ASCA observations of the coronal X-ray emission of Algol

Antunes, A.; Nagase, F.; White, N. E.

doi:10.1086/187638

Cited by 42 publications

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“…This is exemplified in Table 3, which shows that for example the oxygen abundance changes by a factor two for models with discrete temperature components. A comparison of the abundances derived for Algol in this paper with those derived by Antunes et al (1994) from ASCA using a two-temperature variable abundance modeling approach also shows that the general trend in the run of elemental abundances is captured and the "low" iron abundance and "high" neon abundance are recognized, while the abundances of individual elements can vary by at least a factor of two. Also, the real clue of the Chandra LETGS Algol observation, i.e., the overabundance of nitrogen with its profound physical implications (cf.…”

Section: Discussionmentioning

confidence: 66%

“…Deviations from solar abundances in the X-ray spectra of stars were first reported on the basis of ASCA CCD spectra of stars like Algol (cf. Antunes et al 1994) and AR Lac (cf. White et al 1994); also the even lower resolution PSPC spectra of some active stars were found to be better fitted with metal-depleted rather than solar-abundance plasma models (for example, Algol, cf.…”

Section: Introductionmentioning

confidence: 99%

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Coronal abundances from high-resolution X-ray data: The case of Algol

Schmitt

Ness

2004

A&A

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Abstract.We discuss the determination of elemental abundances from high resolution X-ray data. We emphasize the need for an accurate determination of the underlying temperature structure and advocate the use of a line ratio method which allows us to utilize, first, the strongest lines observed in the X-ray spectra, and second, lines that span a rather wide temperature range. We point out the need to use continuous emission measure distributions and show via example that modeling in terms of individual temperature components yields errors of more than 50%. We stress the need to derive differential emission measure distributions based on physical assumptions and considerations. We apply our methods to the Chandra LETGS spectrum of Algol and show that nitrogen is considerably enhanced compared to cosmic abundances by a factor of 2 while carbon is depleted by at least a factor of 25. Iron, silicon, and magnesium, are all depleted compared to cosmic abundances, while the noble gas neon has the relatively highest abundance.

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Section: Discussionmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Coronal abundances from high-resolution X-ray data: The case of Algol

Schmitt

Ness

2004

A&A

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“…Since the spectral information of ABs in the iron K-shell band has been very limited so far, we estimate the EW from the observed Fe abundance and plasma temperature. The mean temperature and iron abundance are reported to be ∼3 keV, and ∼0.3 solar, respectively (Tsuru et al 1989;Doyle et al 1991;Dempsey et al 1993;Antunes et al 1994;White et al 1994;Güdel et al 1999;Osten et al 2000;Audard et al 2003;Pandey & Singh 2012), and hence the EW 6.4 is negligible, and the sum of EW 6.7 and EW 6.97 is estimated to be ∼650 eV. Recently, Xu et al (2016) obtained EW 6.4 ≤20 eV, EW 6.7 ∼286 eV and EW 6.97 ∼12 eV from the 4 Suzaku samples.…”

Section: Iron Line Equivalent Widths and Scale Heights Of Cvs Abs Anmentioning

confidence: 99%

Scale heights and equivalent widths of the iron K-shell lines in the Galactic diffuse X-ray emission

Yamauchi

Nobukawa

et al. 2016

Publications of the Astronomical Society of Japan

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This paper reports the analysis of the X-ray spectra of the Galactic diffuse X-ray emission (GDXE) in the Suzaku archive. The fluxes of the Fe I Kα (6.4 keV), Fe XXV Heα (6.7 keV) and Fe XXVI Lyα (6.97 keV) lines are separately determined. From the latitude distributions, we confirm that the GDXE is decomposed into the Galactic center (GCXE), the Galactic bulge (GBXE) and the Galactic ridge (GRXE) X-ray emissions. The scale heights (SHs) of the Fe XXV Heα line of the GCXE, GBXE and GRXE are determined to be ∼40, ∼310 and ∼140 pc, while those of the Fe I Kα line are ∼30, ∼160 and ∼70 pc, respectively. The mean equivalent widths (EWs) of the sum of the Fe XXV Heα and Fe XXVI Lyα lines are ∼750 eV, ∼600 eV and ∼550 eV, while those of the Fe I Kα line are ∼150 eV, ∼60 eV and ∼100 eV for the GCXE, GBXE and GRXE, respectively. The origin of the GBXE, GRXE and GCXE is 1 separately discussed based on the new results of the SHs and EWs, in comparison with those of the Cataclysmic Variables (CVs), Active Binaries (ABs) and Coronal Active stars (CAs).

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“…The Ginga and ASCA satellites could constrain the iron abundance (Ginga) and other elemental abundances (O, Mg, Si, S, Ar, Ca: ASCA) separately, typically yielding a coronal underabundance in active binaries (Doyle et al 1991;Antunes, Nagase, & White 1994). There also was evidence of changing abundances during flare intervals (Ottmann & Schmitt 1996;Favata & Schmitt 1999).…”

Section: Introductionmentioning

confidence: 99%

Chandra,Extreme Ultraviolet Explorer, and Very Large Array Observations of the Active Binary System σ²Coronae Borealis

Osten

Ayres

Brown

et al. 2003

ApJ

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We present the results of a coordinated observing campaign on the short-period RS CVn binary 2 Coronae Borealis (F6V þ G0V; P orb ¼ 1:14 days) with the Very Large Array, the Extreme Ultraviolet Explorer, and the Chandra X-Ray Observatory High-Energy Transmission Grating Spectrometer. The radio emission is consistent with previously determined quiescent gyrosynchrotron properties. Multiple flares were seen with Extreme Ultraviolet Explorer, five occurring within two consecutive orbital periods. The first of these flares was observed with Chandra. The Chandra observations of 2 CrB showed no systematic variations of line fluxes, widths, or Doppler shifts with orbital phase, nor any response in line width or offset due to the flare. This is consistent with both stars being equally active coronal emitters. We have developed a self-consistent method of spectral analysis to derive information from the line and continuum emissions concerning the distribution of plasma with temperature and elemental abundances. A bimodal temperature distribution is appropriate for both quiescent and flare intervals, with a stable peak at 6-8 MK and another variable enhancement at higher temperatures, with evidence for significant contribution from temperatures up to 50 MK during the flare, compared to 30 MK during quiescence. The iron abundance is subsolar during quiescence but is enriched by about a factor of 2 during a large flare seen with Chandra. The noble gas elements neon and argon show elevated abundances with respect to iron, but there is no clear evidence for any first ionization potential-based abundance pattern during quiescence or the flare. We have determined coronal electron densities from the helium-like ions O vii, Ne ix, Mg xi, and Si xiii, which imply densities !10 10 cm À3 . There is a small enhancement in the electron densities derived for the flare, but it is not statistically significant. We call attention to electron temperature constraints provided by the ratios of 1s 2 1 S 0 -1snp 1 P 1 transitions of the helium-like ions O vii, Ne ix, Mg xi, and Si xiii. The derived coronal electron pressures change by 1-2 orders of magnitude over a 25% change in temperature, implying nonisobaric coronal conditions. We find no evidence for significant departures from the effectively thin coronal assumption. The electron densities inferred from the soft X-ray spectra are inconsistent with cospatial gyrosynchrotron emission; further observations are necessary to discriminate the relative locations of the radio and soft X-ray-emitting plasma.

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ASCA observations of the coronal X-ray emission of Algol

Cited by 42 publications

References 0 publications

Coronal abundances from high-resolution X-ray data: The case of Algol

Coronal abundances from high-resolution X-ray data: The case of Algol

Scale heights and equivalent widths of the iron K-shell lines in the Galactic diffuse X-ray emission

Chandra,Extreme Ultraviolet Explorer, and Very Large Array Observations of the Active Binary System σ²Coronae Borealis

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ASCA observations of the coronal X-ray emission of Algol

Cited by 42 publications

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Coronal abundances from high-resolution X-ray data: The case of Algol

Coronal abundances from high-resolution X-ray data: The case of Algol

Scale heights and equivalent widths of the iron K-shell lines in the Galactic diffuse X-ray emission

Chandra,Extreme Ultraviolet Explorer, and Very Large Array Observations of the Active Binary System σ2Coronae Borealis

Contact Info

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Chandra,Extreme Ultraviolet Explorer, and Very Large Array Observations of the Active Binary System σ²Coronae Borealis