We conducted a survey of nearby binary systems composed of main sequence stars of spectral types F and Gin order to improve our understanding of the hierarchical nature of multiple star systems. ...Using Robo-AO, the first robotic adaptive optics instrument, we collected high angular resolution images with deep and well-defined detection limits in the Sloan Digital Sky Survey i band. A total of 695 components belonging to 595 systems were observed. We prioritized observations of faint secondary components with separations over 10 to quantify the still poorly constrained frequency of their subsystems. Of the 214 secondaries observed, 39 contain such subsystems; 19 of those were discovered with Robo-AO. We also targeted close binaries with periods less than 100 yr, searching for their distant tertiary components, and discovered 17 certain and 2 potential new triples. Measurements of binary stars with Robo-AO allowed us to compute first orbits for 9 pairs and to improve orbits of another 11 pairs.
Abstract
We present results from the Large Adaptive optics Survey for Substellar Objects, where the goal is to directly image new substellar companions (<70
M
Jup
) at wide orbital separations (≳50 ...au) around young (≲300 Myr), nearby (<100 pc), low-mass (≈0.1–0.8
M
⊙
) stars. We report on 427 young stars imaged in the visible (
i
′) and near-infrared (
J
or
H
) simultaneously with Robo-AO on the Kitt Peak 2.1 m telescope and later the Maunakea University of Hawaii 2.2 m telescope. To undertake the observations, we commissioned a new infrared camera for Robo-AO that uses a low-noise high-speed SAPHIRA avalanche photodiode detector. We detected 121 companion candidates around 111 stars, of which 62 companions are physically associated based on Gaia DR2 parallaxes and proper motions, another 45 require follow-up observations to confirm physical association, and 14 are background objects. The companion separations range from 2 to 1101 au and reach contrast ratios of 7.7 mag in the near-infrared compared to the primary. The majority of confirmed and pending candidates are stellar companions, with ∼5 being potentially substellar and requiring follow-up observations for confirmation. We also detected a 43 ± 9
M
Jup
and an 81 ± 5
M
Jup
companion that were previously reported. We found 34 of our targets have acceleration measurements detected using Hipparcos–Gaia proper motions. Of those,
58
−
14
+
12
% of the 12 stars with imaged companion candidates have significant accelerations (
χ
2
>
11.8
), while only
23
−
6
+
11
% of the remaining 22 stars with no detected companion have significant accelerations. The significance of the acceleration decreases with increasing companion separation. These young accelerating low-mass stars with companions will eventually yield dynamical masses with future orbit monitoring.
ABSTRACT Infrared avalanche photodiode (APD) arrays represent a panacea for many branches of astronomy by enabling extremely low-noise, high-speed, and even photon-counting measurements at ...near-infrared wavelengths. We recently demonstrated the use of an early engineering-grade infrared APD array that achieves a correlated double sampling read noise of 0.73 e− in the lab, and a total noise of 2.52 e− on sky, and supports simultaneous high-speed imaging and tip-tilt wavefront sensing with the Robo-AO visible-light laser adaptive optics (AO) system at the Palomar Observatory 1.5 m telescope. Here we report on the improved image quality simultaneously achieved at visible and infrared wavelengths by using the array as part of an image stabilization control loop with AO-sharpened guide stars. We also discuss a newly enabled survey of nearby late M-dwarf multiplicity, as well as future uses of this technology in other AO and high-contrast imaging applications.
Abstract
In order to assess the multiplicity statistics of stars across spectral types and populations in a volume-limited sample, we censused nearby stars for companions with Robo-AO. We report on ...observations of 1157 stars of all spectral types within 25 pc with decl. >−13° searching for tight companions. We detected 154 companion candidates with separations ranging from ∼0.″15 to 4.″0 and magnitude differences up to Δ
m
i
′
≤
7
using the robotic adaptive optics instrument Robo-AO. We confirmed physical association from Gaia EDR3 astrometry for 53 of the companion candidates, 99 remain to be confirmed, and two were ruled out as background objects. We complemented the high-resolution imaging companion search with a search for comoving objects with separations out to 10,000 au in Gaia EDR3, which resulted in an additional 147 companions registered. Of the 301 total companions reported in this study, 49 of them are new discoveries. Out of the 191 stars with significant acceleration measurements in the Hipparcos–Gaia catalog of accelerations, we detect companions around 115 of them, with the significance of the acceleration increasing as the companion separation decreases. From this survey, we report the following multiplicity fractions (compared to literature values): 40.9% ± 3.0% (44%) for FGK stars and 28.2% ± 2.3% (27%) for M stars, as well as higher-order fractions of 5.5% ± 1.1% (11%) and 3.9% ± 0.9% (5%) for FGK stars and M-type stars, respectively.
Abstract
We present the discovery of TOI 540 b, a hot planet slightly smaller than Earth orbiting the low-mass star 2MASS J05051443-4756154. The planet has an orbital period of
P
= 1.239149 days ...(±170 ms) and a radius of
, and is likely terrestrial based on the observed mass–radius distribution of small exoplanets at similar insolations. The star is 14.008 pc away and we estimate its mass and radius to be
and
, respectively. The star is distinctive in its very short rotational period of
hr and correspondingly small Rossby number of 0.007 as well as its high X-ray-to-bolometric luminosity ratio of
based on a serendipitous XMM-Newton detection during a slew operation. This is consistent with the X-ray emission being observed at a maximum value of
as predicted for the most rapidly rotating M dwarfs. TOI 540 b may be an alluring target to study atmospheric erosion due to the strong stellar X-ray emission. It is also among the most accessible targets for transmission and emission spectroscopy and eclipse photometry with the James Webb Space Telescope, and may permit Doppler tomography with high-resolution spectroscopy during transit. This discovery is based on precise photometric data from the Transiting Exoplanet Survey Satellite and ground-based follow-up observations by the MEarth team.
Abstract
Young eclipsing binaries (EBs) are powerful probes of early stellar evolution. Current models are unable to simultaneously reproduce the measured and derived properties that are accessible ...for EB systems (e.g., mass, radius, temperature, and luminosity). In this study we add a benchmark EB to the pre-main-sequence population with our characterization of TOI 450 (TIC 77951245). Using Gaia astrometry to identify its comoving, coeval companions, we confirm TOI 450 is a member of the ∼40 Myr Columba association. This eccentric (
e
= 0.2969), equal-mass (
q
= 1.000) system provides only one grazing eclipse. Despite this, our analysis achieves the precision of a double-eclipsing system by leveraging information in our high-resolution spectra to place priors on the surface-brightness and radius ratios. We also introduce a framework to include the effect of star spots on the observed eclipse depths. Multicolor eclipse light curves play a critical role in breaking degeneracies between the effects of star spots and limb-darkening. Including star spots reduces the derived radii by ∼2% from a unspotted model (>2
σ
) and inflates the formal uncertainty in accordance with our lack of knowledge regarding the starspot orientation. We derive masses of 0.1768( ± 0.0004) and 0.1767( ± 0.0003)
M
⊙
, and radii of 0.345(±0.006) and 0.346(±0.006)
R
⊙
for the primary and secondary, respectively. We compare these measurements to multiple stellar evolution isochones, finding good agreement with the association age. The MESA MIST and SPOTS (
f
s
= 0.17) isochrones perform the best across our comparisons, but detailed agreement depends heavily on the quantities being compared.
Abstract
Stellar radial-velocity (RV) jitter due to surface activity may bias the RV semiamplitude and mass of rocky planets. The amplitude of the jitter may be estimated from the uncertainty in the ...rotation period, allowing the mass to be more accurately obtained. We find candidate rotation periods for 17 out of 35 TESS Objects of Interest (TOI) hosting <3
R
⊕
planets as part of the Magellan-TESS survey, which is the first-ever statistically robust study of exoplanet masses and radii across the photoevaporation gap. Seven periods are ≥3
σ
detections, two are ≥1.5
σ
, and eight show plausible variability, but the periods remain unconfirmed. The other 18 TOIs are nondetections. Candidate rotators include the host stars of the confirmed planets L 168-9 b, the HD 21749 system, LTT 1445 A b, TOI 1062 b, and the L 98-59 system. Thirteen candidates have no counterpart in the 1000 TOI rotation catalog of Canto Martins et al. We find periods for G3–M3 dwarfs using combined light curves from TESS and the Evryscope all-sky array of small telescopes, sometimes with longer periods than would be possible with TESS alone. Secure periods range from 1.4 to 26 days with Evryscope-measured photometric amplitudes as small as 2.1 mmag in
g
′
. We also apply Monte Carlo sampling and a Gaussian process stellar activity model from
exoplanet
to the TESS light curves of six TOIs to confirm the Evryscope periods.
We have conducted a survey of candidate hot subdwarf (HSD) stars in the southern sky searching for fast transits, eclipses, and sinusoidal-like variability in the Evryscope light curves. The survey ...aims to detect transit signals from Neptune-size planets to gas giants, and eclipses from M-dwarfs and brown dwarfs. The other variability signals are primarily expected to be from compact binaries and reflection effect binaries. Due to the small size of HSDs (R 0.2 R ), transit and eclipse signals are expected to last only 20 minutes, but with large signal depths (up to completely eclipsing if the orientation is edge on). With its 2 minute cadence and continuous observation, the Evryscope is well placed to recover these fast transits and eclipses. The very large field of view (8150 deg2) is critical to obtain enough HSD targets, despite their rarity. We identified 11,000 potential HSDs from the 9.3 M Evryscope light curves for sources brighter than mg = 15. With our machine-learning spectral classifier, we flagged high confidence targets and estimate the total HSDs in the survey to be 1400. The light-curve search detected three planet transit candidates, shown to have stellar companions from follow-up analysis. We discovered several new compact binaries (including two with unseen degenerate companions), two eclipsing binaries with M-dwarf companions, as well as new reflection effect binaries and others with sinusoidal-like variability. Four of the discoveries are being published in separate follow-up papers, and we discuss the follow-up potential of the other discoveries.
IntroductionMultidisciplinary teams (MDTs) are integral to oncology management, involving specialised healthcare professionals who collaborate to develop individualised treatment plans for patients. ...However, as cancer care grows more complex, MDTs must continually adapt to better address patient needs. This scoping review will explore barriers and challenges MDTs have encountered in the past decade; and propose strategies for optimising their utilisation to overcome these obstacles and improve patient care.Methods and analysisThe scoping review will follow Arksey and O’Malley’s framework and begin with a literature search using keywords in electronic databases such as PubMed/MEDLINE, Scopus and PsychINFO, covering the period from January 2013 to December 2022 and limited to English language publications. Four independent reviewers will screen titles and abstracts based on predefined inclusion criteria, followed by full-text review of selected titles. Relevant references cited in the publications will also be examined. A Preferred Reporting Items for Systematic reviews and Meta-Analyses flow diagram will be utilised to illustrate the methodology. Data from selected publications will be extracted, analysed, and categorised for further analysis.Ethics and disseminationThe results of the scoping review will provide a comprehensive overview of the barriers and challenges encountered by oncology MDTs over the past decade. These findings will contribute to the existing literature and provide insights into areas that require improvement in the functioning of MDTs in oncology management. The results will be disseminated through publication in a scientific journal, which will help to share the findings with the wider healthcare community and facilitate further research and discussion in this field.Trial registration detailsThe protocol for this scoping review is registered with Open Science Framework, available at DOI 10.17605/OSF.IO/R3Y8U.
Type Ia supernovae are thought to result from a thermonuclear explosion of an accreting white dwarf in a binary system, but little is known of the precise nature of the companion star and the ...physical properties of the progenitor system. There are two classes of models: double-degenerate (involving two white dwarfs in a close binary system) and single-degenerate models. In the latter, the primary white dwarf accretes material from a secondary companion until conditions are such that carbon ignites, at a mass of 1.38 times the mass of the Sun. The type Ia supernova SN 2011fe was recently detected in a nearby galaxy. Here we report an analysis of archival images of the location of SN 2011fe. The luminosity of the progenitor system (especially the companion star) is 10-100 times fainter than previous limits on other type Ia supernova progenitor systems, allowing us to rule out luminous red giants and almost all helium stars as the mass-donating companion to the exploding white dwarf.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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