- ID:
- ivo://CDS.VizieR/J/AJ/149/168
- Title:
- Differential VRI photometry of HI Dra
- Short Name:
- J/AJ/149/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed investigation of the low-amplitude contact binary HI Dra based on the new VR_c_I_c_ CCD photometric light curves (LCs) combined with published radial velocity (RV) curves. Our completely covered LCs were analyzed using PHOEBE and revealed that HI Dra is an overcontact binary with low fill-out factor f=24+/-4(%) and temperature difference between the components of 330K. Two spotted models are proposed to explain the LC asymmetry, between which the A subtype of W UMa type eclipsing systems, with a cool spot on the less massive and cooler component, proves to be more plausible on evolutionary grounds. The results and stability of the solutions were explored by heuristic scan and parameter perturbation to provide a consistent and reliable set of parameters and their errors. Our photometric modeling and RV curve solution give the following absolute parameters of the hot and cool components, respectively: M_h_=1.72+/-0.08M_{sun}_ and M_c_=0.43+/-0.02M_{sun}_, R_h_=1.98+/-0.03R_{sun}_ and R_c_=1.08+/-0.02R_{sun}_, and L_h_=9.6+/-0.1L_{sun}_ and L_c_=2.4+/-0.1L_{sun}_. Based on these results the initial masses of the progenitors (1.11+/-0.03M_{sun}_ and 2.25+/-0.07M_{sun}_, respectively) and a rough estimate of the age of the system of 2.4Gyr are discussed.
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- ID:
- ivo://CDS.VizieR/J/A+A/601/A76
- Title:
- DIRECT lightcurves of 21 luminous YSGs in M33
- Short Name:
- J/A+A/601/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of massive stars surviving the red supergiant (RSG) stage remains unexplored due to the rarity of such objects. The yellow hypergiants (YHGs) appear to be the warm counterparts of post-RSG classes located near the Humphreys-Davidson upper luminosity limit, which are characterized by atmospheric instability and high mass-loss rates. We aim to increase the number of YHGs in M33 and thus to contribute to a better understanding of the pre-supernova evolution of massive stars. Optical spectroscopy of five dust-enshrouded YSGs selected from mid-IR criteria was obtained with the goal of detecting evidence of extensive atmospheres. We also analyzed BVIc photometry for 21 of the most luminous YSGs in M33 to identify changes in the spectral type. To explore the properties of circumstellar dust, we performed SED-fitting of multi-band photometry of the 21 YSGs. We find three luminous YSGs in our sample to be YHG candidates, as they are surrounded by hot dust and are enshrouded within extended, cold dusty envelopes. Our spectroscopy of star 2 shows emission of more than one H{alpha} component, as well as emission of CaII, implying an extended atmospheric structure. In addition, the long-term monitoring of the star reveals a dimming in the visual light curve of amplitude larger than 0.5mag that caused an apparent drop in the temperature that exceeded 500K. We suggest the observed variability to be analogous to that of the Galactic YHG {rho} Cas. Five less luminous YSGs are suggested as post-RSG candidates showing evidence of hot or/and cool dust emission. We demonstrate that mid-IR photometry, combined with optical spectroscopy and time-series photometry, provide a robust method for identifying candidate YHGs. Future discovery of YHGs in Local Group galaxies is critical for the study of the late evolution of intermediate-mass massive stars.
- ID:
- ivo://CDS.VizieR/J/A+A/464/641
- Title:
- Double stars CCD photometry and astrometry. III
- Short Name:
- J/A+A/464/641
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent CCD observations were performed in the period 1998-2004 for a large sample of visual double and multiple stars selected from the Hipparcos Catalogue (Cat. <I/239>) and/or from the Gliese Catalogue of Nearby Stars (Cat. <V/70>). Accurate astrometric and photometric data allowing us to characterise the individual components are provided. These data are compared to Hipparcos data or to data from an older epoch to assess the nature of the observed systems. We simultaneously apply a Moffat-Lorentz profile with a similar shape to all detected components and adjust the profile parameters from which we obtain the relative astrometric position (epoch, position angle, angular separation) as well as differential multi-colour photometry (filters (B)VRI).
- ID:
- ivo://CDS.VizieR/J/A+A/463/503
- Title:
- Early-type dwarf galaxies in Fornax cluster
- Short Name:
- J/A+A/463/503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse the photometric properties of the early-type Fornax cluster dwarf galaxy population, based on a wide field imaging study of the central cluster area in V and I. We used the instrument/telescope combination IMACS/Magellan at Las Campanas Observatory. We create a fiducial sample of Fornax cluster dwarf ellipticals (dEs) in the following three steps: (1) To verify cluster membership, we measured I-band surface brightness fluctuation (SBF) distances to candidate dEs; (2) We re-assessed morphological classifications for candidate dEs too faint for SBF detection; and (3) We searched for new candidate dEs in the size-luminosity regime close to the resolution limit of previous surveys. (1) We confirm cluster membership for 28 candidate dEs in the range -16.6<M_V_<-10.1mag by means of SBF distances. We find no SBF background galaxy. (2) Of 51 further candidate dEs in the range -13.2<M_V_<-8.6mag, 2/3 are confirmed as probable cluster members by morphological re-assessment, while 1/3 are re-classified as probable background objects. (3) We find 12 new dE candidates in the range -12.3<M_V_<-8.8mag. The surface brightness-magnitude relation defined by the resulting fiducial dE sample shows that Fornax dEs are about 40% larger than Local Group dEs. The Fornax dE sample furthermore defines a colour-magnitude relation that appears slightly shallower than that of Local Group dEs. The early-type dwarf galaxy luminosity function in Fornax has a faint end slope alpha=-1.1+/- 0.1.
- ID:
- ivo://CDS.VizieR/J/MNRAS/292/499
- Title:
- EFAR photometric data
- Short Name:
- J/MNRAS/292/499
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present R-band CCD photometry for 776 galaxies observed in the EFAR (Elliptical FAR away) project. The photometry is compared with photoelectric data, showing that a common zero-point good to better than 1% and a precision of 0.03mag per zero-point have been achieved. We give the circularly averaged surface brightness profiles and the photometric parameters of the 762 program galaxies, D(n) diameters (at 20.5mag/arcsec^2^), half-luminosity radii Re, total magnitudes m_T_, and average effective surface brightnesses <SBe>. More than 80% of the profiles have a global S/N ratio larger than 300. The extrapolation needed to derive total magnitudes is less than 10% for 80% of the fits. More than 80% of the galaxies have mean effective surface brightness larger than the observed sky brightness. In 90% of the profiles the estimate of the contamination of the sky by the galaxy light is less than 1%. We derive total magnitudes and half-luminosity radii to better than 0.15mag and 25%, respectively, for 90% of our sample. In contrast, external comparisons show that data in the literature can be strongly affected by systematic errors due to large extrapolations, small radial range, sky subtraction errors, seeing effects, and the use of a simple R^1/4^ fit. The resulting errors can easily amount to more than 0.5mag in the total magnitudes and 50% in the half-luminosity radii.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A153
- Title:
- EMCCD observations of the 2018 Draconids
- Short Name:
- J/A+A/635/A153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Several authors predicted an outburst of the Draconid meteor shower in 2018, but with an uncertain level of activity. Optical meteor observations were used to derive the population and mass indices, flux, and radiant positions of Draconid meteors. We performed 90 minutes of multi-station observations after the predicted peak of activity were performed using highly sensitive Electron Multiplying Charge Coupled Device (EMCCD) cameras. The data calibration is discussed in detail. A novel maximum likelihood estimation method of computing the population and mass index with robust error estimation was developed. We apply the method to observed Draconids and use the values to derive the flux. Meteor trajectories are computed and compared to predicted radiant positions from meteoroid ejection models. We find a mass index of 1.74+/-0.18 in the 30 min bin after the predicted peak, and 2.32+/-0.27 in the subsequent 60 min. The location and the dispersion of the radiant are a good match to modeled values, but there is an offset of 0.4{deg} in solar longitude.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A43
- Title:
- EPOCH Project. EROS-2 LMC periodic variables
- Short Name:
- J/A+A/566/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The EPOCH (EROS-2 periodic variable star classification using machine learning) project aims to detect periodic variable stars in the EROS-2 light curve database. In order to classify these variables, we first build a training set by compiling known variables in the Large Magellanic Could area from the OGLE and MACHO surveys. We crossmatch these variables with the EROS-2 sources and extract 22 variability features from 28,392 light curves of the corresponding EROS-2 sources. We then use Random Forests to classify the EROS-2 sources in the training set. We design the model to separate not only Delta Scuti stars, RR Lyraes, Cepheids, eclipsing binaries and long-period variables, the "superclasses", but also their subclasses, such as RRab, RRc, RRd and RRe for RR Lyraes, and similarly for the other variable types. We apply the trained model to the entire EROS-2 LMC database containing about 29 million sources and find 117,234 periodic variable candidates. Out of these 117,234 periodic variables, 55,285 have not been discovered by either OGLE or MACHO variability studies. This set comprises 1906 Delta Scuti stars, 6,607 RR Lyraes, 638 Cepheids, 178 Type II Cepheids, 34,562 eclipsing binaries and 11,394 long-period variables.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A74
- Title:
- Extended main-sequence turn-offs isochrones
- Short Name:
- J/A+A/632/A74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extended main-sequence turn-offs (eMSTO) are a commonly observed property of young clusters. A global theoretical interpretation for the eMSTOs is still lacking, but stellar rotation is considered a necessary ingredient to explain the eMSTO. We aim to assess the importance of core-boundary and envelope mixing in stellar interiors for the interpretation of eMSTOs in terms of one coeval population. We construct isochrone-clouds based on interior mixing profiles of stars with a convective core calibrated from asteroseismology of isolated galactic field stars. We fit these isochrone-clouds to the measured eMSTO to estimate the age and core mass of the stars in the two young clusters NGC 1850 and NGC 884, assuming one coeval population and fixing the metallicity to the one measured from spectroscopy. We assess the correlations between the interior mixing properties of the cluster members and their rotational and pulsational properties. We find that stellar models based on asteroseismically-calibrated interior mixing profiles lead to enhanced core masses of eMSTO stars and can explain a good fraction of the observed eMSTOs of the two considered clusters in terms of one coeval population of stars, with similar ages to those in the literature, given the large uncertainties. The rotational and pulsational properties of the stars in NGC 884 are not sufficiently well known to perform asteroseismic modelling, as it is achieved for field stars from space photometry. The stars in NGC 884 for which we have vsini and a few pulsation frequencies show no correlation between these properties and the core masses of the stars that set the cluster age. Future cluster space asteroseismology may allow to interpret the values of the core masses in terms of the physical processes that cause them, based on the modelling of the interior mixing profiles for the individual member stars with suitable identified modes.
- ID:
- ivo://CDS.VizieR/J/A+AS/130/359
- Title:
- Faint photometric BVR CCD sequences
- Short Name:
- J/A+AS/130/359
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometric standard stars in the BVRc system of Johnson and Cousins are presented for two regions of importance in studies of galactic structure and kinematics: the North galactic pole (NGP), and a second galactic plane region (GPR) toward the anticenter. Precision and accuracy are better than 0.05mag down to V=18-18.5. These data are part of the Second Guide Photometric Catalog (GSPC-II).
- ID:
- ivo://CDS.VizieR/J/AJ/152/91
- Title:
- Faint UBVRI standard stars at +50{deg} declination
- Short Name:
- J/AJ/152/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Precise and accurate CCD-based UBVRI photometry is presented for ~2000 stars distributed around the sky in a declination zone centered approximately at +50{deg}. Their photometry has been calibrated to the standard Johnson UBV and Kron-Cousins RI systems through observations of the UBVRI standard stars presented in the various works of Landolt. The magnitude and color range for these stars are 12<~V<~22 and -0.3<~(B-V)<~1.8, respectively. Each star averages 13 measures in each UBVRI filter from data taken on 41 different photometric nights obtained over a 21 month period. Hence, there now exists a network of faint UBVRI photometric standard stars centered on the declination zones {delta}=-50{deg}, 0{deg}, and +50{deg}.
