- ID:
- ivo://CDS.VizieR/J/A+A/535/A55
- Title:
- 4 stars with long-period planets
- Short Name:
- J/A+A/535/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of four new long-period planets within the HARPS high-precision sample: HD137388b (Msini=0.22M_Jup_), HD204941b (Msini=0.27M_Jup_), HD7199b (Msini=0.29M_Jup_), HD7449b (Msini=1.04M_Jup_). A long-period companion, probably a second planet, is also found orbiting HD7449. Planets around HD137388, HD204941, and HD7199 have rather low eccentricities (less than 0.4) relative to the 0.82 eccentricity of HD7449b. All these planets were discovered even though their hosting stars have clear signs of activity.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/825/62
- Title:
- Stars with M_p_sin(i)>0.1M_Jup_ hot Jupiter
- Short Name:
- J/ApJ/825/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The origin of Jupiter-mass planets with orbital periods of only a few days is still uncertain. It is widely believed that these planets formed near the water-ice line of the protoplanetary disk, and subsequently migrated into much smaller orbits. Most of the proposed migration mechanisms can be classified either as disk-driven migration, or as excitation of a very high eccentricity followed by tidal circularization. In the latter scenario, the giant planet that is destined to become a hot Jupiter spends billions of years on a highly eccentric orbit, with apastron near the water-ice line. Eventually, tidal dissipation at periastron shrinks and circularizes the orbit. If this is correct, then it should be especially rare for hot Jupiters to be accompanied by another giant planet interior to the water-ice line. Using the current sample of giant planets discovered with the Doppler technique, we find that hot Jupiters with P_orb_<10d are no more or less likely to have exterior Jupiter-mass companions than longer-period giant planets with P_orb_>=10d. This result holds for exterior companions both inside and outside of the approximate location of the water-ice line. These results are difficult to reconcile with the high-eccentricity migration scenario for hot Jupiter formation.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/159
- Title:
- Statistical analysis of exoplanet surveys
- Short Name:
- J/ApJ/794/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conduct a statistical analysis of a combined sample of direct imaging data, totalling nearly 250 stars. The stars cover a wide range of ages and spectral types, and include five detections ({kappa} And b, two ~60 M_J_ brown dwarf companions in the Pleiades, PZ Tel B, and CD-35 2722B). For some analyses we add a currently unpublished set of SEEDS observations, including the detections GJ 504b and GJ 758B. We conduct a uniform, Bayesian analysis of all stellar ages using both membership in a kinematic moving group and activity/rotation age indicators. We then present a new statistical method for computing the likelihood of a substellar distribution function. By performing most of the integrals analytically, we achieve an enormous speedup over brute-force Monte Carlo. We use this method to place upper limits on the maximum semimajor axis of the distribution function derived from radial-velocity planets, finding model-dependent values of ~30-100 AU. Finally, we model the entire substellar sample, from massive brown dwarfs to a theoretically motivated cutoff at ~5 M_J_, with a single power-law distribution. We find that p(M,a){prop.to}M^-0.65+/-0.60^a^-0.85+/-0.39^ (1{sigma} errors) provides an adequate fit to our data, with 1.0%-3.1% (68% confidence) of stars hosting 5-70 M_J_ companions between 10 and 100 AU. This suggests that many of the directly imaged exoplanets known, including most (if not all) of the low-mass companions in our sample, formed by fragmentation in a cloud or disk, and represent the low-mass tail of the brown dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/25
- Title:
- Stellar and planet properties for K2 candidates
- Short Name:
- J/ApJ/809/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The extended Kepler mission, K2, is now providing photometry of new fields every three months in a search for transiting planets. In a recent study, Foreman-Mackey and collaborators presented a list of 36 planet candidates orbiting 31 stars in K2 Campaign 1. In this contribution, we present stellar and planetary properties for all systems. We combine ground-based seeing-limited survey data and adaptive optics imaging with an automated transit analysis scheme to validate 21 candidates as planets, 17 for the first time, and identify 6 candidates as likely false positives. Of particular interest is K2-18 (EPIC 201912552), a bright (K=8.9) M2.8 dwarf hosting a 2.23+/-0.25 R_{earth}_ planet with T_eq_=272+/-15 K and an orbital period of 33 days. We also present two new open-source software packages which enable this analysis. The first, isochrones, is a flexible tool for fitting theoretical stellar models to observational data to determine stellar properties using a nested sampling scheme to capture the multimodal nature of the posterior distributions of the physical parameters of stars that may plausibly be evolved. The second is vespa, a new general-purpose procedure to calculate false positive probabilities and statistically validate transiting exoplanets.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A7
- Title:
- Stellar and substellar companions from Gaia EDR3
- Short Name:
- J/A+A/657/A7
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The multiplicity fraction of stars, down to the substellar regime, is a parameter of fundamental importance for stellar formation, evolution, and planetology. The census of multiple stars in the solar neighborhood is however incomplete. The presence of a companion in orbit around a star affects its proper motion. We aim at detecting companions of Hipparcos catalog stars from the proper motion anomaly (PMa) they induce on their host star, that is, the difference between their long-term Hipparcos-Gaia and short-term Gaia proper motion vectors. We also aim at detecting resolved, gravitationally bound companions of the Hipparcos catalog stars (117955 stars), and of the Gaia EDR3 stars closer than 100 c (542232 stars). Using the Hipparcos and EDR3 data, we revise the PMa catalog for the Hipparcos stars. To identify gravitationally bound visual companions of our sample, we search the Gaia EDR3 catalog for common proper motion (CPM) candidates. The detection of tangential velocity anomalies with a median accuracy of 26cm/s per parsec of distance is demonstrated with the EDR3. This improvement by a factor 2.5 in accuracy compared to the Gaia DR2 results in PMa detection limits on companions well into the planetary mass regime for many targets. We identify 37515 Hipparcos stars presenting a PMa at significant level (S/N>3), that is, a fraction of 32% (compared to 30% for the DR2) and 12914 (11%) hosting CPM bound candidate companions. Including the Gaia EDR3 RUWE>1.4 as an additional indicator, 50,720 stars of the Hipparcos catalog (43%) exhibit at least one signal of binarity. Among the Gaia EDR3 stars located within 100 pc, we find CPM bound candidate companions for 39,490 stars (7.3% of the sample). The search for companions using a combination of the PMa, CPM and RUWE indicators significantly improves the exhaustivity of the multiplicity survey. The detection of CPM companions of very bright stars (heavily saturated on the Gaia detectors) that are classical benchmark objects for stellar physics provides a useful proxy to estimate their distance with a higher accuracy than Hipparcos.
- ID:
- ivo://CDS.VizieR/J/AN/341/996
- Title:
- Stellar companions of (C)TOIs
- Short Name:
- J/AN/341/996
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first results of a new survey are reported, which explores the 2nd data release of the ESA-Gaia mission, in order to search for stellar companions of (Community) TESS Objects of Interest and to characterize their properties. In total, 193 binary and 15 hierarchical triple star systems are presented, detected among 1391 target stars, which are located at distances closer than about 500pc around the Sun. The companions and the targets are equidistant and share a common proper motion, as it is expected for gravitationally bound stellar systems, proven with their accurate Gaia astrometry. The companions exhibit masses in the range between about 0.08M_{sun}_ and 3M_{sun}_ and are most frequently found in the mass range between 0.13 and 0.6M_{sun}_. The companions are separated from the targets by about 40 up to 9900au, and their frequency continually decreases with increasing separation. While most of the detected companions are late K to mid M dwarfs, also 5 white dwarf companions were identified in this survey, whose true nature is revealed by their photometric properties.
- ID:
- ivo://CDS.VizieR/J/AN/342/840
- Title:
- Stellar companions of (C)TOIs
- Short Name:
- J/AN/342/840
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the latest results of our ongoing multiplicity study of (Community) TESS Objects of Interest, using astro- and photometric data from the ESA-Gaia mission, to detect stellar companions of these stars and to characterize their properties. In total, 107 binary, 5 hierarchical triple star systems, as well as one quadruple system were detected among 585 targets surveyed, which are all located at distances closer than about 500pc around the Sun. As proven with their accurate Gaia EDR3 astrometry, the companions and the targets are located at the same distance and share a common proper motion, as it is expected for components of gravitationally bound stellar systems. The companions exhibit masses in the range between about 0.09M_{sun}_ and 4.5M_{sun}_ and are most frequently found in the mass range between 0.15 and 0.6M_{sun}_. The companions are separated from the targets by about 120 up to 9500au and their frequency is the highest and constant within about 500au while it continually decreases for larger separations. Beside mainly early to mid M dwarfs, also 5 white dwarf companions were identified in this survey, whose true nature was revealed by their photometric properties.
- ID:
- ivo://CDS.VizieR/J/MNRAS/490/5088
- Title:
- Stellar companions of exoplanet host stars
- Short Name:
- J/MNRAS/490/5088
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new survey is presented, which explores the second data release of the ESA-Gaia mission, in order to search for stellar companions of exoplanet host stars, located at distances closer than about 500pc around the Sun. In total, 176 binaries, 27 hierarchical triples, and one hierarchical quadruple system are detected among more than 1300 exoplanet host stars, whose multiplicity is investigated, yielding a multiplicity rate of the exoplanet host stars of at least about 15 per cent. The detected companions and the exoplanet host stars are equidistant and share a common proper motion, as it is expected for gravitationally bound stellar systems, proven with their accurate Gaia astrometry. The companions exhibit masses in the range between about 0.078 and 1.4M_{sun}_ with a peak in their mass distribution between 0.15 and 0.3M{sun}_. The companions are separated from the exoplanet host stars by about 20 up to 9100au, but are found most frequently within a projected separation of 1000au. While most of the detected companions are early M dwarfs, eight white dwarf companions of exoplanet host stars are also identified in this survey, whose true nature is revealed with their photometric properties. Hence, these degenerated companions and the exoplanet host stars form evolved stellar systems with exoplanets, which have survived (physically but also dynamically) the post-main-sequence evolution of their former primary star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/2498
- Title:
- Stellar companions of exoplanet host stars
- Short Name:
- J/MNRAS/421/2498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To understand the influence of additional wide stellar companions on planet formation, it is necessary to determine the fraction of multiple stellar systems amongst the known extrasolar planet population. We target recently discovered radial velocity exoplanetary systems observable from the Northern hemisphere and with sufficiently high proper motion to detect stellar companions via direct imaging. We utilize the Calar Alto 2.2-m telescope in combination with its lucky imaging camera AstraLux. 71 planet host stars have been observed so far, yielding one new low-mass (0.239+/-0.022M_{sun}_) stellar companion, 4.5-arcsec (227 au of projected separation) north-east of the planet host star HD 185269, detected via astrometry with AstraLux. We also present follow-up astrometry on three previously discovered stellar companions, showing for the first time common proper motion of the 0.5-arcsec companion to HD 126614. Additionally, we determined the achieved detection limits for all targets, which allow us to characterize the detection space of possible further companions of these stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/441/2361
- Title:
- Stellar magnetism, age and rotation
- Short Name:
- J/MNRAS/441/2361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate how the observed large-scale surface magnetic fields of low-mass stars (~0.1-2M_{sun}_), reconstructed through Zeeman-Doppler imaging, vary with age t, rotation and X-ray emission. Our sample consists of 104 magnetic maps of 73 stars, from accreting pre-main sequence to main-sequence objects (1Myr<~t<~10Gyr). For non-accreting dwarfs we empirically find that the unsigned average large-scale surface field is related to age as t^-0.655+/-0.045^. This relation has a similar dependence to that identified by Skumanich, used as the basis for gyrochronology. Likewise, our relation could be used as an age-dating method ('magnetochronology'). The trends with rotation we find for the large-scale stellar magnetism are consistent with the trends found from Zeeman broadening measurements (sensitive to large- and small-scale fields). These similarities indicate that the fields recovered from both techniques are coupled to each other, suggesting that small- and large-scale fields could share the same dynamo field generation processes. For the accreting objects, fewer statistically significant relations are found, with one being a correlation between the unsigned magnetic flux and rotation period. We attribute this to a signature of star-disc interaction, rather than being driven by the dynamo.
