C.D.S. - SIMBAD4 rel 1.7 - 2020.08.04CEST22:37:36

2007A&A...471..645C - Astronomy and Astrophysics, volume 471, 645-654 (2007/8-4)

X-ray flares in Orion low-mass stars.


Abstract (from CDS):

X-ray flares are common phenomena in pre-main sequence stars. Their analysis gives insights into the physics at work in young stellar coronae. The Orion Nebula Cluster offers a unique opportunity to study large samples of young low mass stars. This work is part of the Chandra Orion Ultradeep project (COUP), an ∼10 day long X-ray observation of the Orion Nebula Cluster (ONC). Our main goal is to statistically characterize the flare-like variability of 165 low mass (0.1-0.3M) ONC members in order to test and constrain the physical scenario in which flares explain all the observed emission. We adopt a maximum likelihood piece-wise representation of the observed X-ray light curves and detect flares by taking into account both the amplitude and time derivative of the count-rate. We then derive the frequency and energy distribution of the flares. The high energy tail of the energy distribution of flares is well described by a power-law with index ∼2.2. We test the hypothesis that light curves are built entirely by overlapping flares with a single power law energy distribution. We constrain the parameters of this simple model for every single light curve. The analysis of synthetic light curves obtained from the model indicates a good agreement with the observed data. Comparing low mass stars with stars in the mass interval (0.9-1.2M), we establish that, at ∼1Myr, low mass and solar mass stars of similar X-ray luminosity have very similar flare frequencies. Our observational results are consistent with the following model/scenario: the light curves are entirely built by overlapping flares with a power-law intensity distribution; the intense flares are individually detected, while the weak ones merge and form a pseudo-quiescent level, which we indicate as the characteristic level.

Abstract Copyright:

Journal keyword(s): stars: activity - stars: coronae - stars: flare - stars: pre-main sequence - stars: late-type - X-ray: stars

Simbad objects: 5

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Number of rows : 5

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
1 V* V1455 Ori Or* 05 34 50.8589308908 -05 29 25.083769806   18.720 17.575 16.15 14.149 M4.5 38 0
2 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 1985 1
3 Brun 556 Y*O 05 35 11.8838836502 -05 31 55.408419093 17.183 15.490 14.482 13.92 12.262 M0.5 44 0
4 V* V1515 Ori Or* 05 35 19.9461841192 -05 33 53.550818051 19.216 17.602 16.458 15.16 13.455 M3.5 40 0
5 BD+20 2465 Er* 10 19 36.2808024653 +19 52 12.014037746   10.82 9.52 9.19   M4Vae 1150 0

    Equat.    Gal    SGal    Ecl

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