In this Letter, we present a cosmic Bell experiment with polarization-entangled photons, in which measurement settings were determined based on real-time measurements of the wavelength of photons ...from high-redshift quasars, whose light was emitted billions of years ago; the experiment simultaneously ensures locality. Assuming fair sampling for all detected photons and that the wavelength of the quasar photons had not been selectively altered or previewed between emission and detection, we observe statistically significant violation of Bell's inequality by 9.3 standard deviations, corresponding to an estimated p value of ≲7.4×10^{-21}. This experiment pushes back to at least ∼7.8 Gyr ago the most recent time by which any local-realist influences could have exploited the "freedom-of-choice" loophole to engineer the observed Bell violation, excluding any such mechanism from 96% of the space-time volume of the past light cone of our experiment, extending from the big bang to today.
Abstract
We present high-precision radial velocities (RVs) from the HARPS-N spectrograph for HD 79210 and HD 79211, two M0V members of a gravitationally bound binary system. We detect a planet ...candidate with a period of
24.421
−
0.017
+
0.016
days around HD 79211 in these HARPS-N RVs, validating the planet candidate originally identified in CARMENES RV data alone. Using HARPS-N, CARMENES, and RVs spanning a total of 25 yr, we further refine the planet candidate parameters to
P
= 24.422 ± 0.014 days,
K
= 3.19 ± 0.27 m s
−1
,
M
sin
i
= 10.6 ± 1.2
M
⊕
, and
a
= 0.142 ± 0.005 au. We do not find any additional planet candidate signals in the data of HD 79211, nor do we find any planet candidate signals in HD 79210. This system adds to the number of exoplanets detected in binaries with M-dwarf members and serves as a case study for planet formation in stellar binaries.
Abstract
Radial velocity (RV) measurements of transiting multiplanet systems allow us to understand the densities and compositions of planets unlike those in the solar system. Kepler-102, which ...consists of five tightly packed transiting planets, is a particularly interesting system since it includes a super-Earth (Kepler-102d) and a sub-Neptune-sized planet (Kepler-102e) for which masses can be measured using RVs. Previous work found a high density for Kepler-102d, suggesting a composition similar to that of Mercury, while Kepler-102e was found to have a density typical of sub-Neptune size planets; however, Kepler-102 is an active star, which can interfere with RV mass measurements. To better measure the mass of these two planets, we obtained 111 new RVs using Keck/HIRES and Telescopio Nazionale Galileo/HARPS-N and modeled Kepler-102's activity using quasiperiodic Gaussian process regression. For Kepler-102d, we report a mass upper limit
M
d
< 5.3
M
⊕
(95% confidence), a best-fit mass
M
d
= 2.5 ± 1.4
M
⊕
, and a density
ρ
d
= 5.6 ± 3.2 g cm
−3
, which is consistent with a rocky composition similar in density to the Earth. For Kepler-102e we report a mass
M
e
= 4.7 ± 1.7
M
⊕
and a density
ρ
e
= 1.8 ± 0.7 g cm
−3
. These measurements suggest that Kepler-102e has a rocky core with a thick gaseous envelope comprising 2%–4% of the planet mass and 16%–50% of its radius. Our study is yet another demonstration that accounting for stellar activity in stars with clear rotation signals can yield more accurate planet masses, enabling a more realistic interpretation of planet interiors.
For more than 20 years, the atmosphere above the Telescopio Nazionale Galileo and its surroundings at the Roque de Los Muchachos Observatory have been monitored. From the first instruments installed ...in the early ‘90s to characterize and show the quality of the sky at the chosen site (particularly the Automatic Weather Station and the DIMM) we evolved into the actual set up of remote sensing devices. They are as a fundamental aid for the telescope, in particular for its safety and the optimization of the scientific throughput. We will resume here the lessons learned, some results and the new choices for monitoring the atmosphere at the TNG.
A microphotonic astrocomb is demonstrated via temporal dissipative Kerr solitons in photonic-chip-based silicon nitride microresonators with a precision of 25 cm s–1 (radial velocity equivalent), ...useful for Earth-like planet detection and cosmological research.
The atmospheres of gaseous giant exoplanets orbiting close to their parent stars (hot Jupiters) have been probed for nearly two decades
. They allow us to investigate the chemical and physical ...properties of planetary atmospheres under extreme irradiation conditions
. Previous observations of hot Jupiters as they transit in front of their host stars have revealed the frequent presence of water vapour
and carbon monoxide
in their atmospheres; this has been studied in terms of scaled solar composition
under the usual assumption of chemical equilibrium. Both molecules as well as hydrogen cyanide were found in the atmosphere of HD 209458b
, a well studied hot Jupiter (with equilibrium temperature around 1,500 kelvin), whereas ammonia was tentatively detected there
and subsequently refuted
. Here we report observations of HD 209458b that indicate the presence of water (H
O), carbon monoxide (CO), hydrogen cyanide (HCN), methane (CH
), ammonia (NH
) and acetylene (C
H
), with statistical significance of 5.3 to 9.9 standard deviations per molecule. Atmospheric models in radiative and chemical equilibrium that account for the detected species indicate a carbon-rich chemistry with a carbon-to-oxygen ratio close to or greater than 1, higher than the solar value (0.55). According to existing models relating the atmospheric chemistry to planet formation and migration scenarios
, this would suggest that HD 209458b formed far from its present location and subsequently migrated inwards
. Other hot Jupiters may also show a richer chemistry than has been previously found, which would bring into question the frequently made assumption that they have solar-like and oxygen-rich compositions.
HARPS-N OBSERVES THE SUN AS A STAR Dumusque, Xavier; Glenday, Alex; Phillips, David F. ...
Astrophysical journal. Letters,
12/2015, Letnik:
814, Številka:
2
Journal Article
Recenzirano
Odprti dostop
ABSTRACT Radial velocity (RV) perturbations induced by stellar surface inhomogeneities including spots, plages and granules currently limit the detection of Earth-twins using Doppler spectroscopy. ...Such stellar noise is poorly understood for stars other than the Sun because their surface is unresolved. In particular, the effects of stellar surface inhomogeneities on observed stellar radial velocities are extremely difficult to characterize, and thus developing optimal correction techniques to extract true stellar radial velocities is extremely challenging. In this paper, we present preliminary results of a solar telescope built to feed full-disk sunlight into the HARPS-N spectrograph, which is in turn calibrated with an astro-comb. This setup enables long-term observation of the Sun as a star with state-of-the-art sensitivity to RV changes. Over seven days of observing in 2014, we show an average 50 cm s−1 RV rms over a few hours of observation. After correcting observed radial velocities for spot and plage perturbations using full-disk photometry of the Sun, we lower by a factor of two the weekly RV rms to 60 cm s−1. The solar telescope is now entering routine operation, and will observe the Sun every clear day for several hours. We will use these radial velocities combined with data from solar satellites to improve our understanding of stellar noise and develop optimal correction methods. If successful, these new methods should enable the detection of Venus over the next two to three years, thus demonstrating the possibility of detecting Earth-twins around other solar-like stars using the RV technique.
Abstract
Exoplanet detection with precise radial velocity (RV) observations is currently limited by spurious RV signals introduced by stellar activity. We show that machine-learning techniques such ...as linear regression and neural networks can effectively remove the activity signals (due to starspots/faculae) from RV observations. Previous efforts focused on carefully filtering out activity signals in time using modeling techniques like Gaussian process regression. Instead, we systematically remove activity signals using only changes to the average shape of spectral lines, and use no timing information. We trained our machine-learning models on both simulated data (generated with the SOAP 2.0 software) and observations of the Sun from the HARPS-N Solar Telescope. We find that these techniques can predict and remove stellar activity both from simulated data (improving RV scatter from 82 to 3 cm s
−1
) and from more than 600 real observations taken nearly daily over 3 yr with the HARPS-N Solar Telescope (improving the RV scatter from 1.753 to 1.039 m s
−1
, a factor of ∼1.7 improvement). In the future, these or similar techniques could remove activity signals from observations of stars outside our solar system and eventually help detect habitable-zone Earth-mass exoplanets around Sun-like stars.
ABSTRACT
Using images from the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory, we extract the radial velocity (RV) signal arising from the suppression of convective blueshift ...and from bright faculae and dark sunspots transiting the rotating solar disc. We remove these rotationally modulated magnetic-activity contributions from simultaneous RVs observed by the HARPS-N (High Accuracy Radial velocity Planet Searcher for the Northern hemisphere) solar feed to produce an RV time series arising from the magnetically quiet solar surface (the ‘inactive-region RVs’). We find that the level of variability in the inactive-region RVs remains constant over the almost 7-yr baseline and shows no correlation with well-known activity indicators. With an root-mean-square scatter of roughly 1 ${\rm m\, s}^{-1}$, the inactive-region RV time series dominates the total RV variability budget during the decline of solar cycle 24. Finally, we compare the variability amplitude and time-scale of the inactive-region RVs with simulations of supergranulation. We find consistency between the inactive-region RV and simulated time series, indicating that supergranulation is a significant contribution to the overall solar RV variability, and may be the main source of variability towards solar minimum. This work highlights supergranulation as a key barrier to detecting Earth twins.
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