- ID:
- ivo://CDS.VizieR/J/ApJ/896/1
- Title:
- SEAMBHs. XI. Mrk 142 X-ray to optical light curves
- Short Name:
- J/ApJ/896/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We performed an intensive accretion disk reverberation mapping campaign on the high accretion rate active galactic nucleus Mrk142 in early 2019. Mrk 142 was monitored with the Neil Gehrels Swift Observatory for four months in X-rays and six different UV/optical filters. Ground-based photometric monitoring was obtained from the Las Cumbres Observatory, the Liverpool Telescope, and the Dan Zowada Memorial Observatory in ugriz filters, as well as from the Yunnan Astronomical Observatory in V. Mrk 142 was highly variable throughout, displaying correlated variability across all wavelengths. We measure significant time lags between the different wavelength lightcurves. In the UV and optical, we find that the wavelength-dependent lags, {tau}({lambda}), generally follow the relation {tau}({lambda}){propto}{lambda}^4/3^, as expected for the T{propto}R^-3/4^ profile of a steady-state, optically thick, geometrically thin accretion disk, though they can also be fit by {tau}({lambda}){propto}{lambda}^2^, as expected for a slim disk. The exceptions are the u and U bands, where an excess lag is observed, as has been observed in other active galactic nuclei and attributed to continuum emission arising in the broad-line region. Furthermore, we perform a flux-flux analysis to separate the constant and variable components of the spectral energy distribution, finding that the flux dependence of the variable component is consistent with the f{nu}{propto}{nu}^1/3^ spectrum expected for a geometrically thin accretion disk. Moreover, the X-ray to UV lag is significantly offset from an extrapolation of the UV/optical trend, with the X-rays showing a poorer correlation with the UV than the UV does with the optical. The magnitude of the UV/optical lags is consistent with a highly super-Eddington accretion rate.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/460/695
- Title:
- Search for Associations Containing Young stars
- Short Name:
- J/A+A/460/695
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results from a high-resolution optical spectroscopic survey aimed to search for nearby young associations and young stars among optical counterparts of ROSAT All-Sky Survey (<IX/10> and <IX/29>, X-ray sources in the Southern Hemisphere. We selected 1953 late-type (B-V>=0.6), potentially young, optical counterparts out of a total of 9574 1RXS sources for follow-up observations. At least one high-resolution spectrum was obtained for each of 1511 targets. This paper is the first in a series presenting the results of the SACY survey. Here we describe our sample and our observations. We describe a convergence method in the (UVW) velocity space to find associations. As an example, we discuss the validity of this method in the framework of the Beta Pic Association.
- ID:
- ivo://CDS.VizieR/J/ApJ/736/89
- Title:
- Search for companions around nearby massive stars
- Short Name:
- J/ApJ/736/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this study, we present high-contrast imaging of 18 nearby massive stars of which 15 are in the B2-A0 spectral-type range and provide excellent sensitivity to wide companions. By comparing our sensitivities to model predictions of disk instability based on physical criteria for fragmentation and cooling, and using Monte Carlo simulations for orbital distributions, we find that ~85% of such companions should have been detected in our images on average. Given this high degree of completeness, stringent statistical limits can be set from the null-detection result, even with the limited sample size. We find that <30% of massive stars form and retain disk instability planets, brown dwarfs, and very low mass stars of <100M_jup_ within 300AU, at 99% confidence. These results, combined with previous findings in the literature, lead to the conclusion that core accretion is likely the dominant mode of planet formation.
- ID:
- ivo://CDS.VizieR/J/A+A/509/A52
- Title:
- Search for companions with VLT/NACO
- Short Name:
- J/A+A/509/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since November 2002, we have conducted the largest deep imaging survey of the young, nearby associations of the southern hemisphere. Our goal is detection and characterization of substellar companions at intermediate (10-500AU) physical separations. We have observed a sample of 88 stars, mostly G to M dwarfs, that we essentially identify as younger than 100Myr and closer to Earth than 100pc. The VLT/NACO adaptive optics instrument of the ESO Paranal Observatory was used to explore the faint circumstellar environment between typically 0.1 and 10". We report the discovery of 17 new close (0.1-5.0") multiple systems. HIP 108195AB and C (F1III-M6), HIP 84642AB (a~14AU, K0-M5) and TWA 22AB (a~1.8AU; M6-M6) confirmed comoving systems. TWA 22AB is likely to be a astrometric calibrator that can be used to test evolutionary predictions. Among our complete sample, a total of 65 targets observed with deep coronagraphic imaging. About 240 faint candidates were detected around 36 stars. Follow-up observations VLT or HST for 83% of these stars enabled us to identify a fraction of contaminants. The latest results about the substellar companions to GSC 08047-00232, AB Pic and 2M1207, confirmed during this survey and published earlier, are reviewed. Finally, the statistical analysis of our complete set of coronagraphic limits enables us to place constraints on the physical and properties of giant planets between typically 20 and 150AU.
- ID:
- ivo://CDS.VizieR/J/A+A/385/488
- Title:
- Search for duplicity in periodic Be stars
- Short Name:
- J/A+A/385/488
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Four Be stars, HR 1960, HR 2968, HR 3237 and HR 3642, selected according to their periodic variations in Hipparcos and Geneva photometries, have been monitored from 1998 until 2001 with the Coralie spectrograph. HR 1960 and HR 3237 are two new spectroscopic binaries, HR 3642 is a new lambda Eri star, and HR 2968 is stable.
- ID:
- ivo://CDS.VizieR/J/ApJ/700/1647
- Title:
- Search for planetary companions with Spitzer/IRAC
- Short Name:
- J/ApJ/700/1647
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Fomalhaut and {epsilon} Eridani are two young, nearby stars that possess extended debris disks whose structures suggest the presence of perturbing planetary objects. With its high sensitivity and stable point-spread function, Spitzer/Infrared Array Camera (IRAC) is uniquely capable of detecting cool, Jupiter-like planetary companions whose peak emission is predicted to occur near 4.5um. We report on deep IRAC imaging of these two stars, taken at 3.6 and 4.5um using subarray mode and in all four channels in wider-field full array mode. Observations acquired at two different telescope roll angles allowed faint surrounding objects to be separated from the stellar diffraction pattern. No companion candidates were detected at the reported position of Fomalhaut b with 3{sigma} model-dependent mass upper limits of 3M_J_ (for an age of 200Myr). Around {epsilon} Eridani, we instead set a limit of 4 and <~1M_J_ (1Gyr model age) at the inner and outer edge of the submillimeter debris ring, respectively. These results are consistent with non-detections in recent near-infrared imaging searches, and set the strongest limits to date on the presence of planets outside {epsilon} Eridani submillimeter ring.
- ID:
- ivo://CDS.VizieR/J/AcA/70/181
- Title:
- Search for Planets in Hot Jupiter Systems
- Short Name:
- J/AcA/70/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Origins of giant planets on tight orbits, so called hot Jupiters, are a long-lasting question in the planetary formation and evolution theory. The answer seems to be hidden in architectures of those systems that remain only partially understood. Using multi-sector time-series photometry from the Transiting Exoplanet Survey Satellite, we searched for additional planets in the KELT-18, KELT-23, KELT-24, Qatar-8, WASP-62, WASP-100, WASP-119, and WASP-126 planetary systems using both the transit technique and transit timing method. Our homogeneous analysis has eliminated the presence of transiting companions down to the terrestrial-size regime in the KELT-23 and WASP-62 systems, and down to mini-Neptunes or Neptunes in the remaining ones. Transit timing analysis has revealed no sign of either long-term trends or periodic perturbations for all the studied hot Jupiters, including the WASP-126 b for which deviations from a Keplerian model were claimed in the literature. The loneliness of the planets of the sample speaks in favor of the high-eccentricity migration mechanism that probably brought them to their tight orbits observed nowadays. As a by-product of our study, the transit light curve parameters were redetermined with a substantial improvement of the precision for six systems. For KELT-24 b, a joint analysis allowed us to place a tighter constraint on its orbital eccentricity.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A205
- Title:
- Search for transiting planets around sdBs
- Short Name:
- J/A+A/650/A205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hot subdwarfs experienced strong mass loss on the red giant branch (RGB) and are now hot and small He-burning objects. These stars constitute excellent opportunities for addressing the question of the evolution of exoplanetary systems directly after the RGB phase of evolution. In this project we aim to perform a transit survey in all available light curves of hot subdwarfs from space-based telescopes (Kepler, K2, TESS, and CHEOPS) with our custom-made pipeline SHERLOCK in order to determine the occurrence rate of planets around these stars as a function of orbital period and planetary radius. We also aim to determine whether planets that were previously engulfed in the envelope of their red giant host star can survive, even partially, as a planetary remnant. For this first paper, we performed injection-and-recovery tests of synthetic transits for a selection of representative Kepler, K2, and TESS light curves to determine which transiting bodies in terms of object radius and orbital period we will be able to detect with our tools. We also provide estimates for CHEOPS data, which we analyzed with the pycheops package. Transiting objects with a radius <~1.0R_{Earth}_ can be detected in most of the Kepler, K2, and CHEOPS targets for the shortest orbital periods (1d and shorter), reaching values as low as ~0.3R_{Earth}_ in the best cases. Sub-Earth-sized bodies are only reached for the brightest TESS targets and for those that were observed in a significant number of sectors. We also give a series of representative results for larger planets at greater distances, which strongly depend on the target magnitude and on the length and quality of the data. The TESS sample will provide the most important statistics for the global aim of measuring the planet occurrence rate around hot subdwarfs. The Kepler, K2, and CHEOPS data will allow us to search for planetary remnants, that is, very close and small (possibly disintegrating) objects.
- ID:
- ivo://CDS.VizieR/J/A+A/591/A84
- Title:
- Search for UMa group companions
- Short Name:
- J/A+A/591/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey to detect low-mass companions of Ursa Major (UMa) group members, carried out in 2003-2006 with NACO at the ESO VLT. While many extra-solar planets and planetary candidates have been found in close orbits around stars by the radial velocity and the transit methods, direct detections at wider orbits are rare. The UMa group, a young nearby stellar association at an age of about 200-600Myr, has not yet been addressed as a whole although its members represent a very interesting sample to search for and characterize substellar companions by direct imaging. Our goal was to find or to provide detection limits on wide substellar companions around nearby UMa group members using high-resolution imaging. We searched for faint companions around 20 UMa group members within 30pc. The primaries were placed below a semi-transparent coronagraph, a rarely used mode of NACO, to increase the dynamic range of the images. In most cases, second epoch images of companion candidates were taken to check whether they share common proper motion with the primary.
- ID:
- ivo://CDS.VizieR/J/ApJS/241/6
- Title:
- Searching for super-fast rotators using PS1
- Short Name:
- J/ApJS/241/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A class of asteroids, called large super-fast rotators (large SFRs), have rotation periods shorter than 2hr and diameters larger than ~0.3km. They pose challenges to the usual interior rubble-pile structure unless a relatively high bulk density is assumed. So far, only six large SFRs have been found. Therefore, we present a survey of asteroid rotation periods using the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) 1 telescope during 2016 October 26-31 to search for more large SFRs and to study their properties. A total of 876 reliable rotation periods are measured, among which seven are large SFRs, thereby increasing the inventory of known large SFRs. These seven newly discovered large SFRs have diverse colors and locations in the main asteroid belt, suggesting that the taxonomic tendency and the location preference in the inner main belt of the six previously known large SFRs could be a bias due to various observational limits. Interestingly, five out of the seven newly discovered large SFRs are mid main-belt asteroids (MBAs). Considering the rare discovery rates of large SFR in the previously similar surveys and the survey condition in this work, the chance of detecting a large SFR in the inner main belt seems to be relatively low. This probably suggests that the inner main belt harbors fewer large SFRs than the mid main belt. From our survey, we also found a drop in the number appearing at f>5rev/day on the spin-rate distribution for the outer MBAs of D<3km, which was reported for the inner and mid main belt by Chang et al. (2015, J/ApJS/219/27 ; 2016ApJ...816...71C).