The Chandra Deep Field-North survey. XVII. Evolution of magnetic activity in old late-type stars

E. D. Feigelson, A. E. Hornschemeier, G. Micela, F. E. Bauer, D. M. Alexander, W. N. Brandt, F. Favata, S. Sciortino, G. P. Garmire

Research output: Contribution to journalReview article

43 Citations (Scopus)

Abstract

The extremely sensitive Chandra Deep Field-North (CDF-N) pencil-beam X-ray survey is used to identify and characterize the X-ray emission from old high-latitude main-sequence Galactic stars. Our principal goal is to investigate the expected long-term decay of magnetic activity of late-type stars due to the gradual spin-down of stellar rotation from a magnetized stellar wind. Thirteen X-ray sources are associated with late-type stars; 11 of these constitute a well-defined sample for statistical analysis. This sample consists of two G, two K0-K4, and seven M2-M5 stars with median V-band magnitude around 19 and median distance around 300 pc. X-ray luminosities are typically log LX ≃ 27 ergs s-1 but are substantially higher in two cases. The combination of large-amplitude variations on timescales of hours and plasma temperatures around 5-30 MK indicates that the observed X-ray emission is dominated by magnetic reconnection flares rather than quiescent coronal emission. These X-ray properties are quantitatively similar to those seen in the active contemporary Sun. The CDF-N stellar sample is compared to simulations based on convolution of X-ray luminosity functions (XLFs) with the known spatial distribution of old-disk stars. The model indicates that the CDF-N stars are the most magnetically active old-disk stars. A substantial decline in X-ray luminosities over the 1 Gyr < t < 11 Gyr age interval is required: 39 rather than 11 stars should have been detected if the XLF does not evolve over this time interval. This is a clear demonstration that the coronal and flaring components of stellar magnetic activity - and presumably the interior magnetic dynamos responsible for the reconnecting fields at the stellar surface - exhibit long-term decay over the age of the Galactic disk. The model that best fits the magnitudes, spectral types, and X-ray luminosities of the sample has L x ∞ t-2 ergs s-1, which is faster than the t-1 decay rate predicted from widely accepted rotational spin-down rates and X-ray-activity relations.

Original languageEnglish (US)
Pages (from-to)1107-1120
Number of pages14
JournalAstrophysical Journal
Volume611
Issue number2 I
DOIs
StatePublished - Aug 20 2004

Fingerprint

stars
x rays
luminosity
erg
intervals
stellar rotation
pencil beams
rotating generators
plasma temperature
stellar winds
decay
extremely high frequencies
convolution integrals
statistical analysis
polar regions
flares
decay rates
spatial distribution
timescale
plasma

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Feigelson, E. D., Hornschemeier, A. E., Micela, G., Bauer, F. E., Alexander, D. M., Brandt, W. N., ... Garmire, G. P. (2004). The Chandra Deep Field-North survey. XVII. Evolution of magnetic activity in old late-type stars. Astrophysical Journal, 611(2 I), 1107-1120. https://doi.org/10.1086/422248
Feigelson, E. D. ; Hornschemeier, A. E. ; Micela, G. ; Bauer, F. E. ; Alexander, D. M. ; Brandt, W. N. ; Favata, F. ; Sciortino, S. ; Garmire, G. P. / The Chandra Deep Field-North survey. XVII. Evolution of magnetic activity in old late-type stars. In: Astrophysical Journal. 2004 ; Vol. 611, No. 2 I. pp. 1107-1120.
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abstract = "The extremely sensitive Chandra Deep Field-North (CDF-N) pencil-beam X-ray survey is used to identify and characterize the X-ray emission from old high-latitude main-sequence Galactic stars. Our principal goal is to investigate the expected long-term decay of magnetic activity of late-type stars due to the gradual spin-down of stellar rotation from a magnetized stellar wind. Thirteen X-ray sources are associated with late-type stars; 11 of these constitute a well-defined sample for statistical analysis. This sample consists of two G, two K0-K4, and seven M2-M5 stars with median V-band magnitude around 19 and median distance around 300 pc. X-ray luminosities are typically log LX ≃ 27 ergs s-1 but are substantially higher in two cases. The combination of large-amplitude variations on timescales of hours and plasma temperatures around 5-30 MK indicates that the observed X-ray emission is dominated by magnetic reconnection flares rather than quiescent coronal emission. These X-ray properties are quantitatively similar to those seen in the active contemporary Sun. The CDF-N stellar sample is compared to simulations based on convolution of X-ray luminosity functions (XLFs) with the known spatial distribution of old-disk stars. The model indicates that the CDF-N stars are the most magnetically active old-disk stars. A substantial decline in X-ray luminosities over the 1 Gyr < t < 11 Gyr age interval is required: 39 rather than 11 stars should have been detected if the XLF does not evolve over this time interval. This is a clear demonstration that the coronal and flaring components of stellar magnetic activity - and presumably the interior magnetic dynamos responsible for the reconnecting fields at the stellar surface - exhibit long-term decay over the age of the Galactic disk. The model that best fits the magnitudes, spectral types, and X-ray luminosities of the sample has L x ∞ t-2 ergs s-1, which is faster than the t-1 decay rate predicted from widely accepted rotational spin-down rates and X-ray-activity relations.",
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Feigelson, ED, Hornschemeier, AE, Micela, G, Bauer, FE, Alexander, DM, Brandt, WN, Favata, F, Sciortino, S & Garmire, GP 2004, 'The Chandra Deep Field-North survey. XVII. Evolution of magnetic activity in old late-type stars', Astrophysical Journal, vol. 611, no. 2 I, pp. 1107-1120. https://doi.org/10.1086/422248

The Chandra Deep Field-North survey. XVII. Evolution of magnetic activity in old late-type stars. / Feigelson, E. D.; Hornschemeier, A. E.; Micela, G.; Bauer, F. E.; Alexander, D. M.; Brandt, W. N.; Favata, F.; Sciortino, S.; Garmire, G. P.

In: Astrophysical Journal, Vol. 611, No. 2 I, 20.08.2004, p. 1107-1120.

Research output: Contribution to journalReview article

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T1 - The Chandra Deep Field-North survey. XVII. Evolution of magnetic activity in old late-type stars

AU - Feigelson, E. D.

AU - Hornschemeier, A. E.

AU - Micela, G.

AU - Bauer, F. E.

AU - Alexander, D. M.

AU - Brandt, W. N.

AU - Favata, F.

AU - Sciortino, S.

AU - Garmire, G. P.

PY - 2004/8/20

Y1 - 2004/8/20

N2 - The extremely sensitive Chandra Deep Field-North (CDF-N) pencil-beam X-ray survey is used to identify and characterize the X-ray emission from old high-latitude main-sequence Galactic stars. Our principal goal is to investigate the expected long-term decay of magnetic activity of late-type stars due to the gradual spin-down of stellar rotation from a magnetized stellar wind. Thirteen X-ray sources are associated with late-type stars; 11 of these constitute a well-defined sample for statistical analysis. This sample consists of two G, two K0-K4, and seven M2-M5 stars with median V-band magnitude around 19 and median distance around 300 pc. X-ray luminosities are typically log LX ≃ 27 ergs s-1 but are substantially higher in two cases. The combination of large-amplitude variations on timescales of hours and plasma temperatures around 5-30 MK indicates that the observed X-ray emission is dominated by magnetic reconnection flares rather than quiescent coronal emission. These X-ray properties are quantitatively similar to those seen in the active contemporary Sun. The CDF-N stellar sample is compared to simulations based on convolution of X-ray luminosity functions (XLFs) with the known spatial distribution of old-disk stars. The model indicates that the CDF-N stars are the most magnetically active old-disk stars. A substantial decline in X-ray luminosities over the 1 Gyr < t < 11 Gyr age interval is required: 39 rather than 11 stars should have been detected if the XLF does not evolve over this time interval. This is a clear demonstration that the coronal and flaring components of stellar magnetic activity - and presumably the interior magnetic dynamos responsible for the reconnecting fields at the stellar surface - exhibit long-term decay over the age of the Galactic disk. The model that best fits the magnitudes, spectral types, and X-ray luminosities of the sample has L x ∞ t-2 ergs s-1, which is faster than the t-1 decay rate predicted from widely accepted rotational spin-down rates and X-ray-activity relations.

AB - The extremely sensitive Chandra Deep Field-North (CDF-N) pencil-beam X-ray survey is used to identify and characterize the X-ray emission from old high-latitude main-sequence Galactic stars. Our principal goal is to investigate the expected long-term decay of magnetic activity of late-type stars due to the gradual spin-down of stellar rotation from a magnetized stellar wind. Thirteen X-ray sources are associated with late-type stars; 11 of these constitute a well-defined sample for statistical analysis. This sample consists of two G, two K0-K4, and seven M2-M5 stars with median V-band magnitude around 19 and median distance around 300 pc. X-ray luminosities are typically log LX ≃ 27 ergs s-1 but are substantially higher in two cases. The combination of large-amplitude variations on timescales of hours and plasma temperatures around 5-30 MK indicates that the observed X-ray emission is dominated by magnetic reconnection flares rather than quiescent coronal emission. These X-ray properties are quantitatively similar to those seen in the active contemporary Sun. The CDF-N stellar sample is compared to simulations based on convolution of X-ray luminosity functions (XLFs) with the known spatial distribution of old-disk stars. The model indicates that the CDF-N stars are the most magnetically active old-disk stars. A substantial decline in X-ray luminosities over the 1 Gyr < t < 11 Gyr age interval is required: 39 rather than 11 stars should have been detected if the XLF does not evolve over this time interval. This is a clear demonstration that the coronal and flaring components of stellar magnetic activity - and presumably the interior magnetic dynamos responsible for the reconnecting fields at the stellar surface - exhibit long-term decay over the age of the Galactic disk. The model that best fits the magnitudes, spectral types, and X-ray luminosities of the sample has L x ∞ t-2 ergs s-1, which is faster than the t-1 decay rate predicted from widely accepted rotational spin-down rates and X-ray-activity relations.

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