New Dynamical Mass Estimates of the beta Pictoris Planetary System Through Gaussian Process Stellar Activity Modelling

2020 ◽  
Author(s):  
Thomas Vandal ◽  
Julien Rameau ◽  
René Doyon
Keyword(s):  
Gaussian Process ◽  
Statistical Treatment ◽  
Nearby Star ◽  
Dynamical Mass ◽  
Stellar Activity ◽  
Orbital Parameters ◽  
Independent Analysis ◽  
Model Complex ◽  
Beta Pictoris ◽  
First Time

<p>Nearly 15 years of radial velocity (RV) monitoring and direct imaging (DI) enabled the detection oftwo giant planets orbiting the young, nearby star β Pictoris. The δ Scuti pulsations of the star, overwhelming planetary signals, need however to be carefully suppress. In this talk, we propose a new and independent analysis of the system, making use of all available data, including photometric light curve from the ground and space, long term RV and DI monitoring. We demonstrate how all data can be consistently modelled in a Bayesian framework. We show how modern and physically motivated kernels for Gaussian Process can effectively model complex stellar activity. Using further carefull statistical treatment of the data to extend the monitoring, we detect both planets from RV data only for the first time. To characterize the system more accurately, we also perform a joint fit of <br />all available relative astrometry and RV data. We provide precise orbital parameters and discuss the whole system architecture. The inferred dynamical mass measurements for both planets are also compared to mass-luminosity evolutionary tracks. This work opens the path towards a precise characterization of young planetary systems combing photometry, spectroscopy, and astrometry.</p>

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

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.

Gaussian process based independent analysis for temporal source separation in fMRI

NeuroImage ◽  
2017 ◽  
Vol 152 ◽  
pp. 563-574 ◽  
Author(s):  
Ditte Høvenhoff Hald ◽  
Ricardo Henao ◽  
Ole Winther
Keyword(s):  
Gaussian Process ◽  
Source Separation ◽  
Independent Analysis

A Study of the Orbital and Intrinsic Variability of the Double-Lined Spectroscopic Binary β Centauri

2002 ◽  
Vol 185 ◽  
pp. 86-87
Author(s):  
M. Ausseloos ◽  
C. Aerts ◽  
K. Uytterhoeven
Keyword(s):  
High Resolution ◽  
Orbital Motion ◽  
High Signal ◽  
Mass Ratio ◽  
Eccentric Orbit ◽  
Intrinsic Variability ◽  
Signal To Noise ◽  
Orbital Parameters ◽  
Spectroscopic Binary ◽  
First Time

AbstractWe introduce our observational study of the orbital motion of β Cen. Using 463 high signal-to-noise, high-resolution spectra obtained over a timespan of 12 years it is shown that the radial velocity of β Cen varies with an orbital period of 357.0 days. We derive for the first time the orbital parameters of β Cen and find a very eccentric orbit (e = 0.81) and similar component masses with a mass ratio M1/M2 = 1.02. Both the primary and the secondary exhibit periodic line-profile variations.

Spectroscopic and photometric survey of the northern sky: Towards understanding of the Galactic chemical environment in the Solar vicinity

2018 ◽  
Vol 14 (S345) ◽  
pp. 248-249
Author(s):  
Š. Mikolaitis ◽  
G. Tautvaišienė ◽  
A. Drazdauskas ◽  
R. Minkevičiūtė ◽  
L. Klebonas ◽  
...  
Keyword(s):  
High Resolution ◽  
Theoretical Physics ◽  
Rotating Stars ◽  
Atmospheric Parameters ◽  
Dwarf Stars ◽  
Orbital Parameters ◽  
Spectral Class ◽  
Stellar Ages ◽  
Vilnius University ◽  
First Time

AbstractHigh-resolution spectra for all bright ( mag) and cooler than F5 spectral class dwarf stars were observed in two fields with radii of 20 degrees (centered at (2000) = 161.03º and (2000) = 86.60º and at (2000) = 265.08º and (2000) = 39.58º) towards the northern ecliptic pole. They coincide with two of the preliminary ESA PLATO fields which also will be targeted by the NASA TESS mission. We use high-resolution spectra obtained with the VUES spectrograph mounted on the 1.65 m telescope at the Moletai Astronomical Observatory of the Institute of Theoretical Physics and Astronomy, Vilnius University. In total we observed 405 stars. Spectroscopic atmospheric parameters and abundances of 23 neutral and ionised atomic species were determined for 261 slowly rotating stars (up to 15 kms-1). 73% of stars were analysed spectroscopically for the first time. We also derived stellar ages and orbital parameters to draw a chemical picture of the Solar vicinity.

scholarly journals Be it therefore resolved: cosmological simulations of dwarf galaxies with 30 solar mass resolution

2019 ◽  
Vol 490 (3) ◽  
pp. 4447-4463 ◽  
Author(s):  
Coral Wheeler ◽  
Philip F Hopkins ◽  
Andrew B Pace ◽  
Shea Garrison-Kimmel ◽  
Michael Boylan-Kolchin ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Stellar Rotation ◽  
Solar Mass ◽  
Dynamical Mass ◽  
Low Mass ◽  
Star Formation Histories ◽  
First Time

ABSTRACT We study a suite of extremely high-resolution cosmological Feedback in Realistic Environments simulations of dwarf galaxies ($M_{\rm halo} \lesssim 10^{10}\rm \, M_{\odot }$), run to z = 0 with $30\, \mathrm{M}_{\odot }$ resolution, sufficient (for the first time) to resolve the internal structure of individual supernovae remnants within the cooling radius. Every halo with $M_{\rm halo} \gtrsim 10^{8.6}\, \mathrm{M}_{\odot }$ is populated by a resolved stellar galaxy, suggesting very low-mass dwarfs may be ubiquitous in the field. Our ultra-faint dwarfs (UFDs; $M_{\ast }\lt 10^{5}\, \mathrm{M}_{\odot }$) have their star formation (SF) truncated early (z ≳ 2), likely by reionization, while classical dwarfs ($M_{\ast }\gt 10^{5}\, \mathrm{M}_{\odot }$) continue forming stars to z < 0.5. The systems have bursty star formation histories, forming most of their stars in periods of elevated SF strongly clustered in both space and time. This allows our dwarf with M*/Mhalo > 10−4 to form a dark matter core ${\gt}200\rm \, pc$, while lower mass UFDs exhibit cusps down to ${\lesssim}100\rm \, pc$, as expected from energetic arguments. Our dwarfs with $M_{\ast }\gt 10^{4}\, \mathrm{M}_{\odot }$ have half-mass radii (R1/2) in agreement with Local Group (LG) dwarfs (dynamical mass versus R1/2 and stellar rotation also resemble observations). The lowest mass UFDs are below surface brightness limits of current surveys but are potentially visible in next-generation surveys (e.g. LSST). The stellar metallicities are lower than in LG dwarfs; this may reflect pre-enrichment of the LG by the massive hosts or Pop-III stars. Consistency with lower resolution studies implies that our simulations are numerically robust (for a given physical model).

scholarly journals Constraining the properties of HD 206893 B

2019 ◽  
Vol 627 ◽  
pp. L9 ◽  
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.

scholarly journals The effect of stellar activity on the spectroscopic stellar parameters of the young solar twin HIP 36515

2019 ◽  
Vol 490 (1) ◽  
pp. L86-L90 ◽  
Author(s):  
Jhon Yana Galarza ◽  
Jorge Meléndez ◽  
Diego Lorenzo-Oliveira ◽  
Adriana Valio ◽  
Henrique Reggiani ◽  
...  
Keyword(s):  
Effective Temperature ◽  
Signal To Noise Ratio ◽  
Activity Cycle ◽  
Magnetic Activity ◽  
Resolving Power ◽  
Strongly Correlated ◽  
Chemical Abundances ◽  
Stellar Activity ◽  
Time Variations ◽  
First Time

ABSTRACT Spectroscopic equilibrium allows us to obtain precise stellar parameters in Sun-like stars. It relies on the assumption of the iron excitation and ionization equilibrium. However, several works suggest that magnetic activity may affect chemical abundances of young active stars, calling into question the validity of this widely used method. We have tested, for the first time, variations in stellar parameters and chemical abundances for the young solar twin HIP 36515 (∼0.4 Gyr), along its activity cycle. This star has stellar parameters very well established in the literature and we estimated its activity cycle in ∼6 yr. Using HARPS spectra with high resolving power (115 000) and signal-to-noise ratio (∼270), the stellar parameters of six different epochs in the cycle were estimated. We found that the stellar activity is strongly correlated with the effective temperature, metallicity, and microturbulence velocity. The possibility of changes in the Li i 6707.8 Å line due to flares and star-spots was also investigated. Although the core of the line profile shows some variations with the stellar cycle, it is compensated by changes in the effective temperature, resulting in a non-variation of the Li abundance.

PROBLEMS OF POLISH ROMANTICISM IN THE PERCEPTION OF LITERARY CRITIC MIHAL GRABOVSKYJ (according to the materials of correspondence)

2019 ◽  
pp. 312-320
Author(s):  
Iryna Rudenko
Keyword(s):  
German Romanticism ◽  
Literary Critic ◽  
Romantic Literature ◽  
Integrated Research ◽  
Independent Analysis ◽  
The World ◽  
Conceptual Reasoning ◽  
Communicative Structure ◽  
First Time ◽  
Second Period

Problems of polish romanticism in the perception of literary critic Mihal Grabovskyj (according to the materials of correspondence). This article is devoted to integrated research into correspondence of polish literary man M. Grabovskyj, analyzed literary and philosophic views of master in a diachronic aspect, his aesthetic priorities, described the evolution of general vital references of theoretician, and outlined the division into periods of creation and philosophic views of figure. A lot of attention is given to elucidation letters’ genres of M. Grabovskyj and its style. For the first time it is the attempt of new valuation of his achievements and intentions, consideration and description epistolary heritage of M. Grabovskyj, which include theoretical-literary dialogues with the famous polish artists of XIX c. In his enormous array there are the conceptual reasoning andestimations of both work of separate writers and of that timeliterary process. The looks of writer were constantly evolved, that does any division into periods of correspondence conditional enough. However there sre distinguished two periods: European-”loyal” (1823 -1843) and later “tendentious” clerical-panslavics’ (1843 – 1863). The range of letters’ problems of of the first period marks adaptation of ideas of European (German) romanticism to national traditions, grouping and consolidation by the leaders of Polish romantic literature. These ideas contain optimistic character and sent to deepening the national perception of the world. The second period is characterized by correlations of the own theory of romanticism, ambiguousness of communicative structure. Grabovskyj comprehended the nomenclature of texts of romantic canon. The letters of М. Grabovskyj, that became the article of independent analysis first, substantially specify presentation in the relation to his literary- aesthetic program realized in the articles. In that correspondences, especially in those that are addressed to the closest friends he was frank and formulated the positions laconically and clearly. In the letters of artist it is legitimate to see continuation of critical articles.

scholarly journals KMOS Clusters and VIRIAL GTO Surveys

2014 ◽  
Vol 10 (S309) ◽  
pp. 293-294
Author(s):  
D. Wilman ◽  
R. Bender ◽  
R. L. Davies ◽  
J. T. Mendel ◽  
J. Chan ◽  
...  
Keyword(s):  
Near Infrared ◽  
Early Type ◽  
Dynamical Mass ◽  
Fundamental Plane ◽  
Cluster Galaxies ◽  
Medium Resolution ◽  
Stellar Velocity ◽  
Time Observation ◽  
Field Unit ◽  
First Time

AbstractWe present the KMOS (K-band Multi-Object Spectrograph) Cluster and VIRIAL (VLT IRIFU Absorption Line) Guaranteed Time Observation (GTO) programs. KMOS provides 24 arms each feeding an integral field unit (14×14 spaxels of 0.2″ pixels) for IZ, YJ, H and K band near infrared (NIR) medium resolution spectroscopy (R ∼ 3500). Targets are selected from a 7.2′ diameter patrol field. Ultra-deep spectroscopy of ∼ 80 early-type cluster galaxies (∼ 20hr on source) and ∼ 200 (∼ 10hr on source) early-type field galaxies at 1 < z < 2 will dramatically improve the situation at z > 1 for which measurements of stellar velocity dispersions and absorption indices are limited to a few, often relatively young passively evolving galaxies (e.g. Bezanson 2013). In ESO Periods P92 and P93, 15 nights worth of data has been collected for KMOS-Clusters and 6 nights for VIRIAL: this will be supplemented with more data in upcoming semesters. All galaxies have multiband HST imaging including existing or upcoming WFC3 IR imaging, providing stellar mass maps and sizes. Combined with our dispersion measurements, this will allow us to examine the fundamental plane and the dynamical mass of a large sample of z > 1 galaxies for the first time, for both cluster and field galaxies.

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