- ID:
- ivo://CDS.VizieR/J/MNRAS/402/691
- Title:
- SMC RR Lyrae stars light curve analysis
- Short Name:
- J/MNRAS/402/691
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a careful and detailed light curve analysis of RR Lyrae stars in the Small Magellanic Cloud (SMC) discovered by the Optical Gravitational Lensing Experiment (OGLE) project. Out of 536 single-mode RR Lyrae stars selected from the data base, we have investigated the physical properties of 335 'normal-looking' RRab stars and 17 RRc stars that have good quality photometric light curves. We have also been able to estimate the distance modulus of the cloud which is in good agreement with those determined from other independent methods.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/893/67
- Title:
- Smoothed amplitudes from Kepler, K2 and TESS phot.
- Short Name:
- J/ApJ/893/67
- Date:
- 03 Dec 2021 00:35:27
- Publisher:
- CDS
- Description:
- We investigate starspot distributions consistent with space-based photometry of F, G, and K stars in six stellar associations ranging in age from 10Myr to 4Gyr. We show that a simple light-curve statistic called the "smoothed amplitude" is proportional to stellar age as t^-1/2^, following a Skumanich-like spin-down relation. We marginalize over the unknown stellar inclinations by forward modeling the ensemble of light curves for direct comparison with the Kepler, K2, and TESS photometry. We sample the posterior distributions for spot coverage with approximate Bayesian computation. We find typical spot coverages in the range 1%-10%, which decrease with increasing stellar age. The spot coverage is proportional to t^n^ where n=-0.37+/-0.16, also statistically consistent with a Skumanich-like t^-1/2^ decay of starspot coverage with age. We apply two techniques to estimate the spot coverage of young exoplanet-hosting stars likely to be targeted for transmission spectroscopy with the James Webb Space Telescope, and estimate the bias in exoplanet radius measurements due to varying starspot coverage.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/2251
- Title:
- Southern Catalina Survey type-ab RR Lyrae
- Short Name:
- J/MNRAS/446/2251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a deep, wide-area variability survey in the Southern hemisphere. As part of the Catalina Sky Surveys, the Siding Spring Survey (SSS) has covered 14,800 square degrees in the declination range of -75{deg}<delta<-15{deg} To mine the enormous SSS dataset efficiently we have developed two algorithms: Automatic Period Selection (APS) and Automatic Fourier Decomposition (AFD), which aim to sharpen the period estimation and produce robust lightcurve models. Armed with the APS and AFD outputs we classify 10540 ab-type RR Lyrae (RRab) stars (~90% of which are new) across the Southern sky.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A40
- Title:
- Spectral significance for 15 delta Scuti
- Short Name:
- J/A+A/614/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is known that the observed distribution of frequencies in CoRoT and Kepler {delta} Scuti stars has no parallelism with any theoretical model. Pre-whitening is a widespread technique in the analysis of time series with gaps from pulsating stars located in the classical instability strip such as {delta} Scuti stars. However, some studies have pointed out that this technique might introduce biases in the results of the frequency analysis. This work aims at studying the biases that can result from pre-whitening in asteroseismology. The results will depend on the intrinsic range and distribution of frequencies of the stars. The periodic nature of the gaps in CoRoT observations, just in the range of the pulsational frequency content of the {delta} Scuti stars, is shown to be crucial to determine their oscillation frequencies, the first step to perform asteroseismology of these objects. Hence, here we focus on the impact of pre-whitening on the asteroseismic characterization of {delta} Scuti stars. We select a sample of 15 {delta} Scuti stars observed by the CoRoT satellite, for which ultra-high quality photometric data have been obtained by its seismic channel. In order to study the impact on the asteroseismic characterization of {delta} Scuti stars we perform the pre-whitening procedure on three datasets: gapped data, linearly interpolated data, and data with gaps interpolated using Autoregressive and Moving Average models (ARMA). The different results obtained show that at least in some cases pre-whitening is not an efficient procedure for the deconvolution of the spectral window. Therefore, in order to reduce the effect of the spectral window to the minimum it is necessary to interpolate with an algorithm that is aimed to preserve the original frequency content, and not only to perform a pre-whitening of the data.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A43
- Title:
- Spectra of NGC 1333 Class I-Class II stars
- Short Name:
- J/A+A/650/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass accretion rate (dM/dt_acc_) is the fundamental parameter to understand the process of mass assembly that results in the formation of a low-mass star. This parameter has been largely studied in Classical T Tauri stars in star-forming regions with ages of ~1-10Myr. However, little is known about the accretion properties of young stellar objects (YSOs) in younger regions and early stages of star formation, such as in the Class 0/I phases. We present new near-infrared spectra of 17 Class I/Flat and 35 Class II sources located in the young (<1Myr) NGC 1333 cluster, acquired with the KMOS instrument at the Very Large Telescope. Our goal is to study whether the mass accretion rate evolves with age, as suggested by the widely adopted viscous evolution model, by comparing the properties of the NGC 1333 members with samples of older regions. For the Class II sources in our sample, we measured the stellar parameters (SpT, AV, and L*) through a comparison of the IR spectra with a grid of non-accreting Class III stellar templates. We then computed the accretion luminosity by using the known correlation between Lacc and the luminosity of HI lines (Pa{beta} and Br{gamma}). For the Class I sample, where the presence of a large IR excess makes it impossible to use the same spectral typing method, we applied a procedure that allowed us to measure the stellar and accretion luminosity in a self-consistent way. Mass accretion rates dM/dt_acc_ were then measured once masses and radii were estimated adopting suitable evolutionary tracks. The NGC 1333 Class II sources of our sample have L_acc_~10^-4^-1L_{sun}_ and dM/dt_acc_~10^-11^-10^-7^M_{sun}_/yr. We find a correlation between accretion and stellar luminosity in the form of log L_acc_=(1.5+/-0.2)logL*+(-1.0+/-0.1), and a correlation between the mass accretion rate and stellar mass in the form of log(dM/dt_acc_)=(2.6+/-0.9)logM*+(-7.3+/-0.7). Both correlations are compatible within the errors with the older Lupus star-forming region, while only the latter is consistent with results from Chamaeleon I. The Class I sample shows larger accretion luminosities (~10^-2^-10^2^L_{sun}_) and mass accretion rates (~10^-9^-10^-6^M_{sun}_/yr) with respect to the Class II stars of the same cloud. However, the derived mass accretion rates are not sufficiently high to build up the inferred stellar masses, assuming steady accretion during the Class I lifetime. This suggests that the sources are not in their main accretion phase and that most of their mass has already been accumulated during a previous stage and/or that the accretion is an episodic phenomenon. We show that some of the targets originally classified as Class I through Spitzer photometry are in fact evolved or low accreting objects. This evidence can have implications for the estimated protostellar phase lifetimes. The accretion rates of our sample are larger in more embedded and early stage YSOs. Further observations of larger samples in young star-forming regions are needed to determine if this is a general result. In addition, we highlight the importance of spectroscopic surveys of YSOs to confirm their classification and perform a more correct estimate of their lifetime.
- ID:
- ivo://CDS.VizieR/J/MNRAS/489/2595
- Title:
- Spectro-interferometry of 8 evolved stars
- Short Name:
- J/MNRAS/489/2595
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine the physical parameters of the outer atmosphere of a sample of eight evolved stars, including the red supergiant {alpha} Scorpii, the red giant branch stars {alpha} Bootis and {gamma} Crucis, the K giant {lambda} Velorum, the normal M giants BK Virginis and SW Virginis, and the Mira star W Hydrae (in two different luminosity phases) by spatially resolving the stars in the individual carbon monoxide (CO) first overtone lines. We used the Astronomical Multi-BEam combineR (AMBER) instrument at the Very Large Telescope Interferometer (VLTI), in high-resolution mode ({lambda}/{Delta}{lambda}~=12000) between 2.28 and 2.31um in the K band. The maximal angular resolution is 10mas, obtained using a triplet telescope configuration, with baselines from 7 to 48m. By using a numerical model of a molecular atmosphere in a spherical shells (MOLsphere), called PAMPERO (an acronym for the 'physical approach of molecular photospheric ejection at high angular resolution for evolved stars'), we add multiple extended CO layers above the photospheric MARCS model at an adequate spatial resolution. We use the differential visibilities and the spectrum to estimate the size (R) of the CO MOLsphere, its column density (NCO) and temperature (Tmol) distributions along the stellar radius. The combining of the {chi}^2^ minimization and a fine grid approach for uncertainty analysis leads to reasonable NCO and Tmol distributions along the stellar radius of the MOLsphere.
- ID:
- ivo://CDS.VizieR/J/A+A/383/188
- Title:
- Spectrophotometric atlas of symbiotic stars
- Short Name:
- J/A+A/383/188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A multi-epoch, absolute-fluxed spectral atlas extending from about 3200 to 9000{AA} is presented for 130 symbiotic stars, including members of the LMC, SMC and Draco dwarf galaxies. The fluxes are accurate to better than 5% as shown by comparison with Tycho and ground-based photometric data. The spectra of 40 reference objects (MK cool giant standards, Mira and Carbon stars, planetary nebulae, white dwarfs, hot sub-dwarfs, Wolf-Rayet stars, classical novae, VV Cep and Herbig Ae/Be objects) are provided to assist the interpretation of symbiotic star spectra. Astrometric positions and counterparts in astrometric catalogues are derived for all program symbiotic stars. The spectra are available in electronic form from the authors.
- ID:
- ivo://CDS.VizieR/J/PAZh/32/672
- Title:
- Spectrophotometry of 77 variable stars
- Short Name:
- J/PAZh/32/672
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of visual and near-infrared spectrophotometric observations for 77 variable stars obtained during 1971-1991 in Chile, Armenia and Bolivia. The quasi-monochromatic extra-atmospheric fluxes from the stars are given in absolute energy units (W/m^2^/m) at all wavelengths of the spectral range at 2.5 nm intervals.
- ID:
- ivo://CDS.VizieR/J/AJ/159/43
- Title:
- Spectroscopically identified CVs from LAMOST survey. I.
- Short Name:
- J/AJ/159/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of cataclysmic variables (CVs) is presented including spectroscopically identified 380 spectra of 245 objects, of which 58 CV candidates are new discoveries. The BaggingTopPush and the Random Forest algorithms are applied to the Fifth Data Release (DR5) of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) to retrieve CVs with strong emission lines and with broad absorption lines respectively. Based on spectroscopic classification, 134 dwarf novae, 41 nova-like variables, and 19 magnetic CVs are identified from the sample. In addition, 89 high-inclination systems and 33 CVs showing companion stars are recognized and discussed for their distinct spectral characteristics. Comparisons between CVs from LAMOST and from published catalogs are made in spatial and magnitude distribution, and the difference of their locus in the Gaia color-absolute magnitude diagram (CaMD) are also investigated. More interestingly, for two dwarf novae observed through LAMOST and SDSS in different epochs, their spectra both in quiescence phase and during outburst are exhibited.
- ID:
- ivo://CDS.VizieR/J/AJ/152/207
- Title:
- Spectroscopic Indicators in SeisMic Archive (SISMA)
- Short Name:
- J/AJ/152/207
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We created a large database of physical parameters and variability indicators by fully reducing and analyzing the large number of spectra taken to complement the asteroseismic observations of the COnvection, ROtation and planetary Transits (CoRoT) satellite. 7103 spectra of 261 stars obtained with the ESO echelle spectrograph HARPS have been stored in the VO-compliant database Spectroscopic Indicators in a SeisMic Archive (SISMA), along with the CoRoT photometric data of the 72 CoRoT asteroseismic targets. The remaining stars belong to the same variable classes of the CoRoT targets and were observed to better characterize the properties of such classes. Several useful variability indicators (mean line profiles, indices of differential rotation, activity and emission lines) together with vsini and radial-velocity measurements have been extracted from the spectra. The atmospheric parameters T_eff_,logg, and [Fe/H] have been computed following a homogeneous procedure. As a result, we fully characterize a sample of new and known variable stars by computing several spectroscopic indicators, also providing some cases of simultaneous photometry and spectroscopy.
