We have been making sustained observations of the earthshine from Big Bear Solar Observatory in California since late 1998. We also have intermittent observations from 1994–1995. We have ...reinvigorated and modernized a nearly forgotten way of measuring the Earth's albedo, and hence its energy balance, previously studied by A. Danjon and his followers for about 25 years early in the last century using their observations of the earthshine from France. This is the first in a series of papers covering observations and simulations of the Earth's reflectance from photometric and spectral observations of the Moon. Here, we develop a modern method of measuring, instantaneously, the large‐scale reflectance of the Earth. From California we see the Moon reflecting sunlight from the third of the Earth to the west of us in our evening (before midnight, which is during the Moon's rising phase) and from the third of the Earth to our east in our morning (after midnight, which is during the Moon's declining phase). We have precisely measured the scattering from the Moon as a function of lunar phase, which enables us to measure, in a typical night's observations, the Earth's reflectance to an accuracy of 2.0% (equivalent to measuring the Earth's emission temperature to ∼0.8 K). We have also identified the lunar phase function as the major source of discrepancy between Danjon's estimates of the albedo and more recent measurements. The albedo is due to the interplay of cloud cover and different landscapes.
Since late 1998, we have been making sustained measurements of the Earth's reflectance by observing the earthshine from Big Bear Solar Observatory. Further, we have simulated the Earth's reflectance ...for both the parts of the Earth in the earthshine and for the whole Earth. The simulations employ scene models of the Earth from the Earth Radiation Budget Experiment, simulated snow/ice cover, and near‐real‐time satellite cloud cover data. Broadly, the simulations and observations agree; however, there are important and significant differences, with the simulations showing more muted variations. During the rising phase of the Moon we measure the sunlit world to the west of California, and during the declining lunar phase we measure the sunlit world to the east. Somewhat surprisingly, the one third of the Earth to the west and that to the east have very similar reflectances, in spite of the fact that the topographies look quite different. The part to the west shows less stability, presumably because of the greater variability in the Asian cloud cover. We find that our precision, with steady observations since December 1998, is sufficient to detect a seasonal cycle. We have also determined the annual mean albedos both from our observations and from simulations. To determine a global albedo, we integrate over all lunar phases. Various methods are developed to perform this integration, and all give similar results. Despite sizable variation in the reflectance from night to night and from season to season (which arises from changing cloud cover), we use the earthshine to determine annual albedos to better than 1%. As such, these measurements are significant for measuring climate variation and are complementary to satellite determinations.
We report the analysis of additional multiband photometry and spectroscopy and new adaptive optics (AO) imaging of the nearby planetary microlensing event TCP J05074264+2447555 (Kojima-1), which was ...discovered toward the Galactic anticenter in 2017 (Nucita et al.). We confirm the planetary nature of the light-curve anomaly around the peak while finding no additional planetary feature in this event. We also confirm the presence of apparent blending flux and the absence of significant parallax signal reported in the literature. The AO image reveals no contaminating sources, making it most likely that the blending flux comes from the lens star. The measured multiband lens flux, combined with a constraint from the microlensing model, allows us to narrow down the previously unresolved mass and distance of the lens system. We find that the primary lens is a dwarf on the K/M boundary (0.581 0.033 M ) located at 505 47 pc, and the companion (Kojima-1Lb) is a Neptune-mass planet (20.0 2.0 M⊕) with a semimajor axis of au. This orbit is a few times smaller than those of typical microlensing planets and is comparable to the snow-line location at young ages. We calculate that the a priori detection probability of Kojima-1Lb is only ∼35%, which may imply that Neptunes are common around the snow line, as recently suggested by the transit and radial velocity techniques. The host star is the brightest among the microlensing planetary systems (Ks = 13.7), offering a great opportunity to spectroscopically characterize this system, even with current facilities.
The EBLM project Chew, Y Gomez Maqueo; Morales, J C; Faedi, F ...
Astronomy and astrophysics (Berlin),
12/2014, Letnik:
572
Journal Article, Publication
Recenzirano
Odprti dostop
In this paper, we derive the fundamental properties of 1SWASPJ011351.29+314909.7 (JO113+31), a metal-poor (-0.40 + or - 0.04 dex), eclipsing binary in an eccentric orbit (~0.3) with an orbital period ...of ~14.277 d. Eclipsing M dwarfs that orbit solar-type stars (EBLMs), like JO113+31, have been identified from their light curves and follow-up spectroscopy in the course of the WASP transiting planet search. We present the analysis of the first binary of the EBLM sample for which masses, radii and temperatures of both components are derived, and thus, define here the methodology. The primary component with a mass of 0.945 + or - 0.045 M sub(middot in circle) has a large radius (1.378 + or - 0.058 R sub(middot in circle)) indicating that the system is quite old, ~9.5 Gyr. The M-dwarf secondary mass of 0.186 + or - 0.010 M sub(middot in circle) and radius of 0.209 + or - 0.011 R sub(middot in circle) are fully consistent with stellar evolutionary models. However, from the near-infrared secondary eclipse light curve, the M dwarf is found to have an effective temperature of 3922 + or - 42 K, which is ~600 K hotter than predicted by theoretical models. We discuss different scenarios to explain this temperature discrepancy. The case of J0113+31 for which we can measure mass, radius, temperature, and metallicity highlights the importance of deriving mass, radius, and temperature as a function of metallicity for M dwarfs to better understand the lowest mass stars. The EBLM Project will define the relationship between mass, radius, temperature, and metallicity for M dwarfs providing important empirical constraints at the bottom of the main sequence.
We present the first redundant detection of sporadic impact flashes on the Moon from a systematic survey performed between 2001 and 2004. Our wide-field lunar monitoring allows us to estimate the ...impact rate of large meteoroids on the Moon as a function of the luminous energy received on Earth. It also shows that some historical well-documented mysterious lunar events fit in a clear impact context. Using these data and traditional values of the luminous efficiency for this kind of event we obtain that the impact rate on Earth of large meteoroids (0.1–10 m) would be at least one order of magnitude larger than currently thought. This discrepancy indicates that the luminous efficiency of the hypervelocity impacts is higher than 10
−2, much larger than the common belief, or the latest impact fluxes are somewhat too low, or, most likely, a combination of both. Our nominal analysis implies that on Earth, collisions of bodies with masses larger than 1 kg can be as frequent as 80,000 per year and blasts larger than 15-kton could be as frequent as one per year, but this is highly dependent on the exact choice of the luminous efficiency value. As a direct application of our results, we expect that the impact flash of the SMART-1 spacecraft should be detectable from Earth with medium-sized telescopes.
Observations of the Earth as a planet using the earthshine technique (i.e. looking at the light reflected from the dark side of the Moon) have been used for climate and astrobiology studies. They ...provide information about the planetary albedo, a fundamental parameter of the Earth's energy balance. Here we present, for the first time, observations of the earthshine taken at high spectral resolution. The high spectral resolution was chosen in order to investigate the possibility of detecting metallic layers in the Earth's atmosphere of geological or meteoritic origin. The Spettrografo Alta Risoluzione Galileo echelle spectrograph at the Telescopio Nazionale Galileo in La Palma was used to acquire the earthshine data. Observations were carried out on several nights in 2011 February, with the spectral resolution set at 29 000, covering a spectral range from the near-ultraviolet (360 nm) to near-infrared (1011.9 nm). While we find evidence for the detection of a Na layer in the earthshine, other atomic species are not detected, perhaps due to the low signal-to-noise ratio of the observations and the difficult telluric corrections. The Na layer is found to vary between observation dates, which we speculate is due to physical variations in mesospheric Na concentrations.
A reduced intrinsic threshold voltage (V/sub T/) in addition to its variability has a direct impact on circuit design. Worst-case design styles assume that all transistors use the same worst-case ...V/sub T/ whose average and standard deviation come from inter-die statistical variations. However, intra-die differences, such as random local V/sub T/ variations are not considered and may pose a serious problem for designs based on low-voltage low-power premises, e.g. clock skews, excessive leakage current, out of spec critical-path delays, etc. This paper formulates a fault model based on threshold voltage mismatch and analyzes its impact on circuit design. Simulation and experimental results support the fault model.
Ultra-hot Jupiters orbit very close to their host star and consequently receive strong irradiation, causing their atmospheric chemistry to be different from the common gas giants. Here, we have ...studied the atmosphere of one of these particular hot planets, MASCARA-2b/KELT-20b, using four transit observations with high resolution spectroscopy facilities. Three of these observations were performed with HARPS-N and one with CARMENES. Additionally, we simultaneously observed one of the transits with MuSCAT2 to monitor possible spots in the stellar surface. At high resolution, the transmission residuals show the effects of Rossiter-McLaughlin and centre-to-limb variations from the stellar lines profiles, which we have corrected to finally extract the transmission spectra of the planet. We clearly observe the absorption features of CaII, FeII, NaI, Hα, and Hβ in the atmosphere of MASCARA-2b, and indications of Hγ and MgI at low signal-to-noise ratio. In the case of NaI, the true absorption is difficult to disentangle from the strong telluric and interstellar contamination. The results obtained with CARMENES and HARPS-N are consistent, measuring an Hα absorption depth of 0.68 ± 0.05 and 0.59 ± 0.07%, and NaI absorption of 0.11 ± 0.04 and 0.09 ± 0.05% for a 0.75 Å passband, in the two instruments respectively. The Hα absorption corresponds to ~1.2 Rp, which implies an expanded atmosphere, as a result of the gas heating caused by the irradiation received from the host star. For Hβ and Hγ only HARPS-N covers this wavelength range, measuring an absorption depth of 0.28 ± 0.06 and 0.21 ± 0.07%, respectively. For CaII, only CARMENES covers this wavelength range measuring an absorption depth of 0.28 ± 0.05, 0.41 ± 0.05 and 0.27 ± 0.06% for CaII λ8498Å, λ8542Å and λ8662Å lines, respectively. Three additional absorption lines of FeII are observed in the transmission spectrum by HARPS-N (partially covered by CARMENES), measuring an average absorption depth of 0.08 ± 0.04% (0.75 Å passband). The results presented here are consistent with theoretical models of ultra-hot Jupiters atmospheres, suggesting the emergence of an ionised gas on the day-side of such planets. Calcium and iron, together with other elements, are expected to be singly ionised at these temperatures and be more numerous than its neutral state. The Calcium triplet lines are detected here for the first time in transmission in an exoplanet atmosphere.
Here, we report the NIR transmission spectrum of Jupiter, with high signal-to-noise ratio, as if it were a transiting planet. Our technique was to observe Ganymede, when crossing Jupiter's shadow. ...During the eclipse, the spectral features of the Jovian atmosphere are imprinted in the sunlight that, after passing through Jupiter's planetary limb, is reflected from Ganymede towards the Earth. The ratio spectrum of Ganymede before and during the eclipse removes the spectral features of the Sun, the local telluric atmosphere on top of the telescopes, and the spectral albedo of Ganymede. Ganymede is a practically atmosphere-less body and do not suffer any significant weather variability.
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