X-exoplanets: an X-ray and EUV database for exoplanets

AbstractExtreme Ultraviolet (EUV) and X-ray emission is of great importance in several phenomena related to the formation of planetary systems and the atmospheres of planets. The atmospheric composition, and the mass of an exoplanet, are partly dependent on the X-ray and EUV radiation received during the first stages of formation and even during main sequence of the star. Biological life developing on exoplanets would depend severely on the high energy radiation arriving from its parent star.Here we present a database of the X-ray and EUV emission of all the stars currently known to host exoplanets. The archive is public and accessible through the Spanish Virtual Observatory (SVO). The database gives the user the option to download observed X-rays and EUV spectra. Synthetic spectra covering the spectral range 1–912 Å are also available (present day telescopes do not give access to the EUV range at λ > 180 Å). These spectra are created using coronal models after fitting observed spectra.

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RESIK and RHESSI observations of the 20 September 2002 flare

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038434 ◽

2020 ◽

Vol 642 ◽

pp. A112

Author(s):

A. Kepa ◽

R. Falewicz ◽

M. Siarkowski ◽

M. Pietras

Keyword(s):

Extreme Ultraviolet ◽

High Energy ◽

Spectral Energy ◽

Data Sets ◽

X Rays ◽

Heliospheric Observatory ◽

X Ray ◽

Physical Conditions ◽

Synthetic Spectra ◽

Cross Calibration

Context. Soft X-ray spectra (3.33 Å–6.15 Å) from the RESIK instrument on CORONAS-F constitute a unique database for the study of the physical conditions of solar flare plasmas, enabling the calculation of differential emission measures. The two RESIK channels for the shortest wavelengths overlap with the lower end of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spectral energy range, which is located around 3 keV, making it possible to compare both data sets. Aims. We aim to compare observations from RESIK and RHESSI spectrometers and cross-correlate these instruments. Observations are compared with synthetic spectra calculated based on the results of one-dimensional hydrodynamical (1D-HD) modelling. The analysis was performed for the flare on 20 September 2002 (SOL2002-09-20T09:28). Methods. We estimated the geometry of the flaring loop, necessary for 1D-HD modelling, based on images from RHESSI and the Extreme-Ultraviolet Imaging Telescope aboard the Solar and Heliospheric Observatory. The distribution of non-thermal electrons (NTEs) was determined from RHESSI spectra. The 1D-HD model assumes that non-thermal electrons with a power-law spectrum were injected at the apex of the flaring loop. The NTEs then heat and evaporate the chromosphere, filling the loop with hot and dense plasma radiating in soft X-rays. The total energy of electrons was constrained by comparing observed and calculated fluxes from Geostationary Operational Environmental Satellite 1–8 Å data. We determined the temperature and density at every point of the flaring loop throughout the evolution of the flare, calculating the resulting X-ray spectra. Results. The synthetic spectra calculated based on the results of hydrodynamic modelling for the 20 September 2002 flare are consistent within a factor of two with the observed RESIK spectra during most of the duration of the flare. This discrepancy factor is probably related to the uncertainty on the cross-calibration between RESIK and RHESSI instruments.

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The X-ray stellar population of the LMC

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308028202 ◽

2008 ◽

Vol 4 (S256) ◽

pp. 20-29 ◽

Cited By ~ 1

Author(s):

Yaël Nazé

Keyword(s):

Stellar Population ◽

Main Sequence ◽

Massive Stars ◽

High Energy ◽

Magellanic Clouds ◽

X Rays ◽

X Ray ◽

Energy Domain ◽

X Ray Binaries

AbstractIn the study of stars, the high energy domain occupies a place of choice, since it is the only one able to directly probe the most violent phenomena: indeed, young pre-main sequence objects, hot massive stars, or X-ray binaries are best revealed in X-rays. However, previously available X-ray observatories often provided only crude information on individual objects in the Magellanic Clouds. The advent of the highly efficient X-ray facilities XMM-Newton and Chandra has now dramatically increased the sensitivity and the spatial resolution available to X-ray astronomers, thus enabling a fairly easy determination of the properties of individual sources in the LMC.

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High-energy radiation from natural lightning observed in coincidence with a VHF Lightning Interferometer

10.5194/egusphere-egu2020-16383 ◽

2020 ◽

Author(s):

Michele Urbani ◽

Joan Montanyà ◽

Oscar Van der Velde ◽

Jesús Alberto López

Keyword(s):

High Energy ◽

Strong Absorption ◽

X Rays ◽

Coverage Area ◽

Radiation Mechanism ◽

High Energy Radiation ◽

Energy Radiation ◽

X Ray ◽

Cloud To Ground Lightning ◽

Energy Emissions

In the last two decades, it has been discovered that lightning strikes can emit high-energy radiation. In particular, a phenomenon has been observed from space called "Terrestrial Gamma-ray Flash'' (TGF), which consists of an intense burst of gamma radiation that can be produced during thunderstorms. This phenomenon has met with considerable interest in the scientific community and its mechanism is still not fully understood. Nowadays several satellites for astrophysics like AGILE and FERMI are able to detect and map TGFs and specific instruments like the ASIM detector on the ISS are studying this phenomenon from space. In the atmosphere, the high-energy radiation undergoes a strong absorption exponentially proportional to the air density which makes it more difficult to detect TGFs on the ground. Nonetheless, ground measurements were conducted and observed that even in cloud-to-ground lightning high-energy radiation were produced. In particular, the works of Moore et al. [2001] and Dwyer et al. [2005] highlight two lightning processes in which the X-ray emission could be produced: downward negative stepped leader and dart leader. Currently, it is not clear if the emissions revealed on the ground and the TGFs observed in space are essentially the same phenomenon or how these phenomena are related. For these reasons, it is particularly interesting to study high-energy emissions also from ground instruments because, despite the strong absorption of the high-energy radiation, ground observations can reach a better accuracy in time and space and provide crucial information to investigate the origin and conditions under which these emissions occur. A privileged instrument for this research is the VHF Lightning Interferometer, a system of antennas that allows you to map lightning through the very high frequency (VHF) emission. Due to the high resolution of this instrument, should be possible to locate the origin of the high-energy emissions and hopefully provide a better understanding of the radiation mechanism. The aim of this research is, therefore, to develop a 3D interferometry system to identify as accurately as possible the origin and the conditions in which the X-ray emission occurs in cloud-to-ground lightning and investigate the relation of the VHF emissions with the TGFs. Recently an observation campaign was conducted in Colombia with two VHF Lightning Interferometers and two X-rays detectors. This interferometry system was installed in the coverage area of a Lightning Mapping Array (LMA) and LINET to take advantage of the complementary information that these lightning location networks could provide. At the moment, about 15 lightning events with X-ray emissions were observed, including five X-ray bursts from downward negative leaders and two emissions from dart leaders. Further studies and analysis of the collected data are still ongoing.

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Non thermal emission from T Tauri stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310016492 ◽

2010 ◽

Vol 6 (S275) ◽

pp. 404-405

Author(s):

María V. del Valle ◽

Gustavo E. Romero

Keyword(s):

Main Sequence ◽

Thermal Emission ◽

High Energy ◽

Magnetic Activity ◽

T Tauri Stars ◽

Main Sequence Stars ◽

High Energy Radiation ◽

X Ray ◽

T Tauri ◽

Low Mass

AbstractT Tauri stars are low mass, pre-main sequence stars. These objects are surrounded by an accretion disk and present strong magnetic activity. T Tauri stars are copious emitters of X-ray emission which belong to powerful magnetic reconnection events. Strong magnetospheric shocks are likely outcome of massive reconnection. Such shocks can accelerate particles up to relativistic energies through Fermi mechanism. We present a model for the high-energy radiation produced in the environment of T Tauri stars. We aim at determining whether this emission is detectable. If so, the T Tauri stars should be very nearby.

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Mechanism for X-ray production in extars

Symposium - International Astronomical Union ◽

10.1017/s0074180900004629 ◽

1970 ◽

Vol 37 ◽

pp. 413-423

Author(s):

O. P. Manley ◽

S. Olbert

Keyword(s):

High Energy ◽

X Rays ◽

Interested Reader ◽

High Energy Radiation ◽

Energy Radiation ◽

Astrophysical Interest ◽

X Ray ◽

Theory Of Production

This presentation attempts to describe in very qualitative terms a theory of production of high energy radiation (soft and hard X-rays) in magnetoactive plasmas of astrophysical interest. Special emphasis has been placed on the application of our model to extars and in particular to Sco X-1. More rigorous arguments may be found elsewhere [1] and the interested reader is urged to consult that reference for more details.

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EUV irradiation of exoplanet atmospheres occurs on Gyr time-scales

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa186 ◽

2020 ◽

Vol 501 (1) ◽

pp. L28-L32

Author(s):

George W King ◽

Peter J Wheatley

Keyword(s):

Mass Loss ◽

Time Scales ◽

High Energy ◽

Planetary Atmospheres ◽

X Rays ◽

X Ray ◽

Atmospheric Escape ◽

Euv Emission ◽

Energy Emission ◽

High Energy Emission

ABSTRACT Exoplanet atmospheres are known to be vulnerable to mass-loss through irradiation by stellar X-ray and extreme-ultraviolet (EUV) emission. We investigate how this high-energy irradiation varies with time by combining an empirical relation describing stellar X-ray emission with a second relation describing the ratio of solar X-ray to EUV emission. In contrast to assumptions commonly made when modelling atmospheric escape, we find that the decline in stellar EUV emission is much slower than in X-rays, and that the total EUV irradiation of planetary atmospheres is dominated by emission after the saturated phase of high-energy emission (which lasts around 100 Myr after the formation of the star). The EUV spectrum also becomes much softer during this slow decline. Furthermore, we find that the total combined X-ray and EUV emission of stars occurs mostly after the saturated phase. Our results suggest that models of atmospheric escape that focus on the saturated phase of high-energy emission are oversimplified, and when considering the evolution of planetary atmospheres it is necessary to follow EUV-driven escape on Gyr time-scales. This may make it more difficult to use stellar age to separate the effects of photoevaporation and core-powered mass-loss when considering the origin of the planet radius valley.

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Magnetic activity, high-energy radiation and variability: from young solar analogs to low-mass objects

Proceedings of the International Astronomical Union ◽

10.1017/s174392130999295x ◽

2009 ◽

Vol 5 (S264) ◽

pp. 375-384

Author(s):

Manuel Güdel

Keyword(s):

Extreme Ultraviolet ◽

High Energy ◽

Magnetic Activity ◽

Energy Output ◽

Stellar Winds ◽

High Energy Radiation ◽

X Ray ◽

Cool Stars ◽

Low Mass ◽

Solar Analogs

AbstractMagnetic activity on cool stars expresses itself in a bewildering variety of radiative and particle output originating from magnetic regions between the photosphere and the corona. Given its origin in evolving magnetic fields, most of this output is variable in time. Radiation in the ultraviolet, the extreme ultraviolet, and the X-ray ranges are important for heating and ionizing upper planetary atmospheres and thus driving atmospheric evaporation. Additionally, stellar winds interact with the upper atmospheres and may lead to further erosion. The stellar high-energy output is therefore a prime factor in determining habitability of planets. We summarize our knowledge of magnetic activity in young solar analogs and lower-mass stars and show how the stellar output changes on evolutionary timescales.

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High Energy Radiation from Spider Pulsars

Galaxies ◽

10.3390/galaxies7040093 ◽

2019 ◽

Vol 7 (4) ◽

pp. 93 ◽

Cited By ~ 5

Author(s):

Chung Yue Hui ◽

Kwan Lok Li

Keyword(s):

High Energy ◽

X Rays ◽

The Novel ◽

Large Area ◽

High Energy Radiation ◽

X Ray ◽

Compact Binaries ◽

Low Mass ◽

Γ Rays ◽

Γ Ray

The population of millisecond pulsars (MSPs) has been expanded considerably in the last decade. Not only is their number increasing, but also various classes of them have been revealed. Among different classes of MSPs, the behaviours of black widows and redbacks are particularly interesting. These systems consist of an MSP and a low-mass companion star in compact binaries with an orbital period of less than a day. In this article, we give an overview of the high energy nature of these two classes of MSPs. Updated catalogues of black widows and redbacks are presented and their X-ray/ γ -ray properties are reviewed. Besides the overview, using the most updated eight-year Fermi Large Area Telescope point source catalog, we have compared the γ -ray properties of these two MSP classes. The results suggest that the X-rays and γ -rays observed from these MSPs originate from different mechanisms. Lastly, we will also mention the future prospects of studying these spider pulsars with the novel methodologies as well as upcoming observing facilities.

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Multiple Electron Acceleration Instances during a Series of Solar Microflares Observed Simultaneously at X-Rays and Microwaves

The Astrophysical Journal ◽

10.3847/1538-4357/ac2aa6 ◽

2021 ◽

Vol 922 (2) ◽

pp. 134

Author(s):

Marina Battaglia ◽

Rohit Sharma ◽

Yingjie Luo ◽

Bin Chen ◽

Sijie Yu ◽

...

Keyword(s):

Active Region ◽

Extreme Ultraviolet ◽

High Sensitivity ◽

Electron Acceleration ◽

High Energy ◽

Continuum Emission ◽

X Rays ◽

Very Large Array ◽

X Ray ◽

Flare Site

Abstract Even small solar flares can display a surprising level of complexity regarding their morphology and temporal evolution. Many of their properties, such as energy release and electron acceleration can be studied using highly complementary observations at X-ray and radio wavelengths. We present X-ray observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager and radio observations from the Karl G. Jansky Very Large Array (VLA) of a series of GOES A3.4–B1.6 class flares observed on 2013 April 23. The flares, as seen in X-ray and extreme ultraviolet, originated from multiple locations within active region NOAA 11726. A veritable zoo of different radio emissions between 1 GHz and 2 GHz was observed cotemporally with the X-ray flares. In addition to broadband continuum emission, broadband short-lived bursts and narrowband spikes, indicative of accelerated electrons, were observed. However, these sources were located up to 150″ away from the flaring X-ray sources but only some of these emissions could be explained as signatures of electrons that were accelerated near the main flare site. For other sources, no obvious magnetic connection to the main flare site could be found. These emissions likely originate from secondary acceleration sites triggered by the flare, but may be due to reconnection and acceleration completely unrelated to the cotemporally observed flare. Thanks to the extremely high sensitivity of the VLA, not achieved with current X-ray instrumentation, it is shown that particle acceleration happens frequently and at multiple locations within a flaring active region.

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Radio and X-ray Observations of Short-lived Episodes of Electron Acceleration in a Solar Microflare

10.5194/egusphere-egu21-14293 ◽

2021 ◽

Author(s):

Rohit Sharma ◽

Marina Battaglia ◽

Yingjie Luo ◽

Bin Chen ◽

Sijie Yu

Keyword(s):

Extreme Ultraviolet ◽

Magnetic Energy ◽

Electron Acceleration ◽

High Energy ◽

Nonthermal Electron ◽

X Rays ◽

Solar Dynamics Observatory ◽

Lower Corona ◽

X Ray ◽

Multi Wavelength

Solar flares release enormous magnetic energy into the corona, producing the heating of ambient plasma and acceleration of particles. The flaring process is complex and often shows multiple spatially separated temporal individual episodes of energy releases, which can be hard to resolve based on the instrument capability. We analysed the multi-wavelength imaging and spectroscopy observations of multiple electron acceleration episodes during a GOES B1.7-class two-ribbon flare observed simultaneously with the Karl G. Jansky Very Large Array (VLA) at 1--2 GHz, the Reuven Ramatay High Energy Solar Spectroscopic Imager (RHESSI) in X-rays, and the Solar Dynamics Observatory in extreme ultraviolet (EUV). We observed a total of six radio bursts. First three bursts were co-temporal, but not co-spatial nonthermal X-ray source and represent multiple electron acceleration episodes. We model the radio spectra by optically thick gyrosynchrotron emission and estimate the magnetic field strength and nonthermal electron spectral parameters in each acceleration episode. We note that the nonthermal parameters derived from X-rays differ considerably from the nonthermal parameters inferred from the radio and originates in the lower corona. Although co-temporal, our multi-wavelength analysis shows that different electron populations produce multiple acceleration episodes in radio and X-rays wavelengths.&#160;

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