sun ◽

Proper Motions ◽

Velocity Measurements ◽

Degree Of Confidence ◽

High Degree

Proxima and α Centauri AB have almost identical distances and proper motions with respect to the Sun. Although the probability of such similar parameters is, in principle, very low, the question as to whether they actually form a single gravitationally bound triple system has been open since the discovery of Proxima one century ago. Owing to HARPS high-precision absolute radial velocity measurements and the recent revision of the parameters of the α Cen pair, we show that Proxima and α Cen are gravitationally bound with a high degree of confidence. The orbital period of Proxima is ≈ 550 000 yr. With an eccentricity of 0.50+0.08-0.09, Proxima comes within 4.3+1.1-0.9 kau of α Cen at periastron, and is currently close to apastron (13.0+0.3-0.1 kau). This orbital motion may have influenced the formation or evolution of the recently discovered planet orbiting Proxima, as well as circumbinary planet formation around α Cen.

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