- 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.
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- 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/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.
- 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).
- 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).
- 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/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.
- ID:
- ivo://CDS.VizieR/J/A+A/621/A6
- Title:
- Spectro-interferometric observation of SW Vir
- Short Name:
- J/A+A/621/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a near-infrared spectro-interferometric observation of the non-Mira-type, semiregular asymptotic giant branch star SW Vir. Our aim is to probe the physical properties of the outer atmosphere with spatially resolved data in individual molecular and atomic lines. We observed SW Vir in the spectral window between 2.28 and 2.31 micron with the near-infrared interferometric instrument AMBER at ESO's Very Large Telescope Interferometer (VLTI). Thanks to AMBER's high spatial resolution and high spectral resolution of 12000, the atmosphere of SW Vir has been spatially resolved not only in strong CO first overtone lines but also in weak molecular and atomic lines of H_2_O, CN, HF, Ti, Fe, Mg, and Ca. While the uniform-disk diameter of the star is 16.23+/-0.20mas in the continuum, it increases up to 22-24mas in the CO lines. Comparison with the MARCS photospheric models reveals that the star appears larger than predicted by the hydrostatic models not only in the CO lines but also even in the weak molecular and atomic lines. We found that this is primarily due to the H2O lines (but also possibly due to the HF and Ti lines) originating in the extended outer atmosphere. Although the H_2_O lines manifest themselves very little in the spatially unresolved spectrum, the individual rovibrational H_2_O lines from the outer atmosphere can be identified in the spectro-interferometric data. Our modeling suggests an H_2_O column density of 10^19^-10^20^cm^-2^ in the outer atmosphere extending out to ~2R*. Our study has revealed that the effects of the nonphotospheric outer atmosphere are present in the spectro-interferometric data not only in the strong CO first overtone lines but also in the weak molecular and atomic lines. Therefore, analyses of spatially unresolved spectra, such as for example analyses of the chemical composition, should be carried out with care even if the lines appear to be weak.
- 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.
