Strong Flares Research Articles

Quasi-periodic Oscillation of Blazar PKS 1424–418 in γ-Ray Band

We perform the quasi-periodic oscillation (QPO) analysis of blazar PKS 1424−418 in the γ-ray (0.1–300 GeV) band from 2009 May 12 to 2019 September 17 (MJD 54963−58743). Using the spectral domain methods, Bhatta & Dhital reported that this source has 353 days periodic flux oscillations in the γ-ray flux. Adopting time domain methods, we confirm the previous detection that a possible γ-ray QPO of ∼355 days with the high significance level. Combining two methods of time domain and spectral domain provides stronger evidence for the existence of the QPO. Especially, after the strongest flare, γ-ray light-curve exhibits stronger periodic significance compared with the whole observation period. Assuming that the QPO is come from the orbital motion in a supermassive binary black hole system, the mass of primary black hole for this source is estimate as M ∼ 3.5 × 108–5.5 × 109 M ⊙.

Simulations of Switchback, Fragmentation and Sunspot Pair in δ-Sunspots during Magnetic Flux Emergence.

Strong flares and coronal mass ejections (CMEs), launched from -sunspots, are the most catastrophic energy-releasing events in the solar system. The formations of -sunspots and relevant polarity inversion lines (PILs) are crucial for the understanding of flare eruptions and CMEs. In this work, the kink-stable, spot-spot-type -sunspots induced by flux emergence are simulated, under different subphotospheric initial conditions of magnetic field strength, radius, twist, and depth. The time evolution of various plasma variables of the -sunspots are simulated and compared with the observation data, including magnetic bipolar structures, relevant PILs, and temperature. The simulation results show that magnetic polarities display switchbacks at a certain stage and then split into numerous fragments. The simulated fragmentation phenomenon in some -sunspots may provide leads for future observations in the field.

Prediction of the amplitude of solar cycle 25 using polar faculae observations

Based on the monthly number of polar faculae, a forecast of the amplitude of solar cycle 25 (SC25) is provided, as well as a prediction of the number of solar flares. Faculae near both solar poles have been visually observed using a commercial off-the-shelf 20 cm Schmidt-Cassegrain telescope since 1995. The monthly averages were corrected for varying seeing conditions and the heliographic latitude of the center of the solar diskB0. From the deduced relationship between the smoothed number of monthly polar faculae during the solar cycle minimum, and the subsequent maximum of the monthly sunspot number, a prediction has been made for the amplitude of the next solar cycle. The methodology used can be considered as a precursor technique. The expected number of M- and X-class flares was calculated based on a statistical approach. The maximum of SC25 is predicted to be 118 ± 29, of similar strength than the previous SC24. Also the number of M5 or stronger flares is expected to be comparable to that of the previous solar cycle.

Evolution of OH Maser Emission in the Active Star-Forming Region W75N. I. Research in the 1665 MHz Line

The monitoring results of the OH maser source in W75 N in the main line at 1665 MHz performed in 2007–2020 using the Nancay Radio Telescope (France) are presented. Generally, the maser in 2007–2009 is characterized by a high activity. During the monitoring, time variations of the Stokes parameters were found for all spectral features in the radial velocity range from –1 to 14 km/s. We found that its positional angle $$\chi $$ and the degree of linear polarization $${{m}_{{\text{L}}}}$$ , as well as the degree of circular polarization $${{m}_{{\text{C}}}}$$ of most features, change with time according to certain regularities, not chaotically. Or they can change very weakly and there is a correlation with the variability of the flux density. In this case, the radial velocities of the features change very little. It is shown that the main feature at 12 km/s during 50 years since the discovery of the OH maser in W75 N had two maxima of activity with an interval of about 30 years between them. The identification of spectral features in the 1665 MHz line with maser spots on VLBA maps has been carried out. We showed that a strong flare of the main features in 2007–2009 occurred in the VLA 2 source. During this flare, small changes in the angle $$\chi $$ and significant changes in the degree of both linear and circular polarization of features at 1.75, 2.1, and 3.05 km/s were observed. For the 0.65 km/s feature, significant changes in all emission parameters were observed. The emission in the 1612 MHz satellite line is broadband. The broadening of the line to 1.9 km/s indicates that, in addition to thermal motion of matter, there is also turbulent motion of matter in the medium.

Thermal-nonthermal energy partition in solar flares derived from X-ray, EUV, and bolometric observations

Context.In solar flares, energy is released impulsively and is partly converted into thermal energy of hot plasmas and kinetic energy of accelerated nonthermal particles. It is crucial to constrain the partition of these two energy components to understand energy release and transport as well as particle acceleration in solar flares. Despite numerous efforts, no consensus on quantifying this energy balance has yet been reached.Aims.We aim to understand the reasons for the contradicting results on energy partition obtained by various recent studies. The overarching question we address is whether there is sufficient energy in nonthermal particles to account for the thermal flare component.Methods.We considered five recent studies that address the thermal-nonthermal energy partition in solar flares. Their results are reviewed, and their methods are compared and discussed in detail.Results.The main uncertainties in deriving the energy partition are identified as (a) the derivation of the differential emission measure distribution and (b) the role of the conductive energy loss for the thermal component, as well as (c) the determination of the low-energy cutoff for the injected electrons. The bolometric radiated energy, as a proxy for the total energy released in the flare, is a useful independent constraint on both thermal and nonthermal energetics. In most of the cases, the derived energetics are consistent with this constraint. There are indications that the thermal-nonthermal energy partition changes with flare strength: in weak flares, there appears to be a deficit of energetic electrons, while the injected nonthermal energy is sufficient to account for the thermal component in strong flares. This behavior is identified as the main cause of the dissimilar results in the studies we considered. The changing partition has two important consequences: (a) an additional direct (i.e. non-beam) heating mechanism has to be present, and (b) considering that the bolometric emission originates mainly from deeper atmospheric layers, conduction or waves are required as additional energy transport mechanisms.

Space weather and earthquakes: possible triggering of seismic activity by strong solar flares

The studies completed to-date on a relation of the Earth’s seismicity and solar processes provided the fuzzy and contradictory results. The main problem of this research is a lack of physical explanation of a mechanism of earthquake triggering by strong variations of space weather conditions. Based on results obtained in the field and laboratory experiments on earthquake triggering by DC pulses injection into the Earth crust we may assume that the similar triggering phenomena may occur after the strong electromagnetic impact to the earthquake source due to solar flares or geomagnetic storms. Numerical estimations demonstrated that telluric currents induced by geomagnetic pulsations generated by solar flare have the similar density at the depth of earthquake source location (10-6 A/m2) in comparison with the current density generated by artificial power sources (10-7 – 10-8 A/m2) resulted in observed spatiotemporal redistribution of seismic activity in the regions of Pamirs and Northern Tien Shan. For supporting the idea of a possible earthquake triggering by solar flares we carried out a statistical analysis of global and regional (Greece) seismicity behavior during the solar flare of X9.3 class occurred on September 6, 2017 (the strongest flare over the past thirteen years). We have discovered a new evidence of earthquake triggering due to the Sun-Earth interaction by simple comparison of a number of earthquakes before and after the strong solar flare. The global number of earthquakes (USGS catalog, M ≥ 4) for time window of ±11 days after the solar flare has increased by 68%, and the regional seismicity (Greece, EMSC catalog, M ≥ 3) has increased by 120%.

Is OJ 287 a Single Supermassive Black Hole?

Light curves for more than century optical photometric observations of the blazar OJ 287 reveals strong flares with a quasi-period of about 12 years. For a long time, this period has been interpreted by processes in a binary black hole system. We propose an alternative explanation for this period, which is based on Doppler factor periodic variations of the emitting region caused by jet helicity. Using multi-epoch very large baseline interferometry (VLBI) observations carried out in a framework of the MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) program and other VLBA (Very Long Baseline Array) archival experiments at the observing frequency of 15 GHz, we derived geometrical parameters of the jet helix. To reach an agreement between the VLBI and photometric optical observation data, the jet component motion at a small angle to the radial direction is necessary. Such non-radial motion is observed and, together with the jet helical shape, can be naturally explained by the development of the Kelvin–Helmholtz instability in the parsec-scale outflow. In this case, the true precession of the OJ 287 jet may manifest itself in differences between the peak flux values of the 12-year optical flares. A possibility to create this precession due to Lense–Thirring effect of a single supermassive black hole is also discussed.

Comprehensive Analysis of Magnetospheric Gaps around Kerr Black Holes Using 1D GRPIC Simulations

Abstract Spark gaps are likely the source of plasma in active black hole (BH) magnetospheres. In this paper, we present results of 1D general relativistic particle-in-cell simulations of a starved BH magnetosphere with a realistic treatment of inverse-Compton scattering and pair production, for a broad range of conditions, run times longer than in previous studies, and different setups. We find that following the initial discharge, the system undergoes gradual evolution over prolonged time until either restoring the vacuum state or reaching a state of quasiperiodic oscillations, depending on the spectral shape and luminosity of the ambient radiation field. The oscillations occur near the null charge surface in cases where the global magnetospheric current is in the direction defined by the product of the asymptotic Goldreich–Julian charge density and the radial velocity, while they occur near the boundary of the simulation box when it is the opposite direction (return current). Their amplitude and the resultant luminosity of TeV photons emitted from the gap depend sensitively on the conditions; for the cases studied here the ratio of TeV luminosity to the Blandford–Znajek power ranges from 10−5 to 10−2, suggesting that strong flares may be generated by moderate changes in disk emission. We also examined the dependence of the solution on the initial number of particles per cell (PPC) and found convergence for PPC of about 50 for the cases examined. At lower PPC values the pair multiplicity is found to be artificially high, affecting the solution considerably.

Predicting >10 MeV SEP Events from Solar Flare and Radio Burst Data

The prediction of solar energetic particle (SEP) events or solar radiation storms is one of the most important problems in the space weather field. These events may have adverse effects on technology infrastructures and humans in space; they may also irradiate passengers and flight crews in commercial aircraft flying at polar latitudes. This paper explores the use of ≥ M2 solar flares and radio burst observations as proxies for predicting >10 MeV SEP events on Earth. These observations are manifestations of the parent event at the sun associated with the SEP event. As a consequence of processing data at the beginning of the physical process that leads to the radiation storm, the model may provide its predictions with large anticipation. The main advantage of the present approach is that the model analyzes solar data that are updated every 30 min and, as such, it may be operational; however, a disadvantage is that those SEP events associated with strong well-connected flares cannot be predicted. For the period from November 1997 to February 2014, we obtained a probability of detection of 70.2%, a false alarm ratio of 40.2%, and an average anticipation time of 9 h 52 min. In this study, the prediction model was built using decision trees, an interpretable machine learning technique. This approach leads to outputs and results comparable to those derived by the Empirical model for Solar Proton Event Real Time Alert (ESPERTA) model. The obtained decision tree shows that the best criteria to differentiate pre-SEP scenarios and non-pre-SEP scenarios are the peak and integrated flux for soft X-ray flares and the radio type III bursts.

Exploring the Origin of Multiwavelength Emission from High-Redshift Blazar B3 1343 + 451

B3 1343 + 451 is a distant ( z = 2.534 ) and bright flat-spectrum radio quasar observed in the γ -ray band. The results from the multiwavelength observations of B3 1343 + 451 with Fermi-LAT and Swift are reported. In the γ -ray band, strong flares were observed on 05 December 2011 and on 13 December 2009 when the flux increased up to (8.78 ± 0.83)·10-7 photon cm-2 s-1. The hardest photon index Γ = 1.73 ± 0.24 has been observed on MJD 58089 which is not common for flat-spectrum radio quasars. The analysis of Swift XRT data shows that in 2014 the X-ray flux of the source increased ~2 times as compared to 2009, but in both periods the X-ray emission is characterized by a hard photon index of ΓX-ray = 1.2–1.3. During the γ -ray flares, the shortest flux halving timescale was ~2.34 days, implying the emission had been produced in a very compact region, R ≤ δ ct /(1 + z) = 3.43·1016 cm (when δ = 20 ). The spectral energy distribution of B3 1343 + 451 is modeled during the quiescent and flaring periods assuming a compact emitting region outside the BLR. It is found that the flares can be explained by only changing the bulk Lorentz factor of the emitting region without significant modification of the emitting electron parameters and luminosity of the jet.

High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare

Context. We present a ~130 ks observation of the prototypical wind-accreting, high-mass X-ray binary Vela X-1 collected with XMM-Newton at orbital phases between 0.12 and 0.28. A strong flare took place during the observation that allows us to investigate the reaction of the clumpy stellar wind to the increased X-ray irradiation. Aims. To examine the wind’s reaction to the flare, we performed both time-averaged and time-resolved analyses of the RGS spectrum and examined potential spectral changes. Methods. We focused on the high-resolution XMM-Newton RGS spectra and divided the observation into pre-flare, flare, and post-flare phases. We modeled the time-averaged and time-resolved spectra with phenomenological components and with the self-consistent photoionization models calculated via CLOUDY and XSTAR in the pre-flare phase, where strong emission lines due to resonant transitions of highly ionized ions are seen. Results. In the spectra, we find emission lines corresponding to K-shell transitions in highly charged ions of oxygen, neon, magnesium, and silicon as well as radiative recombination continua (RRC) of oxygen. Additionally, we observe potential absorption lines of magnesium at a lower ionization stage and features identified as iron L lines. The CLOUDY and XSTAR photoionization models provide contradictory results, either pointing towards uncertainties in theory or possibly a more complex multi-phase plasma, or both. Conclusions. We are able to demonstrate the existence of a plethora of variable narrow features, including the firm detection of oxygen lines and RRC that RGS enables to observe in this source for the first time. We show that Vela X-1 is an ideal source for future high-resolution missions, such as XRISM and Athena.

Solar Gamma-Ray Flares and Activity Complexes

Strong flare events with an extended phase of gamma ray emission from the catalog by Share et al. have been analyzed in order to explain the characteristics of the impulsive and extended phases of such flares and reveal their connection with activity complexes and coronal holes. It is shown that 74% of such events are closely related to activity complexes. It has been qualitatively demonstrated that the particle acceleration processes during the flare development are associated with the changes in the magnetic topology of the flare region and the evolution of the coronal mass ejection. The possible relation of coronal holes to activity complexes and the role of “exchange” reconnection in these processes are discussed.

Ionospheric disturbances in a large area of the terrestrial globe by two strong solar flares of September 6, 2017, the strongest space weather events in the last decade

On September 6, 2017, the solar active region AR 2673 emitted two solar flares: the first at 08:57 UT (X2.2) and the second at 11:53 UT (X9.3); both were powerful enough to black-out high and low frequency radio waves (where UT is universal time). The X9.3 was the strongest solar flare event in the past decade. In this study, we took the advantage of these two extreme flare events to investigate corresponding effects on the ionosphere using multi-instrument observations from magnetometers, Global Positioning System – Total Electron content (GPS-TEC) receivers, ionosondes and Swarm satellites over a large geographical extent covering South American, African and European sectors. During the X2.2 flare, European and African sectors were sunlit and during X9.3 European, African, and South American sectors were sunlit and exposed to the solar flare radiation. During the X2.2 flare, there was an ionosonde blackout for a duration of about 45 min, while during the X9.3 flare this blackout lasted for 1 h and 30 min. The blackout are seen over a large global extent which demonstrates the severity of solar flare events in disrupting the radio communication. The horizontal component of Earth’s geomagnetic field has shown ripples and enhancements during these flare events. The ionospheric Vertical Total Electron Content (VTEC) showed a positive phase along with an intensification of the Equatorial Ionization Anomaly (EIA) over the South American and African sectors. The dynamical and physical processes associated with the TEC and EIA variabilities due to solar flare are discussed.

Evolution of OH and H2O Maser Emission in the Active Star Formation Region NGC 2071

We present the observation results of the star forming region NGC 2071 in the 1.35-cm H2O line and 18-cm OH lines obtained with the 22-m radio telescope in Pushchino (Russia) and the large radio telescope in Nancay (France), respectively. The catalog of H2O maser emission spectra from December 2010 to January 2020 is given. The total flux variability for the entire monitoring period (1979–2020) has two activity cycles of close duration (approximately 20 years), which were accompanied by strong flares at intervals of one to four years. It is shown that the medium for the generation of H2O maser emission is greatly fragmented and contains small-scale turbulent motions of matter. The observed drift and radial velocity jumps of the H2O emission features can be a consequence of the complex, inhomogeneous structure of the maser emission regions. OH emission in the 1665 and 1667 MHz main lines and in the 1612 MHz satellite line in the radial velocity range of 7–12 km/s is broadband. The ratio of intensities differs from equilibrium. The substantiation of the observed ratio between the intensities of this emission and absorption in the 1720 MHz line is given. OH maser emission was observed in 2007 in the left circular polarization in the 1667 MHz line at 13.02 and 13.55 km/s with a flux density of ~0.3 Jy and a width of ~0.25 km/s for each of the velocities.

Influence of the Sun-like magnetic cycle on exoplanetary atmospheric escape

ABSTRACT Stellar high-energy radiation (X-ray and extreme ultraviolet, XUV) drives atmospheric escape in close-in exoplanets. Given that stellar irradiation depends on the stellar magnetism and that stars have magnetic cycles, we investigate how cycles affect the evolution of exoplanetary atmospheric escape. First, we consider a hypothetical HD209458b-like planet orbiting the Sun. For that, we implement the observed solar XUV radiation available over one and a half solar cycles in a 1D hydrodynamic escape model of HD209458b. We find that atmospheric escape rates show a cyclic variation (from 7.6 to 18.5 × 1010 g s−1), almost proportional to the incident stellar radiation. To compare this with observations, we compute spectroscopic transits in two hydrogen lines. We find non-detectable cyclic variations in Ly α transits. Given the temperature sensitiveness of the H α line, its equivalent width has an amplitude of 1.9 mÅ variation over the cycle, which could be detectable in exoplanets such as HD209458b. We demonstrate that the XUV flux is linearly proportional to the magnetic flux during the solar cycle. Secondly, we apply this relation to derive the cyclic evolution of the XUV flux of HD189733 using the star’s available magnetic flux observations from Zeeman Doppler Imaging over nearly a decade. The XUV fluxes are then used to model escape in HD189733b, which shows escape rate varying from 2.8 to 6.5 × 1010 g s−1. Like in the HD209458b case, this introduces variations in Ly α and H α transits, with H α variations more likely to be observable. Finally, we show that a strong stellar flare would enhance significantly Ly α and H α transit depths.

EvryFlare. II. Rotation Periods of the Cool Flare Stars in TESS across Half the Southern Sky

Abstract We measure rotation periods and sinusoidal amplitudes in Evryscope light curves for 122 two-minute K5–M4 TESS targets selected for strong flaring. The Evryscope array of telescopes has observed all bright nearby stars in the south, producing 2-minute cadence light curves since 2016. Long-term, high-cadence observations of rotating flare stars probe the complex relationship between stellar rotation, starspots, and superflares. We detect periods from 0.3487 to 104 days and observe amplitudes from 0.008 to 0.216 g′ mag. We find that the Evryscope amplitudes are larger than those in TESS with the effect correlated to stellar mass (p-value = 0.01). We compute the Rossby number (R o ) and find that our sample selected for flaring has twice as many intermediate rotators (0.04 < R o < 0.4) as fast (R o < 0.04) or slow (R o > 0.44) rotators; this may be astrophysical or a result of period detection sensitivity. We discover 30 fast, 59 intermediate, and 33 slow rotators. We measure a median starspot coverage of 13% of the stellar hemisphere and constrain the minimum magnetic field strength consistent with our flare energies and spot coverage to be 500 G, with later-type stars exhibiting lower values than earlier-type stars. We observe a possible change in superflare rates at intermediate periods. However, we do not conclusively confirm the increased activity of intermediate rotators seen in previous studies. We split all rotators at R o ∼ 0.2 into bins of P Rot < 10 days and P Rot > 10 days to confirm that short-period rotators exhibit higher superflare rates, larger flare energies, and higher starspot coverage than do long-period rotators, at p-values of 3.2 × 10−5, 1.0 × 10−5, and 0.01, respectively.

Low Geo‐Effectiveness of Fast Halo CMEs Related to the 12 X‐Class Flares in 2002

AbstractIt is generally accepted that extreme space weather events tend to be related to strong flares and fast halo coronal mass ejections (CMEs). In the present paper, we carefully identify the chain of events from the Sun to the Earth induced by all 12 X‐class flares that occurred in 2002. In this small sample, we find an unusual high rate (58%) of solar sources with a longitude larger than 74°. Yet all 12 X‐class flares are associated with at least one CME. The fast halo CMEs (50%) are related to interplanetary CMEs (ICMEs) at L1 and weak Dst minimum values (more than −51 nT), while five (41%) of the 12 X‐class flares are related to solar proton events (SPEs).We conclude that (i) all 12 analyzed solar events, even those associated with fast halo CMEs originating from the central disk region, and those ICMEs and SPEs were not very geo‐effective. This unexpected result demonstrates that the suggested events in the chain (fast halo CME, X‐class flares, central disk region, ICME, and SPE) are not infallible proxies for geo‐effectiveness. (ii) The low value of integrated and normalized southward component of the interplanetary magnetic field ( ) may explain the low geo‐effectiveness for this small sample. In fact, is well correlated to the weak Dst and low auroral electrojet activity. Hence, the only space weather impact at Earth in 2002 we can explain is based on at L1.

Nowcast of an EUV dynamic spectrum during solar flares

In addition to X-rays, extreme ultraviolet (EUV) rays radiated from solar flares can cause serious problems, such as communication failures and satellite drag. Therefore, methods for forecasting EUV dynamic spectra during flares are urgently required. Recently, however, owing to the lack of instruments, EUV dynamic spectra have rarely been observed. Hence, we develop a new method that converts the soft X-ray light curve observed during large flare events into an EUV dynamic spectrum by using the Solar Dynamics Observatory/Atmospheric Imaging Assembly images, a numerical simulation, and atomic database. The simulation provides the solution for a coronal loop that is heated by a strong flare, and the atomic database calculates its dynamic spectrum, including X-ray and EUV irradiances. The coefficients needed for the conversion can be calculated by comparing the observed soft X-ray light curve with that of the simulation. We apply our new method to three flares that occurred in the active region 12673 on September 06, 2017. The results show similarities to those of the Flare Irradiance Spectral Model, and reconstruct some of the EUV peaks observed by the EUV Variability Experiment onboard the Solar Dynamics Observatory.

Predicting Solar Flares with Machine Learning: Investigating Solar Cycle Dependence

Abstract A deep learning network, long short-term memory (LSTM), is used to predict whether an active region (AR) will produce a flare of class Γ in the next 24 hr. We consider Γ to be ≥M (strong flare), ≥C (medium flare), and ≥A (any flare) class. The essence of using LSTM, which is a recurrent neural network, is its ability to capture temporal information on the data samples. The input features are time sequences of 20 magnetic parameters from the space weather Helioseismic and Magnetic Imager AR patches. We analyze ARs from 2010 June to 2018 December and their associated flares identified in the Geostationary Operational Environmental Satellite X-ray flare catalogs. Our results produce skill scores consistent with recently published results using LSTMs and are better than the previous results using a single time input. The skill scores from the model show statistically significant variation when different years of data are chosen for training and testing. In particular, 2015–2018 have better true skill statistic and Heidke skill scores for predicting ≥C medium flares than 2011–2014, when the difference in flare occurrence rates is properly taken into account.

The swift observations of distant high-energy peaked BL Lacertae objects

In this paper, we present the timing and spectral results for the seven distant and poorly investigated BL Lacertae sources with redshifts $z\gtrsim 0.5$, using the archival data obtained with the Swift and other multifrequency instruments during 2006 August–2015 July. Our timing study has revealed a number of the 0.3–10 keV flux changes from the fluctuations observed within one day to the variabilities on timescales of a few months. Namely, the relatively densely-sampled observations of BZB J1517+6525 showed a strong X-ray flare by a factor of ∼5 during 2014 September-December. While this instance can be explained by the propagation of shock wave though the blazar jet which causes a strong heat-up of the relativistic plasma, the lower-amplitude flux fluctuations observed in higher X-ray states could be related to the interaction between the shock front and jet inhomogeneities. The curved 0.3–10 keV spectra showed the ranges of the photon index at 1 keV $a=1.27$(0.10)–2.30(0.09), curvature parameter $b = 0.12$(0.08)–1.19(0.27), synchrotron SED peak position $E_{p} = 0.49$(0.09)–3.39(0.97) keV, while some spectra do not exhibit spectral curvature and fit well with a simple power law model yielding the 0.3–10 keV photon-index $\Gamma =1.48$(0.15)–2.32(0.08). Large spectral curvatures observed for the majority of the log-parabolic spectra hint at the importance of the second-order Fermi mechanism for our targets. Our targets show very high isotropic luminosity $L_{0.3\text{--}10~\text{keV}}\sim 10^{46}~\mbox{erg}\,\mbox{s}^{-1}$ compared to the nearby bright BL Lacertae objects.