- ID:
- ivo://CDS.VizieR/J/A+A/542/A89
- Title:
- Hvar survey for roAp stars. I.
- Short Name:
- J/A+A/542/A89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rapidly oscillating Ap (roAp) stars exhibit short time scale photometric and/or radial velocity variations, which are most important to test current pulsation models as well as our assumptions of the atmospheric structure characteristics. In addition, their chemical peculiarity makes them very interesting for probing stellar formation and evolution in the presence of a global magnetic field. To date, only a limited number of about 45 roAp stars are known. In order to increase the sample, we obtained photometric time series of 20 good roAp candidates to search for pulsations. We present the time series analysis of about 60 hours of CCD photometry taken at the 1 meter Austrian-Croatian Telescope (Hvar Observatory) and derive effective temperatures for the programme objects. The upper amplitude limits of the Fourier spectra are typically below 2mmag in Bessell B with one good candidate for follow-up observations to find possible pulsation. In addition, we present a list of further roAp candidates, worth to be (re)investigated.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/116/2549
- Title:
- HW Per UBV differential photometry
- Short Name:
- J/AJ/116/2549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A complete photometric analysis for the eclipsing binary candidate HW Persei is presented. The UBV observations were taken at Lowell Observatory in 1996 January. Three epochs of minimum light were determined, and an improved linear ephemeris was calculated. The O-C residuals, spanning some 60 years, show no evidence of a period change. Standard magnitudes are given, and reddening estimates are made. The first published synthetic light curve solutions of HW Per reveal that it is near a state of critical contact, which we define as both components exactly filling their respective Roche lobes. The primary component is of A8 spectral type, and the secondary component is a K3-K4 spectral type. The nature of the model is discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3181
- Title:
- HW Vir differential VR light curves
- Short Name:
- J/AJ/137/3181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the very short period subdwarf B eclipsing binary HW Vir, we present new CCD photometry made from 2000 through 2008. In order to obtain consistency of the binary parameters, our new light curves, showing sharp eclipses and a striking reflection effect, were analyzed simultaneously with previously published radial velocity data. The secondary star parameters of M_2_=0.14M_{sun}_, R_2_=0.18R_{sun}_, and T_2_=3084K are consistent with those of an M6-7 main-sequence star. A credibility issue regarding bolometric corrections is emphasized. More than 250 times of minimum light, including our 41 timings and spanning more than 24yr, were used for a period study. From a detailed analysis of the O-C diagram, it emerged that the orbital period of HW Vir has varied as a combination of a downward-opening parabola and two sinusoidal variations, with cycle lengths of P_3_=15.8yr and P_4_=9.1yr and semiamplitudes of K_3_=77s and K_4_=23s, respectively. The continuous period decrease with a rate of -8.28x10^-9^d/yr may be produced by angular momentum loss due to magnetic stellar wind braking but not by gravitational radiation.
2834. Hyades binaries
- ID:
- ivo://CDS.VizieR/J/A+A/310/879
- Title:
- Hyades binaries
- Short Name:
- J/A+A/310/879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived accurate and homogeneous lithium abundances in 49 Main Sequence binary systems belonging to the Hyades open cluster by using a deconvolution method to determine individual magnitudes and colors for the primary and secondary components of the binary. The input parameters of the model are the observed Li equivalent width, the actual distance to the binary, the integrated apparent magnitude and the integrated colors of the binaries -BV(RI)_K_. We show that the general behavior is the same in binaries and in single stars (Li is depleted faster in K stars than in G stars and there is a deep dip for mid-F stars). However, there is a larger scatter in the abundances of binary systems than in single stars. Moreover, in general, binary systems have an overabundance, which is more conspicuous in close binaries. In fact, there is a cut-off period, which can be estimated as P_orb_~9d. This value is in excellent agreement with the theoretical prediction of Zahn (1994).
- ID:
- ivo://CDS.VizieR/J/A+A/481/661
- Title:
- Hyades brown dwarfs and very low mass stars
- Short Name:
- J/A+A/481/661
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a search for brown dwarfs (BDs) and very low mass (VLM) stars in the 625Myr-old Hyades cluster in order to derive the cluster's mass function across the stellar-substellar boundary. We performed a deep (I=23, z=22.5) photometric survey over 16deg^2^ around the cluster center and followed up with K-band photometry to measure the proper motion of candidate members and with optical and near-IR spectroscopy of probable BD and VLM members.
- ID:
- ivo://CDS.VizieR/J/A+A/585/A7
- Title:
- Hyades single stars fiducial photometry
- Short Name:
- J/A+A/585/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Age and mass determinations for isolated stellar objects remain model-dependent. While stellar interior and atmospheric theoretical models are rapidly evolving, we need a powerful tool to test them. Open clusters are good candidates for this role. We aim to create a fiducial sequence of stellar objects for testing stellar and atmospheric models. We complement previous studies on the Hyades multiplicity by Lucky Imaging observations with the AstraLux Norte camera. This allows us to exclude possible binary and multiple systems with companions outside 2-7AU separation and to create a "single-star sequence" for the Hyades. The sequence encompasses 250 main-sequence stars ranging from A5V to M6V. Using the "Tool for Astrophysical Data Analysis" (TA-DA), we create various theoretical isochrones applying different combinations of interior and atmospheric models. We compare the isochrones with the observed Hyades single-star sequence on J vs. J-Ks, J vs. J-H and Ks vs. H-Ks color-magnitude diagrams. As a reference we also compute absolute fluxes and magnitudes for all stars from X-ray to mid-infrared based on photometric measurements available in the literature (ROSAT X-ray, GALEX UV, APASS gri, 2MASS JHKs, and WISE W1 to W4). We find that combinations of both PISA and DARTMOUTH stellar interior models with BT-Settl 2010 atmospheric models describe the observed sequence well. We use PISA in combination with BT-Settl 2010 models to derive theoretical predictions for physical parameters (Teff, mass, logg) of 250 single stars in the Hyades. The full sequence covers the mass range 0.13 to 2.3M_{sun}_, and effective temperatures between 3060K and 8200K. Conclusions. Within the measurement uncertainties, the current generation of models agree well with the single-star sequence. The primary limitations are the uncertainties in the measurement of the distance to individual Hyades members, and uncertainties in the photometry. Gaia parallaxes, photometry and spectroscopy will greatly reduce the uncertainties in particular at the lowest mass range, and will enable us to test model predictions with greater confidence. Additionally, a small (~0.05mag) systematic offset can be noted on J vs. J-K and K vs. H-K diagrams - the observed sequence is shifted to redder colors from the theoretical predictions.
- ID:
- ivo://CDS.VizieR/J/A+A/486/697
- Title:
- Hydra I Cluster Catalogue (HCC)
- Short Name:
- J/A+A/486/697
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse the properties of the early-type dwarf galaxy population in the Hydra I cluster. We investigate the galaxy luminosity function, the colour-magnitude relation, and the magnitude-surface brightness relation down to M_V_=-10mag. Deep VLT/FORS1 images in V and I bands were examined. We identify cluster members by radial velocity measurements and select other cluster galaxy candidates by their morphology. The candidates' total magnitudes and central surface brightnesses were derived from the analysis of their surface brightness profiles.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A92
- Title:
- HydraI galaxy cluster dwarf catalog (HCDC)
- Short Name:
- J/A+A/659/A92
- Date:
- 10 Mar 2022 07:25:32
- Publisher:
- CDS
- Description:
- Due to their relatively low stellar mass content and diffuse nature, the evolution of dwarf galaxies can be strongly affected by their environment. Analyzing the properties of the dwarf galaxies over a wide range of luminosities, sizes, morphological types, and environments, we can obtain insights about their evolution. At ~50Mpc, the Hydra I cluster of galaxies is among the closest cluster in the z=~0 Universe, and an ideal environment to study dwarf galaxy properties in a cluster environment. We exploit deep imaging data of the Hydra I cluster to construct a new photometric catalog of dwarf galaxies in the cluster core, which is then used to derive properties of the Hydra I cluster dwarf galaxy population as well as to compare it with other clusters. Moreover, we investigate the dependency of dwarf galaxy properties on their surrounding environment. The new wide-field g- and r-band images of the Hydra I cluster obtained with the OmegaCAM camera on the VLT Survey Telescope (VST) in the context of the VST Early-type GAlaxy Survey (VEGAS) were used to study the dwarf galaxy population in the Hydra I cluster core down to r-band magnitude Mr=-11.5mag. We used an automatic detection tool to identify dwarf galaxies from a ~1deg^2^ field centered on the Hydra I core, covering almost half of the cluster virial radius. The photometric pipeline was used to estimate the principal photometric parameters for all targets. Scaling relations and visual inspection were used to assess the cluster membership and construct a new dwarf galaxy catalog. Finally, based on the new catalog, we studied the structural (Sersic index n, effective radius Re, and axis ratio) and photometric (colors and surface brightness) properties of the dwarf galaxies, also investigating how they vary as a function of clustercentric distance. The new Hydra I dwarf catalog contains 317 galaxies with a luminosity between -18.5<Mr<-11.5mag, a semi-major axis larger than ~200pc (a=0.84"), of which 202 are new detections, and previously unknown dwarf galaxies in the Hydra I central region. We estimate that our detection efficiency reaches 50% at the limiting magnitude Mr=-11.5mag, and at the mean effective surface brightness <{mu}_e,r_=26.5mag/arcsec^2^. We present the standard scaling relations for dwarf galaxies, which are color-magnitude, size-luminosity, and Sersic n-magnitude relations, and compare them with other nearby clusters. We find that there are no observational differences for dwarfs scaling relations in clusters of different sizes. We study the spatial distribution of galaxies, finding evidence for the presence of substructures within half the virial radius. We also find that mid- and high-luminosity dwarfs (Mr<-14.5mag) become, on average, redder toward the cluster center, and that they have a mild increase in Re with increasing clustercentric distance, similar to what is observed for the Fornax cluster. No clear clustercentric trends are reported for surface brightness and Sersic index. Considering galaxies in the same magnitude bins, we find that for high and mid-luminosity dwarfs (Mr<-13.5mag), the g-r color is redder for the brighter surface brightness and higher Sersic n index objects. This finding is consistent with the effects of harassment and/or partial gas stripping.
- ID:
- ivo://CDS.VizieR/J/ApJ/818/39
- Title:
- Hydra I wide-field imaging and spectroscopy obs.
- Short Name:
- J/ApJ/818/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Eastern Banded Structure (EBS) and Hydra I halo overdensities are very nearby (d~10kpc) objects discovered in Sloan Digital Sky Survey (SDSS) data. Previous studies of the region have shown that EBS and Hydra I are spatially coincident, cold structures at the same distance, suggesting that Hydra I may be the EBS's progenitor. We combine new wide-field Dark Energy Camera (DECam) imaging and MMT/Hectochelle spectroscopic observations of Hydra I with SDSS archival spectroscopic observations to quantify Hydra I's present-day chemodynamical properties, and to infer whether it originated as a star cluster or dwarf galaxy. While previous work using shallow SDSS imaging assumed a standard old, metal-poor stellar population, our deeper DECam imaging reveals that Hydra I has a thin, well-defined main sequence turnoff of intermediate age (~5-6Gyr) and metallicity ([Fe/H]=-0.9dex). We measure statistically significant spreads in both the iron and alpha-element abundances of {sigma}_[Fe/H]_=0.13+/-0.02dex and {sigma}_[{alpha}/Fe]_=0.09+/-0.03dex, respectively, and place upper limits on both the rotation and its proper motion. Hydra I's intermediate age and [Fe/H] --as well as its low [{alpha}/Fe], apparent [Fe/H] spread, and present-day low luminosity-- suggest that its progenitor was a dwarf galaxy, which has subsequently lost more than 99.99% of its stellar mass.
- ID:
- ivo://CDS.VizieR/II/40
- Title:
- Hydrogen-Line Absorption in Early-Type Stars
- Short Name:
- II/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photoelectric determinations of H-{gamma} absorption line intensity have been made of stars in selected clusters and associations as well as in the general galactic field. Interference filters having a width at half intensity of 45{AA} were used to isolate spectral regions centered on 4280{AA}, H-{gamma} and 4410{AA}. The {Gamma} indices derived, which represent a measure of H-{gamma} absorption, can be used in conjunction with unreddened values of either (U-B) or (B-V) for spectral and luminosity class determinations of stars in the spectral range O6 to A0.
