- ID:
- ivo://CDS.VizieR/J/A+A/469/783
- Title:
- Code for automatic determination of EW (ARES)
- Short Name:
- J/A+A/469/783
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new automatic code (ARES) for determining equivalent widths of the absorption lines present in stellar spectra. We also describe its use for determining fundamental spectroscopic stellar parameters. The code is written in C++ based on the standard method of determining EWs and is available for the community. The code automates the manual procedure that the users normally carry out when using interactive routines such as the splot routine implemented in IRAF. Results.We test the code using both simulated and real spectra with different levels of resolution and noise and comparing its measurements to the
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/536/A63
- Title:
- Collinder 69 very low mass stars and brown dwarfs
- Short Name:
- J/A+A/536/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied age dependent features in optical and near-infrared spectra of candidate members to the cluster (such as alkali lines and accretion associated indicators). In addition, we have complemented that study with the analysis of other youth indicators like X-ray emission or mid-infrared excess. We have confirmed the membership to Collinder 69 of ~90 photometric candidate members. As a byproduct we have determined a temperature scale for young M, very low-mass stars and brown dwarfs. We have assembled one of the most complete Initial Mass Functions from 0.016 to 20M_{sun}_. And, finally, we have studied the implications of the spatial distribution of the confirmed members on the proposed mechanisms of brown dwarfs formation.
- ID:
- ivo://CDS.VizieR/J/AJ/153/165
- Title:
- Collisions of terrestrial worlds
- Short Name:
- J/AJ/153/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an investigation into the occurrence and properties (stellar age and mass trends) of low- mass field stars exhibiting extreme mid-infrared (MIR) excesses (LIR/L*~>~0.01). Stars for the analysis were initially selected from the Motion Verified Red Stars (MoVeRS) catalog of photometric stars with Sloan Digital Sky Survey, 2MASS, and WISE photometry and significant proper motions. We identify 584 stars exhibiting extreme MIR excesses, selected based on an empirical relationship for main-sequence W1-W3 colors. For a small subset of the sample, we show, using spectroscopic tracers of stellar age (H{alpha} and LiI) and luminosity class, that the parent sample is most likely comprised of field dwarfs (>1Gyr). We also develop the Low-mass Kinematics (LoKi) galactic model to estimate the completeness of the extreme MIR excess sample. Using Galactic height as a proxy for stellar age, the completeness-corrected analysis indicates a distinct age dependence for field stars exhibiting extreme MIR excesses. We also find a trend with stellar mass (using r-z color as a proxy). Our findings are consistent with the detected extreme MIR excesses originating from dust created in a short-lived collisional cascade (<100000-years) during a giant impact between two large planetismals or terrestrial planets. These stars with extreme MIR excesses also provide support for planetary collisions being the dominant mechanism in creating the observed Kepler dichotomy (the need for more than a single mode, typically two, to explain the variety of planetary system architectures Kepler has observed), rather than different formation mechanisms.
- ID:
- ivo://CDS.VizieR/J/ApJ/582/668
- Title:
- Colours and H{alpha} in galaxy pairs
- Short Name:
- J/ApJ/582/668
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxy-galaxy interactions rearrange the baryons in galaxies and trigger substantial star formation; the aggregate effects of these interactions on the evolutionary histories of galaxies in the universe are poorly understood. We combine B- and R-band photometry and optical spectroscopy to estimate the strengths and timescales of bursts of triggered star formation in the centers of 190 galaxies in pairs and compact groups. Based on an analysis of the measured colors and EW(H{alpha}), we characterize the preexisting and triggered populations separately. The best-fitting burst scenarios assume stronger reddening corrections for line emission than for the continuum and continuous star formation lasting for >~100Myr. The most realistic scenarios require an initial mass function that is deficient in the highest mass stars. The color of the preexisting stellar population is the most significant source of uncertainty. Triggered star formation contributes substantially (probably >~50%) to the R-band flux in the central regions of several galaxies; tidal tails do not necessarily accompany this star formation. Many of the galaxies in our sample have bluer centers than outskirts, suggesting that pre- or nonmerger interactions may lead to evolution along the Hubble sequence. These objects would appear blue and compact at higher redshifts; the older, redder outskirts of the disks would be difficult to detect. Our data indicate that galaxies with larger separations on the sky contain weaker, and probably older, bursts of star formation on average. However, confirmation of these trends requires further constraints on the colors of the older stellar populations and on the reddening for individual galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/367/1049
- Title:
- Comet C/1995 O1 (Hale-Bopp) emission lines
- Short Name:
- J/A+A/367/1049
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution and high signal-to-noise ratio spectra of Comet C/1995 O1 (Hale-Bopp), which provided continuous wavelength coverage from 5500{AA} to 8500{AA} and partial coverage from 4000{AA} to 5500{AA}, were obtained with the Coude Echelle Spectrograph at Beijing Astronomical Observatory on March 26, 28 and April 22, 1997. In the spectra we found 532 emission features, among which 459 lines from H, O, Na, C_2_, C_3_, CN, CH, NH_2_ and H_2_O^+^ were identified. The intensity of sodium emission lines at 5890 {AA} and 5896 {AA} on April 22 increased about 5 fold compared to that recorded on March 26 and 28. The intensity ratio I_{lambda}5577_/(I_{lambda}6300_+I_{lambda}6364_) of [O I] is consistent with the formation of excited O atoms from the photodissociation of H_2_O.
- ID:
- ivo://CDS.VizieR/J/AJ/136/2483
- Title:
- Comoving group associated with HD 141569
- Short Name:
- J/AJ/136/2483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for a young stellar moving group associated with the star HD 141569 - a nearby, isolated Herbig AeBe primary member of a 5+/-3Myr-old triple star system on the outskirts of the Sco-Cen complex. Our spectroscopic survey identified a population of 21 Li-rich, >~30Myr-old stars within 30{deg} of HD 141569 which possess similar proper motions with the star. The spatial distribution of these Li-rich stars, however, is not suggestive of a moving group associated with the HD 141569 triplet, but rather this sample appears cospatial with Upper Scorpius (US) and Upper Centaurus Lupus (UCL). We apply a modified moving cluster parallax method to compare the kinematics of these youthful stars with those of the US and UCL. Eight new potential members of US and five new potential members of UCL are identified. A substantial moving group with an identifiable nucleus within 15{deg} (~30pc) of HD 141569 is not found in this sample. Evidently, the HD 141569 system formed ~5Myr ago in relative isolation, tens of parsecs away from the recent sites of star formation in the Ophiucus-Scorpius-Centaurus region.
- ID:
- ivo://CDS.VizieR/J/ApJ/815/L13
- Title:
- Compton-thick AGNs from the 70-month Swift/BAT cat.
- Short Name:
- J/ApJ/815/L13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Heavily obscured accretion is believed to represent an important stage in the growth of supermassive black holes and to play an important role in shaping the observed spectrum of the cosmic X-ray background. Hard X-ray (E>10keV) selected samples are less affected by absorption than samples selected at lower energies, and are therefore one of the best ways to detect and identify Compton-thick (CT, logN_H_>=24) active galactic nuclei (AGNs). In this letter we present the first results of the largest broadband (0.3-150keV) X-ray spectral study of hard X-ray selected AGNs to date, focusing on the properties of heavily obscured sources. Our sample includes the 834 AGNs (728 non-blazar, average redshift z~0.055) reported in the 70-month catalog of the all-sky hard X-ray Swift/Burst Alert Monitor survey. We find 55 CT AGNs, which represent 7.6_-2.1_^+1.1^% of our non-blazar sample. Of these, 26 are reported as candidate CT AGNs for the first time. We correct for selection bias and derive the intrinsic column density distribution of AGNs in the local universe in two different luminosity ranges. We find a significant decrease in the fraction of obscured Compton-thin AGNs for increasing luminosity, from 46+/-3% (for logL_14-195_=40-43.7) to 39+/-3% (for logL_14-195_=43.7-46). A similar trend is also found for CT AGNs. The intrinsic fraction of CT AGNs with logN_H_=24-25 normalized to unity in the logN_H_=20-25 range is 27+/-4%, and is consistent with the observed value obtained for AGNs located within 20Mpc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/2561
- Title:
- CONCH-SHELL catalog of nearby M dwarfs
- Short Name:
- J/MNRAS/443/2561
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an all-sky catalogue of 2970 nearby (d<~50pc), bright (J<9) M- or late K-type dwarf stars, 86% of which have been confirmed by spectroscopy. This catalogue will be useful for searches for Earth-size and possibly Earth-like planets by future space-based transit missions and ground-based infrared Doppler radial velocity surveys. Stars were selected from the SUPERBLINK proper motion catalogue (Cat. I/298) according to absolute magnitudes, spectra, or a combination of reduced proper motions and photometric colours. From our spectra, we determined gravity-sensitive indices, and identified and removed 0.2% of these as interloping hotter or evolved stars. 13% of the stars exhibit H{alpha} emission, an indication of stellar magnetic activity and possible youth. The mean metallicity is [Fe/H]=-0.07 with a standard deviation of 0.22dex, similar to nearby solar-type stars. We determined stellar effective temperatures by least-squares fitting of spectra to model predictions calibrated by fits to stars with established bolometric temperatures, and estimated radii, luminosities, and masses using empirical relations. 6% of stars with images from integral field spectra are resolved doubles. We inferred the planet population around M dwarfs using Kepler data and applied this to our catalogue to predict detections by future exoplanet surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/158/87
- Title:
- 86 cool dwarfs observed during K2 Campaigns 1-17
- Short Name:
- J/AJ/158/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present revised stellar properties for 172 K2 target stars that were identified as possible hosts of transiting planets during Campaigns 1-17. Using medium-resolution near-infrared spectra acquired with the NASA Infrared Telescope Facility/SpeX and Palomar/TripleSpec, we found that 86 of our targets were bona fide cool dwarfs, 74 were hotter dwarfs, and 12 were giants. Combining our spectroscopic metallicities with Gaia parallaxes and archival photometry, we derived photometric stellar parameters and compared them to our spectroscopic estimates. Although our spectroscopic and photometric radius and temperature estimates are consistent, our photometric mass estimates are systematically {Delta}M_*_=0.11 M_{sun}_ (34%) higher than our spectroscopic mass estimates for the least massive stars (M_*,phot_<0.4 M_{sun}_). Adopting the photometric parameters and comparing our results to parameters reported in the Ecliptic Plane Input Catalog, our revised stellar radii are {Delta}R_*_=0.15 R_{sun}_ (40%) larger, and our revised stellar effective temperatures are roughly {Delta}T_eff_=65 K cooler. Correctly determining the properties of K2 target stars is essential for characterizing any associated planet candidates, estimating the planet search sensitivity, and calculating planet occurrence rates. Even though Gaia parallaxes have increased the power of photometric surveys, spectroscopic characterization remains essential for determining stellar metallicities and investigating correlations between stellar metallicity and planetary properties.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A119
- Title:
- CoRoT red giants abundances
- Short Name:
- J/A+A/564/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A precise characterisation of the red giants in the seismology fields of the CoRoT satellite is a prerequisite for further in-depth seismic modelling. High-resolution FEROS and HARPS spectra were obtained as part of the ground-based follow-up campaigns for 19 targets holding great asteroseismic potential. These data are used to accurately estimate in a self-consistent manner their fundamental parameters and the abundances of 16 chemical species. Some powerful probes of mixing are investigated (the Li and CNO abundances, as well as the carbon isotopic ratio in a few cases). The information provided by the spectroscopic and seismic data is combined to provide more accurate physical parameters and abundances. The stars in our sample follow the general trends between various abundance ratios and the metallicity observed in stars of the Galactic disk. After allowance is made for the chemical evolution of the interstellar medium, the observational signature of internal mixing phenomena is revealed through the detection at the stellar surface of the products of the CN and, in the case of the most massive stars, NeNa cycles. Together with the asteroseismic constraints, these data will pave the way for a detailed theoretical investigation of the physical processes responsible for the transport of chemical elements in evolved, low- and intermediate-mass stars.
