Establishing HZ43 A, Sirius B, and RX J185635-3754 as soft X-ray standards: a
cross-calibration between the Chandra LETG+HRC-S, the EUVE spectrometer,
and the ROSAT PSPC

Beuermann, K.; Burwitz, V.; Rauch, T.

doi:10.1051/0004-6361:20065478

Cited by 42 publications

(91 citation statements)

References 59 publications

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“…RX J1856.4−3754 was established as a low-energy calibration target for missions such as Chandra, Suzaku, Swift, and XMM-Newton 1 , and exhibits a high soft X-ray and low optical flux. Its spectrum is free from prominent line features and described well by two black bodies (Beuermann et al 2006). We compare archival XMM-Newton EPIC data of RX J1856.4−3754, which span more than five years, with the model spectra of Beuermann et al (2006) and carefully adjust the instrumental effective areas.…”

Section: Introductionmentioning

confidence: 99%

“…Its spectrum is free from prominent line features and described well by two black bodies (Beuermann et al 2006). We compare archival XMM-Newton EPIC data of RX J1856.4−3754, which span more than five years, with the model spectra of Beuermann et al (2006) and carefully adjust the instrumental effective areas. In this approach, we assume that the energy redistribution is independent of the incident energy when considering only objects with very soft X-ray spectra.…”

Section: Introductionmentioning

confidence: 99%

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X-ray spectroscopy and photometry of the long-period polar AI Trianguli with XMM-Newton

Traulsen

Reinsch

Schwarz

et al. 2010

A&A

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Context. The energy balance of cataclysmic variables with strong magnetic fields is a central subject in understanding accretion processes on magnetic white dwarfs. With XMM-Newton, we perform a spectroscopic and photometric study of soft X-ray selected polars during their high states of accretion. Aims. On the basis of X-ray and optical observations of the magnetic cataclysmic variable AI Tri, we derive the properties of the spectral components, their flux contributions, and the physical structure of the accretion region in soft polars.Methods. We use multi-temperature approaches in our xspec modeling of the X-ray spectra to describe the physical conditions and the structures of the post-shock accretion flow and the accretion spot on the white-dwarf surface. In addition, we investigate the accretion geometry of the system by completing a timing analysis of the photometric data. Results. Flaring soft X-ray emission from the heated surface of the white dwarf dominates the X-ray flux during roughly 70% of the binary cycle. This component deviates from a single black body and can be described by a superimposition of mildly absorbed black bodies with a Gaussian temperature distribution between kT bb,low := 2 eV and kT bb,high = 43.9 +3.3 −3.2 eV, and N H,ISM = 1.5 +0.8 −0.7 ×10 20 cm −2 . In addition, weaker hard X-ray emission is visible nearly all the time. The spectrum from the cooling post-shock accretion flow is most closely fitted by a combination of thermal plasma mekal models with temperature profiles adapted from prior stationary two-fluid hydrodynamic calculations. The resulting plasma temperatures lie between kT MEKAL,low = 0.8 +0.4 −0.2 keV and kT MEKAL,high = 20.0 +9.9 −6.1 keV; additional intrinsic, partial-covering absorption is on the order of N H,int = 3.3 +2.5 −1.2 × 10 23 cm −2 . The soft X-ray light curves show a dip during the bright phase, which can be interpreted as self-absorption in the accretion stream. Phase-resolved spectral modeling supports the picture of one-pole accretion and self-eclipse. One of the optical light curves corresponds to an irregular mode of accretion. During a short XMM-Newton observation at the same epoch, the X-ray emission of the system is clearly dominated by the soft component.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

X-ray spectroscopy and photometry of the long-period polar AI Trianguli with XMM-Newton

Traulsen

Reinsch

Schwarz

et al. 2010

A&A

Self Cite

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“…HZ 43A is monitored regularly since then, but as we are only interested in the ratio of the spectra of Sirius B to HZ 43A, and HZ 43 A is the strongest source, the statistical uncertainty on the ratio is dominated by the statistical uncertainty of the Sirius B spectrum. Moreover, the sensitivity of the LETGS slowly decreases over time (Beuermann et al 2006), and therefore it is important to compare observations not too far apart in time.…”

Section: Discussionmentioning

confidence: 99%

“…For instance, the source could have a more complicated atmosphere, or there may be multiple hot spots or a single spot with multi-temperature structure. Also, comparing our model calculations to the models derived by Beuermann et al (2006) shows some significant differences, even if the same stellar parameters are used (see Sect. 5.5).…”

Section: Introductionmentioning

confidence: 96%

“…More recently, Beuermann et al (2006) have tackled the problem of cross-calibration again using LETGS spectra of Sirius B, HZ 43A as well as RXJ 1856.5−3754. Assuming a double blackbody model for the latter source, and running grids of white dwarf models for the first two sources, they derived the effective area of the LETGS by fitting simultaneously the parameters of these stars and the effective area correction factor.…”

Section: Introductionmentioning

confidence: 99%

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Effective area calibration of the reflection grating spectrometers of XMM-Newton

Kaastra

Lanz

Hubený

et al. 2009

A&A

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Context. White dwarf spectra have been widely used as a calibration source for X-ray and EUV instruments. The in-flight effective area calibration of the reflection grating spectrometers (RGS) of XMM-Newton depend upon the availability of reliable calibration sources. Aims. We investigate how well these white dwarf spectra can be used as standard candles at the lowest X-ray energies in order to gauge the absolute effective area scale of X-ray instruments. Methods. We calculate a grid of model atmospheres for Sirius B and HZ 43A, and adjust the parameters using several constraints until the ratio of the spectra of both stars agrees with the ratio as observed by the low energy transmission grating spectrometer (LETGS) of Chandra. This ratio is independent of any errors in the effective area of the LETGS. Results. We find that we can constrain the absolute X-ray spectrum of both stars with better than 5% accuracy. The best-fit model for both stars is close to a pure hydrogen atmosphere, and we put tight limits to the amount of helium or the thickness of a hydrogen layer in both stars. Our upper limit to the helium abundance in Sirius B is 4 times below the previous detection based on EUVE data. We also find that our results are sensitive to the adopted cut-off in the Lyman pseudo-continuum opacity in Sirius B. We get best agreement with a long wavelength cut-off. Conclusions. White dwarf model atmospheres can be used to derive the effective area of X-ray spectrometers in the lowest energy band. An accuracy of 3-4% in the absolute effective area can be achieved.

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Unification of strongly magnetized neutron stars with regard to X‐ray emission from hot spots

et al. 2019

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Strongly magnetized isolated neutron stars (NSs) are categorized into two families according, mainly, to their magnetic field strength. The one with a higher magnetic field of 10 14 -10 15 Gauss is called "magnetar," and the other is the X-ray isolated neutron star (XINS) with 10 13 Gauss. Both magnetars and XINSs show thermal emission in X-rays, whose spectra are different. The soft X-ray spectrum (below 10 keV) of a magnetar is reproduced with a two-temperature blackbody (2BB), whereas that of an XINS shows only a single-temperature blackbody (1BB), and its temperature is even lower than that of magnetars. On the basis of the magnetic field and temperature, it is often speculated that XINSs may be old and cooled magnetars. However, no other strong observational evidence has yet been reported to support the speculation. Here, we report that all the seven known XINSs show high-temperature emission, which should have a similar origin to that of magnetars. Analyzing all the XMM-Newton data of the XINSs with the highest statistics ever achieved, we find that their X-ray spectra are all reproduced with a 2BB model, similar to magnetars, as opposed to the traditional 1BB model. Their emission radii and temperature ratios are also similar to those of magnetars except for two XINSs, which show significantly smaller radii than the others. The remarkable similarity in the X-ray spectra between XINSs and magnetars suggests that the origins of their emitting regions are also the same. The lower temperature in XINSs can be explained if XINSs are older than magnetars. Therefore, this result is another observational indication that supports the standard hypothesis of classification of highly magnetized NSs. This article is based on our paper Yoneyama et al. (2019; accepted to PASJ).

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Establishing HZ43 A, Sirius B, and RX J185635-3754 as soft X-ray standards: a cross-calibration between the Chandra LETG+HRC-S, the EUVE spectrometer, and the ROSAT PSPC

Cited by 42 publications

References 59 publications

X-ray spectroscopy and photometry of the long-period polar AI Trianguli with XMM-Newton

X-ray spectroscopy and photometry of the long-period polar AI Trianguli with XMM-Newton

Effective area calibration of the reflection grating spectrometers of XMM-Newton

Unification of strongly magnetized neutron stars with regard to X‐ray emission from hot spots

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