scholarly journals A Simultaneous Optical and X‐Ray Variability Study of the Orion Nebula Cluster. II. A Common Origin in Magnetic Activity

2007 ◽  
Vol 660 (1) ◽  
pp. 704-711 ◽  
Author(s):  
Keivan G. Stassun ◽  
M. van den Berg ◽  
Eric Feigelson
Keyword(s):  
Magnetic Activity ◽  
Common Origin ◽  
Orion Nebula ◽  
X Ray ◽  
Variability Study

scholarly journals A Simultaneous Optical and X‐Ray Variability Study of the Orion Nebula Cluster. I. Incidence of Time‐correlated X‐Ray/Optical Variations

2006 ◽  
Vol 649 (2) ◽  
pp. 914-926 ◽  
Author(s):  
Keivan G. Stassun ◽  
M. van den Berg ◽  
Eric Feigelson ◽  
Ettore Flaccomio
Keyword(s):  
Orion Nebula ◽  
X Ray ◽  
Variability Study

scholarly journals Magnetic Activity of Pre-main Sequence Stars

2004 ◽  
Vol 219 ◽  
pp. 211-222
Author(s):  
Eric D. Feigelson
Keyword(s):  
Main Sequence ◽  
Magnetic Activity ◽  
T Tauri Stars ◽  
X Rays ◽  
Orion Nebula ◽  
Main Sequence Stars ◽  
Nearby Star ◽  
X Ray ◽  
T Tauri ◽  
Pms Stars

I review here recent advances in our understanding of magnetic activity in pre-main sequence (PMS) protostars and T Tauri stars. Results are based on recent imaging, spectroscopic and temporal studies of nearby star forming regions from the Chandra X — ray Observatory and XMM — Newton, including a first look at an ultradeep Chandra exposure of the Orion Nebula Cluster.Pre-main sequence stars exhibit a high level of X-ray emission dominated by a bewildering variety of magnetic reconnection flares. Activity is linked to bulk stellar properties — Lbol, mass, surface area or volume — rather than rotation. This suggests that dynamo processes in deeply convective PMS stars may fundamentally differ from the tachocline dynamo operating in main sequence stars.X-rays and MeV particles from magnetic flares will affect the circumstellar environment in PMS systems, particularly the protoplanetary disk. X-ray emission may influence: disk ionization, turbulence and viscosity; Jovian planet formation and migration; the production of meteoritic isotopes and melting of meteoritic chondrules; the heating and chemistry of the disk. X-ray surveys are also effective in locating post-T Tauri stars for disk evolution studies.

X‐Ray Emission from Early‐Type Stars in the Orion Nebula Cluster

2005 ◽  
Vol 160 (2) ◽  
pp. 557-581 ◽  
Author(s):  
B. Stelzer ◽  
E. Flaccomio ◽  
T. Montmerle ◽  
G. Micela ◽  
S. Sciortino ◽  
...  
Keyword(s):  
Orion Nebula ◽  
Early Type ◽  
X Ray ◽  
Early Type Stars

X-ray variability study of ROSAT sources

1998 ◽  
Vol 319 (1-2) ◽  
pp. 3-6 ◽  
Author(s):  
W. Voges ◽  
T. Boller
Keyword(s):  
X Ray ◽  
Variability Study

scholarly journals Coronal Magnetic Fields of Algol Binaries from Microwave Spectra

1991 ◽  
Vol 130 ◽  
pp. 498-500
Author(s):  
G. Umana ◽  
C. Trigilio ◽  
R. M. Hjellming ◽  
S. Catalano ◽  
M. Rodonò
Keyword(s):  
Magnetic Fields ◽  
Radio Emission ◽  
Mass Exchange ◽  
Thermal Emission ◽  
Magnetic Activity ◽  
Microwave Emission ◽  
X Ray ◽  
Coronal Magnetic Fields ◽  
Hydrodynamic Processes ◽  
Hot Corona

Algol-type binaries are basically known to undergo hydrodynamic processes related to mass exchange between components. Recent observations on radio, X-ray emission and flare-like events have raised the question of possible magnetic activity in the secondary component of these systems (Hall, 1989).From a microwave emission survey we have shown that the radio emission from Algol systems cannot be accounted for by thermal emission from an hot corona (T ≥ 107K) and that their radio luminosities compare very well with those of the magnetically active RS CVn systems (Umana et al., 1990).

scholarly journals Radio Flare Activity of RS CVn Stars

1980 ◽  
Vol 88 ◽  
pp. 403-403
Author(s):  
Paul A. Feldman
Keyword(s):  
Binary Star ◽  
Quantitative Model ◽  
Magnetic Activity ◽  
Flare Activity ◽  
Radio Observatory ◽  
X Ray ◽  
Rs Cvn Stars ◽  
Solar Magnetic Activity ◽  
Radio Flare ◽  
Systematic Program

For several years, a systematic program to observe RS CVn and similar binaries has been undertaken with the 46-m telescope of the Algonquin Radio Observatory. A number of large radio outbursts at 2.8 cm wavelength has been found from HR 1099, AR Lac, SZ Psc, UX Ari, and HR 5110. In several cases, simultaneous, or nearly simultaneous, observations of these stars were made by cooperating observers at (other) radio, optical, UV, and X-ray wavelengths. It is now clearly established that the mechanism responsible for the cm-wavelength radio emission is nonthermal gyrosynchrotron radiation in a volume whose characteristic dimension is comparable with the binary star separation. More generally, a semi-quantitative model for the radio flare activity of these stars seems to be possible using greatly scaled-up analogues of solar magnetic activity.

scholarly journals Activity and rotation of the X-ray emitting Kepler stars

2019 ◽  
Vol 628 ◽  
pp. A41 ◽  
Author(s):  
D. Pizzocaro ◽  
B. Stelzer ◽  
E. Poretti ◽  
S. Raetz ◽  
G. Micela ◽  
...  
Keyword(s):  
White Light ◽  
Main Sequence ◽  
Magnetic Activity ◽  
Light Curves ◽  
Late Type ◽  
Main Sequence Stars ◽  
Photometric Variability ◽  
X Ray ◽  
Rotation Periods ◽  
Flare Frequency

The relation between magnetic activity and rotation in late-type stars provides fundamental information on stellar dynamos and angular momentum evolution. Rotation-activity studies found in the literature suffer from inhomogeneity in the measurement of activity indexes and rotation periods. We overcome this limitation with a study of the X-ray emitting, late-type main-sequence stars observed by XMM-Newton and Kepler. We measured rotation periods from photometric variability in Kepler light curves. As activity indicators, we adopted the X-ray luminosity, the number frequency of white-light flares, the amplitude of the rotational photometric modulation, and the standard deviation in the Kepler light curves. The search for X-ray flares in the light curves provided by the EXTraS (Exploring the X-ray Transient and variable Sky) FP-7 project allows us to identify simultaneous X-ray and white-light flares. A careful selection of the X-ray sources in the Kepler field yields 102 main-sequence stars with spectral types from A to M. We find rotation periods for 74 X-ray emitting main-sequence stars, 20 of which do not have period reported in the previous literature. In the X-ray activity-rotation relation, we see evidence for the traditional distinction of a saturated and a correlated part, the latter presenting a continuous decrease in activity towards slower rotators. For the optical activity indicators the transition is abrupt and located at a period of ~10 d but it can be probed only marginally with this sample, which is biased towards fast rotators due to the X-ray selection. We observe seven bona-fide X-ray flares with evidence for a white-light counterpart in simultaneous Kepler data. We derive an X-ray flare frequency of ~0.15 d−1, consistent with the optical flare frequency obtained from the much longer Kepler time-series.

scholarly journals Magnetic fields, winds and X-rays of massive stars in the Orion nebula cluster

2010 ◽  
Vol 6 (S272) ◽  
pp. 208-209 ◽  
Author(s):  
Véronique Petit ◽  
Gregg A. Wade ◽  
Evelyne Alecian ◽  
Laurent Drissen ◽  
Thierry Montmerle ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Theoretical Models ◽  
Magnetic Star ◽  
X Rays ◽  
Orion Nebula ◽  
X Ray ◽  
Ob Stars ◽  
The Impact ◽  
The Relationship

AbstractIn some massive stars, magnetic fields are thought to confine the outflowing radiatively-driven wind. Although theoretical models and MHD simulations are able to illustrate the dynamics of such a magnetized wind, the impact of this wind-field interaction on the observable properties of a magnetic star - X-ray emission, photometric and spectral variability - is still unclear. The aim of this study is to examine the relationship between magnetism, stellar winds and X-ray emission of OB stars, by providing empirical observations and confronting theory. In conjunction with the COUP survey of the Orion Nebula Cluster, we carried out spectropolarimatric ESPaDOnS observations to determine the magnetic properties of massive OB stars of this cluster.

scholarly journals Do star clusters form in a completely mass-segregated way?

2019 ◽  
Vol 626 ◽  
pp. A79 ◽  
Author(s):  
Václav Pavlík ◽  
Pavel Kroupa ◽  
Ladislav Šubr
Keyword(s):  
Star Clusters ◽  
Point Of View ◽  
High Mass ◽  
Orion Nebula ◽  
Energy Redistribution ◽  
X Ray ◽  
Star Forming ◽  
Independent Observations ◽  
Mass Segregation ◽  
Rule Out

Context. ALMA observations of the Serpens South star-forming region suggest that stellar protoclusters may be completely mass segregated at birth. Independent observations also suggest that embedded clusters form segregated by mass. Aims. As the primordial mass segregation seems to be lost over time, we aim to study on which timescale an initially perfectly mass-segregated star cluster becomes indistinguishable from an initially not mass-segregated cluster. As an example, the Orion Nebula Cluster (ONC) is also discussed. Methods. We used N-body simulations of star clusters with various masses and two different degrees of primordial mass segregation. We analysed their energy redistribution through two-body relaxation to quantify the time when the models agree in terms of mass segregation, which sets in only dynamically in the models that are primordially not mass segregated. A comprehensive cross-matched catalogue combining optical, infrared, and X-ray surveys of ONC members was also compiled and made available. Results. The models evolve to a similar radial distribution of high-mass stars after the core collapse (about half a median two-body relaxation time, trh) and become observationally indistinguishable from the point of view of mass segregation at time τv ≈ 3.3 trh. In the case of the ONC, using the distribution of high-mass stars, we may not rule out either evolutionary scenario (regardless of whether they are initially mass segregated). When we account for extinction and elongation of the ONC, as reported elsewhere, an initially perfectly mass-segregated state seems to be more consistent with the observed cluster.

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