Hard X-ray Sources Research Articles

4XMM J182531.5−144036: A new persistent Be/X-ray binary found within the XMM-Newton serendipitous survey

Abstract We aim to investigate the nature of time-variable X-ray sources detected in the XMM-Newton serendipitous survey. The X-ray light curves of objects in the XMM-Newton serendipitous survey were searched for variability, and coincident serendipitous sources observed by Chandra were also investigated. Subsequent infrared spectroscopy of the counterparts to the X-ray objects that were identified using UKIDSS was carried out using ISAAC on the VLT. We found that the object 4XMM J182531.5–144036 detected in the XMM-Newton serendipitous survey in 2008 April was also detected by Chandra as CXOU J182531.4–144036 in 2004 July. Both observations reveal a hard X-ray source displaying a coherent X-ray pulsation at a period of 781 s. The source position is coincident with a $K=14$ mag infrared object whose spectrum exhibits strong HeI and Br $\gamma$ emission lines and an infrared excess above that of early B-type dwarf or giant stars. We conclude that 4XMM J182531.5–144036 is a Be/X-ray binary pulsar exhibiting persistent X-ray emission and is likely in a long period, low eccentricity orbit, similar to X Per.

(Invited) Advances in XPS Analysis of Battery Materials

Energy storage (batteries, capacitors) and conversion (solar cells) systems are increasing demand for vehicles, mobile electronics, and other areas as alternatives to fossil fuels.These systems are complex and multi-component with many materials and interfaces that are difficult to handle and characterize. To optimize materials properties and improve battery lifetimes, there is a pressing need for physicochemical characterization approaches with air-free handling capabilities, high spatial resolution, the ability to analyze buried interfaces without damaging the chemistry, and the need to bridge the gap by in situ and operando surface analysis.Developments in X-ray Photoelectron Spectrometers (XPS) open up new capabilities to address these challenges. In this talk, I will discuss how we can overcome obstacles in analyzing battery materials using: Inert environment transfer vessel: This allows for handling battery materials in an air-free environment, which is essential for preventing oxidation and other degradation reactions.Microprobe X-ray source with <5 µm spatial resolution: This provides high spatial resolution for analyzing small areas of interest, such as SEI, dendrites and other features.Hard X-ray source and cluster ion gun source: These allow for the analysis of buried interfaces not accessible by conventional soft X-ray XPS.In situ energy gap measurements: These allow for the study of the changes in the electronic structure of battery materials as they are cycled, which can provide insights into the mechanisms of charge storage and discharge.Operando XPS experiments: These allow for the study of the changes in the surface structure of battery materials as they are operating, which can provide insights into the factors that affect their performance. Figure 1

Observations of a Failed Solar Filament Eruption Involving External Reconnection

We report a failed solar filament eruption that involves external magnetic reconnection in a quadrupolar magnetic configuration. The evolution exhibits three phases of kinematic evolution: a slow rise, an acceleration, and a deceleration. In the early slow rise, extreme-ultraviolet brightenings appear at the expected null point above the filament and are connected to the outer polarities by the hot loops, indicating the occurrence of a breakout reconnection. Subsequently, the filament is accelerated outward, accompanied by the formation of low-lying high-temperature post-flare loops (>15 MK), complying with the standard flare model. However, after 2–3 minutes, the erupting filament starts to decelerate and is finally confined in the corona. The important finding is that the confinement is closely related to an external reconnection as evidenced by the formation of high-lying large-scale hot loops (>10 MK) with their brightened footpoints at the outer polarities, the fragmentation and subsequent falling of the filament along the newly formed large-scale loops, as well as a hard X-ray source close to one of the outer footpoint brightenings. We propose that, even though the initial breakout reconnection and subsequent flare reconnection commence and accelerate the filament eruption, the following external reconnection between the erupting flux rope and overlying field, as driven by the upward filament eruption, causes the eruption to finally fail, as validated by the numerical simulation of a failed flux rope eruption.

Investigations of Flaring Plasma Parameters during an M-class Flare Using the Differential Evolution Method and XSM/Chandrayaan-2 Observations

We employ the differential evolution (DE) method to analyze observations from the Solar X-Ray Monitor on board the Chandrayaan-2 spacecraft. DE belongs to the family of evolutionary algorithms that find solutions using mechanisms inspired by biological processes. This approach enables us to simultaneously calculate the distribution of the differential emission measure and elemental abundances through an iterative process. We establish a model for the emission sources of flaring plasma, incorporating temperature, emission measure, and abundances of eight elements: Mg, Al, Si, S, Ar, Ca, Fe, and Ni, for an M3.9 GOES-class solar flare that occurred on 2021 May 7 (SOL2021-05-07T19:04). Our analysis covers various phases of the flare, determining the evolution of temperature, emission measure, and elemental abundances. Additionally, utilizing data from the Spectrometer Telescope for Imaging X-rays on board the Solar Orbiter, we investigate the evolution of hard X-ray source morphology, source volume, electron density, and thermal behavior of the flaring plasma throughout the event. The results reveal notable variations in elemental abundances between photospheric and coronal values during different flare phases. This emphasizes the significance of elemental abundance information in comprehending X-ray emissions during solar flares.

Dose mapping of hard X-ray radiation due to runaway electrons in Alvand tokamak using combination of high-dose and low-dose level dosimeters

Tokamaks are one of the strongest types of hard x-ray (HXR) sources that always generate energetic hard x-rays because of the bremsstrahlung radiation, when energetic runaway electrons are accelerated in the presence of the toroidal electric field. In addition, the characteristics of small-sized tokamaks make them capable of having a considerable population of runaway electrons during discharge time. In this research, the hard x-ray dose distribution of Alvand tokamak is measured and calculated using EBT3 radiochromic film and GR-200 TLD as a high-dose and low-dose dosimeters, respectively. The purpose of this measurement is to obtain a dose distribution map in the Alvand tokamak laboratory (35 m × 13 m) and its environment. It has been determined that the maximum absorbed dose on the equatorial plane of the vacuum chamber is approximately 73 mSv/shot for a 3 ms discharge. According to the observations, the occurrence of Z instability in the vertical position of the plasma leads to the concentration of a substantial amount of radiation in an upward conical shell, which reaches up to 250 mSv/shot at a 60-degree angle above the horizontal line. Calculating the amount of radiation attenuation of the concrete shield installed in the vicinity of Alvand tokamak Laboratory, which is about 99.3 % ± 0.35, is an important result from the radiation protection point of view. This result indicates that the dose limit in public area is about background level and this area is effectively protected from the intense radiation of Alvand tokamak by the concrete shield.

Infrared spectroscopy of SWIFT J0850.8−4219: identification of the second red supergiant X-ray binary in the Milky Way

ABSTRACT High-mass X-ray binaries hosting red supergiant (RSG) donors are a rare but crucial phase in massive stellar evolution, with only one source previously known in the Milky Way. In this letter, we present the identification of the second Galactic RSG X-ray binary SWIFT J0850.8−4219. We identify the source 2MASS 08504008−4211514 as the likely infrared counterpart with a chance coincidence probability ≈5 × 10−6. We present a $1.0{\!-\!}2.5\, \mu$m spectrum of the counterpart, exhibiting features characteristic of late-type stars and an exceptionally strong He i emission line, corroborating the identification. Based on i) the strength of the 12CO(2,0) band, ii) strong CN bandheads and absent TiO bandheads at ≈1.1 µm and iii) equivalent width of the Mg i$1.71\, \mu$m line, we classify the counterpart to be a K3–K5 type RSG with an effective temperature of 3820 ± 100 K, located at a distance of ≈12 kpc. We estimate the source X-ray luminosity to be (4 ± 1) × 1035 erg s−1, with a hard photon index (Γ &amp;lt; 1), arguing against a white dwarf accretor but consistent with a magnetized neutron star in the propeller phase. Our results highlight the potential of systematic near-infrared spectroscopy of Galactic hard X-ray sources in completing our census of the local X-ray binary population.

A Reemerging Bright Soft X-Ray State of the Changing-look Active Galactic Nucleus 1ES 1927+654: A Multiwavelength View

1ES1927+654 is a nearby active galactic nucleus (AGN) that has shown an enigmatic outburst in optical/UV followed by X-rays, exhibiting strange variability patterns at timescales of months to years. Here we report the unusual X-ray, UV, and radio variability of the source in its postflare state (2022 January–2023 May). First, we detect an increase in the soft X-ray (0.3–2 keV) flux from 2022 May to 2023 May by almost a factor of 5, which we call the bright soft state. The hard X-ray 2–10 keV flux increased by a factor of 2, while the UV flux density did not show any significant changes (≤30%) in the same period. The integrated energy pumped into the soft and hard X-rays during this period of 11 months is ∼3.57 × 1050 erg and 5.9 × 1049 erg, respectively. From the energetics, it is evident that whatever is producing the soft excess (SE) is pumping out more energy than either the UV or hard X-ray source. Since the energy source presumably is ultimately the accretion of matter onto the supermassive black hole, the SE-emitting region must be receiving the majority of this energy. In addition, the source does not follow the typical disk–corona relation found in AGNs, neither in the initial flare (from 2017 to 2019) nor in the current bright soft state (2022–2023). We found that the core (<1 pc) radio emission at 5 GHz gradually increased until 2022 March, but showed a dip in 2022 August. The Güdel–Benz relation (L radio/L X-ray ∼ 10−5), however, is still within the expected range for radio-quiet AGNs, and further follow-up radio observations are currently being undertaken.

Temporal and Spatial Characteristics of Hard X-Ray Sources in a Flare Model with a Vertical Current Sheet

Abstract We analyzed changes in the height of the coronal hard X-ray (HXR) source for flares SOL2013-05-13T01:50 and SOL2013-05-13T15:51. Analysis of the Reuven Ramaty High Energy Solar Spectroscopic Imager data revealed the downward motion of the HXR source and the separation of the sources by energy and height. In the early stages of the flares, a negative correlation was found between the HXR source area in the corona and HXR flux. For the SOL2013-05-13T15:51 event, an increasing trend in the time delay spectra at the footpoints was obtained. For both events, the spectra of the time delays in the coronal HXR source showed a decreasing trend with energy in certain flare phases. To interpret the observed phenomena, we considered a flare model of collapsing traps and calculated the distribution functions of accelerated electrons along the magnetic loop using a nonstationary relativistic kinetic equation. This approach considers betatron and Fermi first-order acceleration mechanisms. The increasing trend of the time delay spectra at the footpoints was explained by the high mirror ratio in the magnetic loop and betatron acceleration mechanism. The observed features in the spatial and temporal behavior of the HXR sources, such as the negative correlation between the HXR source area and HXR flux, can be interpreted by the collapsing trap model.

Observational Signatures of Electron-driven Chromospheric Evaporation in a White-light Flare

We investigate observational signatures of explosive chromospheric evaporation during a white-light flare (WLF) that occurred on 2022 August 27. Using the moment analysis, bisector techniques, and the Gaussian fitting method, redshifted velocities of less than 20 km s−1 are detected in low-temperature spectral lines of Hα, C i, and Si iv at the conjugated flare kernels, which could be regarded as downflows caused by chromospheric condensation. Blueshifted velocities of ∼30−40 km s−1 are found in the high-temperature line of Fe xxi, which can be interpreted as upflows driven by chromospheric evaporation. A nonthermal hard X-ray (HXR) source is cospatial with one of the flare kernels, and the Doppler velocities are temporally correlated with the HXR fluxes. The nonthermal energy flux is estimated to be at least (1.3 ± 0.2) × 1010 erg s−1 cm−2. The radiation enhancement at Fe i 6569.2 Å and 6173 Å suggests that the flare is a WLF. Moreover, the while-light emission at Fe i 6569.2 Å is temporally and spatially correlated with the blueshift of the Fe xxi line, suggesting that both the white-light enhancement and the chromospheric evaporation are triggered and driven by nonthermal electrons. All of our observations support the scenario of an electron-driven explosive chromospheric evaporation in the WLF.

Digging a little deeper: characterizing three new extreme ULX candidates

ABSTRACT A prime motivation for compiling catalogues of any celestial X-ray source is to increase our numbers of rare subclasses. In this work, we take a recent multimission catalogue of ultraluminous X-ray sources (ULXs) and look for hitherto poorly-studied ULX candidates that are luminous ($L_{\rm X} \ge 10^{40}\,{\rm erg\,s}^{-1}$), bright ($f_{\rm X} \ge 5 \times 10^{-13}\,{\rm erg\,cm}^{-2}\,{\rm s}^{-1}$), and have archival XMM–Newton data. We speculate that this luminosity regime may be ideal for identifying new pulsating ULXs (PULXs), given that the majority of known PULXs reach similar high luminosities. We find three sources that match our criteria and study them using archival data. We find 4XMM J165251.5−591503 to possess a bright and variable Galactic optical/IR counterpart, and so conclude it is very likely to be a foreground interloper. 4XMM J091948.8−121429 does appear to be an excellent ULX candidate associated with the dwarf irregular galaxy PGC 26378, but has only one detection to date with low data quality. The best data set belongs to 4XMM J112054.3+531040 which we find to be a moderately variable, spectrally hard (Γ ≈ 1.4) X-ray source located in a spiral arm of NGC 3631. Its spectral hardness is similar to known PULXs, but no pulsations are detected by accelerated pulsation searches in the available data. We discuss whether other missions provide objects for similar studies and compare this method to others suggested for identifying good PULX candidates.

Direct hard X-ray photodetector with superior sensitivity based on ZnGa2O4 epilayer grown by metalorganic chemical vapor deposition

In this work, we have fabricated a highly sensitive direct irradiating X-ray photodetector (DXPD) based on Zinc Gallium Oxide (ZnGa2O4) epilayers with a metal-semiconductor-metal structure. The ZnGa2O4 epilayers were grown on a c-plane sapphire substrate by metalorganic chemical vapor deposition (MOCVD). To test the DXPD's capabilities, we subjected it to a synchrotron hard X-ray source with an energy of 10 keV, and measured incident radiation flux ranging from 5.7✕107 to 4.6 ✕1011 counts/sec. The effect of changing the applied bias voltage on the time response of the DXPD was investigated. The sensitivity of hard XPDs was compared using gallium oxide (β-Ga2O3) epilayer grown by MOCVD. The results showed that ZnGa2O4 DXPD had approximately 104 times greater sensitivity than the β-Ga2O3 based XPD. ZnGa2O4 based detectors also exhibited remarkable sensitivity of 2.87 × 109 μC Gyair−1cm−2 for the incident flux of 5.7✕107 counts/sec at 15 V. Additionally, the sensitivity was examined in terms of applied bias and dose rate. Based on these observations, it can be concluded that ZnGa2O4 epilayers grown by MOCVD hold immense potential for use in high-performance hard XPDs.

High-Cadence Observations of Magnetic Field Dynamics and Photospheric Emission Sources in the Eruptive Near-the-Limb X4.9 Solar Flare on 25 February, 2014: Evidences for Two-Stage Magnetic Reconnection during the Impulsive Phase

—We present an analysis of the pre-limb eruptive X4.9 solar flare on February 25, 2014, by means of which we confirm a hypothesis of the two-stage energy release corresponding to two magnetic reconnection regimes in the flare impulsive phase. This flare is selected, firstly, because of its morphological peculiarities suggesting the presence of the two energy release stages. Secondly, the flare was very suitably located near the solar limb and it was well-observed by many instruments. We performed an analysis of multiwavelength observational data of this flare region to find a connection between changes of the photospheric magnetic field, morphology of hard and soft X-ray sources, dynamics of the photospheric optical emission sources, metric radio bursts, and kinematics of an eruptive structure. The simultaneous usage of the line-of-sight and vector Helioseismic Magnetic Imager (HMI) magnetograms allowed us to trace magnetic field changes during the flare impulsive phase with high temporal resolution. HMI filtergrams allowed to trace displacement of the photospheric emission sources, associated with the magnetic reconnection, with very high temporal resolution up to 2 s. Using all observational results, we argue that the found flare stages are characterized by the following magnetic reconnection regimes. The first stage is predominantly characterized by the three-dimensional zipping reconnection in the strong sheared magnetic field assuming the tether-cutting geometry. The second stage corresponds to the so-called “standard” model of eruptive flares with the quasi-two-dimensional reconnection below the eruptive flux-rope. All observational peculiarities of these two stages are discussed in details.

Magnetic Reconnection Rate in the M6.5 Solar Flare on 2015 June 22

Magnetic reconnection is regarded as the mechanism for the rapid release of magnetic energy stored in active regions during solar flares, and quantitative measurements of the magnetic reconnection rate are essential for understanding solar flares. In the context of the standard two-ribbon flare model, we derive the coronal magnetic reconnection rate of the M6.5 flare on 2015 June 22 in two terms, reconnection flux change rate and reconnection electric field, both of which can be obtained from observations of the flare morphology. Data used include a sequence of chromospheric Hα images with unprecedented resolution during the flare from the Visual Imaging Spectrometer of the Goode Solar Telescope (GST) at the Big Bear Solar Observatory and a preflare line-of-sight photospheric magnetogram from the GST Near-InfraRed Imaging Spectropolarimeter along with hard X-ray data from the Ramaty High Energy Solar Spectroscopic Imager. The temporal correlation between the magnetic reconnection rate and nonthermal emission is found, and the variation of the reconnection electric field is mainly determined by the ribbon speed, not by the local magnetic field encountered by the ribbon front. Spatially, the hard X-ray source overlaps with the location of the strongest electric field obtained at the same time. The ribbon motion shows abundant fine structures, including a local acceleration at the location of a light bridge with a weaker magnetic field.

Estimation of plasma parameters of X-pinch with time-resolved x-ray spectroscopy

We estimate the parameters of a Cu plasma generated by an X-pinch by comparing experimentally measured x-rays with synthetic data. A filtered absolute extreme ultraviolet diode array is used to measure time-resolved x-ray spectra with a spectral resolution of ∼1 keV in the energy range of 1–10 keV. The synthetic spectra of Cu plasmas with different electron temperatures, electron densities, and fast electron fractions are calculated using the FLYCHK code. For quantitative comparison with the measured spectrum, two x-ray power ratios with three different spectral ranges are calculated. We observe three x-ray bursts in X-pinch experiments with two Cu wires conducted on the SNU X-pinch at a current rise rate of ∼0.2 kA/ns. Analysis of the spectra reveals that the first burst comprises x-rays emitted by hot spots and electron beams, with characteristics similar to those observed in other X-pinches. The second and third bursts are both generated by long-lived electron beams formed after the neck structure has been completely depleted. In the second burst, the formation of the electron beam is accompanied by an increase in the electron density of the background plasma. Therefore, the long-lived electron beams generate the additional strong x-ray bursts while maintaining a plasma channel in the central region of the X-pinch. Moreover, they emit many hard x-rays (HXRs), enabling the SNU X-pinch to be used as an HXR source. This study confirms that the generation of long-lived electron beams is crucial to the dynamics of X-pinches and the generation of strong HXRs.

The Improved X-ray Detector (iXRD) on Sharjah-Sat-1, design principles, tests and ground calibration

The iXRD is the primary science payload on Sharjah-Sat-1, a 3U CubeSat expected to be launched in Q4, 2022. Its main scientific goal is monitoring bright hard X-ray sources and transients in 20 - 200 keV band. The iXRD consists of a CdZnTe crystal (6.45 cm2 area, 5 mm thickness), a Tungsten collimator with square holes with an opening angle of 4.26∘, readout and control electronics and power supply circuitry, a back-shield and mechanical structures. Some of the design elements of iXRD have been inherited from the XRD on BeEagleSat with significant improvements in terms of collecting area, X-ray background and electronic noise. In this article, the design of the iXRD is discussed in detail taking into account mechanical, electronic, control software and data handling aspects. Its expected performance is determined after ground calibration. Depending on the pixel size, the energy resolution is 4 - 7 keV at 60 keV and the minimum detectable energy is 19 - 23 keV.

A catalogue of high-mass X-ray binaries in the Galaxy: from the INTEGRAL to theGaiaera

Context.High-mass X-ray binaries (HMXBs) are a particular class of high-energy sources that require multi-wavelength observational efforts to be properly characterised. New identifications and the refinement of previous measurements are regularly published in the literature by independent teams of researchers and might, when they are collected in a catalogue, offer a tool for facilitating further studies of HMXBs.Aims.We update previous instances of HMXB catalogues in the Galaxy and provide the community easy access to the most complete set of observables on Galactic HMXBs. In addition to the fixed version that is available in Vizier, we also aim to host and maintain a dynamic version that can be updated upon request from users. Any modification will be logged in this version.Methods.Using previous HMXB catalogues supplemented by listings of hard X-ray sources detected in the past 20 yr, we produced a base set of HMXBs and candidates by means of identifier and sky coordinate cross matches. We queried in Simbad for unreferenced HMXBs. We searched for as many hard X-ray, soft X-ray, optical, and infrared counterparts to the HMXBs as we could in well-known catalogues and compiled their coordinates. Each HMXB was subjected to a meticulous search in the literature to find relevant measurements and the original reference.Results.We provide a catalogue of 152 HMXBs in the Galaxy with their best known coordinates, the spectral type of the companion star, systemic radial velocities, component masses, orbital period, eccentricity, and spin period when available. We also provide the coordinates and identifiers for each counterpart we found from hard X-rays to the near-infrared, including 111 counterparts from the recentGaiaDR3 catalogue.

A multifrequency characterization of the extragalactic hard X-ray sky

Context. Nowadays, we know that the origin of the cosmic X-ray background (CXB) is mainly due to the integrated emission of active galactic nuclei. Therefore, in order to obtain a precise estimate of the contribution of different source classes to the CXB, it is crucial to achieve full characterization of the hard-X ray sky. Aims. We present a multifrequency analysis of all sources listed in the third release of the Palermo Swift-BAT hard X-ray catalog (3PBC) with the goal of (i) identifying and classifying the largest number of sources adopting multifrequency criteria, with particular emphasis on extragalactic populations and (ii) extracting sources belonging to the class of Seyfert galaxies to present here the release of the second version of the Turin-SyCAT. Methods. We outline a classification scheme based on radio, infrared (IR), and optical criteria that allows us to distinguish between unidentified and unclassified hard X-ray sources, as well as to classify those sources belonging to the Galactic and the extragalactic populations. Results. Our revised version of the 3PBC lists 1176 classified, 820 extragalactic, and 356 Galactic sources, as well as 199 unclassified and 218 unidentified sources. According to our analysis, the hard X-ray sky is mainly populated by Seyfert galaxies and blazars. For the blazar population, we report trends between the hard X-ray and the gamma-ray emissions based on the fact that a large fraction of them also have a counterpart detected by the Fermi satellite. These trends are all in agreement with the expectations of inverse Compton models which are widely adopted to explain the blazar broadband emission. For the Seyfert galaxies, we present the second version of the Turin-SyCAT, including a total of 633 Seyfert galaxies, with 282 new sources corresponding to an increase of ~80% with respect to the previous release. Comparing the hard X-ray and the infrared emissions of Seyfert galaxies, we confirm that there is no clear difference between the flux distribution of the infrared-to-hard X-ray flux ratio of Seyfert galaxies Type 1 and Type 2. However, there is a significant trend between the mid-IR flux and hard X-ray flux, confirming previous statistical results in the literature. Conclusions. We provide two catalog tables. The first is the revised version of the 3PBC catalog based on our multifrequency analyses. The second catalog table is a release of the second version of the Turin-SyCAT catalog. Finally, we highlight that extensive soft X-ray data are already available in the form of the Swift archive which can be used to search for potential counterparts of unidentified hard X-ray sources. All these datasets will be reduced and analyzed in a forthcoming analysis to determine the precise position of low-energy counterparts in the 0.5–10 keV energy range for 3PBC sources that can be targets of future optical spectroscopic campaigns; this is necessary to obtain their precise classification.

Observations of Magnetic Reconnection and Particle Acceleration Locations in Solar Coronal Jets

We present a multiwavelength analysis of two flare-related jets on 2014 November 13, using data from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA), the Reuven High Energy Solar Spectroscopic Imager (RHESSI), the Hinode/X-ray Telescope (XRT), and the Interface Region Imaging Spectrograph (IRIS). Unlike most coronal jets, where hard X-ray (HXR) emissions are usually observed near the jet base, in these events HXR emissions are found at several locations, including in the corona. We carry out the first differential emission measure analysis that combines both AIA (and XRT, when available) bandpass filter data and RHESSI HXR measurements for coronal jets, and obtain self-consistent results across a wide temperature range and into nonthermal energies. In both events, hot plasma first appears at the jet base, but as the base plasma gradually cools, hot plasma also appears near the jet top. Moreover, nonthermal electrons, while only mildly energetic, are found in multiple HXR locations and contain large amounts of total energy. In particular, the energetic electrons that produce the HXR sources at the jet top are accelerated near the top location, rather than traveling from a reconnection site at the jet base. This means that there is more than one particle acceleration site in each event. Jet velocities are consistent with previous studies, including the upward and downward velocities around ∼200 km s−1 and ∼100 km s−1, respectively, and fast outflows of 400–700 km s−1. We also examine the energy partition in the later event, and find that the nonthermal energy in the accelerated electrons is most significant compared to the other energy forms considered. We discuss the interpretations and provide constraints on the mechanisms for coronal jet formation.

Solar flare hard X-rays from the anchor points of an eruptive filament

Context.We present an analysis of a GOES M1.8 flare with excellent observational coverage in UV, extreme-UV (EUV), and X-ray, including observations from the Interface Region Imaging Spectrograph (IRIS), from the Solar Dynamics Observatory (SDO) with the Atmospheric Imaging Assembly (AIA), from the Hinode/EUV Imaging Spectrometer (EIS), from the Hinode/X-ray Telescope (XRT), and from Solar Orbiter with the Spectrometer/Telescope for Imaging X-rays (STIX). Hard X-ray emission is often observed at the footpoints of flare loops and is occasionally observed in the corona. In this flare, four nonthermal hard X-ray sources are seen.Aims.Our aim is to understand why we can observe four individual nonthermal sources in this flare and how we can characterize the physical properties of these four sources.Methods.We used the multiwavelength approach to analyze the flare and characterize the four sources. To do this, we combined imaging at different wavelengths and spectroscopic fitting in the EUV and X-ray range.Results.The flare is eruptive with an associated coronal mass ejection, and it shows the classical flare picture of a heated flare loop seen in EUV and X-rays, and two nonthermal hard X-ray footpoints at the loop ends. In addition to the main flare sources, we observed two outer sources in the UV, EUV, and nonthermal X-ray range located away from the main flare loop to the east and west. The two outer sources are clearly correlated in time, and they are only seen during the first two minutes of the impulsive phase, which lasts a total of about four minutes.Conclusions.Based on the analysis, we determine that the outer sources are the anchor points of an erupting filament. The hard X-ray emission is interpreted as flare-accelerated electrons that are injected upward into the filament and then precipitate along the filament toward the chromosphere, producing Bremsstrahlung. While sources like this have been speculated to exist, this is the first report of their detection.

New Active Galactic Nuclei Detected by the ART-XС and eROSITA Telescopes during the First Five SRG All-Sky X-ray Surveys

We present the results of our identification of 14 X-ray sources detected in the eastern Galactic sky ( $$0^{\circ}<l<180^{\circ}$$ ) in the 4–12 keV energy band on the combined map of the first five all-sky surveys (from December 2019 to March 2022) with the Mikhail Pavlinsky ART-XC telescope onboard the SRG observatory. All 14 sources are reliably detected by the SRG/eROSITA telescope in the 0.2–8 keV energy band. Six of them have been detected in X-rays for the first time, while the remaining ones have already been known previously as X-ray sources, but their nature has remained unknown. We have taken optical spectra for 12 sources with the 1.6-m AZT-33IK telescope at the Sayan Observatory (the Institute of Solar–Terrestrial Physics, the Siberian Branch of the Russian Academy of Sciences). For two more objects we have analyzed the archival spectra taken during the 6dF survey. All objects have turned out to be Seyfert galaxies (one NLSy1, three Sy1, four Sy1.9, and six Sy2) at redshifts $$z=0.015$$ –0.238. Based on data from the eROSITA and ART-XC telescopes onboard the SRG observatory, we have obtained X-ray spectra for all objects in the energy range 0.2–12 keV. In four of them the intrinsic absorption exceeds $$N_{\textrm{H}}>10^{22}$$ cm $${}^{-2}$$ at a 90 $${\%}$$ confidence level, with one of them being probably heavily obscured ( $$N_{\textrm{H}}>5\times 10^{22}$$ cm $${}^{-2}$$ with 90 $${\%}$$ confidence). This paper continues our series of publications on the identification of hard X-ray sources detected during the all-sky survey with the SRG orbital X-ray observatory.