The Closest Known Flyby of a Star to the Solar System

Passing stars can perturb the Oort Cloud, triggering comet showers and potentially extinction events on Earth. We combine velocity measurements for the recently discovered, nearby, low-mass binary system WISE J072003.20-084651.2 ("Scholz's star") to calculate its past trajectory. Integrating the Galactic orbits of this ~0.15 M_⊙ binary system and the Sun, we find that the binary passed within only 52^(+23)_(−14) kAU (0.25^(+0.11)_(−0.07) pc) of the Sun 70^(+15)_(−10) kya (1σ uncertainties), i.e., within the outer Oort Cloud. This is the closest known encounter of a star to our solar system with a well-constrained distance and velocity. Previous work suggests that flybys within 0.25 pc occur infrequently (~0.1 Myr^(−1)). We show that given the low mass and high velocity of the binary system, the encounter was dynamically weak. Using the best available astrometry, our simulations suggest that the probability that the star penetrated the outer Oort Cloud is ~98%, but the probability of penetrating the dynamically active inner Oort Cloud (<20 kAU) is ~10^(−4). While the flyby of this system likely caused negligible impact on the flux of long-period comets, the recent discovery of this binary highlights that dynamically important Oort Cloud perturbers may be lurking among nearby stars

Planet Populations as a Function of Stellar Properties

Exoplanets around different types of stars provide a window into the diverse environments in which planets form. This chapter describes the observed relations between exoplanet populations and stellar properties and how they connect to planet formation in protoplanetary disks. Giant planets occur more frequently around more metal-rich and more massive stars. These findings support the core accretion theory of planet formation, in which the cores of giant planets form more rapidly in more metal-rich and more massive protoplanetary disks. Smaller planets, those with sizes roughly between Earth and Neptune, exhibit different scaling relations with stellar properties. These planets are found around stars with a wide range of metallicities and occur more frequently around lower mass stars. This indicates that planet formation takes place in a wide range of environments, yet it is not clear why planets form more efficiently around low mass stars. Going forward, exoplanet surveys targeting M dwarfs will characterize the exoplanet population around the lowest mass stars. In combination with ongoing stellar characterization, this will help us understand the formation of planets in a large range of environments.Comment: Accepted for Publication in the Handbook of Exoplanet

A young hierarchical triple system harbouring a candidate debris disc

We report the detection of a wide young hierarchical triple system where the primary has a candidate debris disc. The primary, TYC 5241-986-1 A, is a known Tycho star which we classify as a late-K star with emission in the X-ray, near- and far-ultraviolet (UV) and Hα suggestive of youth. Its proper motion, photometric distance (65–105 pc) and radial velocity lead us to associate the system with the broadly defined Local Association of young stars but not specifically with any young moving group. The presence of weak lithium absorption and X-ray and calcium H and K emission support an age in the 20 to ∼125 Myr range. The secondary is a pair of M4.5 ± 0.5 dwarfs with near- and far-UV and Hα emission separated by approximately 1 arcsec (∼65–105 au projected separation) which lie of 145 arcsec (9200–15200 au) from the primary. The primary has a Wide-field Infrared Survey Explorer (WISE) 22 μm excess and follow-up Herschel observations also detect an excess at 70 μm. The excess emissions are indicative of a 100–175 K debris disc. We also explore the possibility that this excess could be due to a coincident background galaxy and conclude that this is unlikely. Debris discs are extremely rare around stars older than 15 Myr, hence if the excess is caused by a disc this is an extremely novel system

Detecting Weak Spectral Lines in Interferometric Data through Matched Filtering

Modern radio interferometers enable observations of spectral lines with unprecedented spatial resolution and sensitivity. In spite of these technical advances, many lines of interest are still at best weakly detected and therefore necessitate detection and analysis techniques specialized for the low signal-to-noise ratio (S/N) regime. Matched filters can leverage knowledge of the source structure and kinematics to increase sensitivity of spectral line observations. Application of the filter in the native Fourier domain improves S/N while simultaneously avoiding the computational cost and ambiguities associated with imaging, making matched filtering a fast and robust method for weak spectral line detection. We demonstrate how an approximate matched filter can be constructed from a previously observed line or from a model of the source, and we show how this filter can be used to robustly infer a detection significance for weak spectral lines. When applied to ALMA Cycle 2 observations of CH3OH in the protoplanetary disk around TW Hya, the technique yields a ≈53% S/N boost over aperture-based spectral extraction methods, and we show that an even higher boost will be achieved for observations at higher spatial resolution. A Python-based open-source implementation of this technique is available under the MIT license at http://github.com/AstroChem/VISIBLE

Distribution and evaluation of sense of coherence among older immigrants before and after a health promotion intervention &ndash; results from the RCT study promoting aging migrants&rsquo; capability

LA Arola,1&ndash;5 E Barenfeld,1&ndash;3 S Dahlin-Ivanoff,1&ndash;3,* G H&auml;ggblom-Kronl&ouml;f1&ndash;3,* 1Institute of Neuroscience and Physiology, Section for Health and Rehabilitation, The Sahlgrenska Academy, University of Gothenburg, Sweden; 2Centre for Person-Centred Care (GPCC), The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; 3Centre for Ageing and Health &ndash; Agecap, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; 4National Graduate School on Ageing and Health &ndash; SWEAH, Faculty of Medicine, Lund University, Lund, Sweden; 5Department of Health and Welfare, Arcada University of Applied Science, Helsinki, Finland *These authors contributed equally to this work Background: The migration process can be a threat to a person&rsquo;s sense of coherence (SOC) and to their ability to experience life as comprehensible, manageable, and meaningful. Seen from a salutogenic perspective, this may have a negative impact on the experience of health.Purpose: We describe the distribution of SOC and its components among older persons with an immigrant background now aging in Sweden. In addition, we evaluated whether a group-based health promotion program with a person-centered approach could support the SOC among older persons in this group.Materials and methods: A randomized controlled trial with postintervention follow-ups at 6 and 12 months was conducted with 131 independently living persons aged &ge;70 years from Finland and the Balkan Peninsula. Participants were randomly allocated to an intervention group (4 weeks of group intervention and one follow-up home visit) and a control group (no intervention but access to ordinary health care services). The outcome measure was the SOC measured by SOC-13. Chi-square and ORs were calculated.Results: There was a significant improvement in total SOC scores for the intervention group at 6-month follow-up. Also, the ORs for the SOC components were higher in the person-centered intervention group. However, we found no significant between-group differences nor did the effect last until the 12-month follow-up.Conclusion: Persons who have lived a long time in a host country after migration seem to have a SOC similar to native-born persons. Interventions with a person-centered approach could support the SOC by capturing individual life situations. Such interventions could support older persons by making everyday life more comprehensible and manageable and helping them to cope with challenges in daily life caused by aging. Keywords: sense of coherence, salutogenesis, health, old age, migration&nbsp