- ID:
- ivo://CDS.VizieR/J/A+A/630/A50
- Title:
- Combining HCI and RV of nearby stars
- Short Name:
- J/A+A/630/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nearby stars are prime targets for exoplanet searches and characterization using a variety of detection techniques. Combining constraints from the complementary detection methods of high-contrast imaging (HCI) and radial velocity (RV) can further constrain the planetary architectures of these systems because these methods place limits at different regions of the companion mass and semi-major axis parameter space. Compiling a census of the planet population in the solar neighborhood is important to inform target lists for future space missions that will specifically target nearby stars to search for Earth analogs. We aim to constrain the planetary architectures from the combination of HCI and RV data for six nearby stars within 6pc: tau Ceti, Kapteyn;s star, AX Mic, 40 Eri, HD 36395, and HD 42581. We explored where HCI adds information to constraints from the long-term RV monitoring data for these stars. We compiled the sample from stars with available archival VLT/NACO HCI data at L' band (3.8um), where we expect substellar companions to be brighter for the typically older ages of nearby field stars (>1Gyr). The NACO data were fully reanalyzed using the state-of-the-art direct imaging pipeline PynPoint and combined with RV data from HARPS, Keck/HIRES, and CORALIE. A Monte Carlo approach was used to assess the completeness in the companion mass and semi-major axis parameter space from the combination of the HCI and RV data sets. We find that the HCI data add significant information to the RV constraints, increasing the completeness for certain companions masses and semi-major axes by up to 68-99% for four of the six stars in our sample, and by up to 1-13% for the remaining stars. The improvements are strongest for intermediate semi-major axes (15-40AU), corresponding to the semi-major axes of the ice giants in our own solar system. The HCI mass limits reach 5-20M_Jup_ in the background-limited regime, depending on the age of the star. Through the combination of HCI and RV data, we find that stringent constraints can be placed on the possible substellar companions in these systems. Applying these methods systematically to nearby stars will quantify our current knowledge of the planet population in the solar neighborhood and inform future observations.
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4082. COMBS III
- ID:
- ivo://CDS.VizieR/J/MNRAS/509/122
- Title:
- COMBS III
- Short Name:
- J/MNRAS/509/122
- Date:
- 08 Feb 2022 11:31:21
- Publisher:
- CDS
- Description:
- The characteristics of the stellar populations in the Galactic bulge inform and constrain the Milky Way's formation and evolution. The metal-poor population is particularly important in light of cosmological simulations, which predict that some of the oldest stars in the Galaxy now reside in its centre. The metal-poor bulge appears to consist of multiple stellar populations that require dynamical analyses to disentangle. In this work, we undertake a detailed chemodynamical study of the metal-poor stars in the inner Galaxy. Using R ~ 20 000 VLT/GIRAFFE spectra of 319 metal-poor (-2.55dex<=[Fe/H]<=0.83dex, with mean [Fe/H]=-0.84dex) stars, we perform stellar parameter analysis and report 12 elemental abundances (C, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Zn, Ba, and Ce) with precisions of ~0.10 dex. Based on kinematic and spatial properties, we categorize the stars into four groups, associated with the following Galactic structures: the inner bulge, the outer bulge, the halo, and the disc. We find evidence that the inner and outer bulge population is more chemically complex (i.e. higher chemical dimensionality and less correlated abundances) than the halo population. This result suggests that the older bulge population was enriched by a larger diversity of nucleosynthetic events. We also find one inner bulge star with a [Ca/Mg] ratio consistent with theoretical pair-instability supernova yields and two stars that have chemistry consistent with globular cluster stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/488/2283
- Title:
- COMBS survey. Galactic Bulge metal-poor stars
- Short Name:
- J/MNRAS/488/2283
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemistry and kinematic studies can determine the origins of stellar population across the Milky Way. The metallicity distribution function of the bulge indicates that it comprises multiple populations, the more metal-poor end of which is particularly poorly understood. It is currently unknown if metal-poor bulge stars ([Fe/H]<-1dex) are part of the stellar halo in the inner most region, or a distinct bulge population or a combination of these. Cosmological simulations also indicate that the metal-poor bulge stars may be the oldest stars in the Galaxy. In this study, we successfully target metal-poor bulge stars selected using SkyMapper photometry. We determine the stellar parameters of 26 stars and their elemental abundances for 22 elements using R~47000 VLT/UVES spectra and contrast their elemental properties with that of other Galactic stellar populations. We find that the elemental abundances we derive for our metal-poor bulge stars have lower overall scatter than typically found in the halo. This indicates that these stars may be a distinct population confined to the bulge. If these stars are, alternatively, part of the inner-most distribution of the halo, this indicates that the halo is more chemically homogeneous at small Galactic radii than at large radii. We also find two stars whose chemistry is consistent with second-generation globular cluster stars. This paper is the first part of the Chemical Origins of Metal-poor Bulge Stars (COMBS) survey that will chemo-dynamically characterize the metal-poor bulge population.
- ID:
- ivo://CDS.VizieR/J/MNRAS/501/5981
- Title:
- COMBS Survey. Metal-poor bulge stars
- Short Name:
- J/MNRAS/501/5981
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The metal-poor stars in the bulge are important relics of the Milky Way's formation history, as simulations predict that they are some of the oldest stars in the Galaxy. In order to determine if they are truly ancient stars, we must understand their origins. Currently, it is unclear if the metal-poor stars in the bulge ([Fe/H]<-1dex) are merely halo interlopers, a unique accreted population, part of the boxy/peanut-shaped bulge, or a classical bulge population. In this work, we use spectra from the VLT/FLAMES spectrograph to obtain metallicity estimates using the Ca-II triplet of 473 bulge stars (187 of which have [Fe/H]<-1dex), targeted using SkyMapper photometry. We also use Gaia DR2 data to infer the Galactic positions and velocities along with orbital properties for 523 stars. We employ a probabilistic orbit analysis and find that about half of our sample has a >50 per cent probability of being bound to the bulge, and half are halo interlopers. We also see that the occurrence rate of halo interlopers increases steadily with decreasing metallicity across the full range of our sample (-3<[Fe/H]<0.5). Our examination of the kinematics of the confined compared to the unbound stars indicates the metal-poor bulge comprises at least two populations; those confined to the boxy/peanut bulge and halo stars passing through the inner galaxy. We conclude that an orbital analysis approach, as we have employed, is important to understand the composite nature of the metal-poor stars in the inner region.
- ID:
- ivo://CDS.VizieR/J/A+A/571/A73
- Title:
- Cometary activity of comet C/2006 S3 (LONEOS)
- Short Name:
- J/A+A/571/A73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of small bodies that have a cometary activity at a large heliocentric distance (larger than 5AU) is important for a better understanding of the physical properties of comets and their origin. Such studies require long-term monitoring and a significant observational effort. Our goal is to monitor the cometary activity and search for possible emission lines of C/2006 S3 (LONEOS), which is a distant comet that was discovered in 2006 and passed perihelion at 5.13AU in April 2012.
- ID:
- ivo://CDS.VizieR/J/A+A/563/A39
- Title:
- Cometary HII regions of DR21
- Short Name:
- J/A+A/563/A39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep Very Large Array H66{alpha} radio recombination line (RRL) observations of the two cometary HII regions in DR 21. With these sensitive data, we test the "hybrid" bow shock/champagne flow model previously proposed for the DR 21 HII regions.
- ID:
- ivo://CDS.VizieR/J/AJ/156/68
- Title:
- Comet C/2017 E4 composition with iSHELL at NASA/IRTF
- Short Name:
- J/AJ/156/68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In 2017 April, we acquired comprehensive high-resolution spectra of newly discovered comet C/2017 E4 (Lovejoy) as it approached perihelion, and before its disintegration. We detected many cometary emission lines in the range (2.8-5.3) {mu}m, in four customized instrument settings (L1-c, L3, Lp1-c, and M1) of iSHELL - the new near-IR high-resolution immersion echelle spectrograph at NASA/IRTF (Maunakea, Hawaii). We identified 12 molecular species: nine primary volatiles (H_2_O, HCN, NH_3_, CO, C_2_H_2_, C_2_H_6_, CH_4_, CH_3_OH, H_2_CO) and three product species (CN, NH_2_, OH). We detected 85 H_2_O emission lines from 12 water vibrational bands across L1-c and M1 settings. The many detected water emission lines enabled retrieval of accurate measures for ortho- and para-H_2_O independently, thereby reducing systematic uncertainty in the derived ortho-para ratio and nuclear spin temperature. Excitation analyses and emission profile analyses were performed for all species, and molecular abundance ratios relative to water are compared with values found for other Oort Cloud comets in our infrared database. Abundance ratios are consistent for most species, with the exception of underabundant methanol and overabundant ammonia in E4.
- ID:
- ivo://CDS.VizieR/J/A+A/656/A160
- Title:
- Comet C/2020 F3 (NEOWISE) emission lines
- Short Name:
- J/A+A/656/A160
- Date:
- 21 Mar 2022 09:16:33
- Publisher:
- CDS
- Description:
- Comet C/2020 F3 (NEOWISE) is considered to be the brightest comet observed in the northern hemisphere since the passage of comet C/1995 O1 (Hale-Bopp) in 1997. Since the study of comets offers a unique opportunity to investigate the early stages of the formation and evolution of our Sun and the Solar System, we obtained high-resolution optical spectra (R={lambda}/{Delta}{lambda}=115000) of comet NEOWISE. The unique passage and its brightness yielded spectra with a large number of emission lines, providing information on the coma composition and the physical and chemical processes occurring in the nucleus. The spectra have been used to generate a catalog of emission lines to be used for future studies of comets since there are no catalogs in the literature with such a high spectral resolution. Two high-resolution spectra of comet NEOWISE were obtained, on 26 July 2020 (geocentric distance of 0.7au) and 5 August 2020 (geocentric distance of 0.89au), with the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) echelle spectrograph installed on the 360cm Telescopio Nazionale Galileo (TNG). The spectra cover the range between 383 and 693nm, and have been extracted using the HARPS-N Data Reduction Pipeline. To analyze the spectra and compile the high-resolution catalog, we collected several laboratory molecular line lists that cover the same wavelength range as that of our spectra. To validate the final identification, we compared our catalog with other atlases that resulted from the spectral analysis of other comets. We generate a high-spectral-resolution catalog of emission lines observed in comet NEOWISE, providing the identification for 4488 lines. We found cometary lines due to CN, CH, C_2_, C_3_, and NH_2_ and atomic lines due to NaI and [OI].
- 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/A+A/619/A127
- Title:
- Comet C/2016 R2 (PanSTARRS) IRAM spectra
- Short Name:
- J/A+A/619/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multi-wavelength study of comet C/2016 R2 (PanSTARRS). This comet was observed on 23-24 January 2018 with the IRAM 30m telescope, and in January to March 2018 with the Nancay radio telescope. Visible spectroscopy was performed in December 2017 and February 2018 with small amateur telescopes. We report on measurements of CO, CH_3_OH, H_2_CO and HCN production rates, and on the determination of the N2/CO abundance ratio. Several other species, especially OH, were searched for but not detected. The inferred relative abundances, including upper limits for sulfur species, are compared to those measured in other comets at about the same heliocentric distance of ~2.8AU. The coma composition of comet C/2016 R2 is very different from all other comets observed so far, being rich in N2 and CO and dust poor. This suggests that this comet might belong to a very rare group of comets formed beyond the N_2_ ice line. Alternatively, comet C/2016 R2 (PanSTARRS) could be the fragment of a large and differentiated transneptunian object, with properties characteristic of volatile-enriched layers.
