Hunting for hot Jupiters around young stars

2016 ◽  
Vol 12 (S328) ◽  
pp. 282-289 ◽  
Author(s):  
Louise Yu ◽  
Keyword(s):  
Planetary System ◽  
Gaussian Process Regression ◽  
Young Stars ◽  
Doppler Imaging ◽  
Conference Paper ◽  
Hot Jupiters ◽  
T Tauri ◽  
Order Of Magnitude ◽  
Host Stars ◽  
Observation Programme

AbstractThis conference paper reports the recent discoveries of two hot Jupiters (hJs) around weak-line T Tauri stars (wTTS) V830 Tau and TAP 26, through the analysis of spectropolarimetric data gathered within the Magnetic Topologies of Young Stars and the Survival of massive close-in Exoplanets (MaTYSSE) observation programme. HJs are thought to form in the outskirts of protoplanetary discs, then migrate inwards close to their host stars as a result of either planet-disc type II migration or planet-planet scattering. Looking for hJs around young forming stars provides key information on the nature and time scale of such migration processes, as well as how their migration impacts the subsequent architecture of their planetary system. Young stars are however extremely active, to the point that their radial velocity (RV) jitter is around an order of magnitude larger than the potential signatures of close-in gas giants, making them difficult to detect with velocimetry. Three techniques to filter out this activity jitter are presented here, two using Zeeman Doppler Imaging (ZDI) and one using Gaussian Process Regression (GPR).

scholarly journals T Tauri stars: magnetic fields and planets

2021 ◽  
Vol 2 (1) ◽  
pp. 9-20
Author(s):  
Konstantin Grankin
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Magnetic Coupling ◽  
Short Review ◽  
T Tauri Stars ◽  
Young Stars ◽  
Doppler Imaging ◽  
Hot Jupiters ◽  
T Tauri

In this short review we present the results of a study of the large-scale magnetic topologies of T Tauri stars (TTS). A small spectropolarimetric survey of 8 young stars was carried out within two international projects MaPP (Magnetic Protostars and Planets) and MaTYSSE (Magnetic Topologies of Young Stars and the Survival of massive close-in Exoplanets) between 2009 and 2016. For each of our targets we reconstructed the brightness map and the magnetic field topology using Zeeman–Doppler imaging (ZDI). This review contains a brief description of spectropolarimetricdata, the ZDI method, one example of the reconstruction of brightness and magnetic maps, and the properties of magnetic fields of 8 TTS. Our results suggest that AA Tau and LkCa 15 interact with their disks in the propeller mode when their rotation is actively slowed by the star/disk magnetic coupling. We find that magnetic fields of some TTS are variable on a time scale of a few years and are thus intrinsically nonstationary. We report on the detection of a giant exoplanet around V830 Tau and TAP 26. These two new detections suggest that the type II disk migration is efficient at generating newborn hot Jupiters (hJs) around young TTS. The result of our survey is compared to the global picture of magnetic field properties of twenty TTS in the Hertzsprung–Russell diagram. The comparison shows that WTTS exhibit a wider range of field topologies as compared to CTTS, and that magnetic fields of all TTS (CTTS and WTTS as a whole) are mostly poloidal and axisymmetric when they are mostly convective and cooler than 4300 K. This needs to be confirmed with a larger sample of stars.

scholarly journals Magnetic field, activity, and companions of V410 Tau

2019 ◽  
Vol 489 (4) ◽  
pp. 5556-5572 ◽  
Author(s):  
L Yu ◽  
J-F Donati ◽  
K Grankin ◽  
A Collier Cameron ◽  
C Moutou ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Differential Rotation ◽  
Gaussian Process Regression ◽  
Doppler Imaging ◽  
Intrinsic Variability ◽  
Data Set ◽  
T Tauri ◽  
Field Activity ◽  
Hot Jupiter

ABSTRACT We report the analysis, conducted as part of the MaTYSSE programme, of a spectropolarimetric monitoring of the ∼0.8 Myr, ∼1.4 M⊙ disc-less weak-line T Tauri star V410 Tau with the ESPaDOnS instrument at the Canada–France–Hawaii Telescope and NARVAL at the Télescope Bernard Lyot, between 2008 and 2016. With Zeeman-Doppler Imaging, we reconstruct the surface brightness and magnetic field of V410 Tau, and show that the star is heavily spotted and possesses a ∼550 G relatively toroidal magnetic field. We find that V410 Tau features a weak level of surface differential rotation between the equator and pole ∼5 times weaker than the solar differential rotation. The spectropolarimetric data exhibit intrinsic variability, beyond differential rotation, which points towards a dynamo-generated field rather than a fossil field. Long-term variations in the photometric data suggest that spots appear at increasing latitudes over the span of our data set, implying that, if V410 Tau has a magnetic cycle, it would have a period of more than 8 yr. Having derived raw radial velocities (RVs) from our spectra, we filter out the stellar activity jitter, modelled either from our Doppler maps or using Gaussian process regression. Thus filtered, our RVs exclude the presence of a hot Jupiter-mass companion below ∼0.1 au, which is suggestive that hot Jupiter formation may be inhibited by the early depletion of the circumstellar disc, which for V410 Tau may have been caused by the close (few tens of au) M dwarf stellar companion.

scholarly journals Cool Jupiters greatly outnumber their toasty siblings: occurrence rates from the Anglo-Australian Planet Search

2019 ◽  
Vol 492 (1) ◽  
pp. 377-383 ◽  
Author(s):  
Robert A Wittenmyer ◽  
Songhu Wang ◽  
Jonathan Horner ◽  
R P Butler ◽  
C G Tinney ◽  
...  
Keyword(s):  
Solar System ◽  
Radial Velocity ◽  
Planetary System ◽  
Planetary Systems ◽  
Giant Planets ◽  
Occurrence Rate ◽  
Hot Jupiters ◽  
The Past ◽  
Order Of Magnitude

ABSTRACT Our understanding of planetary systems different to our own has grown dramatically in the past 30 yr. However, our efforts to ascertain the degree to which the Solar system is abnormal or unique have been hindered by the observational biases inherent to the methods that have yielded the greatest exoplanet hauls. On the basis of such surveys, one might consider our planetary system highly unusual – but the reality is that we are only now beginning to uncover the true picture. In this work, we use the full 18-yr archive of data from the Anglo-Australian Planet Search to examine the abundance of ‘cool Jupiters’ – analogues to the Solar system’s giant planets, Jupiter and Saturn. We find that such planets are intrinsically far more common through the cosmos than their siblings, the hot Jupiters. We find that the occurrence rate of such ‘cool Jupiters’ is $6.73^{+2.09}_{-1.13}$ per cent, almost an order of magnitude higher than the occurrence of hot Jupiters (at $0.84^{+0.70}_{-0.20}$ per cent). We also find that the occurrence rate of giant planets is essentially constant beyond orbital distances of ∼1 au. Our results reinforce the importance of legacy radial velocity surveys for the understanding of the Solar system’s place in the cosmos.

scholarly journals The Secret of the Titius-Bode Law: A New Theory on How Our Planetary System Came Into Existence

2020 ◽  
Vol 11 (4) ◽  
pp. 58
Author(s):  
Hans Merkl
Keyword(s):  
Physical Mechanism ◽  
Planetary System ◽  
Young Stars ◽  
Asteroid Belt ◽  
Slow Rotation ◽  
The Sun ◽  
The Moon ◽  
High Iron Content ◽  
T Tauri ◽  
Dust Disk

Our planetary system still has several unsolved riddles. One of them is the Titius-Bode law. With the aid of this law, it is easy to find the distances of planets from the sun. For many astronomers, this is coincidence. They argue that there is no known physical mechanism that generates a particular sequence of planets’ distances. However, if one investigates the structure of the law, it quickly becomes clear that the Titius-Bode law is directly connected with the formation of planets. Our planets did not come into existence through so-called accretion. At the beginning of its existence, the sun was presumably a T-Tauri star. These are young stars in the process of their formation. They pulsate irregularly, thereby accelerating clouds of plasma in the surrounding dust disk. Each of these eruptions thus generated a planet. This of course goes much more quickly than if they had to be formed from the dust of planetary disks. This new theory not only describes how the planets and the distances of the planets came into existence. It also gives a new description of how the moon came into existence, the cause for large moon craters, the slow rotation of Venus, the formation of the asteroid belt, the high iron content of the planet Mercury, and the sun’s loss of rotational impulse, among other things.

scholarly journals How Complete Are Surveys for Nearby Transiting Hot Jupiters?

2021 ◽  
Vol 162 (6) ◽  
pp. 240
Author(s):  
Samuel W. Yee ◽  
Joshua N. Winn ◽  
Joel D. Hartman
Keyword(s):  
Planet Formation ◽  
Galactic Plane ◽  
Selection Function ◽  
Limited Sample ◽  
Hot Jupiters ◽  
Kepler Mission ◽  
Order Of Magnitude ◽  
Host Stars ◽  
Hot Jupiter

Abstract Hot Jupiters are a rare and interesting outcome of planet formation. Although more than 500 hot Jupiters (HJs) are known, most of them were discovered by a heterogeneous collection of surveys with selection biases that are difficult to quantify. Currently, our best knowledge of HJ demographics around FGK stars comes from the sample of ≈40 objects detected by the Kepler mission, which have a well-quantified selection function. Using the Kepler results, we simulate the characteristics of the population of nearby transiting HJs. A comparison between the known sample of nearby HJs and simulated magnitude-limited samples leads to four conclusions. (1) The known sample of HJs appears to be ≈75% complete for stars brighter than Gaia G ≤ 10.5, falling to ≲50% for G ≤ 12. (2) There are probably a few undiscovered HJs with host stars brighter than G ≈ 10 located within 10° of the Galactic plane. (3) The period and radius distributions of HJs may differ for F-type hosts (which dominate the nearby sample) and G-type hosts (which dominate the Kepler sample). (4) To obtain a magnitude-limited sample of HJs that is larger than the Kepler sample by an order of magnitude, the limiting magnitude should be approximately G ≈ 12.5. This magnitude limit is within the range for which NASA’s Transiting Exoplanet Survey Satellite can easily detect HJs, presenting the opportunity to greatly expand our knowledge of hot-Jupiter demographics.

scholarly journals The Observational Evidence for Accretion

1997 ◽  
Vol 182 ◽  
pp. 391-405 ◽  
Author(s):  
Lee Hartmann
Keyword(s):  
Large Range ◽  
Observational Evidence ◽  
Young Stars ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
T Tauri ◽  
Accretion Rates ◽  
Low Mass ◽  
Stellar Magnetospheres ◽  
Mass Ejection

Outflows from low-mass young stellar objects are thought to draw upon the energy released by accretion onto T Tauri stars. I briefly summarize the evidence for this accretion and outline present estimates of mass accretion rates. Young stars show a very large range of accretion rates, and this has important implications for both mass ejection and for the structure of stellar magnetospheres which may truncate T Tauri disks.

Can complex T Tauri star light curves be modelled with star-spots?

2020 ◽  
Vol 500 (1) ◽  
pp. 1366-1379
Author(s):  
C Koen
Keyword(s):  
Ridge Regression ◽  
Young Stars ◽  
Light Curves ◽  
Stellar Surface ◽  
Tauri Star ◽  
T Tauri ◽  
Almost All

ABSTRACT ‘Transiting Exoplanet Survey Satellite’ photometry of 10 young stars with very complex periodic light curves is considered. Previous findings that these cannot be due to dark surface spots are re-evaluated by allowing arbitrarily shaped areas on the stellar surface to have sub-photospheric fluxes. This is done by approximating flux integrals by sums over surface elements. The unknown ratios of spot to photospheric fluxes are determined by lasso or ridge regression procedures. It is found that almost all light curves can be modelled very accurately in this way. The usual, if rarely stated, caveat applies – star-spot models presented in the paper are not unique.

scholarly journals Variability of young stars: Determination of rotational periods of weak-line T Tauri stars in the Cepheus-Cassiopeia star-forming region

2009 ◽  
Vol 330 (5) ◽  
pp. 482-492
Author(s):  
A. Koeltzsch ◽  
M. Mugrauer ◽  
St. Raetz ◽  
T.O.B. Schmidt ◽  
T. Roell ◽  
...  
Keyword(s):  
T Tauri Stars ◽  
Young Stars ◽  
Weak Line ◽  
Star Forming ◽  
T Tauri

scholarly journals What do weak magnetic fields mean for magnetospheric accretion in Herbig AeBe star+disk systems?

2013 ◽  
Vol 9 (S302) ◽  
pp. 80-83
Author(s):  
A. N. Aarnio ◽  
J. D. Monnier ◽  
T. J. Harries ◽  
D. M. Acreman
Keyword(s):  
Main Sequence ◽  
Planetary System ◽  
Spectral Lines ◽  
Data Set ◽  
T Tauri ◽  
Weak Magnetic Fields ◽  
Fundamental Process ◽  
Dipolar Fields ◽  
Solar Analogs ◽  
Magnetospheric Accretion

AbstractIn the presently favored picture of star formation, mass is transferred from disk to star via magnetospheric accretion and out of the system via magnetically driven outflows. This magnetically mediated mass flux is a fundamental process upon which the evolution of the star, disk, and forming planetary system depends. Our current understanding of these processes is heavily rooted in young solar analogs, T Tauri Stars (TTS). We have come to understand recently, however, that the higher mass pre-main sequence (PMS) Herbig AeBe (HAeBe) stars have dramatically weaker dipolar fields than their lower mass counterparts. We present our current observational and theoretical efforts to characterize magnetospherically mediated mass transfer within HAeBe star+disk systems. We have gathered a rich spectroscopic and interferometric data set for several dozen HAeBe stars in order to measure accretion and mass loss rates, assess wind and magnetospheric accretion properties, and determine how spectral lines and interferometric visibilities are diagnostic of these processes. For some targets, we have observed spectral line variability and will discuss ongoing time-series spectroscopic efforts.

scholarly journals From thermal dissociation to condensation in the atmospheres of ultra hot Jupiters: WASP-121b in context

2018 ◽  
Vol 617 ◽  
pp. A110 ◽  
Author(s):  
Vivien Parmentier ◽  
Mike R. Line ◽  
Jacob L. Bean ◽  
Megan Mansfield ◽  
Laura Kreidberg ◽  
...  
Keyword(s):  
Thermal Dissociation ◽  
Spectral Features ◽  
Chemical Abundances ◽  
Hot Jupiters ◽  
New Class ◽  
Thermal Structures ◽  
Water Band ◽  
Order Of Magnitude ◽  
Molecular Bond ◽  
Analytical Quantification

Context. A new class of exoplanets has emerged: the ultra hot Jupiters, the hottest close-in gas giants. The majority of them have weaker-than-expected spectral features in the 1.1−1.7 μm bandpass probed by HST/WFC3 but stronger spectral features at longer wavelengths probed by Spitzer. This led previous authors to puzzling conclusions about the thermal structures and chemical abundances of these planets. Aims. We investigate how thermal dissociation, ionization, H− opacity, and clouds shape the thermal structures and spectral properties of ultra hot Jupiters. Methods. We use the SPARC/MITgcm to model the atmospheres of four ultra hot Jupiters and discuss more thoroughly the case of WASP-121b. We expand our findings to the whole population of ultra hot Jupiters through analytical quantification of the thermal dissociation and its influence on the strength of spectral features. Results. We predict that most molecules are thermally dissociated and alkalies are ionized in the dayside photospheres of ultra hot Jupiters. This includes H2O, TiO, VO, and H2 but not CO, which has a stronger molecular bond. The vertical molecular gradient created by the dissociation significantly weakens the spectral features from H2O while the 4.5 μm CO feature remains unchanged. The water band in the HST/WFC3 bandpass is further weakened by the continuous opacity of the H− ions. Molecules are expected to recombine before reaching the limb, leading to order of magnitude variations of the chemical composition and cloud coverage between the limb and the dayside. Conclusions. Molecular dissociation provides a qualitative understanding of the lack of strong spectral features of water in the 1−2 μm bandpass observed in most ultra hot Jupiters. Quantitatively, our model does not provide a satisfactory match to the WASP-121b emission spectrum. Together with WASP-33b and Kepler-33Ab, they seem the outliers among the population of ultra hot Jupiters, in need of a more thorough understanding.

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