- ID:
- ivo://CDS.VizieR/J/MNRAS/410/1262
- Title:
- Supernova Legacy Survey. Type Ia supernovae
- Short Name:
- J/MNRAS/410/1262
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical long-slit spectroscopy at the Gemini-North telescope using the Gemini Multi-Object Spectrograph (GMOS) was used to classify targets from the Supernova Legacy Survey (SNLS) from 2005 July and 2006 May-2008 May. During this time, 95 objects were observed. Where possible, the objects' redshifts (z) were measured from narrow emission or absorption features in the host galaxy spectrum, otherwise they were measured from the broader supernova features. We present spectra of 68 confirmed or probable SNe Ia from SNLS with redshifts in the range 0.17<=z<=1.02.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/491/215
- Title:
- Supplementary data for 146 candidate young stars
- Short Name:
- J/MNRAS/491/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The past two decades have seen dramatic progress in our knowledge of the population of young stars of age <200Myr that lie within 150pc of the Sun. These nearby, young stars, most of which are found in loose, comoving groups, provide the opportunity to explore (among many other things) the dissolution of stellar clusters and their diffusion into the field star population. Here, we exploit the combination of astrometric and photometric data from Gaia and photometric data from GALEX (UV) and 2MASS (near-IR) in an attempt to identify additional nearby, young, late-type stars. Specifically, we present a sample of 146 GALEX UV-selected late-type (predominantly K-type) field stars with Gaia-based distances <125pc (based on Gaia Data Release 1) that have isochronal ages <80Myr even if equal-components binaries. We investigate the spectroscopic and kinematic properties of this sample. Despite their young isochronal ages, only ~10 per cent of stars among this sample can be confidently associated with established nearby, young moving groups (MGs). These candidate MG members include five stars newly identified in this study. The vast majority of our sample of 146 nearby young star candidates have anomalous kinematics relative to the known MGs. These stars may hence represent a previously unrecognized population of young stars that has recently mixed into the older field star population. We discuss the implications and caveats of such a hypothesis - including the intriguing fact that, in addition to their non-young-star-like kinematics, the majority of the UV-selected, isochronally young field stars within 50pc appear surprisingly X-ray faint.
- ID:
- ivo://CDS.VizieR/J/ApJ/850/74
- Title:
- Swift/BAT AGN Spectroscopic Survey. I.
- Short Name:
- J/ApJ/850/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first catalog and data release of the Swift-BAT AGN Spectroscopic Survey. We analyze optical spectra of the majority of the detected AGNs (77%, 642/836) based on their 14-195keV emission in the 70-month Swift-BAT all-sky catalog. This includes redshift determination, absorption and emission-line measurements, and black hole mass and accretion rate estimates for the majority of obscured and unobscured AGNs (74%, 473/642), with 340 measured for the first time. With ~90% of sources at z<0.2, the survey represents a significant advance in the census of hard X-ray-selected AGNs in the local universe. In this first catalog paper, we describe the spectroscopic observations and data sets, and our initial spectral analysis. The FWHMs of the emission lines show broad agreement with the X-ray obscuration (~94%), such that Sy 1-1.8 have N_H_<10^21.9^cm^-2^, and Seyfert 2 have N_H_>10^21.9^cm^-2^. Seyfert 1.9, however, show a range of column densities. Compared to narrow-line AGNs in the SDSS, the X-ray-selected AGNs have a larger fraction of dusty host galaxies (H{alpha}/H{beta}>5), suggesting that these types of AGN are missed in optical surveys. Using the [OIII]{lambda}5007/H{beta} and [NII]{lambda}6583/H{alpha} emission-line diagnostic, about half of the sources are classified as Seyferts; ~15% reside in dusty galaxies that lack an H{beta} detection, but for which the upper limits on line emission imply either a Seyfert or LINER, ~15% are in galaxies with weak or no emission lines despite high-quality spectra, and a few percent each are LINERS, composite galaxies, H II regions, or in known beamed AGNs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/2695
- Title:
- Symbiotic recurrent nova T CrB spectroscopy
- Short Name:
- J/MNRAS/462/2695
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- T CrB is a symbiotic recurrent nova known to exhibit active phases, characterized by apparent increases in the hot component temperature and the appearance of flickering, i.e. changes in the observed flux on the time-scale of minutes. Historical UV observations have ruled out orbital variability as an explanation for flickering and instead suggest flickering is caused by variable mass transfer. We have analysed optical and X-ray observations to investigate the nature of the flickering as well as the active phases in T CrB. The spectroscopic and photometric observations confirm that the active phases follow two periods of ~1000d and ~5000d. Flickering in the X-rays is detected and follows an amplitude-flux relationship similar to that observed in the optical. The flickering is most prominent at harder X-ray energies, suggesting that it originates in the boundary layer between the accretion disc and the white dwarf. The X-ray radiation from the boundary layer is then reprocessed by a thick accretion disc or a nebula into UV radiation. A more detailed understanding of flickering would benefit from long-term simultaneous X-ray and optical monitoring of the phenomena in symbiotic recurrent novae and related systems such as Z And type symbiotic stars.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A111
- Title:
- Systematic diff. in spectroscopic analysis
- Short Name:
- J/A+A/622/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A spectroscopic analysis of stellar spectra can be carried out using multiple approaches such as different methods, line lists, atmospheric models, atomic parameters, and solar abundances. The resulting atmospheric parameters from these choices can vary beyond the quoted uncertainties in the literature. We characterize these differences by systematically comparing some of the commonly adopted ingredients such as line lists, equivalent width measurements, and atomic parameters. High-resolution and high signal-to-noise (S/N) spectroscopic data of one helium-core-burning red giant star in each of the three open clusters, NGC 6819, M67, and NGC 188 were obtained with the FIES spectrograph at the Nordic Optical Telescope. The M67 target was used to benchmark the analysis, as it is a well-studied cluster with asteroseismic data from the K2 mission. For the other two clusters we obtained higher quality data than had been analyzed before, which allows us to establish their chemical composition more securely. Using a line by line analysis, we tested several different combinations of line lists and programs to measure equivalent widths of stellar absorption lines to characterize systematic differences within the same spectroscopic method. The obtained parameters for the benchmark star in M67 vary up to ~170K in effective temperature, ~0.4dex in logg and ~0.25dex in [Fe/H] between the tested setups. Using the combination of an equivalent width measurement program and line list that best reproduce the inferred surface gravity from asteroseismology, we determined the atmospheric parameters for the three stars and securely established the chemical composition of NGC 6819 to be close to solar, [Fe/H]=-0.02+/-0.01dex. We highlighted the significantly different results obtained with different combinations of line lists, programs, and atomic parameters. The results emphasize the importance of benchmark stars studied with several methods to anchor spectroscopic analyses.
- ID:
- ivo://CDS.VizieR/J/ApJ/803/90
- Title:
- {tau} Cet chemical composition
- Short Name:
- J/ApJ/803/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- {tau} Ceti (HD10700), a G8 dwarf with mass 0.78M_{sun}_, is a close (3.65pc) Sun-like star where five possibly terrestrial planet candidates (minimum masses of 2, 3.1, 3.5, 4.3, and 6.7M_{Earth}_) have recently been discovered. We report abundances of 23 elements using spectra from the MIKE spectrograph on Magellan. We find [Fe/H]=-0.49 and T_eff_=5387K. Using stellar models with the abundances determined here, we calculate the position of the classical habitable zone (HZ) with time. At the current best fit age, 7.63_-1.5_^+0.87^Gyr, up to two planets (e and f) may be in the HZ, depending on atmospheric properties. The Mg/Si ratio of the star is found to be 1.78, which is much greater than for Earth (~1.2). With a system that has such an excess of Mg/Si ratio it is possible that the mineralogical make-up of planets around {tau} Ceti could be significantly different from that of Earth, with possible oversaturation of MgO, resulting in an increase in the content of olivine and ferropericlase compared with Earth. The increase in MgO would have a drastic impact on the rheology of the mantles of the planets around {tau} Ceti.
- ID:
- ivo://CDS.VizieR/J/ApJ/800/85
- Title:
- Teff, radii and luminosities of cool dwarfs
- Short Name:
- J/ApJ/800/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Interferometric radius measurements provide a direct probe of the fundamental parameters of M dwarfs. However, interferometry is within reach for only a limited sample of nearby, bright stars. We use interferometrically measured radii, bolometric luminosities, and effective temperatures to develop new empirical calibrations based on low-resolution, near-infrared spectra. We find that H-band Mg and Al spectral features are good tracers of stellar properties, and derive functions that relate effective temperature, radius, and log luminosity to these features. The standard deviations in the residuals of our best fits are, respectively, 73K, 0.027R_{sun}_, and 0.049dex (an 11% error on luminosity). Our calibrations are valid from mid K to mid M dwarf stars, roughly corresponding to temperatures between 3100 and 4800K. We apply our H-band relationships to M dwarfs targeted by the MEarth transiting planet survey and to the cool Kepler Objects of Interest (KOIs). We present spectral measurements and estimated stellar parameters for these stars. Parallaxes are also available for many of the MEarth targets, allowing us to independently validate our calibrations by demonstrating a clear relationship between our inferred parameters and the stars' absolute K magnitudes. We identify objects with magnitudes that are too bright for their inferred luminosities as candidate multiple systems. We also use our estimated luminosities to address the applicability of near-infrared metallicity calibrations to mid and late M dwarfs. The temperatures we infer for the KOIs agree remarkably well with those from the literature; however, our stellar radii are systematically larger than those presented in previous works that derive radii from model isochrones. This results in a mean planet radius that is 15% larger than one would infer using the stellar properties from recent catalogs. Our results confirm the derived parameters from previous in-depth studies of KOIs 961 (Kepler-42), 254 (Kepler-45), and 571 (Kepler-186), the latter of which hosts a rocky planet orbiting in its star's habitable zone.
- ID:
- ivo://CDS.VizieR/J/ApJS/224/36
- Title:
- The AllWISE motion survey (AllWISE2)
- Short Name:
- J/ApJS/224/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the AllWISE Data Release to continue our search for Wide-field Infrared Survey Explorer (WISE)-detected motions. In this paper, we publish another 27846 motion objects, bringing the total number to 48000 when objects found during our original AllWISE motion survey are included. We use this list, along with the lists of confirmed WISE-based motion objects from the recent papers by Luhman (2014, J/ApJ/781/4) and by Schneider et al. (2016, J/ApJ/817/112), and candidate motion objects from the recent paper by Gagne et al. (2014, J/ApJ/783/121), to search for widely separated, common-proper-motion systems. We identify 1039 such candidate systems. All 48000 objects are further analyzed using color-color and color-mag plots to provide possible characterizations prior to spectroscopic follow-up. We present spectra of 172 of these, supplemented with new spectra of 23 comparison objects from the literature, and provide classifications and physical interpretations of interesting sources. Highlights include: (1) the identification of three G/K dwarfs that can be used as standard candles to study clumpiness and grain size in nearby molecular clouds because these objects are currently moving behind the clouds, (2) the confirmation/discovery of several M, L, and T dwarfs and one white dwarf whose spectrophotometric distance estimates place them 5-20pc from the Sun, (3) the suggestion that the Na I "D" line be used as a diagnostic tool for interpreting and classifying metal-poor late-M and L dwarfs, (4) the recognition of a triple system including a carbon dwarf and late-M subdwarf, for which model fits of the late-M subdwarf (giving [Fe/H]~-1.0) provide a measured metallicity for the carbon star, and (5) a possible 24pc distant K5 dwarf + peculiar red L5 system with an apparent physical separation of 0.1pc.
- ID:
- ivo://CDS.VizieR/J/ApJ/856/158
- Title:
- The B[e] phenomenon. VII. AS 386 follow-up
- Short Name:
- J/ApJ/856/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of spectroscopic and photometric observations of the emission-line object AS 386. For the first time we found that it exhibits the B[e] phenomenon and fits the definition of an FS CMa type object. The optical spectrum shows the presence of a B-type star with the following properties: Teff=11000+/-500K, log L/L_{sun}_=3.7+/-0.3, a mass of 7+/-1M_{sun}_, and a distance D=2.4+/-0.3kpc from the Sun. We detected regular radial velocity variations of both absorption and emission lines with the following orbital parameters: Porb=131.27+/-0.09 days, semiamplitude K1=51.7+/-3.0km/s, systemic radial velocity {gamma}=-31.8+/-2.6km/s, and a mass function of f(m)=1.9+/-0.3M_{sun}_. AS 386 exhibits irregular variations of the optical brightness (V=10.92+/-0.05mag), while the near-IR brightness varies up to ~0.3mag following the spectroscopic period. We explain this behavior by a variable illumination of the dusty disk inner rim by the B-type component. Doppler tomography based on the orbital variations of emission-line profiles shows that the material is distributed near the B-type component and in a circumbinary disk. We conclude that the system has undergone a strong mass transfer that created the circumstellar material and increased the B-type component mass. The absence of any traces of a secondary component, whose mass should be >=7M_{sun}_, suggests that it is most likely a black hole.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/129
- Title:
- The Be phenomenon. V. MWC728
- Short Name:
- J/ApJ/809/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a long-term spectroscopic monitoring of the FS CMa type object MWC 728. We found that it is a binary system with a B5Ve (Teff=14000+/-1000K) primary and a G8III type (Teff~5000K) secondary. Absorption line positions of the secondary vary, with a semi-amplitude of ~20km/s and a period of 27.5 days. The system's mass function is 2.3x10^-2^M_{sun}_, and its orbital plane is ~13{deg}-15{deg} tilted from the plane of the sky. The primary's vsini~110km/s, combined with this tilt, implies that it rotates at a nearly breakup velocity. We detected strong variations of the Balmer and HeI emission-line profiles on timescales from days to years. This points to a variable stellar wind of the primary in addition to the presence of a circum-primary gaseous disk. The strength of the absorption-line spectrum, along with the optical and near infrared (IR) continuum, suggest that the primary contributes ~60% of the V-band flux, the disk contributes ~30%, and the secondary contributes ~10%. The system parameters, along with the interstellar extinction, suggest a distance of ~1kpc, that the secondary does not fill its Roche lobe, and that the companions' mass ratio is q~0.5. Overall, the observed spectral variability and the presence of a strong IR-excess are in agreement with a model of a close binary system that has undergone a non-conservative mass-transfer.
