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Start Over Subject variable stars Validation Level 2
1261. SMC RR Lyrae stars light curve analysis
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.
1262. Smoothed amplitudes from Kepler, K2 and TESS phot.
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.
1263. Solar-like oscillations in alpha Cen B
ID:
ivo://CDS.VizieR/J/A+A/406/L23
Title:
Solar-like oscillations in alpha Cen B
Short Name:
J/A+A/406/L23
Date:
21 Oct 2021
Publisher:
CDS
Description:
The K1 dwarf alpha Cen B was observed with the CORALIE spectrograph on the 1.2-m Swiss telescope at La Silla in April 2003. Thirteen nights of observations have made it possible to collect 3626 radial velocity measurements with a standard deviation of 1.4m/s exhibiting a mean noise level in the amplitude spectrum of only 3.75cm/s. Twelve oscillation modes have been identified in the power spectrum between 3 and 4.6mHz with amplitudes in the range 8.7 to 13.7cm/s and showing a regularity with a large separation of 161.1uHz.
1264. Southern Catalina Survey type-ab RR Lyrae
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.
1265. Spectral analysis of V510 Pup
ID:
ivo://CDS.VizieR/J/AZh/81/333
Title:
Spectral analysis of V510 Pup
Short Name:
J/AZh/81/333
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have carried out a detailed identification of lines in the optical spectrum of the post-AGB star V510Pup associated with the infrared source IRAS08005-2356. Absorbtion lines of the ions FeII, TiII, CrII, YII are presented at wavelengths from 4549 to 8546 A. The absorptions YII and other s-process elements are anomalously strong. There is also strong in the circumstellar C_2_ Swan bands. The profiles of most of the lines (of hydrogen and metals) display absorption-emission P Cyg type profiles. All the absorption lines are shifted toward shorter wavelengths, suggesting an outflow of stellar material. The expansion velocity of the envelope derived from the Swan bands arising there is Vexp=42km/s. The highest wind velocity determined from the absorptional wings of FeII(42) P Cygni profiles reachs 240km/s. Based on the star's kinematic characteristics and the amount of interstellar absorption, the distance to this object is d~3-4kpc.
1266. Spectral and UBV analysis of {epsilon} Aur
ID:
ivo://CDS.VizieR/J/A+A/530/A146
Title:
Spectral and UBV analysis of {epsilon} Aur
Short Name:
J/A+A/530/A146
Date:
21 Oct 2021
Publisher:
CDS
Description:
A series of 353 red electronic spectra (from three observatories, mostly from 6300 to 6700{AA}) obtained between 1994 and 2010, and of 171 UBV photometric observations (from two observatories) of the 2010 eclipse, were analyzed in an effort to better understand epsilon Aur, the well-known, but still enigmatic eclipsing binary with the longest known orbital period (~27yrs).
1267. Spectral observations of symbiotic LL Cas
ID:
ivo://CDS.VizieR/J/A+A/479/529
Title:
Spectral observations of symbiotic LL Cas
Short Name:
J/A+A/479/529
Date:
21 Oct 2021
Publisher:
CDS
Description:
All tables contain the results of the spectral and photometric observations of the symbiotic star LL Cas. Observations were carried out within 1986-2006 with a slit spectrograph attached to the 0.7-m telescope of the Fessenkov Astrophysical Institute (Almaty, Kazakhstan). Some photoelectric observations of LL Cas with broad-band filters were carried out on a photoelectric polarimeter mounted on the 1-m Zeiss telescope (Assy-Turgen, Kazakhstan).
1268. Spectral significance for 15 delta Scuti
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.
1269. Spectra of NGC 1333 Class I-Class II stars
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.
1270. Spectra of unusual optical transient SCP 06F6
ID:
ivo://CDS.VizieR/J/ApJ/690/1358
Title:
Spectra of unusual optical transient SCP 06F6
Short Name:
J/ApJ/690/1358
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present observations of SCP 06F6, an unusual optical transient discovered during the Hubble Space Telescope Cluster Supernova Survey. The transient brightened over a period of ~100 days, reached a peak magnitude of ~21.0 in both i_775_ and z_850_, and then declined over a similar timescale. There is no host galaxy or progenitor star detected at the location of the transient to a 3{sigma} upper limit of i_775_>=26.4 and z_850_>=26.1, giving a corresponding lower limit on the flux increase of a factor of ~120. Multiple spectra show five broad absorption bands between 4100{AA} and 6500{AA}, and a mostly featureless continuum longward of 6500{AA}. The shape of the light curve is inconsistent with microlensing. The transient's spectrum, in addition to being inconsistent with all known supernova types, does not match any spectrum in the Sloan Digital Sky Survey database. We suggest that the transient may be one of a new class.