- ID:
- ivo://CDS.VizieR/J/PASP/118/1238
- Title:
- Radial velocity curve of RBS 490
- Short Name:
- J/PASP/118/1238
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- RBS (ROSAT Bright Source) 0490 is a cataclysmic variable star (CV) with unusually strong emission lines. The strength of the emission lines has led to a suggestion that the object is intrinsically faint and correspondingly nearby (33pc), which, if true, would strongly affect estimates of the CV space density. Here we report astrometry, filter photometry, and time-series spectroscopy of this object. The astrometry gives an absolute parallax of 4.5+/-1.5mas and a relative proper motion of 102mas/yr. A Bayesian procedure gives a very uncertain distance estimate of d~300pc, and the small parallax alone implies d>133pc (at 2 standard deviations). The mean V magnitude is 17.4, which implies M_V_=10.9-5log[d/(200pc)], neglecting extinction. At 200pc, the space velocity would be over 90km/s with respect to the local standard of rest. The time-series spectroscopy shows a possible emission-line radial velocity period near 46 minutes. This would be unusually short for an orbital period, and it may represent some other clock in the system.
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- ID:
- ivo://CDS.VizieR/J/AJ/135/2470
- Title:
- Radio observations of the HDFS region. IV.
- Short Name:
- J/AJ/135/2470
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Australia Telescope Hubble Deep Field-South (ATHDF-S) survey of the Hubble Deep Field-South (HDF-S) reaches sensitivities of ~10uJy at 1.4, 2.5, 5.2, and 8.7GHz, making the ATHDF-S one of the deepest surveys ever performed with the Australia Telescope Compact Array (ATCA). Here, we present the optical identifications of the ATHDF-S radio sources using data from the literature. We find that ~66% of the radio sources have optical counterparts to I=23.5mag. Deep Hubble Space Telescope (HST) imaging of the area identifies a further 12% of radio sources. We present new spectroscopic observations for 98 of the radio sources and supplement these spectroscopic redshifts with photometric ones calculated from five-band optical imaging.
- ID:
- ivo://CDS.VizieR/J/ApJS/185/124
- Title:
- 58 radio sources near BNGSs
- Short Name:
- J/ApJS/185/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a preliminary survey of 58 radio sources within the isoplanatic patches (r<25") of bright (11<R<12) stars suitable for use as natural guide stars with high-order adaptive optics (AO). An optical and near-infrared imaging survey was conducted utilizing tip-tilt corrections in the optical and AO in the near-infrared. Spectral energy distributions were fit to the multi-band data for the purpose of obtaining photometric redshifts using the Hyperz code. Several of these photometric redshifts were confirmed with spectroscopy, a result that gives more confidence to the redshift distribution for the whole sample. Additional long-wavelength data from Spitzer, SCUBA, SHARC2, and VLA supplement the optical and near-infrared data. We find the sample generally follows and extends the magnitude-redshift relation found for more powerful local radio galaxies. The survey has identified several reasonably bright (H=19-20) objects at significant redshifts (z>1) that are now within the capabilities of the current generation of AO-fed integral-field spectrographs. These objects constitute a unique sample that can be used for detailed ground-based AO studies of galactic structure, evolution, and active galactic nucleus formation at high redshift.
- ID:
- ivo://CDS.VizieR/J/AJ/157/63
- Title:
- Radius relations for low-metallicity M-dwarf stars
- Short Name:
- J/AJ/157/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M subdwarfs are low-metallicity M dwarfs that typically inhabit the halo population of the Galaxy. Metallicity controls the opacity of stellar atmospheres; in metal-poor stars, hydrostatic equilibrium is reached at a smaller radius, leading to smaller radii for a given effective temperature. We compile a sample of 88 stars that span spectral classes K7 to M6 and include stars with metallicity classes from solar-metallicity dwarf stars to the lowest metallicity ultra subdwarfs to test how metallicity changes the stellar radius. We fit models to Palomar Double Spectrograph (DBSP) optical spectra to derive effective temperatures (T_eff_) and we measure bolometric luminosities (L_bol_) by combining broad wavelength-coverage photometry with Gaia parallaxes. Radii are then computed by combining the T_eff_ and L_bol_ using the Stefan-Boltzman law. We find that for a given temperature, ultra subdwarfs can be as much as five times smaller than their solar-metallicity counterparts. We present color-radius and color-surface brightness relations that extend down to [Fe/H] of -2.0 dex, in order to aid the radius determination of M subdwarfs, which will be especially important for the WFIRST exoplanetary microlensing survey.
- ID:
- ivo://CDS.VizieR/J/AN/333/242
- Title:
- Recent photometry of symbiotic stars
- Short Name:
- J/AN/333/242
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new multicolour (U,B,V,Rc,Ic) photometric observations of classical symbiotic stars, EG And, Z And, BF Cyg, CH Cyg, CI Cyg, V1329 Cyg, TX CVn, AG Dra, Draco C1, AG Peg and AX Per, carried out between 2007.1 and 2011.9. The aim of this paper is to present new data of our monitoring programme, to describe the main features of their light curves (LC) and to point problems for their future investigation. The data were obtained by the method of the classical photoelectric and CCD photometry.
- ID:
- ivo://CDS.VizieR/J/ApJ/870/115
- Title:
- Reddening, distance modulus & Fe/H of RRLs in w Cen
- Short Name:
- J/ApJ/870/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We developed a new approach to provide accurate estimates of the metal content, reddening, and true distance modulus of RR Lyrae stars (RRLs). The method is based on homogeneous optical (BVI) and near-infrared (JHK) mean magnitudes and on predicted period-luminosity-metallicity relations (IJHK) and absolute mean magnitude-metallicity relations (BV). We obtained solutions for three different RRL samples in {omega}Cen: first overtone (RRc, 90), fundamental (RRab, 80), and global (RRc+RRab) in which the period of first overtones were fundamentalized. The metallicity distribution shows a well defined peak at [Fe/H]~-1.98 and a standard deviation of {sigma}=0.54dex. The spread is, as expected, metal-poor ([Fe/H]<=-2.3) objects. The current metallicity distribution is ~0.3dex more metal-poor than similar estimates for RRLs available in the literature. The difference vanishes if the true distance modulus we estimated is offset by -0.06/-0.07mag in true distance modulus. We also found a cluster true distance modulus of {mu}=13.720{+/-}0.002{+/-}0.030mag, where the former error is the error on the mean and the latter is the standard deviation. Moreover, we found a cluster reddening of E(B-V)=0.132{+/-}0.002{+/-}0.028mag and spatial variations of the order of a few arcmin across the body of the cluster. Both the true distance modulus and the reddening are slightly larger than similar estimates available in the literature, but the difference is within 1{sigma}. The metallicity dependence of distance diagnostics agrees with theory and observations, but firm constraints require accurate and homogeneous spectroscopic measurements.
- ID:
- ivo://CDS.VizieR/J/AJ/137/4282
- Title:
- Red giant stars in clusters. II. M13 and M92
- Short Name:
- J/AJ/137/4282
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution spectra of 123 red giant stars in the globular cluster M13 and 64 red giant stars in M92 were obtained with Hectochelle at the MMT telescope. Emission and line asymmetries in H{alpha} and CaIIK are identified, characterizing motions in the extended atmospheres and seeking differences attributable to metallicity in these clusters and M15. On the red giant branch, emission in H{alpha} generally appears in stars with T_eff_<~4500K and logL/L_{sun}_>~2.75. Fainter stars showing emission are asymptotic giant branch (AGB) stars or perhaps binary stars. The line-bisector for H{alpha} reveals the onset of chromospheric expansion in stars more luminous than log(L/L_{sun}_)~2.5 in all clusters, and this outflow velocity increases with stellar luminosity. However, the coolest giants in the metal-rich M13 show greatly reduced outflow in H{alpha} most probably due to decreased T_eff_ and changing atmospheric structure. The CaIIK_3_ outflow velocities are larger than shown by H{alpha} at the same luminosity and signal accelerating outflows in the chromospheres. Stars clearly on the AGB show faster chromospheric outflows in H{alpha} than RGB objects. While the H{alpha} velocities on the RGB are similar for all metallicities, the AGB stars in the metal-poor M15 and M92 have higher outflow velocities than in the metal-rich M13. Comparison of these chromospheric line profiles in the paired metal-poor clusters, M15 and M92, shows remarkable similarities in the presence of emission and dynamical signatures, and does not reveal a source of the "second-parameter" effect.
- ID:
- ivo://CDS.VizieR/J/A+A/363/517
- Title:
- Redshift from UBRI photometry method
- Short Name:
- J/A+A/363/517
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new method is developed for estimating photometric redshifts, using realistic template Spectral Energy Distributions (SEDs), extending over four decades in wavelength (i.e. from 0.05{mu}m to 1mm). The template SEDs are constructed for four different spectral types of galaxies (elliptical, spiral, irregular and starburst), satisfying the following characteristics: a) they are normalised to produce the observed colours of galaxies at z~0; b) incorporate the chemo-photometric spectral evolution of galaxies of different types, in agreement with the observations; c) allow treatment of dust contribution and its evolution with redshift, consistent with the spectral evolution models; d) include absorption and re-emission of radiation by dust and hence, realistic estimates of the far-infrared radiation; e) include correction for inter-galactic absorption by Lyman continuum and Lyman forest. Using these template SEDs, the photometric redshifts are estimated to an accuracy of {Delta}z=0.11. The simultaneous and self-consistent modelling of both the photometric and chemical evolution of galaxies and the effect of dust, makes this technique particularly useful for high redshift galaxies. The effects on the estimated photometric redshifts, due to assumptions in the evolutionary population synthesis models, are investigated and discussed. Also, the degeneracy in the predicted photometric redshifts and spectral types are examined, using a simulated galaxy catalogue.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2867
- Title:
- Red supergiants in Magellanic Clouds
- Short Name:
- J/AJ/126/2867
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the red supergiant (RSG) content of the SMC and LMC using multiobject spectroscopy on a sample of red stars previously identified by BVR CCD photometry. We obtained high-accuracy (<1km/s) radial velocities for 118 red stars seen toward the SMC and 167 red stars seen toward the LMC, confirming most of these (89% and 95%, respectively) as red supergiants. Spectral types were also determined for most of these RSGs.
- ID:
- ivo://CDS.VizieR/J/ApJ/781/22
- Title:
- Region I of La Silla QUEST RR Lyrae star survey
- Short Name:
- J/ApJ/781/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A search for RR Lyrae stars (RRLSs) in ~840deg^2^ of the sky in right ascension 150{deg}-210{deg} and declination -10{deg} to + 10{deg} yielded 1013 type ab and 359 type c RRLS. This sample is used to study the density profile of the Galactic halo, halo substructures, and the Oosterhoff type of the halo over distances (d_{sun}_) from ~5 to ~80kpc. The halo is flattened toward the Galactic plane, and its density profile steepens in slope at galactocentric distances greater than ~25kpc. The RRLS in the stellar stream from the Sagittarius dwarf spheroidal (dSph) galaxy match well the model of Law & Majewski for the stars that were stripped 1.3-3.2Gyr ago, but not for the ones stripped 3.2-5.0Gyr ago. Over densities are found at the locations of the Virgo Overdensity and the Virgo Stellar Stream. Within 1{deg} of 1220-1, which Jerjen et al. identify as a halo substructure at d_{sun}_~24kpc, there are four RRLS that are possibly members. Away from substructures, the RRLS are a mixture of Oosterhoff types I and II, but mostly OoI (~73%). The accretion of galaxies resembling in RRLS content the most massive Milky Way satellites (LMC, SMC, For, Sgr) may explain this preponderance of OoI. Six new RRLS and three new anomalous Cepheids were found in the Sextans dSph galaxy.
