0000000000398799
AUTHOR
J. J. Drake
showing 6 related works from this author
High Resolution X-ray Spectroscopy of Pre-Main-Sequence Stars: TWA 5 and PZ Tel
2004
We report on the analysis of high resolution X-ray spectra of two pre-main-sequence stars: TWA 5 (observed with XMM-Newton) and PZ Telescopii (observed with Chandra/HETGS). TWA 5 is a classical T Tauri star in the TW Hydrae association while PZ Tel is a rapidly rotating weak-lined T Tauri star in the beta-Pictoris moving group. For both stars we have reconstructed the emission measure distribution and derived the coronal abundances to check for possible patterns of the abundances related to the first ionization potential of the various elements. We have also derived estimates of the plasma density from the analysis of the He-like triplets. We compare the characteristics of our targets with …
Simultaneous Kepler/K2 and XMM-Newton observations of superflares in the Pleiades
2019
Flares are powerful events ignited by a sudden release of magnetic energy. With the aim of studying flares in the 125-Myr-old stars in the Pleiades observed simultaneously in optical and X-ray light, we obtained new XMM-Newton observations of this cluster during the observations of Kepler K2 Campaign 4. Our objective is to characterize the most powerful flares observed in both bands and to constrain the energy released in the optical and X-ray, the geometry of the loops, and their time evolution. We aim to compare our results to existing studies of flares occurring in the Sun and stars at different ages. We selected bright X-ray/optical flares occurred in 12 known members of the Pleiades fr…
The second data release of the INT Photometric Hα Survey of the Northern Galactic Plane (IPHAS DR2)
2014
The INT/WFC Photometric H-Alpha Survey of the Northern Galactic Plane (IPHAS) is a 1800 square degrees imaging survey covering Galactic latitudes |b| < 5 deg and longitudes l = 30 to 215 deg in the r, i and H-alpha filters using the Wide Field Camera (WFC) on the 2.5-metre Isaac Newton Telescope (INT) in La Palma. We present the first quality-controlled and globally-calibrated source catalogue derived from the survey, providing single-epoch photometry for 219 million unique sources across 92% of the footprint. The observations were carried out between 2003 and 2012 at a median seeing of 1.1 arcsec (sampled at 0.33 arcsec/pixel) and to a mean 5\sigma-depth of 21.2 (r), 20.0 (i) and 20.3 (H-a…
Simultaneous Kepler/K2 and XMM‐Newton observations of superflares in the Pleiades
2019
Proceeding of a contributed talk given at the meeting: "TIME-DOMAIN ASTRONOMY: A HIGH ENERGY VIEW" held at ESAC, Madrid, 13 - 15 JUNE 2018 Together with coronal mass ejection, flares are the most energetic stellar magnetic events, ignited by a sudden release of magnetic energy, which triggers a cascade of interconnected phenomena, each resulting in emission in different bands. For this reason, flares are intrinsic multiwavelength phenomena. In particular, optical and soft X-ray emission probes two different events occurring during flares: the heating of plasma in the upper photosphere at the footpoints of the magnetic loops and the heating and cooling of the plasma confined in the loops in …
X-ray optical depth diagnostics of T Tauri accretion shocks
2009
In classical T Tauri stars, X-rays are produced by two plasma components: a hot low-density plasma, with frequent flaring activity, and a high-density lower temperature plasma. The former is coronal plasma related to the stellar magnetic activity. The latter component, never observed in non-accreting stars, could be plasma heated by the shock formed by the accretion process. However its nature is still being debated. Our aim is to probe the soft X-ray emission from the high-density plasma component in classical T Tauri stars to check whether this is plasma heated in the accretion shock or whether it is coronal plasma. High-resolution X-ray spectroscopy allows us to measure individual line f…
Size of coronal structures in active stellar coronae from the detection of x-ray resonant scattering
2005
We have analyzed high-resolution X-ray spectra of a large sample of active stars observed with the High Energy Transmission Grating Spectrometer on Chandra in order to investigate the properties of optical thickness of the coronal plasma. The analysis of Lyman series lines arising from hydrogen-like oxygen and neon ions shows in the coronae of the active RS CVn-type binaries II Peg and IM Peg significant decrements in the Ly alpha/Ly beta ratios as compared with theoretical predictions and with the same ratios observed in similar active binaries. We interpret these depletions in terms of resonance scattering of line photons out of the line-of-sight. These observations present the first stro…