- ID:
- ivo://CDS.VizieR/J/A+A/554/A108
- Title:
- Periodic variables in NGC 3766
- Short Name:
- J/A+A/554/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the population of periodic variable stars in the open cluster NGC3766 based on a 7-year multiband monitoring campaign conducted on the 1.2m Swiss Euler telescope at La Silla, Chili. The data reduction, light curve cleaning, and period search procedures, combined with the long observation time line, allowed us to detect variability amplitudes down to the mmag level. The variability properties were complemented with the positions in the color-magnitude and color-color diagrams to classify periodic variable stars into distinct variability types. We find a large population (36 stars) of new variable stars between the red edge of slowly pulsating B (SPB) stars and the blue edge of delta Sct stars, a region in the Hertzsprung-Russell (HR) diagram where no pulsation is predicted to occur based on standard stellar models. The bulk of their periods ranges from 0.1 to 0.7d, with amplitudes between 1 and 4mmag for the majority of them. About 20% of stars in that region of the HR diagram are found to be variable, but the number of members of this new group is expected to be higher, with amplitudes below our mmag detection limit. The properties of this new group of variable stars are summarized and arguments set forth in favor of a pulsation origin of the variability, with g-modes sustained by stellar rotation. Potential members of this new class of low-amplitude periodic (most probably pulsating) A and late-B variables in the literature are discussed. We additionally identify 16 eclipsing binary, 13 SPB, 14 delta Sct, and 12 gamma Dor candidates, as well as 72 fainter periodic variables. All are new discoveries. We encourage searching for this new class of variables in other young open clusters, especially in those hosting a rich population of Be stars.
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- ID:
- ivo://CDS.VizieR/J/A+AS/113/483
- Title:
- Photometric and radial velocity of RRLyr stars
- Short Name:
- J/A+AS/113/483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Almost simultaneous measurements in the Geneva seven-colour photometric system and in radial velocities with the spectrometer CORAVEL for five RR Lyrae field stars were obtained in order to apply the Baade-Wesselink method to this kind of variable stars. In this paper the observational data on these stars are presented; the analysis of their physical parameters will be published in the forthcoming paper of the series.
- ID:
- ivo://CDS.VizieR/J/A+AS/106/141
- Title:
- Photometry of luminous blue variables
- Short Name:
- J/A+AS/106/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An extensive photometric dataset has been compiled for six Luminous Blue Variables (LBVs). The dataset comprises published and unpublished measurements in the Stroemgren, Geneva and Walraven photometric systems. The measurements within each individual system are presented in a uniform manner. Combining observations from these three photometric systems, a VJ light curve has been constructed for each LBV. Examination of the light curves reveals variations on widely different magnitude and time scales. For explanation about the photometric sytems, see the definitions in the General Catalogue of Photometric Data: about uvby (Stroemgren) <GCPD/04> ; Geneva <GCPD/13> ; Walraven VBLUW <GCPD/11>
- ID:
- ivo://CDS.VizieR/J/A+AS/111/41
- Title:
- Photometry of magnetic CP stars
- Short Name:
- J/A+AS/111/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry in the Stroemgren and Geneva systems is used to improve the ephemerides of the magnetic CP stars 56 Tau, HD 111133, HD 126515 and HD 215441.
- ID:
- ivo://CDS.VizieR/II/25
- Title:
- Photometry of orange-red CaI triplet in Late-Type Stars
- Short Name:
- II/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Calcium absorption lines were measured using narrow-band photometry on 296 high and low velocity G8-K5 stars of all luminosity classes. Because the blue-violet region of the stellar spectra is too crowded for narrow-band photometry, this investigation of abundance involved measurements of the orange-red CaI triplet 4(3)P-5(3)S, with wavelengths 6102.7, 6122.2 and 6162.2{AA}. "Calcium triplet ratio" is defined as "the measured light intensity ratios, comparison/central regions, calibrated in terms of a standard lamp as described in previous Cambridge papers". The catalog (table I of paper) includes HD number, (B-V) color index, Mg b ratio, H{alpha} ratio, Calcium triplet ratio, and a running number.
- ID:
- ivo://CDS.VizieR/II/45
- Title:
- Photometry of strong CN stars
- Short Name:
- II/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A group of 185 late G and K giants, selected from the US Naval Observatory Catalog of Photoelectric Observations (Cat. II/4) because they had Ultraviolet deficiences, were observed with the intermediate band photometric system of the David Dunlap Observatory (defined by McClure and van den Bergh 1968AJ.....73..313M). The DDO photometry is included in Cat. II/17.
- ID:
- ivo://CDS.VizieR/J/ApJ/795/38
- Title:
- Photometry/spectroscopic measurements for KA1858+4850
- Short Name:
- J/ApJ/795/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among the brightest active galaxies monitored by the Kepler mission. We have carried out a reverberation mapping campaign designed to measure the broad-line region size and estimate the mass of the black hole in this galaxy. We obtained 74 epochs of spectroscopic data using the Kast Spectrograph at the Lick 3 m telescope from 2012 February to November, and obtained complementary V-band images from five other ground-based telescopes. We measured the H{beta} light curve lag with respect to the V-band continuum light curve using both cross-correlation techniques (CCF) and continuum light curve variability modeling with the JAVELIN method and found rest-frame lags of {tau}_CCF_=13.53_-2.32_^+2.03^ days and {tau}_JAVELIN_=13.15_-1.00_^+1.08^ days. The H{beta} rms line profile has a width of {sigma}_line_=770+/-49 km/s. Combining these two results and assuming a virial scale factor of f=5.13, we obtained a virial estimate of M_BH_=8.06_-1.72_^+1.59^x10^6^M_{sun}_ for the mass of the central black hole and an Eddington ratio of L/L_Edd_{approx}0.2. We also obtained consistent but slightly shorter emission-line lags with respect to the Kepler light curve. Thanks to the Kepler mission, the light curve of KA1858+4850 has among the highest cadences and signal-to-noise ratios ever measured for an active galactic nucleus; thus, our black hole mass measurement will serve as a reference point for relations between black hole mass and continuum variability characteristics in active galactic nuclei.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/27
- Title:
- Radial velocity measurements in LAMOST-II
- Short Name:
- J/ApJS/244/27
- Date:
- 09 Dec 2021
- Publisher:
- CDS
- Description:
- The radial velocity (RV) is a basic physical quantity that can be determined through the Doppler shift of the spectrum of a star. The precision of the RV measurement depends on the resolution of the spectrum we used and the accuracy of wavelength calibration. In this work, radial velocities of the Large Sky Area Multi-Object Fibre Spectroscopic Telescope-II (LAMOST-II) medium-resolution (R~7500) spectra are measured for 1,594,956 spectra (each spectrum has two wavebands) through matching with templates. A set of RV standard stars are used to recalibrate the zero point of the measurement, and some reference sets with RVs derived from medium-/high-resolution observations are used to evaluate the accuracy of the measurement. By comparing with reference sets, the accuracy of our measurement can get 0.0277km/s with respect to radial velocities of standard stars. The intrinsic precision is estimated with the multiple observations of single stars, which can be achieved to 1.36km/s, 1.08km/s, and 0.91km/s for the spectra at signal-to-noise levels of 10, 20, and 50, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A122
- Title:
- Radial-velocity of CARMENES M dwarfs
- Short Name:
- J/A+A/614/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from ~1cm/s to ~1km/s, depending on various stellar and activity parameters. We investigate the observed relations between RVs, stellar activity, and stellar parameters of M dwarfs by analyzing CARMENES high-resolution visual-channel spectra (0.5-1um), which were taken within the CARMENES RV planet survey during its first 20 months of operation. During this time, 287 of the CARMENES- sample stars were observed at least five times. From each spectrum we derived a relative RV and a measure of chromospheric Halpha emission. In addition, we estimated the chromatic index (CRX) of each spectrum, which is a measure of the RV wavelength dependence. Despite having a median number of only 11 measurements per star, we show that the RV variations of the stars with RV scatter of >10m/s and a projected rotation velocity vsini>2km/s are caused mainly by activity. We name these stars 'active RV-loud stars' and find their occurrence to increase with spectral type: from ~3% for early-type M dwarfs (M0.0-2.5V) through ~30% for mid-type M dwarfs (M3.0-5.5V) to >50% for late-type M dwarfs (M6.0-9.0V). Their RV-scatter amplitude is found to be correlated mainly with vsini. For about half of the stars, we also find a linear RV-CRX anticorrelation, which indicates that their activity-induced RV scatter is lower at longer wavelengths. For most of them we can exclude a linear correlation between RV and Halpha emission. Our results are in agreement with simulated activity-induced RV variations in M dwarfs. The RV variations of most active RV-loud M dwarfs are likely to be caused by dark spots on their surfaces, which move in and out of view as the stars rotate.
- ID:
- ivo://CDS.VizieR/J/A+A/346/586
- Title:
- Rotating models of A and F stars
- Short Name:
- J/A+A/346/586
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnitude differences between rotating and non-rotating copartners for a grid of models with solar metallicity are tabulated here. The results are expressed in terms of the dimensionless angular velocity w-bar- defined in Eq.(1) of the paper, the angle of inclination i and the atmospheric parameters T_e_ and g_e_ defined in Eqs.(22) and (21), respectively. To obtain the absolute magnitudes for a given rotating model, the magnitudes of a non-rotating model with T_eff_=T_e_, g=g_e_ and the same intrinsic luminosity must be added. Results are given for the filters in the Geneva, Johnson and Stroemgren systems. Eq (1): w-bar = {Omega}/{Omega}_c_, where {Omega} is the angular velocity of the star, and {Omega}_c_^2^=8GM/(27R^3^_p_), where M is the mass and R_p_ the polar radius.
