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 Magnetic field, differential rotation and activity of the hot-Jupiter-hosting star HD 179949

2012 ◽  
Vol 423 (2) ◽  
pp. 1006-1017 ◽  
Author(s):  
R. Fares ◽  
J.-F. Donati ◽  
C. Moutou ◽  
M. Jardine ◽  
A. C. Cameron ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Differential Rotation ◽  
Hot Jupiter

Magnetic field and prominences of the young, solar-like, ultra-rapid rotator AP 149

2019 ◽  
Vol 15 (S354) ◽  
pp. 181-184
Author(s):  
Tianqi Cang ◽  
Pascal Petit ◽  
Colin Folsom ◽  
Jean-Francois Donati
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Open Cluster ◽  
Magnetic Activity ◽  
Doppler Imaging ◽  
Surface Distribution ◽  
Data Set ◽  
Young Open Cluster ◽  
Alpha Persei ◽  
Rapid Rotator

AbstractYoung solar analogs reaching the main sequence experience very strong magnetic activity, directly linked to their angular momentum loss through wind and mass ejections. We investigate here the surface and chromospheric activity of the ultra-rapid rotator AP 149 in the young open cluster alpha Persei. With a time-series of spectropolarimetric observations gathered over two nights with ESPaDOnS, we are able to reconstruct the surface distribution of brightness and magnetic field using the Zeeman-Doppler-Imaging (ZDI) method. Using the same data set, we also map the spatial distribution of prominences through tomography of H-alpha emission. We find that AP 149 shows a strong cool spot and magnetic field closed to the polar cap. This star is the first example of a solar-type star to have its magnetic field and prominences mapped together, which will help to explore the respective role of wind and prominences in the angular momentum evolution of the most active stars.

scholarly journals Magnetic geometry and surface differential rotation of the bright Am star Alhena A

2020 ◽  
Vol 492 (4) ◽  
pp. 5794-5810 ◽  
Author(s):  
Aurore Blazère ◽  
Pascal Petit ◽  
Coralie Neiner ◽  
Colin Folsom ◽  
Oleg Kochukhov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Differential Rotation ◽  
Field Measurements ◽  
Doppler Imaging ◽  
High Signal ◽  
Surface Magnetic Field ◽  
Magnetic Structures ◽  
Low Latitudes

ABSTRACT Alhena A (γ Gem A) is a bright Am star, with the strongest disc-integrated magnetic field strength reported so far for an Am star. Its spectrum exhibits standard circularly polarized Zeeman signatures, contrary to all previously studied Am stars that display abnormal signatures dominated by a single-signed lobe. We present here the result of follow-up observations of Alhena, using very high signal-to-noise spectropolarimetric data obtained over 25 observing nights with NARVAL at Télescope Bernard Lyot, in the frame of the BRITE (BRIght Target Explorer) spectropolarimetric survey. We confirm that Alhena A is magnetic and we determine its surface magnetic properties using different methods. Inclined dipole models are used to reproduce the longitudinal field measurements, as well as the Stokes V line profiles themselves. In both cases, the model is consistent with a polar field strength of ∼30 G. This is confirmed by a Zeeman-Doppler Imaging (ZDI) model, which also unveils smaller scale magnetic structures. A rotational period of 8.975 d was identified using intensity line profile variations. The ZDI inversion suggests that the surface magnetic field is sheared by differential rotation, with a difference in rotation rate between high and low latitudes at about 15 per cent of the solar value. This result challenges theories of the development of surface differential rotation in intermediate mass main-sequence stars.

scholarly journals Magnetic field at the inner disk edge

2007 ◽  
Vol 3 (S243) ◽  
pp. 51-62 ◽  
Author(s):  
Moira Jardine ◽  
Scott G. Gregory ◽  
Jean-François Donati
Keyword(s):  
Magnetic Field ◽  
Doppler Imaging ◽  
Evolutionary Stage ◽  
X Rays ◽  
X Ray ◽  
Stellar Radius ◽  
T Tauri ◽  
The Impact ◽  
The Magnetic Field ◽  
Present Understanding

AbstractOur present understanding of the coronal structure of T Tauri stars is fragmentary and observations in different wavelength regimes often appear to give contradictory results. X-ray data suggest the presence of magnetic loops on a variety of scales, from compact loops of size less than a stellar radius, up to very large loops of up to 10 stellar radii which may connect to the disk. While some stars show a clear rotational modulation in X-rays, implying distinct bright and dark regions, many do not. This picture is complicated by the accretion process itself, which also contributes to the X-ray emission. The location of the inner edge of the accretion disk and the nature of the magnetic field there are still hotly-contested issues. Accretion indicators often suggest the presence of discrete accretion funnels. This has implications for the structure of the corona, as does the presence of an outflowing wind. All of these factors are linked to the structure of the magnetic field, which we are now beginning to unravel through Zeeman-Doppler imaging. In this review I will describe the present state of our understanding of the magnetic structure of T Tauri coronae and the impact this has during such an early evolutionary stage.

scholarly journals Surface differential rotation of IL Hya from time-series Doppler images

2013 ◽  
Vol 9 (S302) ◽  
pp. 379-380 ◽  
Author(s):  
Zsolt Kővári ◽  
Levente Kriskovics ◽  
Katalin Oláh ◽  
Krisztián Vida ◽  
János Bartus ◽  
...  
Keyword(s):  
Time Series ◽  
Differential Rotation ◽  
Cross Correlation ◽  
Meridional Circulation ◽  
Imaging Study ◽  
Doppler Imaging ◽  
Surface Pattern ◽  
Cross Correlation Analysis ◽  
Solar Type

AbstractWe present a time-series Doppler imaging study of the K-subgiant component in the RS CVn-type binary system IL Hya (Porb=12.905 d). From re-processing the unique long-term spectroscopic dataset of 70 days taken in 1996/97, we perform a thorough cross-correlation analysis to derive surface differential rotation. As a result we get solar-type differential rotation with a shear value α of 0.05, in agreement with preliminary suggestions from previous attempts. A possible surface pattern of meridional circulation is also detected.

scholarly journals Magnetic field and chromospheric activity evolution of HD 75332: a rapid magnetic cycle in an F star without a hot Jupiter

2020 ◽  
Author(s):  
E L Brown ◽  
S C Marsden ◽  
M W Mengel ◽  
S V Jeffers ◽  
I Millburn ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Magnetic Activity ◽  
Doppler Imaging ◽  
Shallow Convection ◽  
Magnetic Cycle ◽  
Field Polarity ◽  
Chromospheric Activity ◽  
Magnetic Cycles ◽  
Hot Jupiter

Abstract Studying cool star magnetic activity gives an important insight into the stellar dynamo and its relationship with stellar properties, as well as allowing us to place the Sun’s magnetism in the context of other stars. Only 61 Cyg A (K5V) and τ Boo (F8V) are currently known to have magnetic cycles like the Sun’s, where the large-scale magnetic field polarity reverses in phase with the star’s chromospheric activity cycles. τ Boo has a rapid ∼240 d magnetic cycle, and it is not yet clear whether this is related to the star’s thin convection zone or if the dynamo is accelerated by interactions between τ Boo and its hot Jupiter. To shed light on this, we studied the magnetic activity of HD 75332 (F7V) which has similar physical properties to τ Boo and does not appear to host a hot Jupiter. We characterized its long term chromospheric activity variability over 53 yrs and used Zeeman Doppler Imaging to reconstruct the large-scale surface magnetic field for 12 epochs between 2007 and 2019. Although we observe only one reversal of the large-scale magnetic dipole, our results suggest that HD 75332 has a rapid ∼1.06 yr solar-like magnetic cycle where the magnetic field evolves in phase with its chromospheric activity. If a solar-like cycle is present, reversals of the large-scale radial field polarity are expected to occur at around activity cycle maxima. This would be similar to the rapid magnetic cycle observed for τ Boo, suggesting that rapid magnetic cycles may be intrinsic to late-F stars and related to their shallow convection zones.

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.

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).

The Kinematics of Spokes

1984 ◽  
Vol 75 ◽  
pp. 219-222 ◽  
Author(s):  
C.C. Porco ◽  
G.E. Danielson
Keyword(s):  
Magnetic Field ◽  
Near Field ◽  
Imaging Data ◽  
Data Set ◽  
Electromagnetic Processes ◽  
Long Term Behavior ◽  
The Magnetic Field

The results of a study of the long term behavior of spokes are presented. Previous work on a Voyager 1 imaging data set spanning 12 Saturn rotations led to the discovery of a variability in the appearance of spokes on the morning half of the rings, with a period of 621 ± 22 minutes (Porco and Danielson,A. J., May, 1982; hereafter PD). It was found that maximum spoke activity is associated with the same sector of the magnetic field which gives rise to the emission of SKR (Saturn Kilometric Radiation). In addition to suggesting that the spokes have their origin in electromagnetic processes related to Saturn's field, these results have provided another indirect piece of evidence for a possible inhomogeneity in the near field of Saturn.

scholarly journals Revisiting profile instability of PSR J1022+1001

2020 ◽  
Vol 500 (1) ◽  
pp. 1178-1187
Author(s):  
Prajwal V Padmanabh ◽  
Ewan D Barr ◽  
David J Champion ◽  
Ramesh Karuppusamy ◽  
Michael Kramer ◽  
...  
Keyword(s):  
Pulse Shape ◽  
Evaluation Method ◽  
Signal Propagation ◽  
Intrinsic Variability ◽  
Data Set ◽  
Pulsar Timing ◽  
Propagation Effects ◽  
Observed Behaviour ◽  
The Stability

ABSTRACT Millisecond pulsars in timing arrays can act as probes for gravitational wave detection and improving the Solar system ephemerides among several other applications. However, the stability of the integrated pulse profiles can limit the precision of the ephemeris parameters and in turn the applications derived from it. It is thus crucial for the pulsars in the array to have stable integrated pulse profiles. Here we present evidence for long-term profile instability in PSR J1022+1001 which is currently included in the European and Parkes pulsar timing arrays. We apply a new evaluation method to an expanded data set ranging from the Effelsberg Pulsar Observing System backend used in the 1990s to that of data from the current PSRIX backend at the Effelsberg Radio Telescope. We show that this intrinsic variability in the pulse shape persists over time-scales of years. We investigate if systematic instrumental effects like polarization calibration or signal propagation effects in the interstellar medium causes the observed profile instability. We find that the total variation cannot be fully accounted for by instrumental and propagation effects. This suggests additional intrinsic effects as the origin for the variation. We finally discuss several factors that could lead to the observed behaviour and comment on the consequent implications.

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