X-ray flares on the UV Ceti-type star CC Eridani: a ``peculiar'' time-evolution of spectral parameters

Fabio Reale, Fabio Reale, Crespo-Chacón, López-Santiago, Micela, Caramazza

Risultato della ricerca: Article

11 Citazioni (Scopus)

Abstract

Context: Weak flares are supposed to be an important heating agent of the outer layers of stellar atmospheres. However, due to instrumental limitations, only large X-ray flares have been studied in detail until now. Aims: We used an XMM-Newton observation of the very active BY-Dra type binary star CC Eri in order to investigate the properties of two flares that are weaker than those typically studied in the literature. Methods: We performed time-resolved spectroscopy of the data taken with the EPIC-PN CCD camera. A multi-temperature model was used to fit the spectra. We inferred the size of the flaring loops using the density-temperature diagram. The loop scaling laws were applied for deriving physical parameters of the flaring plasma. We also estimated the number of loops involved in the observed flares. Results: A large X-ray variability was found. Spectral analysis showed that all the regions in the light curve, including the flare segments, are well-described by a 3-T model with variable emission measures but, surprisingly, with constant temperatures (values of 3, 10 and 22 MK). The analysed flares lasted ~3.4 and 7.1 ks, with flux increases of factors 1.5-1.9. They occurred in arcades made of a few tens of similar coronal loops. The size of the flaring loops is much smaller than the distance between the stellar surfaces in the binary system, and even smaller than the radius of each of the stars. The obtained results are consistent with the following ideas: (i) the whole X-ray light curve of CC Eri could be the result of a superposition of multiple low-energy flares; and (ii) stellar flares can be scaled-up versions of solar flares.
Lingua originaleEnglish
pagine (da-a)929-939
Numero di pagine11
RivistaASTRONOMY & ASTROPHYSICS
Volume471
Stato di pubblicazionePublished - 2007

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flares
stars
x rays
light curve
stellar flares
stellar atmospheres
coronal loops
binary stars
XMM-Newton telescope
solar flares
CCD cameras
scaling laws
newton
spectrum analysis
temperature
diagrams
heating
radii
spectroscopy

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cita questo

Reale, F., Reale, F., Crespo-Chacón, López-Santiago, Micela, & Caramazza (2007). X-ray flares on the UV Ceti-type star CC Eridani: a ``peculiar'' time-evolution of spectral parameters. ASTRONOMY & ASTROPHYSICS, 471, 929-939.

X-ray flares on the UV Ceti-type star CC Eridani: a ``peculiar'' time-evolution of spectral parameters. / Reale, Fabio; Reale, Fabio; Crespo-Chacón; López-Santiago; Micela; Caramazza.

In: ASTRONOMY & ASTROPHYSICS, Vol. 471, 2007, pag. 929-939.

Risultato della ricerca: Article

Reale, F, Reale, F, Crespo-Chacón, López-Santiago, Micela & Caramazza 2007, 'X-ray flares on the UV Ceti-type star CC Eridani: a ``peculiar'' time-evolution of spectral parameters', ASTRONOMY & ASTROPHYSICS, vol. 471, pagg. 929-939.
Reale, Fabio ; Reale, Fabio ; Crespo-Chacón ; López-Santiago ; Micela ; Caramazza. / X-ray flares on the UV Ceti-type star CC Eridani: a ``peculiar'' time-evolution of spectral parameters. In: ASTRONOMY & ASTROPHYSICS. 2007 ; Vol. 471. pagg. 929-939.
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abstract = "Context: Weak flares are supposed to be an important heating agent of the outer layers of stellar atmospheres. However, due to instrumental limitations, only large X-ray flares have been studied in detail until now. Aims: We used an XMM-Newton observation of the very active BY-Dra type binary star CC Eri in order to investigate the properties of two flares that are weaker than those typically studied in the literature. Methods: We performed time-resolved spectroscopy of the data taken with the EPIC-PN CCD camera. A multi-temperature model was used to fit the spectra. We inferred the size of the flaring loops using the density-temperature diagram. The loop scaling laws were applied for deriving physical parameters of the flaring plasma. We also estimated the number of loops involved in the observed flares. Results: A large X-ray variability was found. Spectral analysis showed that all the regions in the light curve, including the flare segments, are well-described by a 3-T model with variable emission measures but, surprisingly, with constant temperatures (values of 3, 10 and 22 MK). The analysed flares lasted ~3.4 and 7.1 ks, with flux increases of factors 1.5-1.9. They occurred in arcades made of a few tens of similar coronal loops. The size of the flaring loops is much smaller than the distance between the stellar surfaces in the binary system, and even smaller than the radius of each of the stars. The obtained results are consistent with the following ideas: (i) the whole X-ray light curve of CC Eri could be the result of a superposition of multiple low-energy flares; and (ii) stellar flares can be scaled-up versions of solar flares.",
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T1 - X-ray flares on the UV Ceti-type star CC Eridani: a ``peculiar'' time-evolution of spectral parameters

AU - Reale, Fabio

AU - Reale, Fabio

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AU - López-Santiago, null

AU - Micela, null

AU - Caramazza, null

PY - 2007

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N2 - Context: Weak flares are supposed to be an important heating agent of the outer layers of stellar atmospheres. However, due to instrumental limitations, only large X-ray flares have been studied in detail until now. Aims: We used an XMM-Newton observation of the very active BY-Dra type binary star CC Eri in order to investigate the properties of two flares that are weaker than those typically studied in the literature. Methods: We performed time-resolved spectroscopy of the data taken with the EPIC-PN CCD camera. A multi-temperature model was used to fit the spectra. We inferred the size of the flaring loops using the density-temperature diagram. The loop scaling laws were applied for deriving physical parameters of the flaring plasma. We also estimated the number of loops involved in the observed flares. Results: A large X-ray variability was found. Spectral analysis showed that all the regions in the light curve, including the flare segments, are well-described by a 3-T model with variable emission measures but, surprisingly, with constant temperatures (values of 3, 10 and 22 MK). The analysed flares lasted ~3.4 and 7.1 ks, with flux increases of factors 1.5-1.9. They occurred in arcades made of a few tens of similar coronal loops. The size of the flaring loops is much smaller than the distance between the stellar surfaces in the binary system, and even smaller than the radius of each of the stars. The obtained results are consistent with the following ideas: (i) the whole X-ray light curve of CC Eri could be the result of a superposition of multiple low-energy flares; and (ii) stellar flares can be scaled-up versions of solar flares.

AB - Context: Weak flares are supposed to be an important heating agent of the outer layers of stellar atmospheres. However, due to instrumental limitations, only large X-ray flares have been studied in detail until now. Aims: We used an XMM-Newton observation of the very active BY-Dra type binary star CC Eri in order to investigate the properties of two flares that are weaker than those typically studied in the literature. Methods: We performed time-resolved spectroscopy of the data taken with the EPIC-PN CCD camera. A multi-temperature model was used to fit the spectra. We inferred the size of the flaring loops using the density-temperature diagram. The loop scaling laws were applied for deriving physical parameters of the flaring plasma. We also estimated the number of loops involved in the observed flares. Results: A large X-ray variability was found. Spectral analysis showed that all the regions in the light curve, including the flare segments, are well-described by a 3-T model with variable emission measures but, surprisingly, with constant temperatures (values of 3, 10 and 22 MK). The analysed flares lasted ~3.4 and 7.1 ks, with flux increases of factors 1.5-1.9. They occurred in arcades made of a few tens of similar coronal loops. The size of the flaring loops is much smaller than the distance between the stellar surfaces in the binary system, and even smaller than the radius of each of the stars. The obtained results are consistent with the following ideas: (i) the whole X-ray light curve of CC Eri could be the result of a superposition of multiple low-energy flares; and (ii) stellar flares can be scaled-up versions of solar flares.

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