Related papers: Quiet Sun impulsive events observed with NuSTAR du…

We present new constraints on the high-temperature emission measure of a non-flaring solar active region using observations from the recently flown Focusing Optics X-ray Solar Imager sounding rocket payload. FOXSI has performed the first…

Solar Orbiter EUV observations reveal ubiquitous small-scale brightenings in the quiet-Sun low corona. We analyze the spatial and temporal dissipation scales of these events with a focus on the formation, evolution, and dissipation of…

The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing hard X-ray mission in orbit and operates in the 3-79 keV range. NuSTAR's sensitivity is roughly two orders of magnitude better than previous missions in this energy…

Radio emission of the quiet Sun is considered to be due to thermal bremsstrahlung emission of the hot solar atmosphere. The properties of the quiet Sun in the microwave band have been well studied, and they can be well described by the…

We present analysis of a GOES C1-class flare from 2022 September 6, which was jointly observed as occulted by Nuclear Spectroscopic Telescope ARray (NuSTAR) and on-disk by Spectrometer/Telescope for Imaging X-rays (STIX). NuSTAR observed…

The neutron star low-mass X-ray binary SWIFT J1749.4-2807 is the only known eclipsing accreting millisecond X-ray pulsar. In this manuscript we perform a spectral characterization of the system throughout its 2021, two-week-long outburst,…

We report on our investigation of the NuSTAR and AstroSat observations along with simultaneous NICER observations of the accreting millisecond X-ray pulsar SAX J1808.4$-$3658, obtained during its tenth outburst from 2022. The NuSTAR…

Turbulent properties of the quiet Sun represent the basic state of surface conditions, and a background for various processes of solar activity. Therefore understanding of properties and dynamics of this `basic' state is important for…

We present a hard X-ray NuSTAR observation of PSR J0437-4715, the nearest millisecond pulsar. The known pulsations at the apparent pulse period ~5.76 ms are detected at energies up to 20 keV. We measure a photon index $\Gamma= 1.65\pm0.24$…

The Neupert effect refers to the strong correlation between the soft X-ray (SXR) light curve and the time-integrated hard X-rays (HXR) or microwave flux, which is frequently observed in solar flares. In this article, we therefore utilized…

X-ray emission from AGN is believed to be produced via Comptonization of optical/UV seed photons emitted by the accretion disk, up-scattered by hot electrons in a corona surrounding the black hole. A critical compactness vs. temperature…

Nuclear reactions occurring deep in the crust of a transiently accreting neutron star efficiently maintain the core at a temperature >5e7 K. When accretion halts, the envelope relaxes to a thermal equilibrium set by the flux from the hot…

Small-scale eruptions could play an important role in coronal heating, generation of solar energetic particles (SEPs), and mass source of the solar wind. However, they are poorly observed, and their characteristics, distributions, and…

Minifilament (MF) eruption producing small jets and micro-flares is regarded as an important source for coronal heating and the solar wind transients through studies mostly based on coronal observations in the extreme ultraviolet (EUV) and…

New Swift monitoring observations of the variable, radio-quiet quasar, PDS 456, are presented. A bright X-ray flare was captured in September 2018, the flux increasing by a factor of 4 and with a doubling time-scale of 2 days. From the…

The Miniature X-ray Solar Spectrometer (MinXSS-1) CubeSat observed solar X-rays between 0.5 and 10 keV. A two-temperature, two-emission measure model is fit to each daily averaged spectrum. These daily average temperatures and emission…

The heating of the solar corona is one of the big questions in astrophysics. Rapid pulses called nanoflares are among the best candidate mechanisms. The analysis of the time variability of coronal X-ray emission is potentially a very useful…

Ground- and space-based observations of solar flares from radio wavelengths to gamma-rays have produced considerable insights but raised several unsolved controversies. The last unexplored wavelength frontier for solar flares is in the…

Solar neutrino flares and mixing are considered. Most power-full solar flare as the ones occurred on 23th February 1956, September 29th 1989, 28th October and on 2nd-4th November 2003 are sources of cosmic rays, X, gamma and neutrino…

(Abridged). The type-I X-ray bursting low mass X-ray binary KS 1731-260 was recently detected for the first time in quiescence by Wijnands et al., following an approximately 13 yr outburst which ended in Feb 2001. Unlike all other known…