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11. Rotational frequency splitting in Sun-like stars
ID:
ivo://CDS.VizieR/J/A+A/568/L12
Title:
Rotational frequency splitting in Sun-like stars
Short Name:
J/A+A/568/L12
Date:
21 Oct 2021
Publisher:
CDS
Description:
Asteroseismology offers the prospect of constraining differential rotation in Sun-like stars. Here we have identified six high signal-to-noise main-sequence Sun-like stars in the Kepler field, which all have visible signs of rotational splitting of their p-mode frequencies. For each star, we extract the rotational frequency splitting and inclination angle from separate mode sets (adjacent modes with l=2, 0, and 1) spanning the p-mode envelope. We use a Markov chain Monte Carlo method to obtain the best fit and errors associated with each parameter. We are able to make independent measurements of rotational splittings of ~8 radial orders for each star. For all six stars, the measured splittings are consistent with uniform rotation, allowing us to exclude large radial differential rotation. This work opens the possibility of constraining internal rotation of Sun-like stars.
12. Starspot rotation rates vs. activity cycle phase
ID:
ivo://CDS.VizieR/J/A+A/622/A85
Title:
Starspot rotation rates vs. activity cycle phase
Short Name:
J/A+A/622/A85
Date:
21 Oct 2021
Publisher:
CDS
Description:
During the solar magnetic activity cycle the emergence latitudes of sunspots change, leading to the well-known butterfly diagram. This phenomenon is poorly understood for other stars since starspot latitudes are generally unknown. The related changes in starspot rotation rates caused by latitudinal differential rotation can however be measured. Using the set of 3093 Kepler stars with activity cycles identified by Reinhold et al. (2017A&A...603A..52R, Cat. J/A+A/603/A52), we aim to study the temporal change in starspot rotation rates over magnetic activity cycles, and how this relates to the activity level, the mean rotation rate of the star, and its effective temperature. We measured the photometric variability as a proxy for the magnetic activity and the spot rotation rate in each quarter over the duration of the Kepler mission. We phase-fold these measurements with the cycle period. To reduce random errors we perform averages over stars with comparable mean rotation rates and effective temperature at fixed activity-cycle phases. We detect a clear correlation between the variation of activity level and the variation of the starspot rotation rate. The sign and amplitude of this correlation depends on the mean stellar rotation and -- to a lesser extent -- on the effective temperature. For slowly rotating stars (rotation periods between 15-28 days) the starspot rotation rates are clearly anti-correlated with the level of activity during the activity cycles. A transition is observed around rotation periods of 10-15 days, where stars with effective temperature above 4200K instead show positive correlation. Our measurements can be interpreted in terms of a stellar "butterfly diagram", but these appear different from the Sun's since the starspot rotation rates are either in phase or anti-phase with the activity level. Alternatively, the activity cycle periods observed by Kepler are short (around 2.5 years) and may therefore be secondary cycles, perhaps analogous to the solar quasi-biennial oscillations.
13. TESS light curve of beta Pictoris
ID:
ivo://CDS.VizieR/J/A+A/625/L13
Title:
TESS light curve of beta Pictoris
Short Name:
J/A+A/625/L13
Date:
21 Oct 2021
Publisher:
CDS
Description:
We search for signs of falling evaporating bodies (FEBs, also known as exocomets) in photometric time series obtained for {beta} Pictoris after fitting and removing its {delta} Scuti-type pulsation frequencies. Using photometric data obtained by the TESS satellite we determined the pulsational properties of the exoplanet host star {beta} Pictoris through frequency analysis. We then pre-whitened the 54 identified {delta} Scuti p-modes and investigated the residual photometric time series for the presence of FEBs. We identify three distinct dipping events in the light curve of {beta} Pictoris over a 105-day period. These dips have depths from 0.5 to 2-millimagnitudes and durations of up to 2-days for the largest dip. These dips are asymmetric in nature and are consistent with a model of an evaporating comet with an extended tail crossing the disc of the star. We present the first broadband detections of exocomets crossing the disc of {beta} Pictoris, complementing the predictions made 20 years earlier by Lecavelier Des Etangs et al. (1999A&A...343..916L). No periodic transits are seen in this time series. These observations confirm the spectroscopic detection of exocomets in calcium H and K lines that have been seen in high resolution spectroscopy.
14. The VSOP (the VLBI Space Observatory Programme) 5 GHz AGN (Active Galactic Nuclei) Survey Program Analysis Data
ID:
ivo://jvo/isas/darts/halca/halca_vsop_survey_program_data
Title:
The VSOP (the VLBI Space Observatory Programme) 5 GHz AGN (Active Galactic Nuclei) Survey Program Analysis Data
Short Name:
HALCA_AGN
Date:
19 Oct 2021 06:40:34
Publisher:
JVO
Description:
A significant fraction of the mission time of VSOP was to be dedicated to the VSOP Survey Programme of bright compact Active Galactic Nuclei (AGN) at 5 GHz, which was lead by ISAS. The VSOP Survey Sources are an unbiased dataset of 294 targets, of which 82% were successfully observed.
15. XXL Survey: First results
ID:
ivo://CDS.VizieR/IX/49
Title:
XXL Survey: First results
Short Name:
IX/49
Date:
21 Oct 2021
Publisher:
CDS
Description:
The quest for the cosmological parameters that describe our universe continues to motivate the scientific community to undertake very large survey initiatives across the electromagnetic spectrum. Over the past two decades, the Chandra and XMM-Newton observatories have sup- ported numerous studies of X-ray-selected clusters of galaxies, active galactic nuclei (AGNs), and the X-ray background. The present paper is the first in a series reporting results of the XXL-XMM survey; it comes at a time when the Planck mission results are being finalised. We present the XXL Survey, the largest XMM programme totaling some 6.9Ms to date and involving an international consortium of roughly 100 members. The XXL Survey covers two extragalactic areas of 25deg^2^ each at a point-source sensitivity of ~5x10^-15^erg/s/cm^2^ in the [0.5-2]keV band (completeness limit). The survey's main goals are to provide constraints on the dark energy equation of state from the space-time distribution of clusters of galaxies and to serve as a pathfinder for future, wide-area X-ray missions. We review science objectives, including cluster studies, AGN evolution, and large-scale structure, that are being conducted with the support of approximately 30 follow-up programmes. List of XXL papers: I. Scientific motivations - XMM-Newton observing plan - Follow-up observations and simulation programme. II. The bright cluster sample: catalogue and luminosity function. III. Luminosity-temperature relation of the bright cluster sample. IV. Mass-temperature relation of the bright cluster sample. VI. The 1000 brightest X-ray point sources. VII. A supercluster of galaxies at z = 0.43. VIII. MUSE characterisation of intracluster light in a z~0.53 cluster of galaxies. IX. Optical overdensity and radio continuum analysis of a supercluster at z=0.43. X. K-band luminosity - weak-lensing mass relation for groups and clusters of galaxies. XI. ATCA 2.1 GHz continuum observations. XII. Optical spectroscopy of X-ray-selected clusters and the frequency of AGN in superclusters. XIII. Baryon content of the bright cluster sample. XIV. AAOmega redshifts for the southern XXL field.