- ID:
- ivo://CDS.VizieR/J/A+A/506/471
- Title:
- Frequency analysis of CoRoT B stars
- Short Name:
- J/A+A/506/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for new variable B-type pulsators in the CoRoT data assembled primarily for planet detection, as part of CoRoT's Additional Programme. We aim to explore the properties of newly discovered B-type pulsators from the uninterrupted CoRoT spacebased photometry and to compare them with those of known members of the beta Cep and slowly pulsating B star (SPB) classes. We developed automated data analysis tools which include algorithms for jump correction, light curve detrending, frequency detection, frequency combination search and frequency and period spacing search. Besides numerous new classical slowly pulsating B stars, we find evidence for a new class of low-amplitude B-type pulsators between the SPB and delta Sct instability strips, with a very broad range of frequencies and low amplitudes, as well as several slowly pulsating B stars with residual excess power at frequencies typically a factor three above their expected g-mode frequencies. The frequency data we obtained for numerous new B-type pulsators represent an appropriate starting point for further theoretical analyses of these stars, once their effective temperature, gravity, rotation velocity and abundances will be derived spectroscopically in the framework of an ongoing FLAMES survey at VLT.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/598/597
- Title:
- Frequency analysis of fundamental-mode RR Lyrae
- Short Name:
- J/ApJ/598/597
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have frequency-analyzed 6391 variables classified earlier as fundamental-mode RR Lyrae (RR0) stars in the MACHO database on the Large Magellanic Cloud (LMC). The overwhelming majority (i.e., 96%) of these variables have been proved to be indeed RR0 stars, whereas the remaining ones have fallen into one of the following categories: single- and double-mode Cepheids, binaries, first-overtone and double-mode RR Lyrae stars, and nonclassified variables. Special attention has been paid to the properties of the amplitude- and phase-modulated RR0 stars (the Blazhko stars). We found altogether 731 Blazhko variables showing either a doublet or an equidistant triplet pattern at the main pulsation component in their frequency spectra. This sample overwhelmingly exceeds the number of Blazhko stars known in all other systems combined. The incidence rate of the Blazhko variables among the RR0 stars in the LMC is 11.9%, which is 3 times higher than their rate among the first-overtone RR Lyrae stars. No difference is found in the average brightness between the single-mode and Blazhko variables. However, the latter ones show a somewhat lower degree of skewness in their average light curves and a concomitant lower total amplitude in their modulation-free light curves.
- ID:
- ivo://CDS.VizieR/J/A+A/525/A23
- Title:
- Frequency analysis of HD 49434
- Short Name:
- J/A+A/525/A23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD 49434 is a bright (V=5.75mag) and multiperiodic gamma Dor-type pulsator that has been selected for the asteroseismic core programme of the CoRoT satellite. An extensive and detailed study has been carried out to investigate the pulsational content of this object on the basis of the 136.9d (331291 useful datapoints) time series collected by the CoRoT satellite during the long-run LRa01 (October 2007-March 2008).
- ID:
- ivo://CDS.VizieR/J/A+A/506/111
- Title:
- Frequency analysis of HD 180642 (V1449 Aql)
- Short Name:
- J/A+A/506/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the CoRoT light curve of the beta Cep star HD 180642, assembled during the first long run of the space mission, as well as archival single-band photometry. Our goal is to analyse the detailed behaviour present in the light curve and interpret it in terms of excited-mode frequencies. After describing the noise properties in detail, we use various time series analyses and fitting techniques to model the CoRoT light curve, for various physical assumptions. We apply statistical goodness-of-fit criteria that allow us to select the most appropriate physical model fit to the data. We conclude that the light-curve model based on nonlinear resonant frequency and phase locking provides the best representation of the data. Interpretation of the residuals is dependent on the chosen physical model used to prewhiten the data. Our observational results constitute a fruitful starting point for detailed seismic stellar modelling of this large-amplitude and evolved beta Cep star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/4089
- Title:
- Frequency of snowline-region planets
- Short Name:
- J/MNRAS/457/4089
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a statistical analysis of the first four seasons from a 'second-generation' microlensing survey for extrasolar planets, consisting of near-continuous time coverage of 8 deg^2^ of the Galactic bulge by the Optical Gravitational Lens Experiment (OGLE), Microlensing Observations in Astrophysics (MOA), and Wise microlensing surveys. During this period, 224 microlensing events were observed by all three groups. Over 12 per cent of the events showed a deviation from single-lens microlensing, and for ~one-third of those the anomaly is likely caused by a planetary companion. For each of the 224 events, we have performed numerical ray-tracing simulations to calculate the detection efficiency of possible companions as a function of companion-to-host mass ratio and separation. Accounting for the detection efficiency, we find that 55^+34^_-22_ per cent of microlensed stars host a snowline planet. Moreover, we find that Neptune-mass planets are ~10 times more common than Jupiter-mass planets. The companion-to-host mass-ratio distribution shows a deficit at q~10^-2^, separating the distribution into two companion populations, analogous to the stellar-companion and planet populations, seen in radial-velocity surveys around solar-like stars. Our survey, however, which probes mainly lower mass stars, suggests a minimum in the distribution in the super-Jupiter mass range, and a relatively high occurrence of brown-dwarf companions.
- ID:
- ivo://CDS.VizieR/J/ApJS/224/41
- Title:
- Frequency spacing of {delta} Scuti stars. II.
- Short Name:
- J/ApJS/224/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sequence search method was developed for searching for regular frequency spacing in {delta} Scuti stars by visual inspection (VI) and algorithmic search. The sample contains 90 {delta} Scuti stars observed by CoRoT. An example is given to represent the VI. The algorithm (SSA) is described in detail in section 3.2. The data treatment of the CoRoT light curves, the criteria for frequency filtering, and the spacings derived by two methods (i.e., three approaches: VI, SSA, and FT (Fourier Transform)) are given for each target. Echelle diagrams are presented for 77 targets for which at least one sequence of regular spacing was identified. Comparing the spacing and the shifts between pairs of echelle ridges revealed that at least one pair of echelle ridges is shifted to midway between the spacing for 22 stars. The estimated rotational frequencies compared to the shifts revealed rotationally split doublets, triplets, and multiplets not only for single frequencies, but for the complete echelle ridges in 31 {delta} Scuti stars. Using several possible assumptions for the origin of the spacings, we derived the large separation ({Delta}_nu_) that are distributed along the mean density versus large separations relation derived from stellar models.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A127
- Title:
- Frequency tables of KIC4931738 and KIC6352430
- Short Name:
- J/A+A/553/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- OB stars are important in the chemistry and evolution of the Universe, but the sample of targets that is well understood from an asteroseismological point of view is still too limited to provide feedback on the current evolutionary models. We extend this sample with two spectroscopic binary systems. Our goal is to provide orbital solutions, fundamental parameters, and abundances from disentangled high-resolution high signal-to-noise spectra, as well as to analyse and interpret the variations in the Kepler light curve of these carefully selected targets. This way we continue our efforts to map the instability strips of beta Cep and slowly pulsating B stars using the combination of high-resolution ground-based spectroscopy and uninterrupted space-based photometry. We fit Keplerian orbits to radial velocities measured from selected absorption lines of high-resolution spectroscopy using synthetic composite spectra to obtain orbital solutions. We used revised masks to obtain optimal light curves from the original pixel-data from the Kepler satellite, which provided better long-term stability compared to the pipeline-processed light curves. We used various time-series analysis tools to explore and describe the nature of variations present in the light curve. We find two eccentric double-lined spectroscopic binary systems containing a total of three main sequence B-type stars (and one F-type component), of which at least one in each system exhibits light variations. The light curve analysis (combined with spectroscopy) of the system of two B stars points towards the presence of tidally excited g modes in the primary component. We interpret the variations seen in the second system as classical g mode pulsations driven by the kappa mechanism in the B type primary, and explain the unexpected power in the p mode region as the result of nonlinear resonant mode excitation.
- ID:
- ivo://CDS.VizieR/J/A+A/598/A49
- Title:
- FRICAT. FIRST catalog of FR I radio galaxies
- Short Name:
- J/A+A/598/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We built a catalog of 219 FR I radio galaxies (FR Is), called FRICAT, selected from a published sample and obtained by combining observations from the NVSS, FIRST, and SDSS surveys. We included in the catalog the sources with an edge-darkened radio morphology, redshift >=0.15, and extending (at the sensitivity of the FIRST images) to a radius r larger than 30kpc from the center of the host. We also selected an additional sample (sFRICAT) of 14 smaller (10<r<30kpc) FR Is, limiting to z<0.05. The hosts of the FRICAT sources are all luminous (-21>=M_r_>=-24), red early-type galaxies with black hole masses in the range 10^8^<=M_BH_<=3x10^9^M_{sun}_; the spectroscopic classification based on the optical emission line ratios indicates that they are all low excitation galaxies. Sources in the FRICAT are then indistinguishable from the FR Is belonging to the Third Cambridge Catalogue of Radio Sources (3C) on the basis of their optical properties. Conversely, while the 3C-FR Is show a strong positive trend between radio and [O III] emission line luminosity, these two quantities are unrelated in the FRICAT sources; at a given line luminosity, they show radio luminosities spanning about two orders of magnitude and extending to much lower ratios between radio and line power than 3C-FR Is. Our main conclusion is that the 3C-FR Is just represent the tip of the iceberg of a much larger and diverse population of FR Is.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A183
- Title:
- Fried Egg Nebula AMBER and GRAVITY observations
- Short Name:
- J/A+A/635/A183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The objective of this work is to study in detail the nature (i.e., geometry, rates) of the mass-loss episodes associated with the yellow hypergiant IRAS 17163-3907. We analysed a large set of optical/near-infrared data, in spectroscopic, photometric, spectropolarimetric, and interferometric modes. We use the optical observations to determine its spectral type and we present the first model independent reconstructed images of IRAS 17163-3907 at 2 micron tracing milli-arcsecond scales. Lastly, we apply a 2D radiative transfer model to fit the dereddened photometry and the radial profiles of published diffraction limited VISIR images at 8.59um, 11.85um and 12.81um simultaneously, adopting a revised distance determination using the new Gaia measurements (DR2).
- ID:
- ivo://CDS.VizieR/J/A+A/588/A14
- Title:
- Friends-of-friends galaxy group finder
- Short Name:
- J/A+A/588/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We improve the widely used friends-of-friends (FoF) group finding algorithm with membership refinement procedures and apply the method to a combined dataset of galaxies in the local Universe. A major aim of the refinement is to detect subgroups within the FoF groups, enabling a more reliable suppression of the fingers-of-God effect. The FoF algorithm is often suspected of leaving subsystems of groups and clusters undetected. We used a galaxy sample built of the 2MRS, CF2, and 2M++ survey data comprising nearly 80000 galaxies within the local volume of 430Mpc radius to detect FoF groups. We conducted a multimodality check on the detected groups in search for subgroups. We furthermore refined group membership using the group virial radius and escape velocity to expose unbound galaxies. We used the virial theorem to estimate group masses. The analysis results in a catalogue of 6282 galaxy groups in the 2MRS sample with two or more members, together with their mass estimates. About half of the initial FoF groups with ten or more members were split into smaller systems with the multimodality check.