Future Exoplanet Research: Science Questions and How to Address Them

Started approximately in the late 1980s, exoplanetology has up to now unveiled the main gross bulk characteristics of planets and planetary systems. In the future it will benefit from more and more large telescopes and advanced space missions. These instruments will dramatically improve their performance in terms of photometric precision, detection speed, multipixel imaging, high-resolution spectroscopy, allowing to go much deeper in the knowledge of planets. Here we outline some science questions which should go beyond these standard improvements and how to address them. Our prejudice is that one is never too speculative: experience shows that the speculative predictions initially not accepted by the community have been confirmed several years later (like spectrophotometry of transits or circumbinary planets).Comment: Invited review, accepte

Plasma interactions of exoplanets with their parent star and associated radio emissions

The relatively high contrast between planetary and solar low frequency radio emissions suggests that the low–frequency radio range may be well adapted to the direct detection of exoplanets. We review the most significant properties of planetary radio emissions (auroral as well as satellite–induced) and show that their primary engine is the interaction of a plasma flow with an obstacle in the presence of a strong magnetic field (of the flow or of the obstacle). Scaling laws have been derived from solar system planetary radio emissions that relate the emitted radio power to the power dissipated in the various corresponding flow–obstacle interactions. We generalize these scaling laws into a “radio–magnetic” scaling law that seems to relate output radio power to the magnetic energy flux convected on the obstacle, this obstacle being magnetized or unmagnetized. Extrapolating this scaling law to the case of exoplanets, we find that hot Jupiters may produce very intense radio emissions due to either magnetospheric interaction with a strong stellar wind or to unipolar interaction between the planet and a magnetic star (or strongly magnetized regions of the stellar surface). In the former case, similar to the magnetosphere–solar wind interactions in our solar system or to the Ganymede–Jupiter interaction, a hecto–decameter emission is expected in the vicinity of the planet with an intensity possibly 103 to 105 times that of Jupiter's low frequency radio emissions. In the latter case, which is a giant analogy of the Io–Jupiter system, emission in the decameter–to–meter wavelength range near the footprints of the star's magnetic field lines interacting with the planet may reach 106 times that of Jupiter (unless some “saturation” mechanism occurs). The system of HD 179949, where a hot spot has been tentatively detected in visible light near the sub–planetary point, is discussed in some details. Finally, we discuss the interests of direct radio detection, among which access to exoplanetary magnetic field measurements and comparative magnetospheric physics

What Can Be Interesting in the Analysis of Crowded Solar Bursts?

International audienceAt decameter wavelengths the radio astronomy observations reveal a wide variety of solar bursts. They are associated with solar activity manifestations such as movements of electron beams and shock waves in solar corona, flare- related events, coronal mass ejections and others. The analysis of burst features allows one to use them as probing signals which comprise useful information about solar corona parameters and their changes over time. By frequency-time measurements of different types of solar bursts occurred about the same time one can provide a comparative study of their properties, complementing the missing pieces in the complex mosaic of solar events. In this purpose we discuss features of their signal processing by the gradient filtration, as applied to quasi-periodic bursts like a zebra pattern related to Bernstein modes. The measured frequency periodicity of the bursts gives a chance to determine the magnetic field strength in upper corona around the protracted solar minimum of solar activity

Probing Jupiter’s auroral radio sources with Juno

Jupiter is the major auroral radio source in our solar system, producing Jovian low-frequency radio emissions in a broad frequency range of 10 kHz to 40 MHz from both north and south polar regions of the planet. These sporadic nonthermal bursts have been monitored with the radio and plasma wave instrument (Waves) aboard the spinning Juno spacecraft in polar orbit about Jupiter since July 5, 2016. The Waves instrument is composed of one electric dipole antenna, one magnetic search coil sensor, and three on-board receivers that record the electric fields of waves from 50 Hz to 41 MHz and the magnetic fields of waves from 50 Hz to 20 kHz. Juno has three advantageous methods to determine the radio source locations and the beaming properties for the Jovian low-frequency radio emissions: (1) identifying emission frequency close to the local gyrofrequency at the source with in situ particle measurements through Juno's perijove surveys from pole to pole, (2) the spin-modulated spectral density recorded with Juno Waves to estimate the direction of arrival of incoming waves, and (3) with the aid of the Jovian radio beaming model, performing stereoscopic radio observations with Juno, Cassini, STEREO A, WIND, and Earth-based radio telescopes (e.g., LWA1 in New Mexico, USA, and NDA in Nançay, France) or investigating the statistical characteristics of Jovian radio occurrence by Juno. Because the three individual methods are self-consistent and complement each other, Juno observations are useful for determining the Jovian radio beam parameters and radio source locations, which can be traced along magnetic field lines onto Jupiter's atmosphere and further compared with the UV aurora taken by the Hubble Space Telescope. In this talk, we give a brief overview of early radio astronomy results from Juno, providing the recent results from these extended studies by means of the three methods

Treatment of primary varicose veins by endovenous obliteration with the VNUS closure system: Results of a prospective multicentre study

Background. Radio frequency obliteration of the saphenous veins has been introduced as a less invasive alternative to traditional surgery for varicose veins. Objective. To report the efficacy of obliteration and clinical outcomes following endovenous obliteration of the saphenous vein with limited follow-up to 3 years. Materials and methods. Radiofreq uency obliteration (Closure® system, VNUS Medical Technologies, San Jose, CA) was performed in 330 limbs of 294 patients in a prospective worldwide multicentre study with 31 participating sites. Follow-up duplex ultrasound and clinical examinations were performed at annual intervals. The main outcome measures were the completeness of occlusion of the treated vein segment, presence of reflux and presence of signs and symptoms of venous disease. Results. Before treatment 3.9% of limbs were categorised as CEAP clinical class zero or one. This improved to 82.9% at 1 year, 83.1% at 2 years and 86.8% at 3 years following treatment. Varicose vein free rates were 1 year: 90.1%, 2 years: 87.2%, 3 years: 88.2%. Duplex ultrasound demonstrated a reflux-free rate of about 88% over 3 years. Total occlusion (TO) of veins was 1 year: 81%, 2 years: 80.4% and 3 years: 75%. Partial occlusion (PO, 5 cm open segment) was 1 year: 12.7%, 2 years: 12.2% and 3 years: 7.4%. Partial occlusion did not result in any differences in the symptom severity score, the number of symptom free limbs, or the varicose vein absence rates at any follow-up time point when compared to the total occlusion group. The varicose vein absence rates were significantly lower in the IO group comparing to the TO and PO groups. Conclusions. Radiofrequency saphenous vein obliteration improves the symptoms of varicose veins. The reflux-free rates in the treated veins remain constant over a 3 year follow-up period. There is no difference in clinical outcomes between the TO and the PO limbs, suggesting clinical effectiveness of the PO category. Greater than a 5 cm open segment in treated veins poses a risk of recurrence. © 2004 Elsevier Ltd. All rights reserved

Baseline Characteristics and Risk Profiles of Participants in the ISCHEMIA Randomized Clinical Trial

Importance: It is unknown whether coronary revascularization, when added to optimal medical therapy, improves prognosis in patients with stable ischemic heart disease (SIHD) at increased risk of cardiovascular events owing to moderate or severe ischemia. Objective: To describe baseline characteristics of participants enrolled and randomized in the International Study of Comparative Health Effectiveness With Medical and Invasive Approaches (ISCHEMIA) trial and to evaluate whether qualification by stress imaging or nonimaging exercise tolerance test (ETT) influenced risk profiles. Design, Setting, and Participants: The ISCHEMIA trial recruited patients with SIHD with moderate or severe ischemia on stress testing. Blinded coronary computed tomography angiography was performed in most participants and reviewed by a core laboratory to exclude left main stenosis of at least 50% or no obstructive coronary artery disease (CAD) (<50% for imaging stress test and <70% for ETT). The study included 341 enrolling sites (320 randomizing) in 38 countries and patients with SIHD and moderate or severe ischemia on stress testing. Data presented were extracted on December 17, 2018. Main Outcomes and Measures: Enrolled, excluded, and randomized participants' baseline characteristics. No clinical outcomes are reported. Results: A total of 8518 patients were enrolled, and 5179 were randomized. Common reasons for exclusion were core laboratory determination of insufficient ischemia, unprotected left main stenosis of at least 50%, or no stenosis that met study obstructive CAD criteria on study coronary computed tomography angiography. Randomized participants had a median age of 64 years, with 1168 women (22.6%), 1726 nonwhite participants (33.7%), 748 Hispanic participants (15.5%), 2122 with diabetes (41.0%), and 4643 with a history of angina (89.7%). Among the 3909 participants randomized after stress imaging, core laboratory assessment of ischemia severity (in 3901 participants) was severe in 1748 (44.8%), moderate in 1600 (41.0%), mild in 317 (8.1%) and none or uninterpretable in 236 (6.0%), Among the 1270 participants who were randomized after nonimaging ETT, core laboratory determination of ischemia severity (in 1266 participants) was severe (an eligibility criterion) in 1051 (83.0%), moderate in 101 (8.0%), mild in 34 (2.7%) and none or uninterpretable in 80 (6.3%). Among the 3912 of 5179 randomized participants who underwent coronary computed tomography angiography, 79.0% had multivessel CAD (n = 2679 of 3390) and 86.8% had left anterior descending (LAD) stenosis (n = 3190 of 3677) (proximal in 46.8% [n = 1749 of 3739]). Participants undergoing ETT had greater frequency of 3-vessel CAD, LAD, and proximal LAD stenosis than participants undergoing stress imaging. Conclusions and Relevance: The ISCHEMIA trial randomized an SIHD population with moderate or severe ischemia on stress testing, of whom most had multivessel CAD