Tag: X-ray

Superfast fragments and X-ray emission in the supernova remnant SN 1006. The study: “Indication of a fast ejecta fragment in the atomic cloud interacting with the southwestern limb of SN 1006” of R. Giuffrida (UNIPA/INAF) appeared on A&A

Ricerca

Supernova remnants, which are nebulae produced by explosion of supernovae and undergoing rapid expansion, typically serve as intense sources of high-energy radiation, particularly in the form of X-ray emissions. This radiation can be of two different types: thermal and non-thermal. Thermal radiation is emitted by dense material and is contingent upon the temperature of the emitting gas. To emit X-rays,

» Read more
, , , , , , , ,

Star-planet interactions: difficult, but not impossible. The study: “The enigmatic dance of the HD 189733A system: a quest for accretion” of S. Colombo (INAF-OAPA) appeared on A&A

Ricerca

Hot Jupiters represent an interesting class of exoplanets that does not exist in the Solar System. These are giant gaseous planets that orbit at such close distances from their stars that their orbital periods are shorter than 10 days. Due to their proximity to their stars, these planets have very hot atmospheres, with temperatures exceeding 1500 K. For this reason,

» Read more
, , , , , , ,

Different regimes of particle acceleration in supernova remnants. The study: “A Spatially Resolved Study of Hard X-Ray Emission in Kepler’s Supernova Remnant: Indications of Different Regimes of Particle Acceleration” of V. Sapienza (UNIPA/OAPA) appeared on ApJ

Ricerca

Cosmic rays are high-energy charged particles which continuously hit our planet. These particles are accelerated up to such high velocities in different astronomical environments, among which supernova remnants seems to be particularly important. These objects are nebulae in rapid expansion generated by the explosions of very massive stars. In supernova remnants, particle acceleration seems to occurr along the expanding shock

» Read more
, , , , , , , ,

Two bright flares in DS Tuc A and their impact on the nearby planet. The paper: “X-ray flares of the young planet host Ds Tucanae A” of I. Pillitteri recently appeared on A&A

Ricerca

Flares are among the most energetic magnetic phenomena occuring in stars. They are triggered by a sudden release of energy previously stored in the stellar magnetic field, and then they culminate with the formation of magnetic loops in the stellar coronae filled by X-ray and UV emitting plasma at million degrees. Sometimes, these magnetic structures erupt, releasing in the surrounding

» Read more
, , , , , , , , ,

A chapter wrote by M. Barbera, U. Lo Cicero and L. Sciortino (INAF-OAPA) on the filters for X-ray telescopes is included in the: “Handbook of X-ray and gamma ray astrophysics”

Ricerca

X-ray astronomy explores the high-energy Universe. X-rays are, in fact, high energy photons emitted by very hot gas (with temperature of some milion degrees) or by processes involving relativistic particles. Some astronomical sources of X-rays radiation are: accreting black holes, such as the supermassive black holes at the center of active galaxies, stellar coronae, supernova remnants, and clusters of galaxies.

» Read more
, , , , , , , ,

Cepheids and X-ray emission. The study “X-rays in Cepheids: XMM-Newton Observations of η Aql” of N. R. Evans (SAO-CfA) recently appeared on AJ

Ricerca

Cepheids are stars of great importance, since they allow to determine the distance of galaxies within a few hundreds of million of light years from us. This is due to the pulsations that characterize these giant stars, which are going through an instable phase of their evolution. Because of these pulsations, the luminosity of these stars varies with a period

» Read more
, , , , ,

A new diagnostic tool to identify metal-rich ejects in supernova remnants. The study: “Unveiling pure-metal ejecta X-ray emission in supernova remnants through their radiative recombination continuum” of E. Greco (UNIPA/INAF-OAPA/API) recently appeared on A&A

Ricerca

Supernova remnants are nebulae created by supernova explosions. These expanding clouds are formed by the interstellar medium shocked and heated up by the expanding shock produced by the explosion, and the knots of material launched by the exploding star, called ejecta. These ejecta are located behind the expanding shock, traveling with lower velocity, and they are heated up by the reverse shock:

» Read more
, , ,

MHD simulations of the radio emission from a flaring T Tauri star. The study: “Predicting the time variation of radio emission from MHD simulations of a flaring T-Tauri star” of Waterfall C. O. G. (Jodrell Bank Centre for Astrophysics) recently appeared on MNRAS

Ricerca

T Tauri stars are young low-mass stars (typically younger than 5 million of years), which are surrounded by a protoplanetary disk, e.g. a disk of gas and dust orbiting around the star. The disk material does not reach the central star: the dust component sublimates in the inner disk, where the temperature exceeds 1500 degrees, while the gas disk is truncated

» Read more
, , , , , , ,

Discovered an X-ray cycle in a 400 million years old star. The study: “An X-ray activity cycle on the young solar-like star ɛ Eridani” of M. Coffaro (Eberhard-Karls Universität Tübingen) appeared on A&A

Ricerca

The intensity of Solar magnetic activity and of the related phenomena (such as sunspots and flares) varies with an 11-years cycle. In order to understand whether such an activity cycle is common among solar-type stars, since 1966 a project based on the Observatory of Mt. Wilson is collecting measurements of the cromospheric activity of a large sample of low-mass stars

» Read more
, , , , ,

Flares and X-ray fluoresence in protostars. The study: “Deep X-ray view of the Class I YSO Elias 29 with XMM-Newton and NuSTAR” of I. Pillitteri (INAF-OAPA) recently appeared on A&A

Ricerca

“Protostars” are stars a few million years old, which are still accreting gas and contracting for their own gravity, and whose nucleus has not reached yet the temperature and pressure necessary for the onset of thermonuclear reactions. The youngest protostars are still surrounded by a protoplanetary disk of gas and dust (class II protostars) or even by an accreting envelope

» Read more
, , , , , , , , , , ,
1 2 3