X-ray flares in Orion low-mass stars

M. Caramazza, E. Flaccomio, G. Micela, F. Reale, S. J. Wolk, E. D. Feigelson

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Context. 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). Aims. Our main goal is to statistically characterize the flare-like variability of 165 low mass (0.1-0.3 M) ONC members in order to test and constrain the physical scenario in which flares explain all the observed emission. Methods. 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. Results. 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 (0.9-1.2 M), we establish that, at ∼1 Myr, low mass and solar mass stars of similar X-ray luminosity have very similar flare frequencies. Conclusions. 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.

Original languageEnglish (US)
Pages (from-to)645-654
Number of pages10
JournalAstronomy and Astrophysics
Volume471
Issue number2
DOIs
StatePublished - Aug 1 2007

Fingerprint

flares
stars
light curve
power law
Orion nebula
x rays
energy
energy distribution
corona
stellar coronas
physics
pre-main sequence stars
frequency distribution
distribution
luminosity
intervals
test
analysis
young

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Caramazza, M., Flaccomio, E., Micela, G., Reale, F., Wolk, S. J., & Feigelson, E. D. (2007). X-ray flares in Orion low-mass stars. Astronomy and Astrophysics, 471(2), 645-654. https://doi.org/10.1051/0004-6361:20077195
Caramazza, M. ; Flaccomio, E. ; Micela, G. ; Reale, F. ; Wolk, S. J. ; Feigelson, E. D. / X-ray flares in Orion low-mass stars. In: Astronomy and Astrophysics. 2007 ; Vol. 471, No. 2. pp. 645-654.
@article{374adeecf3744a72b2ea0f4d070b5018,
title = "X-ray flares in Orion low-mass stars",
abstract = "Context. 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). Aims. Our main goal is to statistically characterize the flare-like variability of 165 low mass (0.1-0.3 M⊙) ONC members in order to test and constrain the physical scenario in which flares explain all the observed emission. Methods. 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. Results. 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 (0.9-1.2 M⊙), we establish that, at ∼1 Myr, low mass and solar mass stars of similar X-ray luminosity have very similar flare frequencies. Conclusions. 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.",
author = "M. Caramazza and E. Flaccomio and G. Micela and F. Reale and Wolk, {S. J.} and Feigelson, {E. D.}",
year = "2007",
month = "8",
day = "1",
doi = "10.1051/0004-6361:20077195",
language = "English (US)",
volume = "471",
pages = "645--654",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
number = "2",

}

Caramazza, M, Flaccomio, E, Micela, G, Reale, F, Wolk, SJ & Feigelson, ED 2007, 'X-ray flares in Orion low-mass stars', Astronomy and Astrophysics, vol. 471, no. 2, pp. 645-654. https://doi.org/10.1051/0004-6361:20077195

X-ray flares in Orion low-mass stars. / Caramazza, M.; Flaccomio, E.; Micela, G.; Reale, F.; Wolk, S. J.; Feigelson, E. D.

In: Astronomy and Astrophysics, Vol. 471, No. 2, 01.08.2007, p. 645-654.

Research output: Contribution to journalArticle

TY - JOUR

T1 - X-ray flares in Orion low-mass stars

AU - Caramazza, M.

AU - Flaccomio, E.

AU - Micela, G.

AU - Reale, F.

AU - Wolk, S. J.

AU - Feigelson, E. D.

PY - 2007/8/1

Y1 - 2007/8/1

N2 - Context. 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). Aims. Our main goal is to statistically characterize the flare-like variability of 165 low mass (0.1-0.3 M⊙) ONC members in order to test and constrain the physical scenario in which flares explain all the observed emission. Methods. 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. Results. 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 (0.9-1.2 M⊙), we establish that, at ∼1 Myr, low mass and solar mass stars of similar X-ray luminosity have very similar flare frequencies. Conclusions. 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.

AB - Context. 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). Aims. Our main goal is to statistically characterize the flare-like variability of 165 low mass (0.1-0.3 M⊙) ONC members in order to test and constrain the physical scenario in which flares explain all the observed emission. Methods. 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. Results. 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 (0.9-1.2 M⊙), we establish that, at ∼1 Myr, low mass and solar mass stars of similar X-ray luminosity have very similar flare frequencies. Conclusions. 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.

UR - http://www.scopus.com/inward/record.url?scp=34548050696&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34548050696&partnerID=8YFLogxK

U2 - 10.1051/0004-6361:20077195

DO - 10.1051/0004-6361:20077195

M3 - Article

AN - SCOPUS:34548050696

VL - 471

SP - 645

EP - 654

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 2

ER -

Caramazza M, Flaccomio E, Micela G, Reale F, Wolk SJ, Feigelson ED. X-ray flares in Orion low-mass stars. Astronomy and Astrophysics. 2007 Aug 1;471(2):645-654. https://doi.org/10.1051/0004-6361:20077195