Search results for "Flare"
showing 10 items of 153 documents
Flaring Activity in Accretion Flows of Young Stellar Objects
2009
X-ray observations have shown extensive flaring activity in young stellar associations such as the Orion nebula. Observed flares are often very long and intense, and have been associated to very long magnetic loops, which may connect the stellar surface to the circumstellar disk. As such, these loops are candidate to be also the channel of star accretion from the disk, and one then wonders whether they flare during accretion flows. As a first attack to this question we have modelled in detail flares inside long coronal loops containing plasma at high density, comparable to that presumed for accretion flows. Preliminary results show that such flares would decay on time scales smaller than th…
High-resolution spectroscopy of two carbon stars with long-term obscuration events
2012
In this paper, we provide an analysis of the high-resolution optical spectra of two carbon variables, V1983 Cyg and V2074 Cyg, which are presumed to be cool R Corona Borealis (RCB) stars, according to their photometric behaviour. The stars show irregular long-term visual light variations of relatively large amplitude, similar to those exhibited by RCB variables. Based on the comparison of our high-resolution spectra with those of various carbon stars, we conclude that both variables have spectral properties typical for cool N-type carbon stars. However, two major differences from the spectra of normal carbon stars have been noted: the presence of high-velocity (∼−60 km s−1) components in th…
X-ray variability of Pleiades late-type stars as observed with the ROSAT-PSPC
2003
We present a comprehensive analysis of X-ray variability of the late-type (dF7-dM) Pleiades stars, detected in all ROSAT-PSPC observations; X-ray variations on short (hours) and medium (months) time scales have been explored. We have grouped the stars in two samples: 89 observations of 42 distinct dF7-dK2 stars and 108 observations of 61 dK3-dM stars. The Kolmogorov-Smirnov test applied on all X-ray photon time series show that the percentage of cases of significant vari- ability is quite similar on both samples, suggesting that the presence of variability does not depend on mass for the time scales and mass range explored. The comparison between the Time X-ray Amplitude Distribution functi…
Discussion – Periodic variations and asteroseismology of active OB stars
2010
AbstractWe summarize the discussion held after the session on periodic variations and asteroseismology. The session not only included seven talks, but as well thirty excellent posters were shown. It was impossible to summarize all these in the available frame of a discussion, and so this work focuses on very few sub-topics only mentioned in the actual discussion session. These topics were the relation of pulsation and turbulence, pulsation in close binaries, the observed photometric variability, the connection of pulsations and outburst, and bipolar flows.
Coronal Magnetic Field Measurements Through Quasi-Transverse Propagation
2004
The QT-propagation of microwaves as a means to measure coronal magnetic fields and the inversion of circular polarization as an observational proof of the QT-propagation are discussed. The first part of the chapter briefly outlines the relevant geometry and mathematical relations. Then the state of the art in the coronal magnetography and some possibilities are demonstrated. We discuss use of the technique for coronal magnetography and give some estimates concerning the coronal magnetography with the forthcoming Frequency Agile Solar Radiotelescope.
Results from Droxo
2007
AIMS. We study the variability of the Fe 6.4 KeV emission line from the Class I young stellar object Elias 29 in the Rho-Oph cloud. METHODS. We analysed the data from Elias 29 collected by XMM during a nine-day, nearly continuous observation of the Rho-Oph star-forming region (the Deep Rho-Oph X-ray Observation, named Droxo). The data were subdivided into six homogeneous time intervals, and the six resulting spectra were individually analysed. RESULTS. We detect significant variability in the equivalent width of the Fe 6.4 keV emission line from Elias 29. The 6.4 keV line is absent during the first time interval of observation and appears at its maximum strength during the second time inter…
Widespread Nanoflare Variability Detected with Hinode/X-Ray Telescope in a Solar Active Region
2011
It is generally agreed that small impulsive energy bursts called nanoflares are responsible for at least some of the Sun's hot corona, but whether they are the explanation for most of the multimillion-degree plasma has been a matter of ongoing debate. We present here evidence that nanoflares are widespread in an active region observed by the X-Ray Telescope on board the Hinode mission. The distributions of intensity fluctuations have small but important asymmetries, whether taken from individual pixels, multipixel subregions, or the entire active region. Negative fluctuations (corresponding to reduced intensity) are greater in number but weaker in amplitude, so that the median fluctuation i…
CALOS: an experiment to study the solar corona with an array of NTD Ge microcalorimeters
2002
In response to the Italian Space Agency announcement "New Ideas for Space Missions", we have proposed an observatory "CALorimetri per Osservazioni Solari" (CALOS) that will perform spatially resolved (Deltatheta similar to 2) X-ray spectroscopy of the solar corona over the 0.1 - 10 keV band using an array of NTD germanium microcalorimeters. The observatory will also include an X-ray polarimeter of radically new design that will study the hard X-ray solar emission and its polarization and will serve as a flare alarm.
High Flow Nasal Therapy Use in Patients with Acute Exacerbation of COPD and Bronchiectasis: A Feasibility Study
2020
The efficacy and feasibility of high flow nasal therapy (HFNT) use in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and bronchiectasis is unknown. We performed a single-center, single-arm prospective observational study in patients with AECOPD, documented bronchiectasis, pH >= 7.35, respiratory rate (RR) >= 26 breaths/minute despite receiving maximal medical treatment and oxygen via face mask up to 10 L/m. Patients received HFNT (Airvo 2, Fisher & Paykel) at a gas flow of 50 L/min and FIO2 adjusted to maintain SpO(2) >= 92%. Dyspnea, rated by Borg scale, RR, arterial blood gases and mucus production (ranging from 1 to 3) were collected befor…
Exploring the Relationship between Disease Awareness and Outcomes in Patients with Chronic Obstructive Pulmonary Disease
2020
<b><i>Background:</i></b> Disease awareness is a challenge in the management of chronic obstructive pulmonary disease (COPD). <b><i>Objectives:</i></b> The aim of this analysis was to explore the association between COPD optimal and suboptimal awareness, clinical parameters, and the following patient-reported outcomes: modified Medical Research Council (mMRC), Treatment Satisfaction Questionnaire (TSQM-9), COPD Assessment Test (CAT), Morisky Medication-Taking Adherence Scale (MMAS-4), and Brief Illness Perception Questionnaire (B-IPQ). <b><i>Methods:</i></b> This post hoc analysis of the SAT study included all enrolled …