20 research outputs found
Chronostar. II. Kinematic age and substructure of the Scorpius-Centaurus OB2 association
The nearest region of massive star formation - the Scorpius-Centaurus OB2
association (Sco-Cen) - is a local laboratory ideally suited to the study of a
wide range of astrophysical phenomena. Precision astrometry from the Gaia
mission has expanded the census of this region by an order of magnitude.
However, Sco-Cen's vastness and complex substructure make kinematic analysis of
its traditional three regions, Upper Scorpius, Upper Centaurus-Lupus and Lower
Centaurus-Crux, challenging. Here we use Chronostar, a Bayesian tool for
kinematic age determination, to carry out a new kinematic decomposition of
Sco-Cen using full 6-dimensional kinematic data. Our model identifies 8
kinematically distinct components consisting of 8,185 stars distributed in
dense and diffuse groups, each with an independently-fit kinematic age; we
verify that these kinematic estimates are consistent with isochronal ages. Both
Upper Centaurus-Lupus and Lower Centaurus-Crux are split into two parts. The
kinematic age of the component that includes PDS 70, one of the most well
studied systems currently forming planets, is 153 Myr.Comment: Submitted to MNRAS. 19 pages, 9 figure
Pyxis: A ground-based demonstrator for formation-flying optical interferometry
In the past few years, there has been a resurgence in studies towards
space-based optical/infrared interferometry, particularly with the vision to
use the technique to discover and characterise temperate Earth-like exoplanets
around solar analogues. One of the key technological leaps needed to make such
a mission feasible is demonstrating that formation flying precision at the
level needed for interferometry is possible. Here, we present ,
a ground-based demonstrator for a future small satellite mission with the aim
to demonstrate the precision metrology needed for space-based interferometry.
We describe the science potential of such a ground-based instrument, and detail
the various subsystems: three six-axis robots, a multi-stage metrology system,
an integrated optics beam combiner and the control systems required for the
necessary precision and stability. We end by looking towards the next stage of
: a collection of small satellites in Earth orbit.Comment: 27 Pages, 14 Figures, submitted to JATI
A spectroscopically confirmed Gaia-selected sample of 318 new young stars within âŒ200 pc
In the Gaia era, the majority of stars in the Solar neighbourhood have parallaxes and proper motions precisely determined while spectroscopic age indicators are still missing for a large fraction of low-mass young stars. In this work, we select 756 overluminous late K and early M young star candidates in the southern sky and observe them over 64 nights with the ANU 2.3-m Telescope at Siding Spring Observatory using the Echelle (R = 24 000) and Wide Field spectrographs (WiFeS, R = 3000-7000). Our selection is kinematically unbiased to minimize the preference against low-mass members of stellar associations that dissipate first and to include potential members of diffuse components. We provide measurements of Hα and calcium H&K emission, as well as of Li i 6708 Ă
in absorption. This enables identification of stars as young as 10-30 Myr-a typical age range for stellar associations. We report on 346 stars showing detectable lithium absorption, 318 of which are not included in existing catalogues of young stars. We also report 125 additional stars in our sample presenting signs of stellar activity indicating youth but with no detectable lithium. Radial velocities are determined for WiFeS spectra with a precision of 3.2 km s-1 and 1.5 km s-1 for the Echelle sample
Development of the single-mode fiber integral field unit for the RHEA Spectrograph
RHEA is a single-mode Ă©chelle spectrograph designed to be a replicable and cost effective method of undertaking precision radial velocity measurements. The instrument has a novel fiber feed with an integral field unit injecting into a grid of single-mode fibers reformatted to form a pseudo-slit, increasing throughput and enabling highspatial resolution observations when operating behind Subaru and the SCExAO adaptive optics system. The past 18 months have seen a replacement cable constructed for the instrument to address modal noise caused by closely packed fibers with similar path lengths. Here we detail the cable fabrication procedure, design improvements, increased precision in meeting the required sub-micron optical tolerances, throughput gains, and known remaining issues
An innovative integral field unit upgrade with 3D-printed micro-lenses for the RHEA at Subaru
In the new era of Extremely Large Telescopes (ELTs) currently under construction, challenging requirements drive spectrograph designs towards techniques that efficiently use a facility's light collection power. Operating in the single-mode (SM) regime, close to the diffraction limit, reduces the footprint of the instrument compared to a conventional high-resolving power spectrograph. The custom built injection fiber system with 3D-printed micro-lenses on top of it for the replicable high-resolution exoplanet and asteroseismology spectrograph at Subaru in combination with extreme adaptive optics of SCExAO, proved its high efficiency in a lab environment, manifesting up to ~77% of the theoretical predicted performance
International Consensus Statement on Rhinology and Allergy: Rhinosinusitis
Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICARâRS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICARâRSâ2021 as well as updates to the original 140 topics. This executive summary consolidates the evidenceâbased findings of the document. Methods: ICARâRS presents over 180 topics in the forms of evidenceâbased reviews with recommendations (EBRRs), evidenceâbased reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICARâRSâ2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidenceâbased management algorithm is provided. Conclusion: This ICARâRSâ2021 executive summary provides a compilation of the evidenceâbased recommendations for medical and surgical treatment of the most common forms of RS