- ID:
- ivo://CDS.VizieR/J/A+A/608/A63
- Title:
- HADES VI. GJ 3942b activity with HARPS-N
- Short Name:
- J/A+A/608/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Short- to mid-term magnetic phenomena on the stellar surface of M-type stars can resemble the effects of planets in radial velocity data, and may also hide them. We analyze 145 spectroscopic HARPS-N observations of GJ 3942 taken over the past five years and additional photometry in order to disentangle stellar activity effects from genuine Doppler signals as a result of the orbital motion of the star around the common barycenter with its planet. To achieve this, we use the common methods of pre-whitening, and treat the correlated red noise by a first-order moving average term and by Gaussian-process regression following an MCMC analysis. We identify the rotational period of the star at 16.3-days and discover a new super-Earth, GJ 3942b, with an orbital period of 6.9-days and a minimum mass of 7.1M_Earth_. An additional signal in the periodogram of the residuals is present, but at this point we cannot claim with sufficient significance that it is related to a second planet. If confirmed, this planet candidate would have a minimum mass of 6.3M_Earth_ and a period of 10.4-days, which might indicate a 3:2 mean-motion resonance with the inner planet.
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- ID:
- ivo://CDS.VizieR/J/AJ/134/1579
- Title:
- Halo stars in solar neighborhood
- Short Name:
- J/AJ/134/1579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have assembled a sample of halo stars in the solar neighborhood to look for halo substructure in velocity and angular momentum space. Our sample (231 stars) includes red giants, RR Lyrae variable stars, and red horizontal branch stars within 2.5kpc of the Sun with [Fe/H] less than -1.0. It was chosen to include stars with accurate distances, space velocities, and metallicities, as well as well-quantified errors. With our data set, we confirm the existence of the streams found by Helmi and coworkers (1999Natur.402...53H), which we refer to as the H99 streams.
- ID:
- ivo://CDS.VizieR/J/ApJ/698/865
- Title:
- Halo streams in the SDSS-DR7
- Short Name:
- J/ApJ/698/865
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have detected stellar halo streams in the solar neighborhood using data from the seventh public data release of the Sloan Digital Sky Survey (SDSS), which includes the directed stellar program Sloan Extension For Galactic Understanding and Exploration (SEGUE). In order to derive distances to each star, we used the metallicity-dependent photometric parallax relation from Ivezic et al. (2008ApJ...684..287I). Our final sample consists of 22321 nearby (d<=2kpc), metal-poor ([Fe/H]<=-0.5) main-sequence stars with six-dimensional estimates of position and space velocity (r{vec},{nu}{vec}). We characterize the orbits of these stars through suitable kinematic proxies for their "effective" integrals of motion, angular momentum, eccentricity, and orbital polar angle and compare the observed distribution to expectations from a smooth distribution in four [Fe/H] bins. The metallicities provide an additional dimension in parameter space that is well suited to distinguish tidal streams from those of dynamical origin. On this basis, we identify at least five significant "phase-space overdensities" of stars on very similar orbits in the solar neighborhood to which we can assign unambiguously peaked [Fe/H] distributions. Three of them have been identified previously, including the halo stream discovered by Helmi et al. (1999MNRAS.307..495H) at a significance level of {sigma}=12.0. In addition, we find at least two new genuine halo streams, judged by their kinematics and [Fe/H], at {sigma}=2.9 and 4.8, respectively.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A76
- Title:
- H{alpha}-activity in the SARG binary survey
- Short Name:
- J/A+A/596/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar activity influences radial velocity (RV) measurements and can also mimic the presence of orbiting planets. As part of the search for planets around the components of wide binaries performed with the SARG High Resolution Spectrograph at the TNG, it was discovered that HD 200466A shows strong variation in RV that is well correlated with the activity index based on H{alpha}. We used SARG to study the H{alpha} line variations in each component of the binaries and a few bright stars to test the capability of the H{alpha} index of revealing the rotation period or activity cycle. We also analysed the relations between the average activity level and other physical properties of the stars. We finally tried to reveal signals in the RVs that are due to the activity. At least in some cases the variation in the observed RVs is due to the stellar activity. We confirm that H{alpha} can be used as an activity indicator for solar-type stars and as an age indicator for stars younger than 1.5Gyr.
- ID:
- ivo://CDS.VizieR/J/ApJS/178/247
- Title:
- H{alpha} and [NII] survey in local 11 Mpc
- Short Name:
- J/ApJS/178/247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of a broader effort to characterize the population of star-forming galaxies in the local universe, we have carried out an H{alpha}+[NII] imaging survey for an essentially volume-limited sample of galaxies within 11Mpc of the Milky Way. This first paper describes the design of the survey, the observation, data processing, and calibration procedures, and the characteristics of the galaxy sample. The main product of the paper is a catalog of integrated H{alpha} fluxes, luminosities, and equivalent widths for the galaxies in the sample. We briefly discuss the completeness properties of the survey and compare the distribution of the sample and its star formation properties to other large H{alpha} imaging surveys. These data form the foundation for a series of follow-up studies of the star formation properties of the local volume, and the properties and duty cycles of star formation bursts in dwarf galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/384/383
- Title:
- H{alpha} galaxies in Abell 1367 and Coma
- Short Name:
- J/A+A/384/383
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep wide field H{alpha} imaging survey of the central regions of the two nearby clusters of galaxies Coma and Abell 1367, taken with the WFC at the Prime Focus at the NT 2.5m telescope located at Observatorio de El Roque de los Muchachos (La Palma), on April 26th and 28th 2000. We determine for the first time the Schechter parameters of the H{alpha} luminosity function (LF) of cluster galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A87
- Title:
- H{alpha} observations of LSI+61 303
- Short Name:
- J/A+A/559/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 137 spectral observations of the H{alpha} emission line of the radio- and gamma-ray-emitting Be/X-ray binary LSI+61 303 obtained during the period of September 1998 - January 2013. From measuring various H{alpha} parameters, we found that the orbital modulation of the H{alpha} is best visible in the equivalent width ratio EW(B)/EW(R), the equivalent width of the blue hump, and in the radial velocity of the central dip. The periodogram analysis confirmed that the H{alpha} emission is modulated with the orbital and superorbital periods. For the past 20 years the radius of the circumstellar disk is similar to the Roche lobe size at the periastron. It is probably truncated by a 6:1 resonance. The orbital maximum of the equivalent width of H{alpha} emission peaks after the periastron and coincides on average with the X-ray and gamma-ray maxima.
- ID:
- ivo://CDS.VizieR/J/AJ/131/2673
- Title:
- H{alpha} radial velocities of AM Her
- Short Name:
- J/AJ/131/2673
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations in the red region of the spectrum of the magnetic cataclysmic variable prototype AM Her during its 2005 low state. We confirm the unexpected structure of the H{alpha} emission line and verify most of the conclusions of our earlier study: the line is typically triple-peaked, and the radial velocity curves of all three components are phased with the radial velocities of absorption features from the photosphere of the M dwarf secondary star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/4180
- Title:
- H{alpha} stars in M31 HST photometry
- Short Name:
- J/MNRAS/465/4180
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 224 stars that emit H{alpha} (H{alpha} stars) in the Andromeda galaxy (M31). The stars were selected from ~5000 spectra, collected as part of the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo survey using Keck II/DEIMOS. We used six-filter Hubble Space Telescope photometry from the Panchromatic Hubble Andromeda Treasury survey to classify and investigate the properties of the H{alpha} stars. We identified five distinct categories of H{alpha} star: B-type main-sequence (MS) stars, 'transitioning'-MS (T-MS) stars, red core He burning (RHeB) stars, non-C-rich asymptotic giant branch (AGB) stars, and C-rich AGB stars. We found that ~12 per cent of B-type stars exhibit H{alpha} emission (Be stars). The frequency of Be to all B stars is known to vary with the metallicity of their environment. Comparing this proportion of Be stars with other environments around the Local Group, the result could indicate that M31 is more metal-rich than the Milky Way. We predict that the 17 T-MS H{alpha} stars are Be stars evolving off the MS with fading H{alpha} emission. We separated RHeB from AGB H{alpha} stars. We conclude that the 61 RHeB and AGB stars are likely to be long-period variables. We found that ~14 per cent of C-rich AGB stars (C stars) emit H{alpha}, which is an upper limit for the ratio of C-rich Miras to C stars. This catalogue of H{alpha} stars will be useful to constrain stellar evolutionary models, calibrate distance indicators for intermediate-age populations, and investigate the properties of M31.
- ID:
- ivo://CDS.VizieR/J/MNRAS/357/1337
- Title:
- H{alpha} survey of cluster galaxies
- Short Name:
- J/MNRAS/357/1337
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have extended our H{alpha} objective prism survey of eight low-redshift clusters (viz. Abell 262, 347, 400, 426, 569, 779, 1367 and 1656) to include a complete sample of early-type galaxies within 1.5 Abell radii of the cluster centres. Of the 379 galaxies surveyed, 3 per cent of E, E-S0 galaxies, 6 per cent of S0 galaxies, and 9 per cent of S0/a galaxies were detected in emission. From a comparison of cluster and supercluster field galaxies, we conclude that the frequency of emission-line galaxies (ELGs; W>=20{AA}) is similar for field and cluster early-type galaxies. A similar result has previously been obtained for galaxies of types Sa and later. Together, these results confirm the inference of Biviano et al. (1997A&A...321...84B) that the relative frequency of ELGs in clusters and the field can be entirely accounted for by the different mix of morphological types between the differing environments, and that, for galaxies of a given morphological type, the fraction of ELGs is independent of environment. Detected emission is classified as 'compact' or 'diffuse', identified as circumnuclear starburst or active galactic nucleus (AGN) emission and disc emission, respectively. By comparing spectroscopic data for cluster early-type ELGs with data for field galaxies from the Palomar spectroscopic survey of nearby galactic nuclei, we demonstrate that there is modest evidence for an enhancement of compact H II emission relative to AGN emission in the early-type cluster ELGs as compared to the field. For the cluster early-type galaxies, compact H II emission correlates strongly with a disturbed morphology. This suggests that, as for later-type cluster galaxies, this enhanced compact H II emission can readily be explained as an enhancement of circumnuclear starburst emission due to gravitational tidal interactions, most likely caused by subcluster merging and other on-going processes of cluster virialization.
