- ID:
- ivo://CDS.VizieR/J/A+A/634/A98
- Title:
- Corona-Australis DANCe. I.
- Short Name:
- J/A+A/634/A98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Corona-Australis is one of the nearest regions to the Sun with recent and ongoing star formation, but the current picture of its stellar (and substellar) content is not complete yet. We take advantage of the second data release of the Gaia space mission to revisit the stellar census and search for additional members of the young stellar association in Corona-Australis. We applied a probabilistic method to infer membership probabilities based on a multidimensional astrometric and photometric data set over a field of 128deg^2^ around the dark clouds of the region. We identify 313 high-probability candidate members to the Corona-Australis association, 262 of which had never been reported as members before. Our sample of members covers the magnitude range between G>~5mag and G<~20mag, and it reveals the existence of two kinematically and spatially distinct subgroups. There is a distributed 'off-cloud' population of stars located in the north of the dark clouds that is twice as numerous as the historically known 'on-cloud' population that is concentrated around the densest cores. By comparing the location of the stars in the HR-diagram with evolutionary models, we show that these two populations are younger than 10Myr. Based on their infrared excess emission, we identify 28 Class II and 215 Class III stars among the sources with available infrared photometry, and we conclude that the frequency of Class~II stars (i.e. `disc-bearing' stars) in the on-cloud region is twice as large as compared to the off-cloud population. The distance derived for the Corona-Australis region based on this updated census is d=149.4^+0.4^_-0.4_pc, which exceeds previous estimates by about 20 pc. In this paper we provide the most complete census of stars in Corona-Australis available to date that can be confirmed with Gaia data. Furthermore, we report on the discovery of an extended and more evolved population of young stars beyond the region of the dark clouds, which was extensively surveyed in the past.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/645/A84
- Title:
- Coronae of nearby star clusters
- Short Name:
- J/A+A/645/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a novel view on the morphology and dynamical state of ten prominent, nearby (<=500pc), and young (~30-300Myr) open star clusters with Gaia DR2: Per, Blanco 1, IC 2602, IC 2391, Messier 39, NGC 2451A, NGC 2516, NGC 2547, Platais 9, and the Pleiades. We introduce a pioneering member-identification method that is informed by cluster bulk velocities and deconvolves the spatial distribution with a mixture of Gaussians. Our approach enables inferring the true spatial distribution of the clusters by effectively filtering field star contaminants while at the same time mitigating the effect of positional errors along the line of sight. This first application of the method reveals vast stellar coronae that extend for >~100pc and surround the cluster cores, which are comparatively tiny and compact. The coronae and cores form intertwined, coeval, and comoving extended cluster populations, each encompassing tens of thousands of cubic parsec and stretching across tens of degrees on the sky. Our analysis shows that the coronae are gravitationally unbound but largely comprise the bulk of the stellar mass of the populations. Most systems are in a highly dynamic state, showing evidence of expansion and sometimes simultaneous contraction along different spatial axes. The velocity field of the extended populations for the cluster cores appears asymmetric but is aligned along a spatial axis unique to each cluster. The overall spatial distribution and the kinematic signature of the populations are largely consistent with the differential rotation pattern of the Milky Way. This finding underlines the important role of global Galactic dynamics in the fate of stellar systems. Our results highlight the complexity of the Milky Way's open cluster population and call for a new perspective on the characterization and dynamical state of open clusters.
3933. Coronal hole parameters
- ID:
- ivo://CDS.VizieR/J/other/SoPh/294.144
- Title:
- Coronal hole parameters
- Short Name:
- J/other/SoPh/294
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Coronal holes are usually defined as dark structures seen in the extreme ultraviolet and X-ray spectrum which are generally associated with open magnetic fields. Deriving reliably the coronal hole boundary is of high interest, as its area, underlying magnetic field, and other properties give important hints as regards high speed solar wind acceleration processes and compression regions arriving at Earth. In this study we present a new threshold-based extraction method, which incorporates the intensity gradient along the coronal hole boundary, which is implemented as a user-friendly SSW-IDL GUI. The Collection of Analysis Tools for Coronal Holes (CATCH) enables the user to download data, perform guided coronal hole extraction and analyze the underlying photospheric magnetic field. We use CATCH to analyze non-polar coronal holes during the SDO-era, based on 193{AA} filtergrams taken by the Atmospheric Imaging Assembly (AIA) and magnetograms taken by the Heliospheric and Magnetic Imager (HMI), both on board the Solar Dynamics Observatory (SDO). Between 2010 and 2019 we investigate 707 coronal holes that are located close to the central meridian. We find coronal holes distributed across latitudes of about +/-60{deg}, for which we derive sizes between 1.6x10^9^ and 1.8x10^11^km^2^. The absolute value of the mean signed magnetic field strength tends towards an average of 2.9+/-1.9G. As far as the abundance and size of coronal holes is concerned, we find no distinct trend towards the northern or southern hemisphere. We find that variations in local and global conditions may significantly change the threshold needed for reliable coronal hole extraction and thus, we can highlight the importance of individually assessing and extracting coronal holes.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/L58
- Title:
- Coronal type II radio bursts in 2002
- Short Name:
- J/ApJ/710/L58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Major space weather events such as solar flares and coronal mass ejections are usually accompanied by solar radio bursts, which can potentially be used for real-time space weather forecasts. Type II radio bursts are produced near the local plasma frequency and its harmonic by fast electrons accelerated by a shock wave moving through the corona and solar wind with a typical speed of ~1000km/s. The coronal bursts have dynamic spectra with frequency gradually falling with time and durations of several minutes. This Letter presents a new method developed to detect type II coronal radio bursts automatically and describes its implementation in an extended Automated Radio Burst Identification System (ARBIS 2). Preliminary tests of the method with spectra obtained in 2002 show that the performance of the current implementation is quite high, ~80%, while the probability of false positives is reasonably low, with one false positive per 100-200hr for high solar activity and less than one false event per 10000hr for low solar activity periods. The first automatically detected coronal type II radio burst is also presented.
- ID:
- ivo://CDS.VizieR/J/ApJS/182/559
- Title:
- Corotation radii for 153 galaxies of OSUBSGS
- Short Name:
- J/ApJS/182/559
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The potential-density phase-shift method (Zhang et al., 2007AJ....133.2584Z) is an effective new tool for investigating the structure and evolution of galaxies. In this paper, we apply the method to 153 galaxies in the Ohio State University Bright Galaxy Survey (OSUBGS) to study the general relationship between pattern corotation radii and the morphology of spiral galaxies. The analysis is based on near-infrared H-band images that have been deprojected and decomposed assuming a spherical bulge.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A122
- Title:
- CoRoT-30b and CoRoT-31b radial velocity curves
- Short Name:
- J/A+A/635/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery as well as the orbital and physical characterizations of two new transiting giant exoplanets, CoRoT-30 b and CoRoT-31 b, with the CoRoT space telescope. We analyzed two complementary data sets: photometric transit light curves measured by CoRoT, and radial velocity curves measured by the HARPS spectrometer. To derive the absolute masses and radii of the planets, we modeled the stars from available magnitudes and spectra. We find that CoRoT-30 b is a warm Jupiter on a close-to-circular 9.06-day orbit around a G3V star with a semi-major axis of about 0.08AU. It has a radius of 1.01+/-0.08R_Jup_, a mass of 2.90+/-0.22M_Jup_, and therefore a mean density of 3.45+/-0.65g/cm^3^. The hot Jupiter CoRoT-31 b is on a close to circular 4.63-day orbit around a G2 IV star with a semi-major axis of about 0.05AU. It has a radius of 1.46+/-0.30R_Jup_, a mass of 0.84+/-0.34M_Jup_, and therefore a mean density of 0.33+/-0.18g/cm^3^. Neither system seems to support the claim that stars hosting planets are more depleted in lithium. The radii of both planets are close to that of Jupiter, but they differ in mass; CoRoT-30 b is ten times denser than CoRoT-31 b. The core of CoRoT-30 b would weigh between 15 and 75 Earth masses, whereas relatively weak constraints favor no core for CoRoT-31 b. In terms of evolution, the characteristics of CoRoT-31 b appear to be compatible with the high-eccentricity migration scenario, which is not the case for CoRoT-30 b. The angular momentum of CoRoT-31 b is currently too low for the planet to evolve toward synchronization of its orbital revolution with stellar rotation, and the planet will slowly spiral-in while its host star becomes a red giant. CoRoT-30 b is not synchronized either: it looses angular momentum owing to stellar winds and is expected reach steady state in about 2Gyr. CoRoT-30 and 31, as a pair, are a truly remarkable example of diversity in systems with hot Jupiters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/1577
- Title:
- CoRoT 105288363 Blazhko modulation
- Short Name:
- J/MNRAS/415/1577
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the COnvection, ROtation and planetary Transits (CoRoT) star 105288363, a new Blazhko RR Lyrae star of type RRab (f0=1.7623d^-1^), observed with the CoRoT spacecraft during the second long run in the direction of the Galactic Centre (LRc02, time-base 145d). The CoRoT data are characterized by an excellent time-sampling and a low noise amplitude of 0.07mmag in the 2-12d^-1^ range and allow us to study not only the fine details of the variability of the star, but also long-term changes in the pulsation behaviour and the stability of the Blazhko cycle. We use, among other methods, standard Fourier analysis techniques and O-C diagrams to investigate the pulsational behaviour of the Blazhko star 105288363. In addition to the frequency pattern expected for a Blazhko RR Lyrae star, we find an independent mode (f1=2.984d^-1^) showing a f0/f1 ratio of 0.59 which is similar to that observed in other Blazhko RR Lyrae stars. The bump and hump phenomena are also analysed, with their variations over the Blazhko cycle. We carefully investigated the strong cycle-to-cycle changes in the Blazhko modulation (P_B_=35.6d), which seem to happen independently and partly diametrically in the amplitude and phase modulations. Furthermore, the phasing between the two types of modulations is found to change during the course of the observations.
- ID:
- ivo://CDS.VizieR/J/A+A/520/A66
- Title:
- CoRoT-8b light and RV curves
- Short Name:
- J/A+A/520/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of CoRoT-8b, a dense small Saturn-class exoplanet that orbits a K1 dwarf in 6.2 days, and we derive its orbital parameters, mass, and radius. We analyzed two complementary data sets: the photometric transit curve of CoRoT-8b as measured by CoRoT and the radial velocity curve of CoRoT-8 as measured by the HARPS spectrometer. We find that CoRoT-8b is on a circular orbit with a semi-major axis of 0.063+/-0.001AU. It has a radius of 0.57+/-0.02RJ, a mass of 0.22+/-0.03MJ, and therefore a mean density 1.6+/-0.1g/cm^3^. With 67% of the size of Saturn and 72% of its mass, CoRoT-8b has a density comparable to that of Neptune (1.76g/cm^3^). We estimate its content in heavy elements to be 47-63 Earth masses, and the mass of its hydrogen-helium envelope to be 7-23 Earth masses. At 0.063AU, the thermal loss of hydrogen of CoRoT-8b should be no more than about 0.1% over an assumed integrated lifetime of 3Ga.
- ID:
- ivo://CDS.VizieR/III/282
- Title:
- CoRoT Bright Stars Catalogue with variability classes
- Short Name:
- III/282
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The CoRoT bright stars catalogue describes the 143 different objects observed during the mission, in the "bright star" field of CoRoT, and their major properties. The almost continuous observations lasted between 20 and 156 days, with a regular 32s sampling time.
- ID:
- ivo://CDS.VizieR/J/A+A/491/889
- Title:
- CoRoT-Exo-3b observations
- Short Name:
- J/A+A/491/889
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CoRoT space mission routinely provides high-precision photometric measurements of thousands of stars that have been continuously observed for months. The discovery and characterization of the first very massive transiting planetary companion with a short orbital period is reported. A series of 34 transits was detected in the CoRoT light curve of an F3V star, observed from May to October 2007 for 152 days. The radius was accurately determined and the mass derived for this new transiting, thanks to the combined analysis of the light curve and complementary ground-based observations: high-precision radial-velocity measurements, on-off photometry, and high signal-to-noise spectroscopic observations.