Related papers: Coronal Temperature as an Age Indicator
Stellar magnetic activity decays over the main-sequence life of cool stars due to the stellar spin-down driven by magnetic braking. The evolution of chromospheric emission is well-studied for younger stars, but difficulties in determining…
We present a systematic investigation of X-ray thermal coronae in 157 early-type galaxies and 22 late-type galaxies from a survey of 25 hot (kT>3 keV), nearby (z<0.05) clusters, based on CHANDRA archival data. Cool galactic coronae…
Coronal loops are plasma structures in the solar atmosphere with temperatures reaching millions of Kelvin, shaped and sustained by the magnetic field. However, their morphology and fundamental nature remain subjects of debate. By studying…
$\beta$ Cet, 31 Com and $\mu$ Vel represent the main stages through which late-type giants evolve during their lifetime (the Hertzsprung gap (31 Com), the rapid braking zone ($\mu$ Vel) and the core helium burning ``clump'' phase ($\beta$…
We show the existence of a strong trend between neutron star surface temperature and the dipolar component of the magnetic field extending through three orders of field magnitude, a range that includes magnetars, radio-quiet isolated…
What physical mechanisms heat the outer solar or stellar atmosphere to million-Kelvin temperatures is a fundamental but long-standing open question. In particular, the solar corona in active region cores contains an even hotter component…
Gyrochronology, a method for dating aged field stars ($\gtrsim$ a few Gyr) based on their rotation rate, has recently been shown to fail for many stars older than the sun. The explanation most often put forth is that a shutdown or mode…
Millisecond pulsars (MSPs) are believed to be very old neutron stars (NSs) whose age may exceed significantly $10^8$ yrs. Although cooling scenarios of isolated NSs predict for that age a surface temperature $T_s\sim 10^4$ K, observations…
Young stellar objects often drive powerful bipolar outflows which evolve on time scales of a few years. An increasing number of these outflows has been detected in X-rays implying the existence of million degree plasma almost co-spatial…
We study different stages of the neutron star cooling by computing neutron star properties at various temperatures and entropies using an effective chiral model including hadronic and quark degrees of freedom. Macroscopic properties of the…
X-ray observations provide a key tool for exploring the properties of galactic coronae and their formation processes. In an earlier paper, we have presented a Chandra data analysis of the coronae of 53 nearby highly-inclined disc galaxies.…
We used the Project 1640 near-infrared coronagraph and integral field spectrograph to observe 19 young solar type stars. Five of these stars are known binary stars and we detected the late-type secondaries and were able to measure their JH…
In recent years, the development of spectropolarimetric techniques deeply modified our knowledge of stellar magnetism. In the case of solar-type stars, the challenge is to measure a geometrically complex field and determine its evolution…
The extremely sensitive Chandra Deep Field-North (CDF-N) pencil-beam X-ray survey is used to identify and characterize the X-ray emission from old high-latitude main sequence Galactic stars. Our principal goal is to investigate the expected…
We analyzed X-Shooter/VLT spectra of 24 ClassIII sources from three nearby star-forming regions (sigmaOrionis, LupusIII, and TWHya). We determined the effective temperature, surface gravity, rotational velocity, and radial velocity by…
We determine analytically the dependence of the approach to thermal equilibrium of strongly coupled plasmas on the breaking of scale invariance. The theories we consider are the holographic duals to Einstein gravity coupled to a scalar with…
EUV observations of warm coronal loops suggest that they are bundles of unresolved strands that are heated impulsively to high temperatures by nanoflares. The plasma would then have the observed properties (e.g., excess density compared to…
The solar corona, the tenuous outer atmosphere of the Sun, is orders of magnitude hotter than the solar surface. This 'coronal heating problem' requires the identification of a heat source to balance losses due to thermal conduction,…
The million degree plasma of the solar corona must be supplied by the underlying layers of the atmosphere. The mechanism and location of energy release, and the precise source of coronal plasma, remain unresolved. In earlier work we pursued…
Solar flares produce hard X-ray emission of which the photon spectrum is often represented by a combination of thermal and power-law distributions. However, the estimates of the number and total energy of non-thermal electrons are sensitive…