Abstract
Asteroseismology of bright stars has become increasingly important as a method to determine the fundamental properties (in particular ages) of stars. The Kepler Space Telescope initiated a ...revolution by detecting oscillations in more than 500 main-sequence and subgiant stars. However, most Kepler stars are faint and therefore have limited constraints from independent methods such as long-baseline interferometry. Here we present the discovery of solar-like oscillations in
α
Men A, a naked-eye (
V
= 5.1) G7 dwarf in TESS’s southern continuous viewing zone. Using a combination of astrometry, spectroscopy, and asteroseismology, we precisely characterize the solar analog
α
Men A (
T
eff
= 5569 ± 62 K,
R
⋆
= 0.960 ± 0.016
R
⊙
,
M
⋆
= 0.964 ± 0.045
M
⊙
). To characterize the fully convective M dwarf companion, we derive empirical relations to estimate mass, radius, and temperature given the absolute Gaia magnitude and metallicity, yielding
M
⋆
= 0.169 ± 0.006
M
⊙
,
R
⋆
= 0.19 ± 0.01
R
⊙
, and
T
eff
= 3054 ± 44 K. Our asteroseismic age of 6.2 ± 1.4 (stat) ± 0.6 (sys) Gyr for the primary places
α
Men B within a small population of M dwarfs with precisely measured ages. We combined multiple ground-based spectroscopy surveys to reveal an activity cycle of
P
= 13.1 ± 1.1 yr for
α
Men A, a period similar to that observed in the Sun. We used different gyrochronology models with the asteroseismic age to estimate a rotation period of ∼30 days for the primary. Alpha Men A is now the closest (
d
= 10 pc) solar analog with a precise asteroseismic age from space-based photometry, making it a prime target for next-generation direct-imaging missions searching for true Earth analogs.
The CERN Axion Solar Telescope has finished its search for solar axions with (3)He buffer gas, covering the search range 0.64 eV ≲ ma ≲ 1.17 eV. This closes the gap to the cosmological hot dark ...matter limit and actually overlaps with it. From the absence of excess x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of gaγ ≲ 3.3 × 10(-10) GeV(-1) at 95% C.L., with the exact value depending on the pressure setting. Future direct solar axion searches will focus on increasing the sensitivity to smaller values of gaγ, for example by the currently discussed next generation helioscope International AXion Observatory.
Hypothetical low-mass particles, such as axions, provide a compelling explanation for the dark matter in the universe. Such particles are expected to emerge abundantly from the hot interior of stars. ...To test this prediction, the CERN Axion Solar Telescope (CAST) uses a 9 T refurbished Large Hadron Collider test magnet directed towards the Sun. In the strong magnetic field, solar axions can be converted to X-ray photons which can be recorded by X-ray detectors. In the 2013-2015 run, thanks to low-background detectors and a new X-ray telescope, the signal-to-noise ratio was increased by about a factor of three. Here, we report the best limit on the axion-photon coupling strength (0.66 × 10-10 GeV-1 at 95% confidence level) set by CAST, which now reaches similar levels to the most restrictive astrophysical bounds.
A 2-dodecyl benzotriazole and 9,9-dioctylfluorene containing alternating conjugated polymer, poly((9,9-dioctylfluorene)-2,7-diyl-(4,7-bis(thien-2-yl) 2-dodecyl-benzo1,2,3triazole)) (PFTBT), was ...blended with PCBM (1:1, w/w) and spin coated on ITO substrates using varying rotational speeds to obtain different active layer thicknesses. J–V characteristics of the constructed devices were investigated both in dark and under simulated sunlight (AM 1.5G, 100mW/cm2). For the determination of hole mobilities the space charge limited current (SCLC) method was used and found as 1.69×10−6cm2/Vs. In addition, the power conversion efficiency (PCE) of the devices was varied according to active layer thickness and the best power conversion efficiency was recorded as 1.06%. Moreover, incident-photon-to-current-efficiency (IPCE) measurements were carried out and the best efficiency was found to be 51%. Morphology of the active layers was probed using AFM and TEM techniques.
► Active layer thickness optimization. ► Efficiency increased from 0.56% to 1.06% according to previous results. ► Morphology studies conducted. ► Highest IPCE efficiency was achieved as 51%. ► The carrier mobility increases with decreasing the PFTBT:PCBM blend thickness.
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