- ID:
- ivo://CDS.VizieR/J/A+A/655/A86
- Title:
- PILS-Cygnus. observations of CygX-N30
- Short Name:
- J/A+A/655/A86
- Date:
- 10 Mar 2022 07:33:06
- Publisher:
- CDS
- Description:
- Complex organic molecules (COMs) are commonly detected in and near star-forming regions. However, the dominant process in the release of these COMs from the icy grains -- where they predominately form -- to the gas phase is still an open question. We investigate the origin of COM emission in a high-mass protostellar source, CygX-N30 MM1, through high-angular-resolution interferometric observations over a continuous broad frequency range. We used 32 GHz Submillimeter Array (SMA) observations with continuous frequency coverage from 329 to 361GHz at an angular resolution of ~1'' to do a line survey and obtain a chemical inventory of the source. The line emission in the frequency range was used to determine column densities and excitation temperatures for the COMs. We also mapped out the intensity distribution of the different species. We identified approximately 400 lines that can be attributed to 29 different molecular species and their isotopologues. We find that the molecular peak emission is along a linear gradient, and coincides with the axis of red- and blue- shifted H_2_CO and CS emission. Chemical differentiation is detected along this gradient, with the O-bearing molecular species peaking towards one component of the system and the N- and S-bearing species peaking towards the other. The chemical gradient is offset from but parallel to the axis through the two continuum sources. The inferred column densities and excitation temperatures are compared to other sources where COMs are abundant. Only one deuterated molecule is detected, HDO, while an upper limit for CH_2_DOH is derived, leading to a D/H ratio of <0.1%. We conclude that the origin of the observed COM emission is probably a combination of the young stellar sources along with accretion of infalling material onto a disc-like structure surrounding a young protostar and located close to one of the continuum sources. This disc and protostar are associated with the O-bearing molecular species, while the S- and N- bearing species on the other hand are associated with the other continuum core, which is probably a protostar that is slightly more evolved than the other component of the system. The low D/H ratio likely reflects a pre- stellar phase where the COMs formed on the ices at warm temperatures (~30K), where the deuterium fractionation would have been inefficient. The observations and results presented here demonstrate the importance of good frequency coverage and high angular resolution when disentangling the origin of COM emission.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/533/A109
- Title:
- Pisa pre-main sequence tracks and isochrones
- Short Name:
- J/A+A/533/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years new observations of pre-main sequence stars (pre-MS) with Z<Z_{sun}_ have been made available. To take full advantage of the continuously growing amount of data of pre-MS stars in different environments, we need to develop updated pre-MS models for a wide range of metallicity to assign reliable ages and masses to the observed stars. We present updated evolutionary pre-MS models and isochrones for a fine grid of mass, age, metallicity, and helium values. We use a standard and well-tested stellar evolutionary code (i.e. FRANEC), that adopts outer boundary conditions from detailed and realistic atmosphere models. In this code, we incorporate additional improvements to the physical inputs related to the equation of state and the low temperature radiative opacities essential to computing low-mass stellar models. We make available via internet a large database of pre-MS tracks and isochrones for a wide range of chemical compositions (Z=0.0002-0.03), masses (M=0.2-7.0M_{sun}_), and ages (1-100Myr) for a solar-calibrated mixing length parameter alpha (i.e. 1.68). For each chemical composition, additional models were computed with two different mixing length values, namely alpha=1.2 and 1.9. Moreover, for Z>=0.008, we also provided models with two different initial deuterium abundances. The characteristics of the models have been discussed in detail and compared with other work in the literature. The main uncertainties affecting theoretical predictions have been critically discussed. Comparisons with selected data indicate that there is close agreement between theory and observation.
- ID:
- ivo://CDS.VizieR/J/ApJS/222/14
- Title:
- Planetary candidates from 1st yr K2 mission
- Short Name:
- J/ApJS/222/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kepler Space Telescope is currently searching for planets transiting stars along the ecliptic plane as part of its extended K2 mission. We processed the publicly released data from the first year of K2 observations (Campaigns 0, 1, 2, and 3) and searched for periodic eclipse signals consistent with planetary transits. Out of the 59174 targets that we searched, we detect 234 planetary candidates around 208 stars. These candidates range in size from gas giants to smaller than the Earth, and range in orbital periods from hours to over a month. We conducted initial reconnaissance spectroscopy of 68 of the brighter candidate host stars, and present high-resolution optical spectra for these stars. We make all of our data products, including light curves, spectra, and vetting diagnostics available to users online.
- ID:
- ivo://CDS.VizieR/J/A+A/332/721
- Title:
- Planetary nebulae abundances
- Short Name:
- J/A+A/332/721
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Long slit spectrophotometry of 13 bipolar planetary nebulae has been used to study their physical and chemical properties. In each nebula, one to seven different spatial regions have been considered in order to search for possible abundance variations through the nebulae. We obtained the following main results: - within the errors, the He, O, and N abundances are constant through all the nebulae. - the Ne, Ar, and S abundances are also constant, within the errors, but their face values have systematic increases toward the outer regions of the nebulae. These trends may be attributed to inaccuracies in the ionization correction factors, as predicted by Alexander & Balick (1997AJ....114..713A) for long-slit observations of extended PNe. The corresponding increase of the N abundance predicted by those authors is, however, generally not observed (with one exception). - The present sample contains some of the Galactic PNe with the highest He and N/O abundances known to date (M 3-2, He 2-111, NGC 6537). The highest He overabundances cannot by reproduced by any current model of AGB evolution. - Oxygen depletion is suggested for the nebulae with the highest N/O abundances, indicating that efficient ON cycle process has occurred in their progenitors.
- ID:
- ivo://CDS.VizieR/J/A+A/327/736
- Title:
- Planetary nebulae properties
- Short Name:
- J/A+A/327/736
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply a method, described in Gorny et al. (1997, Cat. <J/A+A/318/256>), to derive the masses of 125 central stars of planetary nebulae (PN). This method is self-consistent and distance-independent. It requires the knowledge of the nebular H{beta} fluxes, angular radii and expansion velocities, as well as the stellar visual magnitudes. This method is based on a simple model for the evolution of planetary nebulae, in which the central stars evolve according to the theoretical models of Bloecker (1995, Cat. <J/A+A/299/755>) and Schoenberner (1983ApJ...272..708S). The results are dependent on the assumed total nebular mass. Nevertheless, for any reasonable total nebular mass distribution, we find that the range in planetary nebulae central star masses is very restricted: more than 80% of the objects have a central star mass between 0.55 and 0.65M_{sun}_. We show how to convert, in this mass range, the observed PN central star mass distribution into a zero-age post-AGB star mass distribution.
- ID:
- ivo://CDS.VizieR/J/AJ/155/21
- Title:
- Planet candidates from K2 campaigns 5-8
- Short Name:
- J/AJ/155/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 151 planet candidates orbiting 141 stars from K2 campaigns 5-8 (C5-C8), identified through a systematic search of K2 photometry. In addition, we identify 16 targets as likely eclipsing binaries, based on their light curve morphology. We obtained follow-up optical spectra of 105/141 candidate host stars and 8/16 eclipsing binaries to improve stellar properties and to identify spectroscopic binaries. Importantly, spectroscopy enables measurements of host star radii with ~10% precision, compared to ~40% precision when only broadband photometry is available. The improved stellar radii enable improved planet radii. Our curated catalog of planet candidates provides a starting point for future efforts to confirm and characterize K2 discoveries.
- ID:
- ivo://CDS.VizieR/J/MNRAS/495/3961
- Title:
- Planet-hosting stars chemical compositions
- Short Name:
- J/MNRAS/495/3961
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a line-by-line differential analysis of a sample of 16 planet-hosting stars and 68 comparison stars using high-resolution, high signal-to-noise ratio spectra gathered using Keck. We obtained accurate stellar parameters and high-precision relative chemical abundances with average uncertainties in Teff, logg, [Fe/H], and [X/H] of 15K, 0.034cm/s^2^, 0.012dex, and 0.025dex, respectively. For each planet host, we identify a set of comparison stars and examine the abundance differences (corrected for Galactic chemical evolution effect) as a function of the dust condensation temperature, Tcond, of the individual elements. While we confirm that the Sun exhibits a negative trend between abundance and Tcond, we also confirm that the remaining planet hosts exhibit a variety of abundance-Tcond trends with no clear dependence upon age, metallicity, or Teff. The diversity in the chemical compositions of planet-hosting stars relative to their comparison stars could reflect the range of possible planet-induced effects present in these planet hosts, from the sequestration of rocky material (refractory poor) to the possible ingestion of planets (refractory rich). Other possible explanations include differences in the time-scale, efficiency and degree of planet formation, or inhomogeneous chemical evolution. Although we do not find an unambiguous chemical signature of planet formation among our sample, the high-precision chemical abundances of the host stars are essential for constraining the composition and structure of their exoplanets.
- ID:
- ivo://CDS.VizieR/J/AJ/152/187
- Title:
- Planet occurrence and stellar metallicity for KOIs
- Short Name:
- J/AJ/152/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Host star metallicity provides a measure of the conditions in protoplanetary disks at the time of planet formation. Using a sample of over 20000 Kepler stars with spectroscopic metallicities from the LAMOST survey, we explore how the exoplanet population depends on host star metallicity as a function of orbital period and planet size. We find that exoplanets with orbital periods less than 10 days are preferentially found around metal-rich stars ([Fe/H]{simeq}0.15+/-0.05dex). The occurrence rates of these hot exoplanets increases to ~30% for super-solar metallicity stars from ~10% for stars with a sub-solar metallicity. Cooler exoplanets, which reside at longer orbital periods and constitute the bulk of the exoplanet population with an occurrence rate of >~90%, have host star metallicities consistent with solar. At short orbital periods, P<10days, the difference in host star metallicity is largest for hot rocky planets (<1.7R_{Earth}_), where the metallicity difference is [Fe/H]{simeq}0.25+/-0.07dex. The excess of hot rocky planets around metal-rich stars implies they either share a formation mechanism with hot Jupiters, or trace a planet trap at the protoplanetary disk inner edge, which is metallicity dependent. We do not find statistically significant evidence for a previously identified trend that small planets toward the habitable zone are preferentially found around low-metallicity stars. Refuting or confirming this trend requires a larger sample of spectroscopic metallicities.
- ID:
- ivo://CDS.VizieR/J/AJ/153/136
- Title:
- Planets and their host stars with Gaia parallaxes
- Short Name:
- J/AJ/153/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present empirical measurements of the radii of 116 stars that host transiting planets. These radii are determined using only direct observables - the bolometric flux at Earth, the effective temperature, and the parallax provided by the Gaia first data release - and thus are virtually model independent, with extinction being the only free parameter. We also determine each star's mass using our newly determined radius and the stellar density, a virtually model independent quantity itself from previously published transit analyses. These stellar radii and masses are in turn used to redetermine the transiting-planet radii and masses, again using only direct observables. The median uncertainties on the stellar radii and masses are 8% and 30%, respectively, and the resulting uncertainties on the planet radii and masses are 9% and 22%, respectively. These accuracies are generally larger than previously published model-dependent precisions of 5% and 6% on the planet radii and masses, respectively, but the newly determined values are purely empirical. We additionally report radii for 242 stars hosting radial-velocity (non-transiting) planets, with a median achieved accuracy of ~2%. Using our empirical stellar masses we verify that the majority of putative "retired A stars" in the sample are indeed more massive than ~1.2 M_{sun}_. Most importantly, the bolometric fluxes and angular radii reported here for a total of 498 planet host stars-with median accuracies of 1.7% and 1.8%, respectively-serve as a fundamental data set to permit the re-determination of transiting-planet radii and masses with the Gaia second data release to ~3% and ~5% accuracy, better than currently published precisions, and determined in an entirely empirical fashion.
- ID:
- ivo://CDS.VizieR/J/AJ/155/136
- Title:
- Planets orbiting bright stars in K2 campaigns 0-10
- Short Name:
- J/AJ/155/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since 2014, NASA's K2 mission has observed large portions of the ecliptic plane in search of transiting planets and has detected hundreds of planet candidates. With observations planned until at least early 2018, K2 will continue to identify more planet candidates. We present here 275 planet candidates observed during Campaigns 0-10 of the K2 mission that are orbiting stars brighter than 13 mag (in Kepler band) and for which we have obtained high-resolution spectra (R=44000). These candidates are analyzed using the vespa package in order to calculate their false-positive probabilities (FPP). We find that 149 candidates are validated with an FPP lower than 0.1%, 39 of which were previously only candidates and 56 of which were previously undetected. The processes of data reduction, candidate identification, and statistical validation are described, and the demographics of the candidates and newly validated planets are explored. We show tentative evidence of a gap in the planet radius distribution of our candidate sample. Comparing our sample to the Kepler candidate sample investigated by Fulton et al. (2017, J/AJ/154/109), we conclude that more planets are required to quantitatively confirm the gap with K2 candidates or validated planets. This work, in addition to increasing the population of validated K2 planets by nearly 50% and providing new targets for follow-up observations, will also serve as a framework for validating candidates from upcoming K2 campaigns and the Transiting Exoplanet Survey Satellite, expected to launch in 2018.