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.
TOI-2076 is a transiting three-planet system of sub-Neptunes orbiting a bright (
G
= 8.9 mag), young (340 ± 80 Myr) K-type star. Although a validated planetary system, the orbits of the two ...outer planets were unconstrained as only two non-consecutive transits were seen in TESS photometry. This left 11 and 7 possible period aliases for each.
Aims.
To reveal the true orbits of these two long-period planets, precise photometry targeted on the highest-probability period aliases is required. Long-term monitoring of transits in multi-planet systems can also help constrain planetary masses through TTV measurements.
Methods.
We used the MonoTools package to determine which aliases to follow, and then performed space-based and ground-based photometric follow-up of TOI-2076 c and d with CHEOPS, SAINT-EX, and LCO telescopes.
Results.
CHEOPS observations revealed a clear detection for TOI-2076 c at $P = 21.02538_{ - 0.00074}^{ + 0.00084}$ d, and allowed us to rule out three of the most likely period aliases for TOI-2076 d. Ground-based photometry further enabled us to rule out remaining aliases and confirm the
P
= 35.12537 ± 0.00067 d alias. These observations also improved the radius precision of all three sub-Neptunes to 2.518 ± 0.036, 3.497 ± 0.043, and 3.232 ± 0.063
R
⊕
. Our observations also revealed a clear anti-correlated TTV signal between planets b and c likely caused by their proximity to the 2:1 resonance, while planets c and d appear close to a 5:3 period commensurability, although model degeneracy meant we were unable to retrieve robust TTV masses. Their inflated radii, likely due to extended H-He atmospheres, combined with low insolation makes all three planets excellent candidates for future comparative transmission spectroscopy with JWST.
Intake boosting is an important method to improve fuel economy of internal combustion engines. Engines can be down-sized, down-speeded, and up-loaded to reduce friction losses, parasitic losses, and ...pumping losses, and operate at speed-load conditions that are thermodynamically more efficient. Low-temperature combustion engines (LTE) also benefit from down-sizing, down-speeding, and up-loading, but these engines exhibit very low exhaust enthalpy to drive conventional turbochargers. This paper describes modeling, evaluation, and selection of an efficient boost system for a 1.8L four-cylinder Gasoline Direct-Injection Compression-Ignition (GDCI) engine.
After a preliminary concept selection phase the model was used to develop the boost system parameters to achieve full-load and part-load engine operation objectives. The simulation was used to demonstrate that a practical boost system can provide the boost necessary at reasonable brake efficiency levels over the entire engine operating range. A comprehensive simulation based calibration was performed to determine the most efficient steady operation settings. Also a step change in speed/load engine operation was simulated to demonstrate the system transient response.
The CHEOPS mission Benz, W.; Broeg, C.; Fortier, A. ...
Experimental astronomy,
2021, Letnik:
51, Številka:
1
Journal Article, Web Resource
Recenzirano
Odprti dostop
The CHaracterising ExOPlanet Satellite (CHEOPS) was selected on October 19, 2012, as the first small mission (S-mission) in the ESA Science Programme and successfully launched on December 18, 2019, ...as a secondary passenger on a Soyuz-Fregat rocket from Kourou, French Guiana. CHEOPS is a partnership between ESA and Switzerland with important contributions by ten additional ESA Member States. CHEOPS is the first mission dedicated to search for transits of exoplanets using ultrahigh precision photometry on bright stars already known to host planets. As a follow-up mission, CHEOPS is mainly dedicated to improving, whenever possible, existing radii measurements or provide first accurate measurements for a subset of those planets for which the mass has already been estimated from ground-based spectroscopic surveys. The expected photometric precision will also allow CHEOPS to go beyond measuring only transits and to follow phase curves or to search for exo-moons, for example. Finally, by unveiling transiting exoplanets with high potential for in-depth characterisation, CHEOPS will also provide prime targets for future instruments suited to the spectroscopic characterisation of exoplanetary atmospheres. To reach its science objectives, requirements on the photometric precision and stability have been derived for stars with magnitudes ranging from 6 to 12 in the V band. In particular, CHEOPS shall be able to detect Earth-size planets transiting G5 dwarf stars (stellar radius of 0.9
R
⊙
) in the magnitude range 6 ≤
V
≤ 9 by achieving a photometric precision of 20 ppm in 6 hours of integration time. In the case of K-type stars (stellar radius of 0.7
R
⊙
) of magnitude in the range 9 ≤
V
≤ 12, CHEOPS shall be able to detect transiting Neptune-size planets achieving a photometric precision of 85 ppm in 3 hours of integration time. This precision has to be maintained over continuous periods of observation for up to 48 hours. This precision and stability will be achieved by using a single, frame-transfer, back-illuminated CCD detector at the focal plane assembly of a 33.5 cm diameter, on-axis Ritchey-Chrétien telescope. The nearly 275 kg spacecraft is nadir-locked, with a pointing accuracy of about 1 arcsec rms, and will allow for at least 1 Gbit/day downlink. The sun-synchronous dusk-dawn orbit at 700 km altitude enables having the Sun permanently on the backside of the spacecraft thus minimising Earth stray light. A mission duration of 3.5 years in orbit is foreseen to enable the execution of the science programme. During this period, 20% of the observing time is available to the wider community through yearly ESA call for proposals, as well as through discretionary time approved by ESA’s Director of Science. At the time of this writing, CHEOPS commissioning has been completed and CHEOPS has been shown to fulfill all its requirements. The mission has now started the execution of its science programme.
The CHaracterizing ExOPlanet Satellite (CHEOPS) is set to be launched in December 2019 and will detect and characterize small size exoplanets via ultra high precision photometry during transits. ...CHEOPS is designed as a follow-up telescope and therefore it will monitor a single target at a time. The scientific users will retrieve science-ready light curves of the target that will be automatically generated by the CHEOPS data reduction pipeline of the Science Operations Centre. This paper describes how the pipeline processes the series of raw images and, in particular, how it handles the specificities of CHEOPS data, such as the rotating field of view, the extended irregular point spread function, and the data temporal gaps in the context of the strict photometric requirements of the mission. The current status and performance of the main processing stages of the pipeline, that is the calibration, correction, and photometry, are presented to allow the users to understand how the science-ready data have been derived. Finally, the general performance of the pipeline is illustrated via the processing of representative scientific cases generated by the mission simulator.
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.
In order to test the hypothesis that an imbalance between energy requirement and energy supply regulates mitochondrial genes and ultimately mitochondrial biogenesis, energy supply was challenged in ...HepG2 cells by withdrawal of glucose from the culture medium, making the cells exclusively dependent on mitochondrial ATP production. Such cells showed a 2-fold increase of cytochrome c oxidase activity, elevated levels of mitochondrial DNA, mitochondrial DNA encoded mRNAs and proteins, as well as the nuclear encoded mitochondrial transcription factor A. Lactate production was significantly reduced and glutamine was consumed as an alternative substrate for oxidative metabolism. Longterm adapted cells formed exclusively monolayers, while they normally grow in multilayers forming tumor spheroids. Also, longterm adapted cells proliferated significantly faster. No differences for the ATP/ADP ratio were observed, indicating that this is not the primary signal initiating the adaptative processes. These results show that mitochondrial biogenesis and oxidative metabolism are stimulated in HepG2 cells grown in the absence of fermentable glucose, probably in order to compensate for the diminished supply of glycolytic ATP.
The standardized extract EGb 761 from the dried green leaves of Ginkgo biloba is a complex mixture of ingredients with an uniquely broad spectrum of pharmacological activities on the central nervous ...system e.g. in memory enhancing properties and in the regulation of cerebral glucose/energy metabolism. To test these effects on both behavioral and metabolic brain parameters, the animal model of intracerebroventricular (i.c.v.) streptozotocin (STZ) treatment was used. To quantify the experimental data more precisely, animals that were good performers were separated from poor performers by means of the holeboard test before i.c.v. administration of STZ. Good performers only were considered for the study. After a 1-week training period on the holeboard improvement was seen in all animals in learning, memory and cognition, and the improvement was maintained over the investigation period of 12 weeks in the control group. In this group, the energy pool in the cerebral parietotemporal cortex was found to be large and the energy turnover high. After triplicate i.c.v. STZ injection, working memory (WM), reference memory (RM), and passive avoidance (PA) behavior fell off and continued to deteriorate throughout the investigation period. Otherwise there were no significant differences in locomotor activity, excluding the possibility that activity per se might have contributed to the behavioral abnormalities. These were accompanied by a permanent deficit in cerebral energy metabolism. The ongoing deterioration in behavior and the maintained deficit in cerebral energy metabolism occurring after a triplicate i.c.v. STZ injection were significantly slowed down by EGb761. The deficits in learning, memory and cognition were partially compensated, and the disturbances in cerebral energy metabolism returned to almost completely normal values. These findings underscore the beneficial effect of EGb761 that had been reported in dementia disorders.
AU Mic is a young planetary system with a resolved debris disc showing signs of planet formation and two transiting warm Neptunes near mean-motion resonances. Here we analyse three transits of AU Mic ...b observed with the CHaracterising ExOPlanet Satellite (CHEOPS), supplemented with sector 1 and 27 Transiting Exoplanet Survey Satellite (TESS) photometry, and the All-Sky Automated Survey from the ground. The refined orbital period of AU Mic b is 8.462995 ± 0.000003 d, whereas the stellar rotational period is
P
rot
= 4.8367 ± 0.0006 d. The two periods indicate a 7:4 spin–orbit commensurability at a precision of 0.1%. Therefore, all transits are observed in front of one of the four possible stellar central longitudes. This is strongly supported by the observation that the same complex star-spot pattern is seen in the second and third CHEOPS visits that were separated by four orbits (and seven stellar rotations). Using a bootstrap analysis we find that flares and star spots reduce the accuracy of transit parameters by up to 10% in the planet-to-star radius ratio and the accuracy on transit time by 3–4 min. Nevertheless, occulted stellar spot features independently confirm the presence of transit timing variations (TTVs) with an amplitude of at least 4 min. We find that the outer companion, AU Mic c, may cause the observed TTVs.
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