- ID:
- ivo://CDS.VizieR/J/A+A/632/A95
- Title:
- Light curves of NGC 6910 pulsating stars
- Short Name:
- J/A+A/632/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this study is to obtain the age of the open cluster NGC 6910 by means of ensemble asteroseismology of the early-type pulsating members, to derive their stellar parameters, and to classify the excited modes. We used time-series analysis, performed photometric and spectroscopic mode identification, and calculated grids of evolutionary and seismic models to apply the procedure of ensemble asteroseismology for nine pulsating members of NGC 6910. With two iterations of the procedure of ensemble asteroseismology we derived an age of 10.6^+0.9^_-0.8_Myr for NGC 6910. We also identified the degree l for 8 of 37 modes detected in these stars and classified all modes in terms of p, g, and mixed-mode pulsations. Of the nine pulsating stars examined in the paper, eight are {beta} Cep stars, including three that are hybrid {beta} Cep and slowly pulsating B-type (SPB) pulsators, and one is an SPB star. Interestingly, the least massive {beta} Cep star, NGC 6910-38, has a mass of about 5.6 solar masses. The present theory does not predict unstable p modes in B-type stars with such a low mass. The g modes with relatively high frequencies (>3.5d^-1^), observed in three members of the cluster, are also stable according to seismic modelling. Both findings pose a challenge for theoretical calculations and prompt a revision of the opacities. The procedure of ensemble asteroseismology was found to be successful for NGC 6910 and {chi} Per on the basis of pulsating B-type stars and can therefore be applied to other young open clusters that are rich in such stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/404/621
- Title:
- Light curves of ROTSE-I delta Scuti type stars
- Short Name:
- J/A+A/404/621
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-passband CCD photometry of 20 ROTSE-I {delta} Scuti type pulsating stars and 1 RR Lyrae star to re-classify their variable types using the comparison of amplitudes between V and I passbands. For the re-classification, we used a criterion that pulsating stars have larger amplitude differences between passbands than eclipsing binaries because brightness changes of pulsating stars are mainly due to the temperature variations. As a result, only six stars were re-confirmed as {delta} Scuti variables and thirteen stars turned out to be W UMa type eclipsing binaries. The other two stars were identified as one cataclysmic variable and one non-variable, respectively. Our results suggest that a number of ROTSE-I {delta} Scuti type stars, which do not show typical pulsating light curves of high amplitude {delta} Scuti stars, are W UMa type eclipsing binaries.
- ID:
- ivo://CDS.VizieR/J/A+A/524/A86
- Title:
- Light curves of SDSS J003941.06+005427.5
- Short Name:
- J/A+A/524/A86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present VLT spectroscopy and NTT photometry of the faint cataclysmic binary SDSS J003941.06+005427.5. This object shows triple-peaked H{alpha} emission with all three peaks variable in both strength and velocity. We measure an orbital period of 91.395+/-0.093min from the velocity variations of the wings of the Halpha emission line. Using the GALEX and SDSS photometry of this object, we determine a white dwarf temperature of 15000K and a very late (>=L2) spectral type for the companion star. These measurements, plus the relatively long orbital period, suggest that SDSS J003941.06+005427.5 may be a post-bounce cataclysmic variable. Doppler maps of the H{alpha} and HeI 6678{AA} emission features show an accretion disc with a non-uniform brightness and departures from Keplerian flow. The third emission peak is detected only in H{alpha} and at a relatively low velocity amplitude of 202+/-3km/s. We are unable to explain this emission as arising from either the white dwarf, the secondary star, or the accretion disc. We tentatively attribute this mysterious central peak to a coronal loop anchored at the secondary star. If confirmed, this would be the first example of a slingshot prominence in a CV with a low mass-transfer rate and/or a fully convective secondary star.
- ID:
- ivo://CDS.VizieR/J/A+A/507/929
- Title:
- Light curves of SDSS J100658.40+233724.4
- Short Name:
- J/A+A/507/929
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present time-resolved spectroscopy and photometry of SDSS J100658.40+233724.4, which we have discovered to be an eclipsing cataclysmic variable with an orbital period of 0.18591324 days (267.71507min). The observed velocity amplitude of the secondary star is 276+/-7km/s, which an irradiation correction reduces to 258+/-12km/s. Doppler tomography of emission lines from the infrared calcium triplet supports this measurement. We have modelled the light curve using the LCURVE code and Markov Chain Monte Carlo simulations, finding a mass ratio of 0.51+/-0.08. From the velocity amplitude and the light curve analysis we find the mass of the white dwarf to be 0.78+/-0.12M_{sun}_ and the masses and radii of the secondary star to be 0.40+/-0.10M_{sun}_ and 0.466+/-0.036R_{sun}_, respectively. The secondary component is less dense than a normal main sequence star but its properties are in good agreement with the expected values for a CV of this orbital period. By modelling the spectral energy distribution of the system we find a distance of 676+/-40pc and estimate a white dwarf effective temperature of 16500+/-2000K.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A111
- Title:
- Light curves of two NGC6981 variables
- Short Name:
- J/A+A/553/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two previously unknown variable stars in the crowded central region of the globular cluster NGC 6981 are presented. The observations were made using the electron multiplying CCD (EMCCD) camera at the Danish 1.54m Telescope at La Silla, Chile. The two variables were not previously detected by conventional CCD imaging because of their proximity to a bright star. This discovery demonstrates that EMCCDs are a powerful tool for performing high-precision time-series photometry in crowded fields and near bright stars, especially when combined with difference image analysis.
- ID:
- ivo://CDS.VizieR/J/MNRAS/357/645
- Title:
- LMC far-UV HST observations
- Short Name:
- J/MNRAS/357/645
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new analysis of the deepest pure-ultraviolet (UV) observations with the highest angular resolution ever performed. A set of 12 exposures with the Hubble Space Telescope (HST) WFPC2 and F160BW filter obtained in parallel observing mode, which cover ~12arcmin^2^ in the Large Magellanic Cloud (LMC), north of the bar and in the 'general field' region of the LMC, contain stars with far-UV monochromatic magnitudes as faint as 22mag. The 198 detected UV sources represent an accumulated exposure of 2x10^4^s and reveal stars as faint as m_UV_=~20mag. We combine these observations with deep UBVI charge-coupled device (CCD) imaging of the same region reaching as faint as V=~26mag, and reselect probable optical counterparts for the UV sources. After a two-stage search-and-analysis process, we detect robust counterparts for 129 stars. These are mostly upper main-sequence stars, from early B to early A spectral classes, with several F stars. We point out the lack of blue supergiants, which could have been easily detected in our survey. We measure a foreground extinction E(B-V)=~0.08mag by Galactic dust and a surface density of star formation rate twice the average Galactic value. These observations indicate that relatively recent star formation took place even off the bar of the LMC.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A185
- Title:
- Long-term optical monitoring of TeV Blazars
- Short Name:
- J/A+A/620/A185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ten years of R-band monitoring data of 31 northern blazars which were either detected at very high-energy (VHE) gamma rays or listed as potential VHE gamma-ray emitters. The data comprise 11820 photometric data points in the R-band obtained in 2002-2012. We analyzed the light curves by determining their power spectral density (PSD) slopes assuming a power-law dependence with a single slope beta and a Gaussian probability density function (PDF). We used the multiple fragments variance function (MFVF) combined with a forward-casting approach and likelihood analysis to determine the slopes and perform extensive simulations to estimate the uncertainties of the derived slopes. We also looked for periodic variations via Fourier analysis and quantified the false alarm probability through a large number of simulations. Comparing the obtained PSD slopes to values in the literature, we find the slopes in the radio band to be steeper than those in the optical and gamma rays. Our periodicity search yielded one target, Mrk 421, with a significant (p<5%) period. Finding one significant period among 31 targets is consistent with the expected false alarm rate, but the period found in Mrk 421 is very strong and deserves further consideration.
- ID:
- ivo://CDS.VizieR/J/ApJS/134/103
- Title:
- Low-mass members of IC 2391
- Short Name:
- J/ApJS/134/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified a large sample of probable low-mass members of the young open cluster IC 2391 based on optical (VRIZ) and infrared (JHKs) photometry. Our sample includes 50 probable members and 82 possible members, both very low-mass stars and brown dwarfs. We also provide accurate positions for these stars and brown dwarf candidates derived from red UK Schmidt plates measured using the microdensitometer SuperCOSMOS. Assuming an age of 53Myr, we estimate that we have reached a mass of 0.025M_{sun}_, if the identified objects are indeed members of IC 2391.
- ID:
- ivo://CDS.VizieR/J/MNRAS/333/423
- Title:
- Luminosity function of the Virgo Cluster
- Short Name:
- J/MNRAS/333/423
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the galaxy luminosity function (LF) for the Virgo Cluster between blue magnitudes M_B_=-22 and -11 from wide-field charge-coupled device (CCD) imaging data. The data used here were taken on various observing runs during Spring 1999 and Spring 2000 as part of the INT Wide Field Survey (WFS; http://www.ast.cam.ac.uk/wfcsur ; McMahon et al., 2001NewAR..45...97M).
- ID:
- ivo://CDS.VizieR/J/other/JAVSO/48.201
- Title:
- Maintaining the Ephemeris of 20 CoRoT planets
- Short Name:
- J/other/JAVSO/48
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present 33 transit minimum times of 20 transiting planets discovered by the CoRoT space mission, which have been obtained from ground-based observations since the mission's end in 2012, with the objective to maintain the ephemeris of these planets and to identify potential transit time variations. Twelve of the observed planets are in the CoRoT fields near the galactic center and the remaining eight planets are in the fields near the anticenter. We detect indications for significant transit timing variations in the cases of CoRoT 3b, 11b, 13b, 27b. For two more planets (CoRoT 18b and 20b) we conclude that timing offsets in early follow-up observations led to ephemeris in discovery publications that are inconsistent with timings from follow-up observations in later epochs. In the case of CoRoT-20b, this might be due to the influence from a further non-transiting planet. We also note that a significant majority (23 of 33) of our reported minimum times have negative O-C values, albeit most of them are within the expected uncertainty of the ephemeris.
