Putting gravity to work: Imaging of exoplanets with the solar gravitational lens

2019 ◽  
Vol 28 (10) ◽  
pp. 1950125
Author(s):  
Slava G. Turyshev ◽  
Michael Shao ◽  
Viktor T. Toth
Keyword(s):  
Optical Properties ◽  
High Resolution ◽  
Angular Resolution ◽  
Optical Axis ◽  
Space Mission ◽  
Gravitational Lens ◽  
High Resolution Spectroscopy ◽  
The Sun ◽  
Deep Space ◽  
Focal Area

The remarkable optical properties of the solar gravitational lens (SGL) include major brightness amplification ([Formula: see text] on the optical axis, at a wavelength of [Formula: see text]m) and extreme angular resolution ([Formula: see text][Formula: see text]arcsec). A deep space mission equipped with a modest telescope and coronagraph, traveling to the focal area of the SGL that begins at [Formula: see text] astronomical units (AU) from the Sun, offers an opportunity for direct megapixel imaging and high-resolution spectroscopy of a habitable Earth-like exoplanet. We present a basic overview of this intriguing opportunity.

scholarly journals Quasi-Band-Limited Coronagraph for Extended Sources

2021 ◽  
Vol 10 (01) ◽  
pp. 2150002
Author(s):  
Igor Loutsenko ◽  
Oksana Yermolayeva
Keyword(s):  
High Resolution ◽  
High Ratio ◽  
Gravitational Lens ◽  
High Resolution Imaging ◽  
The Sun ◽  
Extended Source ◽  
Amplitude Image ◽  
Extended Sources ◽  
Resolution Imaging ◽  
Band Limited

We propose a class of graded coronagraphic “amplitude” image masks for a high throughput Lyot-type coronagraph that transmits light from an annular region around an extended source and suppresses light, with extremely high ratio, from elsewhere. The interior radius of the region is comparable with its exterior radius. The masks are designed using an idea inspired by approach due M. J. Kuchner and W. A. Traub (“band-limited” masks) and approach to optimal apodization by D. Slepian. One potential application of our masks is direct high-resolution imaging of exo-planets with the help of the Solar Gravitational Lens, where apparent radius of the “Einstein ring” image of a planet is of the order of an arc-second and is comparable with the apparent radius of the sun and solar corona.

scholarly journals Radial velocity follow-up for confirmation and characterization of transiting exoplanets

2008 ◽  
Vol 4 (S253) ◽  
pp. 129-139 ◽  
Author(s):  
François Bouchy ◽  
Claire Moutou ◽  
Didier Queloz ◽  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Space Mission ◽  
High Resolution Spectroscopy

AbstractRadial Velocity follow-up is essential to establish or exclude the planetary nature of a transiting companion as well as to accurately determine its mass. Here we present some elements of an efficient Doppler follow-up strategy, based on high-resolution spectroscopy, devoted to the characterization of transiting candidates. Some aspects and results of the radial velocity follow-up of the CoRoT space mission are presented in order to illustrate the strategy used to deal with the zoo of transiting candidates.

Two-dimensional high-resolution spectroscopy of quiet regions on the sun

1990 ◽  
Vol 170 (1-2) ◽  
pp. 117-119 ◽  
Author(s):  
D. Bonaccini ◽  
G. Cauzzi ◽  
A. Falchi ◽  
R. Falciani ◽  
L. A. Smaldone
Keyword(s):  
High Resolution ◽  
High Resolution Spectroscopy ◽  
The Sun ◽  
Two Dimensional

scholarly journals The Hamburg/ESO Survey for Bright QSOs — Slitless Spectroscopy at High Resolution

1994 ◽  
Vol 161 ◽  
pp. 723-727 ◽  
Author(s):  
L. Wisotzki
Keyword(s):  
High Resolution ◽  
High Redshift ◽  
Gravitational Lens ◽  
High Resolution Spectroscopy ◽  
Wide Angle ◽  
X Rays ◽  
Digital Revolution ◽  
First Results ◽  
Objective Prism

The digital revolution in the evaluation of photographic plates and the introduction of automated quasar search techniques have drastically increased the number of known QSOs over the past decade. However, most of these QSOs are so faint that their use is limited to statistical studies. The bright end of the quasar population is still dominated by objects selected in other wavebands, such as radio, X-rays, or even infrared. We have started in 1990 a wide-angle objective-prism survey (the Hamburg/ESO Survey, HES) using the 1 m ESO Schmidt telescope (Reimers 1990). The survey is intended to cover 5000 deg2, of which about a third has been acquired up to now. The prime goal is to compile a large sample of bright (B < 17.5) QSOs suited for detailed follow-up studies, in particular for high-resolution spectroscopy. Other objectives are to search for gravitational lens candidates and to directly measure the local luminosity function of quasars. In each Schmidt field, a spectral and a direct plate are scanned with the PDS 1010G microdensitometer at Hamburg, followed by an automated candidate selection and subsequent follow-up spectroscopy with the ESO 1.52 m and 3.6 m telescopes. A novel feature in our survey is the use of an objective-prism with a dispersion of 450 å/mm at Hγ, yielding a seeing-limited spectral resolution of 10–20 å FWHM. A full documentation of the survey techniques is in preparation. First results include the discoveries of the second-brightest QSO in the south (Wisotzki et al. 1991), and of a bright double QSO at high redshift, probably a gravitational lens (Wisotzki et al. 1993). In this contribution I want to show how a wide-angle quasar survey like the HES can benefit from the high resolution of the survey spectra.

scholarly journals Quantifying and containing the curse of high resolution coronal imaging

2008 ◽  
Vol 26 (10) ◽  
pp. 3169-3184 ◽  
Author(s):  
V. Delouille ◽  
P. Chainais ◽  
J.-F. Hochedez
Keyword(s):  
High Resolution ◽  
Scale Invariance ◽  
Angular Resolution ◽  
Signal To Noise Ratio ◽  
Effective Area ◽  
The Sun ◽  
Scientific Success ◽  
Quiet Sun ◽  
Invariance Properties ◽  
High Resolution Images

Abstract. Future missions such as Solar Orbiter (SO), InterHelioprobe, or Solar Probe aim at approaching the Sun closer than ever before, with on board some high resolution imagers (HRI) having a subsecond cadence and a pixel area of about (80 km)2 at the Sun during perihelion. In order to guarantee their scientific success, it is necessary to evaluate if the photon counts available at these resolution and cadence will provide a sufficient signal-to-noise ratio (SNR). For example, if the inhomogeneities in the Quiet Sun emission prevail at higher resolution, one may hope to locally have more photon counts than in the case of a uniform source. It is relevant to quantify how inhomogeneous the quiet corona will be for a pixel pitch that is about 20 times smaller than in the case of SoHO/EIT, and 5 times smaller than TRACE. We perform a first step in this direction by analyzing and characterizing the spatial intermittency of Quiet Sun images thanks to a multifractal analysis. We identify the parameters that specify the scale-invariance behavior. This identification allows next to select a family of multifractal processes, namely the Compound Poisson Cascades, that can synthesize artificial images having some of the scale-invariance properties observed on the recorded images. The prevalence of self-similarity in Quiet Sun coronal images makes it relevant to study the ratio between the SNR present at SoHO/EIT images and in coarsened images. SoHO/EIT images thus play the role of "high resolution" images, whereas the "low-resolution" coarsened images are rebinned so as to simulate a smaller angular resolution and/or a larger distance to the Sun. For a fixed difference in angular resolution and in Spacecraft-Sun distance, we determine the proportion of pixels having a SNR preserved at high resolution given a particular increase in effective area. If scale-invariance continues to prevail at smaller scales, the conclusion reached with SoHO/EIT images can be transposed to the situation where the resolution is increased from SoHO/EIT to SO/HRI resolution at perihelion.

scholarly journals High-resolution spectroscopy of flares and CMEs on AD Leonis

2020 ◽  
Vol 637 ◽  
pp. A13 ◽  
Author(s):  
P. Muheki ◽  
E. W. Guenther ◽  
T. Mutabazi ◽  
E. Jurua
Keyword(s):  
High Resolution ◽  
Spectral Lines ◽  
High Resolution Spectroscopy ◽  
Flare Activity ◽  
The Sun ◽  
M Dwarfs ◽  
Highly Active ◽  
M Stars ◽  
High Level ◽  
M Dwarf

Context. Flares and coronal mass ejections (CMEs) are important for the evolution of the atmospheres of planets and their potential habitability, particularly for planets orbiting M stars at a distance <0.4 AU. Detections of CMEs on these stars have been sparse, and previous studies have therefore modelled their occurrence frequency by scaling up solar relations. However, because the topology and strength of the magnetic fields on M stars is different from that of the Sun, it is not obvious that this approach works well. Aims. We used a large number of high-resolution spectra to study flares, CMEs, and their dynamics of the active M dwarf star AD Leo. The results can then be used as reference for other M dwarfs. Methods. We obtained more than 2000 high-resolution spectra (R ~ 35 000) of the highly active M dwarf AD Leo, which is viewed nearly pole on. Using these data, we studied the behaviour of the spectral lines Hα, Hβ, and He I 5876 in detail and investigated asymmetric features that might be Doppler signatures of CMEs. Results. We detected numerous flares. The largest flare emitted 8.32 × 1031 erg in Hβ and 2.12 × 1032 erg in Hα. Although the spectral lines in this and other events showed a significant blue asymmetry, the velocities associated with it are far below the escape velocity. Conclusions. Although AD Leo shows a high level of flare activity, the number of CMEs is relatively low. It is thus not appropriate to use the same flare-to-CME relation for M dwarfs as for the Sun.

scholarly journals Super-Earth of 8 M⊕ in a 2.2-day orbit around the K5V star K2-216

2018 ◽  
Vol 618 ◽  
pp. A33 ◽  
Author(s):  
C. M. Persson ◽  
M. Fridlund ◽  
O. Barragán ◽  
F. Dai ◽  
D. Gandolfi ◽  
...  
Keyword(s):  
High Resolution ◽  
Infrared Camera ◽  
Magnesium Silicate ◽  
Space Mission ◽  
High Resolution Spectroscopy ◽  
Correlated Noise ◽  
Single Star ◽  
Stellar Spectra ◽  
Theoretical Predictions ◽  
Stellar Properties

Context. Although thousands of exoplanets have been discovered to date, far fewer have been fully characterised, in particular super-Earths. The KESPRINT consortium identified K2-216 as a planetary candidate host star in the K2 space mission Campaign 8 field with a transiting super-Earth. The planet has recently been validated as well. Aims. Our aim was to confirm the detection and derive the main physical characteristics of K2-216 b, including the mass. Methods. We performed a series of follow-up observations: high-resolution imaging with the FastCam camera at the TCS and the Infrared Camera and Spectrograph at Subaru, and high-resolution spectroscopy with HARPS (La Silla), HARPS-N (TNG), and FIES (NOT). The stellar spectra were analyzed with the SpecMatch-Emp and SME codes to derive the fundamental stellar properties. We analyzed the K2 light curve with the pyaneti software. The radial velocity measurements were modelled with both a Gaussian process (GP) regression and the so-called floating chunk offset (FCO) technique to simultaneously model the planetary signal and correlated noise associated with stellar activity. Results. Imaging confirms that K2-216 is a single star. Our analysis discloses that the star is a moderately active K5V star of mass 0.70 ± 0.03 M⊙ and radius 0.72 ± 0.03 R⊙. Planet b is found to have a radius of 1.75−0.10+0.17 R⊕ and a 2.17-day orbit in agreement with previous results. We find consistent results for the planet mass from both models: Mp ≈ 7.4 ± 2.2 M⊕ from the GP regression and Mp ≈ 8.0 ± 1.6 M⊕ from the FCO technique, which implies that this planet is a super-Earth. The incident stellar flux is 2.48−48+220 F⊕. Conclusions. The planet parameters put planet b in the middle of, or just below, the gap of the radius distribution of small planets. The density is consistent with a rocky composition of primarily iron and magnesium silicate. In agreement with theoretical predictions, we find that the planet is a remnant core, stripped of its atmosphere, and is one of the largest planets found that has lost its atmosphere.

scholarly journals Variability of OB stars from TESS southern Sectors 1–13 and high-resolution IACOB and OWN spectroscopy

2020 ◽  
Vol 639 ◽  
pp. A81 ◽  
Author(s):  
S. Burssens ◽  
S. Simón-Díaz ◽  
D. M. Bowman ◽  
G. Holgado ◽  
M. Michielsen ◽  
...  
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Galactic Plane ◽  
Space Mission ◽  
Variable Stars ◽  
Two Dimensions ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
High Resolution Spectroscopy ◽  
Ob Stars

Context. The lack of high-precision long-term continuous photometric data for large samples of stars has impeded the large-scale exploration of pulsational variability in the OB star regime. As a result, the candidates for in-depth asteroseismic modelling have remained limited to a few dozen dwarfs. The TESS nominal space mission has surveyed the southern sky, including parts of the galactic plane, yielding continuous data across at least 27 d for hundreds of OB stars. Aims. We aim to couple TESS data in the southern sky with ground-based spectroscopy to study the variability in two dimensions, mass and evolution. We focus mainly on the presence of coherent pulsation modes that may or may not be present in the predicted theoretical instability domains and unravel all frequency behaviour in the amplitude spectra of the TESS data. Methods. We compose a sample of 98 OB-type stars observed by TESS in Sectors 1–13 and with available multi-epoch, high-resolution spectroscopy gathered by the IACOB and OWN surveys. We present the short-cadence 2 min light curves of dozens of OB-type stars, which have one or more spectra in the IACOB or OWN database. Based on these light curves and their Lomb–Scargle periodograms, we performed variability classification and frequency analysis. We placed the stars in the spectroscopic Hertzsprung–Russell diagram to interpret the variability in an evolutionary context. Results. We deduce the diverse origins of the mmag-level variability found in all of the 98 OB stars in the TESS data. We find among the sample several new variable stars, including three hybrid pulsators, three eclipsing binaries, high frequency modes in a Be star, and potential heat-driven pulsations in two Oe stars. Conclusions. We identify stars for which future asteroseismic modelling is possible, provided mode identification is achieved. By comparing the position of the variables to theoretical instability strips, we discuss the current shortcomings in non-adiabatic pulsation theory and the distribution of pulsators in the upper Hertzsprung–Russell diagram.

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