Tin oxide (SnO2) is an important oxide for efficient dielectrics, catalysis, sensor devices, electrodes and transparent conducting coating oxide technologies. SnO2 thin film is widely used in glass ...applications due to its low infra-red heat emissivity. In this work, the SnO2 electronic band-edge structure and optical properties are studied employing a first-principle and fully relativistic full-potential linearized augmented plane wave (FPLAPW) method within the local density approximation (LDA). The optical band-edge absorption alpha(omega) of intrinsic SnO2 is investigated experimentally by transmission spectroscopy measurements and their roughness in the light of the atomic force microscopy (AFM) measurements. The sample films were prepared by spray pyrolysis deposition method onto glass substrate considering different thickness layers. We found for SnO2 qualitatively good agreement of the calculated optical band-gap energy as well as the optical absorption with the experimental results.
Context
. The long-term ongoing HARPS radial velocity survey of extra-solar planets initiated in 2003 provides a unique data set with a 19-yr baseline that allows the detection of long-period ...exoplanets, brown dwarfs, and low-mass binaries.
Aims
. Our aim is to detect and characterise long-period companions around main sequence stars (spectral types late F to early M). Only 6% of the planets discovered so far have periods longer than 3 yr; we are probing this still largely unknown population.
Methods
. We use the radial velocity method to search for exoplanets around stars. The radial velocity variations are measured with HARPS at the ESO 3.6m telescope. Difficulties in characterising long-period exoplanets arise from the entanglement of the radial velocity with the stellar magnetic cycle. We thoroughly examined the stellar activity indicators to rule out magnetic cycles as the source of the observed variation. The true mass and inclination of our heavier companions are provided by astrometry, for which we use proper motions from H
IPPARCOS
and
Gaia.
Results
. Five Jupiter-mass exoplanets are reported to orbit HIP54597, BD-210397 (×2), HD 74698, and HD 94771 with 8.9 yr, 5.2 yr, 17.4 yr, 9.4 yr, and 5.9 yr orbits, and to have minimum masses of 2.01 ± 0.03, 0.7 ± 0.1, 2.4
−0.2
+1.5
, 0.40 ± 0.06, and 0.53 ± 0.03
M
J
respectively. HD 74698 also hosts a highly irradiated Neptune in a 15 day orbit with a minimum mass of 0.07 ± 0.01
M
J
. The mass and inclination of the exoplanets cannot yet be well constrained by astrometric measurements. Only HIP54597 b, HD 74698 c, and BD-210397 c have weak constraints. The mass of HIP54597 b can maximally increase by 10%–30%, the minimum mass of HD 74698 c is likely equal to its true mass, and BD-210397 c has a mass of 2.66
−0.32
+0.63
M
J
. HD 62364 hosts a brown dwarf with a true mass of 18.77
−0.63
+0.66
M
J
in an orbit of 14 yr. The mass of HD62364 b is around the limit of the masses of brown dwarfs, but its orbit is highly eccentric (
e
= 0.607 ± 0.005), which is more common among brown dwarfs than exoplanets. HD56380B, HD221638B, and HD 33473C have minimum masses within the brown dwarf limits, in orbits of 8.9 yr, 16.6 yr, and 50 yr respectively; however, astro-metric measurements reveal them to be stellar binaries, with masses of 375.3
−8.4
+8.6
, 110.0
−3.7
+3.9
, and 271.0
−3.8
+3.9
M
J
. The orbits of the stellar binaries HD 11938 and HD 61383 are incomplete. The preliminary result for HD 61383 is a 0.190
M
⊙
binary in a 39 yr orbit. The secondary of the binary system HD 11938 has a mass of 0.33
M
⊙
, which is confirmed by a secondary peak in the cross-correlation function, and a preliminary period of 35 yr. The origin of the 3.0 yr radial velocity signal of HD 3964 is uncertain as it shows entanglement with the magnetic cycle of the star. We finally report one more star, HD 11608, with a magnetic cycle that mimics a planetary signal.
Conclusions
. We present the discovery of six exoplanets, one uncertain exoplanet candidate, one brown dwarf, and five stellar binaries around main sequence stars. We also improve the orbital solution of the stellar binary HD 33473C thanks to long-term monitoring.
Context.
Comparing the properties of planets orbiting the same host star, and thus formed from the same accretion disc, helps in constraining theories of exoplanet formation and evolution. As a ...result, the scientific interest in multi-planetary systems is growing with the increasing number of detections of planetary companions.
Aims.
We report the characterisation of a multi-planetary system composed of five exoplanets orbiting the K-dwarf HD 23472 (TOI-174).
Methods.
In addition to the two super-Earths that were previously confirmed, we confirm and characterise three Earth-size planets in the system using ESPRESSO radial velocity observations. The planets of this compact system have periods of
P
d
~
3.98,
P
e
~
7.90,
P
f
~
12.16,
P
b
~ 17.67, and
P
c
~ 29.80 days and radii of
R
d
~ 0.75 ,
R
e
~ 0.82,,
R
f
~ 1.13 ,
R
b
~ 2.01, and,
R
c
~
1.85
R
⊕
.Because of its small size, its proximity to planet d’s transit, and close resonance with planet d, planet e was only recently found.
Results.
The planetary masses were estimated to be
M
d
= 0.54 ± 0.22,
M
e
= 0.76 ± 0.30,
M
f
= 0.64
−0.39
+0.46
,
M
b
= 8.42
−0.84
+0.83
, and
M
c
= 3.37
−0.87
+0.92
M
⊕
. These planets are among the lightest planets, with masses measured using the radial velocity method, demonstrating the very high precision of the ESPRESSO spectrograph. We estimated the composition of the system’s five planets and found that their gas and water mass fractions increase with stellar distance, suggesting that the system was shaped by irradiation. The high density of the two inner planets (
ρ
d
= 7.5
−3.1
+3.9
and
ρ
e
= 7.5
−3.0
+3.9
g cm
−3
) indicates that they are likely to be super-Mercuries. This is supported by the modelling of the internal structures of the planets, which also suggests that the three outermost planets have significant water or gas content.
Conclusions.
If the existence of two super-Mercuries in the system is confirmed, this system will be the only one known to feature two super-Mercuries, making it an excellent testing bed for theories of super-Mercuries formation. Furthermore, the system is close to a Laplace resonance, and further monitoring could shed light on how it was formed. Its uniqueness and location in the continuous viewing zone of the
James Webb
space telescope will make it a cornerstone of future in-depth characterisations.
The exoplanet population characterized by relatively short orbital periods (P < 100 d) around solar-type stars is dominated by super-Earths and sub-Neptunes. However, these planets are missing in our ...Solar System and the reason behind this absence is still unknown. Two theoretical scenarios invoke the role of Jupiter as the possible culprit: Jupiter may have acted as a dynamical barrier to the inward migration of sub-Neptunes from beyond the water iceline; alternatively, Jupiter may have considerably reduced the inward flux of material (pebbles) required to form super-Earths inside that iceline. Both scenarios predict an anti-correlation between the presence of small planets and that of cold Jupiters in exoplanetary systems. To test that prediction, we homogeneously analyzed the radial-velocity measurements of 38 Kepler and K2 transiting small planet systems gathered over nearly ten years with the HARPS-N spectrograph, as well as publicly available radial velocities collected with other facilities. We used Bayesian differential evolution Markov chain Monte Carlo techniques, which in some cases were coupled with Gaussian process regression to model non-stationary variations due to stellar magnetic activity phenomena. We detected five cold Jupiters in three systems: two in Kepler-68, two in Kepler-454, and a very eccentric one in K2-312. We also found linear trends caused by bound companions in Kepler-93, Kepler-454, and K2-12, with slopes that are still compatible with a planetary mass for outer bodies in the Kepler-454 and K2-12 systems. By using binomial statistics and accounting for the survey completeness, we derived an occurrence rate of 9.3−2.9+7.7% for cold Jupiters with 0.3–13 MJup and 1–10 AU, which is lower but still compatible at 1.3σ with the value measured from radial-velocity surveys for solar-type stars, regardless of the presence or absence of small planets. The sample is not large enough to draw a firm conclusion about the predicted anti-correlation between small planets and cold Jupiters; nevertheless, we found no evidence of previous claims of an excess of cold Jupiters in small planet systems. As an important byproduct of our analyses, we homogeneously determined the masses of 64 Kepler and K2 small planets, reaching a precision better than 5, 7.5, and 10σ for 25, 13, and 8 planets, respectively. Finally, we release the 3661 HARPS-N radial velocities used in this work to the scientific community. These radial-velocity measurements mainly benefit from an improved data reduction software that corrects for subtle prior systematic effects.
The surface detector system of the Pierre Auger Observatory Allekotte, I.; Barbosa, A.F.; Bauleo, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2008, Letnik:
586, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The Pierre Auger Observatory is designed to study cosmic rays with energies greater than 1019eV. Two sites are envisaged for the observatory, one in each hemisphere, for complete sky coverage. The ...southern site of the Auger Observatory, now approaching completion in Mendoza, Argentina, features an array of 1600 water-Cherenkov surface detector stations covering 3000km2, together with 24 fluorescence telescopes to record the air shower cascades produced by these particles. The two complementary detector techniques together with the large collecting area form a powerful instrument for these studies. Although construction is not yet complete, the Auger Observatory has been taking data stably since January 2004 and the first physics results are being published. In this paper we describe the design features and technical characteristics of the surface detector stations of the Pierre Auger Observatory.
We characterize the planetary system Kepler-101 by performing a combined differential evolution Markov chain Monte Carlo analysis of Kepler data and forty radial velocities obtained with the HARPS-N ...spectrograph. This system was previously validated and is composed of a hot super-Neptune, Kepler-101b, and an Earth-sized planet, Kepler-101c. These two planets orbit the slightly evolved and metal-rich G-type star in 3.49 and 6.03 days, respectively. With mass M sub(p) = 51.1(ProQuest: Formulae and/or non-USASCII text omitted) M sub(middot in circle), radius R sub(p) = 5.77(ProQuest: Formulae and/or non-USASCII text omitted) R sub(middot in circle), and density rho sub(p) = 1.45(ProQuest: Formulae and/or non-USASCII text omitted) g cm super(-3), Kepler-101b is the first fully characterized super-Neptune, and its density suggests that heavy elements make up a significant fraction of its interior; more than 60% of its total mass. Kepler-101c has a radius of 1.25(ProQuest: Formulae and/or non-USASCII text omitted) R sub(middot in circle), which implies the absence of any H/He envelope, but its mass could not be determined because of the relative faintness of the parent star for highly precise radial-velocity measurements (K sub(p) = 13.8) and the limited number of radial velocities. The 1sigma upper limit, M sub(p) < 3.8 M sub(middot in circle), excludes a pure iron composition with a probability of 68.3%. The architecture of the planetary system Kepler-101 - containing a close-in giant planet and an outer Earth-sized planet with a period ratio slightly larger than the 3:2 resonance - is certainly of interest for scenarios of planet formation and evolution. This system does not follow the previously reported trend that the larger planet has the longer period in the majority of Kepler systems of planet pairs with at least one Neptune-sized or larger planet.
ABSTRACT
Eclipsing binaries are important benchmark objects to test and calibrate stellar structure and evolution models. This is especially true for binaries with a fully convective M-dwarf ...component for which direct measurements of these stars’ masses and radii are difficult using other techniques. Within the potential of M-dwarfs to be exoplanet host stars, the accuracy of theoretical predictions of their radius and effective temperature as a function of their mass is an active topic of discussion. Not only the parameters of transiting exoplanets but also the success of future atmospheric characterization relies on accurate theoretical predictions. We present the analysis of five eclipsing binaries with low-mass stellar companions out of a subsample of 23, for which we obtained ultra-high-precision light curves using the CHEOPS satellite. The observation of their primary and secondary eclipses are combined with spectroscopic measurements to precisely model the primary parameters and derive the M-dwarfs mass, radius, surface gravity, and effective temperature estimates using the PYCHEOPS data analysis software. Combining these results to the same set of parameters derived from TESS light curves, we find very good agreement (better than 1 per cent for radius and better than 0.2 per cent for surface gravity). We also analyse the importance of precise orbits from radial velocity measurements and find them to be crucial to derive M-dwarf radii in a regime below 5 per cent accuracy. These results add five valuable data points to the mass–radius diagram of fully convective M-dwarfs.
The GAPS programme with HARPS-N at TNG Sozzetti, A.; Bonomo, A. S.; Biazzo, K. ...
Astronomy and astrophysics (Berlin),
03/2015, Letnik:
575
Journal Article
Recenzirano
Odprti dostop
We update the TrES-4 system parameters using high-precision HARPS-N radial-velocity measurements and new photometric light curves. A combined spectroscopic and photometric analysis allows us to ...determine a spectroscopic orbit with a semi-amplitude K = 51 ± 3 m s-1. The derived mass of TrES-4b is found to be Mp = 0.49 ± 0.04 MJup, significantly lower than previously reported. Combined with the large radius (Rp = 1.84-0.09+0.08 RJup) inferred from our analysis, TrES-4b becomes the transiting hot Jupiter with the second-lowest density known. We discuss several scenarios to explain the puzzling discrepancy in the mass of TrES-4b in the context of the exotic class of highly inflated transiting giant planets.
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