The Cimmerian orogen resulted from the collision and accretion of several Perigondwanan blocks to the southern margin of Eurasia between the Late Triassic and Early Jurassic, following the closure of ...the Palaeotethys ocean. Remnants of this orogen discontinuously crop out in N (Alborz range) and NE Iran (Mashhad–Fariman area) below the syn- to post-collisional clastic successions of the Shemshak Group (Upper Triassic–Middle Jurassic) and the Kashaf Rud Formation (Bajocian). In NE Iran rock associations exposed in the Binalood Mountains, Fariman and Darreh Anjir areas include mafic–ultramafic intrusive rocks, basalts, silicoclastic turbidites and minor limestones, which have been interpreted in the past as ophiolitic remnants of the Palaeotethys ocean. Original stratigraphic, structural, geochemical and geochronological data, described in this paper, suggest a different interpretation. The volcano-sedimentary units of Fariman and Darreh Anjir complexes where deposited during Permian in a subsiding basin were siliciclastic turbidites, derived from the erosion of a magmatic arc and its basement, interfinger with carbonates and basaltic lava flows with both transitional and calc-alkaline affinity. The coexistence of magmatic rocks with different geochemical signature and the sedimentary evolution of the basin can be related to a supra-subduction setting, possibly represented by a fault-controlled intra-arc basin. The Fariman and the Darreh Anjir complexes are thus interpreted as remnants of a magmatic arc and related basins developed at the southern Eurasia margin, on top of the north-directed Palaeotethys subduction zone long before the collision of Iran with Eurasia. They were later involved in the Cimmerian collision during the Triassic. New radiometric ages obtained on I-type post-collisional granitoids postdating the collision-related deformational structures suggest that the suture zone closed before mid-Norian times. Deformation propagated later northward into the Turan domain involving the Triassic successions of the Aghdarband region.
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•Permian-Triassic volcano-sedimentary successions deposited in arc-related basins in NE Iran.•These basins evolved within the Eurasian plate, in the hangingwall of the Palaeotethys subduction.•After Palaeotethys closure the Fariman and Darreh Anjir units became part of the Cimmerian belt.
Context. One of the main properties of the pyramid wavefront sensor is that, once the loop is closed, and as the reference star image shrinks on the pyramid pin, the wavefront estimation ...signal-to-noise ratio can considerably improve. This has been shown to translate into a gain in limiting magnitude when compared with the Shack-Hartmann wavefront sensor, in which the sampling on the wavefront is performed before the light is split into four quadrants, which does not allow the quality of the focused spot to increase. Since this property is strictly related to the size of the re-imaged spot on the pyramid pin, the better the wavefront correction, the higher the gain. Aims. The goal of this paper is to extend the descriptive and analytical computation of this gain that was given in a previous paper, to partial wavefront correction conditions, which are representative for most of the wide field correction adaptive optics systems. Methods. After focusing on the low Strehl ratio regime, we analyze the minimum spatial sampling required for the wavefront sensor correction to still experience a considerable gain in sensitivity between the pyramid and the Shack-Hartmann wavefront sensors. Results. We find that the gain can be described as a function of the sampling in terms of the Fried parameter.
The continental crust involved in the Alpine orogeny was largely shaped by Paleozoic tectono‐metamorphic and igneous events during oblique collision between Gondwana and Laurussia. In order to shed ...light on the pre‐Alpine basement puzzle disrupted and reamalgamated during the Tethyan rifting and the Alpine orogeny, we provide sensitive high‐resolution ion microprobe U‐Pb zircon and geochemical whole rock data from selected basement units of the Grand St Bernard‐Briançonnais nappe system in the Western Alps and from the Penninic and Lower Austroalpine units in the Central Alps. Zircon U‐Pb ages, ranging from 459.0 ± 2.3 Ma to 279.1 ± 1.1 Ma, provide evidence of a complex evolution along the northern margin of Gondwana including Ordovician transtension, Devonian subduction, and Carboniferous‐to‐Permian tectonic reorganization. Original zircon U‐Pb ages of 371 ± 0.9 Ma and 369.3 ± 1.5 Ma, from calc‐alkaline granitoids of the Grand Nomenon and Gneiss del Monte Canale units, provide the first compelling evidence of Late Devonian orogenic magmatism in the Alps. We propose that rocks belonging to these units were originally part of the Moldanubian domain and were displaced toward the SW by Late Carboniferous strike‐slip faulting. The resulting assemblage of basement units was disrupted by Permian tectonics and by Mesozoic opening of the Alpine Tethys. Remnants of the Moldanubian domain became either part of the European paleomargin (Grand Nomenon unit) or part of the Adriatic paleomargin (Gneiss del Monte Canale unit), to be finally accreted into the Alpine orogenic wedge during the Cenozoic.
Key Points
First compelling radiometric evidence of Late Devonian orogenic magmatism in the European Alps
Geochronologic record of a complex Ordovician to Permian tectonic evolution along the northern Gondwana margin
Part of the Moldanubian domain was dismembered in the Late Carboniferous and is now accreted in the Alpine orogenic wedge
The Global-Multi Conjugated Adaptive Optics (GMCAO) approach offers an alternative way to correct an adequate scientific Field of View (FoV) using only natural guide stars (NGSs) to extremely large ...ground-based telescopes. Thus, even in the absence of laser guide stars, a GMCAO-equipped ELT-like telescope can achieve optimal performance in terms of Strehl Ratio (SR), retrieving impressive results in studying star-poor fields, as in the cases of the deep field observations. The benefits and usability of GMCAO have been demonstrated by studying 6000 mock high redshift galaxies in the Chandra Deep Field South region. However, a systematic study simulating observations in several portions of the sky is mandatory to have a robust statistic of the GMCAO performance. Technical, tomographic and astrophysical parameters, discussed here, are given as inputs to GIUSTO, an IDL-based code that estimates the SR over the considered field, and the results are analyzed with statistical considerations. The best performance is obtained using stars that are relatively close to the Scientific FoV; therefore, the SR correlates with the mean off-axis position of NGSs, as expected, while their magnitude plays a secondary role. This study concludes that the SRs correlate linearly with the galactic latitude, as also expected. Because of the lack of natural guide stars needed for low-order aberration sensing, the GMCAO confirms as a promising technique to observe regions that can not be studied without the use of laser beacons. It represents a robust alternative way or a risk mitigation strategy for laser approaches on the ELTs.
Abstract
The era of the next generation of giant telescopes requires not only the advent of new technologies but also the development of novel methods, in order to exploit fully the extraordinary ...potential they are built for. Global Multi Conjugate Adaptive Optics (GMCAO) pursues this approach, with the goal of achieving good performance over a field of view of a few arcmin and an increase in sky coverage. In this article, we show the gain offered by this technique to an astrophysical application, such as the photometric survey strategy applied to the Chandra Deep Field South as a case study. We simulated a close-to-real observation of a 500 × 500 arcsec2 extragalactic deep field with a 40-m class telescope that implements GMCAO. We analysed mock K-band images of 6000 high-redshift (up to z = 2.75) galaxies therein as if they were real to recover the initial input parameters. We attained 94.5 per cent completeness for source detection with SExtractor. We also measured the morphological parameters of all the sources with the two-dimensional fitting tools galfit. The agreement we found between recovered and intrinsic parameters demonstrates GMCAO as a reliable approach to assist extremely large telescope (ELT) observations of extragalactic interest.
The latest developments of epidemiologic and biochemical research suggest that current upper limits of intake for dietary selenium and for overall selenium exposure may be inadequate to protect human ...health. In particular, recent experimental and observational prospective studies indicate a diabetogenic effect of selenium at unexpectedly low levels of intake. Experimental evidence from laboratory studies and veterinary medicine appears to confirm previous epidemiologic observations that selenium overexposure is associated with an increased risk of amyotrophic lateral sclerosis, and a recent large trial indicated no beneficial effect in preventing prostate cancer. Moreover, the pro-oxidant properties of selenium species and the observation that the selenium-containing enzymes glutathione peroxidases are induced by oxidative stress imply that the increase in enzymatic activity induced by this metalloid may represent at least in part a compensatory response. Taken together, the data indicate that the upper safe limit of organic and inorganic selenium intake in humans may be lower than has been thought and that low-dose chronic overexposure to selenium may be considerably more widespread than supposed.
Epidemiologic studies and case reports have shown that chronic exposure to selenium compounds is associated with several adverse health effects in humans. An early toxic effect of selenium is on ...endocrine function, particularly on the synthesis of thyroid hormones following dietary exposure of around 300 micrograms Se/d, and on the metabolism of growth hormone and insulin-like growth factor-1. Other adverse effects of selenium exposure can be the impairment of natural killer cells activity and at higher levels, hepatotoxicity and gastrointestinal disturbances. Dermatologic effects, such as nail and hair loss and dermatitis, occur after exposure to high levels of environmental selenium. Assessing the toxicity and morbidity after long-term exposure to environmental selenium is difficult: neurotoxicity, particularly the degeneration of motor neurons leading to increased risk of amyotrophic lateral sclerosis, might occur after chronic exposure to both organic and inorganic selenium compounds. The results of laboratory investigations and cohort studies suggest that selenium species exhibit a bivalent effect in cancer, either increasing or decreasing risk. Current environmental selenium exposure limits appear to be inadequate for averting adverse health effects.
The CHEOPS space mission dedicated to exoplanet follow-up was launched in December 2019, equipped with the capacity to perform photometric measurements at the 20 ppm level. As CHEOPS carries out its ...observations in a broad optical passband, it can provide insights into the reflected light from exoplanets and constrain the short-wavelength thermal emission for the hottest of planets by observing occultations and phase curves. Here, we report the first CHEOPS observation of an occultation, namely, that of the hot Jupiter WASP-189 b, a
M
P
≈ 2
M
J
planet orbiting an A-type star. We detected the occultation of WASP-189 b at high significance in individual measurements and derived an occultation depth of dF = 87.9 ± 4.3 ppm based on four occultations. We compared these measurements to model predictions and we find that they are consistent with an unreflective atmosphere heated to a temperature of 3435 ± 27 K, when assuming inefficient heat redistribution. Furthermore, we present two transits of WASP-189 b observed by CHEOPS. These transits have an asymmetric shape that we attribute to gravity darkening of the host star caused by its high rotation rate. We used these measurements to refine the planetary parameters, finding a ~25% deeper transit compared to the discovery paper and updating the radius of WASP-189 b to 1.619 ± 0.021
R
J
. We further measured the projected orbital obliquity to be
λ
= 86.4
−4.4
+2.9°
, a value that is in good agreement with a previous measurement from spectroscopic observations, and derived a true obliquity of Ψ = 85.4 ± 4.3°. Finally, we provide reference values for the photometric precision attained by the CHEOPS satellite: for the
V
= 6.6 mag star, and using a 1-h binning, we obtain a residual RMS between 10 and 17 ppm on the individual light curves, and 5.7 ppm when combining the four visits.
Context.
The detection of a super-Earth and three mini-Neptunes transiting the bright (
V
= 9.2 mag) star HD 108236 (also known as TOI-1233) was recently reported on the basis of TESS and ...ground-based light curves.
Aims.
We perform a first characterisation of the HD 108236 planetary system through high-precision CHEOPS photometry and improve the transit ephemerides and system parameters.
Methods.
We characterise the host star through spectroscopic analysis and derive the radius with the infrared flux method. We constrain the stellar mass and age by combining the results obtained from two sets of stellar evolutionary tracks. We analyse the available TESS light curves and one CHEOPS transit light curve for each known planet in the system.
Results.
We find that HD 108236 is a Sun-like star with
R
⋆
= 0.877 ± 0.008
R
⊙
,
M
⋆
= 0.869
−0.048
+0.050
M
⊙
, and an age of 6.7
−5.1
+4.0
Gyr. We report the serendipitous detection of an additional planet, HD 108236 f, in one of the CHEOPS light curves. For this planet, the combined analysis of the TESS and CHEOPS light curves leads to a tentative orbital period of about 29.5 days. From the light curve analysis, we obtain radii of 1.615 ± 0.051, 2.071 ± 0.052, 2.539
−0.065
+0.062
, 3.083 ± 0.052, and 2.017
−0.057
+0.052
R
⊕
for planets HD 108236 b to HD 108236 f, respectively. These values are in agreement with previous TESS-based estimates, but with an improved precision of about a factor of two. We perform a stability analysis of the system, concluding that the planetary orbits most likely have eccentricities smaller than 0.1. We also employ a planetary atmospheric evolution framework to constrain the masses of the five planets, concluding that HD 108236 b and HD 108236 c should have an Earth-like density, while the outer planets should host a low mean molecular weight envelope.
Conclusions.
The detection of the fifth planet makes HD 108236 the third system brighter than
V
= 10 mag to host more than four transiting planets. The longer time span enables us to significantly improve the orbital ephemerides such that the uncertainty on the transit times will be of the order of minutes for the years to come. A comparison of the results obtained from the TESS and CHEOPS light curves indicates that for a
V
~ 9 mag solar-like star and a transit signal of ~500 ppm, one CHEOPS transit light curve ensures the same level of photometric precision as eight TESS transits combined, although this conclusion depends on the length and position of the gaps in the light curve.
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