35 research outputs found
Kinematics of the Optically Visible YSOs toward the Orion B Molecular Cloud
Interstellar matter and star formatio
Radial velocity variability and stellar properties of FGK stars in the cores of NGC 2516 and NGC 2422
Stars and planetary system
Bright Southern Variable Stars in the bRing Survey
In addition to monitoring the bright star ÎČ Pic during the near-transit event for its giant exoplanet, the ÎČ Pictoris b Ring (bRing) observatories at Siding Springs Observatory, Australia and Sutherland, South Africa have monitored the brightnesses of bright stars (V  4â8 mag) centered on the south celestial pole (ÎŽÂ â€Â â30°) for approximately two years. Here we present a comprehensive study of the bRing time-series photometry for bright southern stars monitored between 2017 June and 2019 January. Of the 16,762 stars monitored by bRing, 353 were found to be variable. Of the variable stars, 80% had previously known variability and 20% were new variables. Each of the new variables was classified, including three new eclipsing binaries (HD 77669, HD 142049, HD 155781), 26 Ύ Scutis, 4 slowly pulsating B stars, and others. This survey also reclassified four stars based on their period of pulsation, light curve, spectral classification, and colorâmagnitude information. The survey data were searched for new examples of transiting circumsecondary disk systems, but no candidates were found.Stars and planetary system
SCExAO/MEC and CHARIS Discovery of a Low Mass, 6 AU-Separation Companion to HIP 109427 using Stochastic Speckle Discrimination and High-Contrast Spectroscopy
We report the direct imaging discovery of a low-mass companion to the nearby
accelerating A star, HIP 109427, with the Subaru Coronagraphic Extreme Adaptive
Optics (SCExAO) instrument coupled with the MKID Exoplanet Camera (MEC) and
CHARIS integral field spectrograph. CHARIS data reduced with reference star PSF
subtraction yield 1.1-2.4 m spectra. MEC reveals the companion in and
band at a comparable signal-to-noise ratio using stochastic speckle
discrimination, with no PSF subtraction techniques. Combined with complementary
follow-up photometry from Keck/NIRC2, the SCExAO data favors a
spectral type, effective temperature, and luminosity of M4-M5.5, 3000-3200 ,
and , respectively.
Relative astrometry of HIP 109427 B from SCExAO/CHARIS and Keck/NIRC2, and
complementary Gaia-Hipparcos absolute astrometry of the primary favor a
semimajor axis of au, an eccentricity of
, an inclination of degrees, and a
dynamical mass of . This work shows the
potential for extreme AO systems to utilize speckle statistics in addition to
widely-used post-processing methods to directly image faint companions to
nearby stars near the telescope diffraction limit.Comment: 13 pages, 7 figures, 3 table
Etude experimentale du comportement rheologique de milieux granulaires a constituants plastiquement deformables: comparaison de poudres de plasticine et d'alliages d'aluminium
SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 79770 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
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Fast-rotating Blue Straggler Stars in the Globular Cluster NGC 3201
We used high-resolution spectra acquired with the Magellan Telescope to measure radial and rotational velocities of approximately 200 stars in the Galactic globular cluster NGC 3201. The surveyed sample includes blue straggler stars (BSSs) and reference stars in different evolutionary stages (main-sequence turnoff, subgiant, red giant, and asymptotic giant branches). The average radial velocity value (ăV r ă = 494.5 ± 0.5 km sâ1) confirms a large systemic velocity for this cluster and was used to distinguish 33 residual field interlopers. The final sample of member stars has 67 BSSs and 114 reference stars. Similarly to what is found in other clusters, the totality of the reference stars has negligible rotation (< 20 km sâ1), while the BSS rotational velocity distribution shows a long tail extending up to âŒ200 km sâ1, with 19 BSSs (out of 67) spinning faster than 40 km sâ1. This sets the percentage of fast-rotating BSSs to âŒ28%. Such a percentage is roughly comparable to that measured in other loose systems (Ï Centauri, M4, and M55) and significantly larger than that measured in high-density clusters (as 47 Tucanae, NGC 6397, NGC 6752, and M30). This evidence supports a scenario where recent BSS formation (mainly from the evolution of binary systems) is occurring in low-density environments. We also find that the BSS rotational velocity tends to decrease for decreasing luminosity and surface temperature, similarly to what is observed in main-sequence stars. Hence, further investigations are needed to understand the impact of BSS internal structure on the observed rotational velocities. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
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A Technology and Science Gap List for Habitable-Zone Exoplanet Imaging with Ground-Based Extremely Large Telescopes
The Pathways to Discovery in Astronomy and Astrophysics for the 2020s decadal survey highlighted the ability of the coming generation of 30-meter-class telescopes âto detect, image, and characterize temperate rocky planets around low-mass stars, measure their atmospheric compositions including searches for oxygen.â However, many of the technologies required to reach the challenging contrast ratios associated with this science case are not yet available, and targeted preparatory science must be carried out well in advance of these observations. In this paper, we draw from the example of NASA's Exoplanet Exploration Program and propose a preliminary version of a âTechnology Gap Listâ and âScience Gap Listâ for the ground-based imaging of rocky planets around the nearest stars with extremely large ground-based telescopes. These lists can be used to prioritize precursor technical demonstrations and observations with current and near-term high contrast instrumentation, so that the community is ready to exploit the collecting area of extremely large telescopes. © 2022 SPIE.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
The CIDA Variability Survey of Orion OB1. II. Demographics of the Young, Low-mass Stellar Populations
Interstellar matter and star formatio
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SCExAO and Keck Direct Imaging Discovery of a Low-mass Companion Around the Accelerating F5 Star HIP 5319
We present the direct imaging discovery of a low-mass companion to the nearby accelerating F star, HIP 5319, using SCExAO coupled with the CHARIS, VAMPIRES, and MEC instruments in addition to Keck/NIRC2 imaging. CHARIS JHK (1.1-2.4 ÎŒm) spectroscopic data combined with VAMPIRES 750 nm, MEC Y, and NIRC2 L p photometry is best matched by an M3-M7 object with an effective temperature of T = 3200 K and surface gravity log(g) = 5.5. Using the relative astrometry for HIP 5319 B from CHARIS and NIRC2, and absolute astrometry for the primary from Gaia and Hipparcos, and adopting a log-normal prior assumption for the companion mass, we measure a dynamical mass for HIP 5319 B of 31 â 11 + 35 M J , a semimajor axis of 18.6 â 4.1 + 10 au, an inclination of 69.4 â 15 + 5.6 degrees, and an eccentricity of 0.42 â 0.29 + 0.39 . However, using an alternate prior for our dynamical model yields a much higher mass of 128 â 88 + 127 M J . Using data taken with the LCOGT NRES instrument we also show that the primary HIP 5319 A is a single star in contrast to previous characterizations of the system as a spectroscopic binary. This work underscores the importance of assumed priors in dynamical models for companions detected with imaging and astrometry, and the need to have an updated inventory of system measurements. © 2022. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]