Working Group
- Members
Vadim Burwitz (chair, ROSAT, Chandra, XMM,eROSITA)
Jelle Kaastra (Chandra, Modeling)
Herman Marshall (Chandra)
Norbert Schulz (Chandra)
Jeremy Drake (Chandra)
Steve Sembay (XMM EPIC-MOS)
Cor de Vries (XMM RGS)
Vadim Burwitz (Chandra)
Tadayasu Dotani, Eric Miller (Suzaku)
Isolated Neutron Stars
- Objects
RX J1856.5-3754
PSR B0656+14 - Data RX J1856.5-375
- Instruments:
- Chandra LETG + ACIS-S / HRC-S
- XMM EPIC-pn SW
- SWIFT
- Astrosat SXT
- Hitomi
- eROSITA calibration observations
- 2019 09 13 80ksec to be done
- 2019 09 24 80ksec to be done
- 2020 03 11 - 04 22 80ksec after survey #1
- Chandra LETGS+HRC-S observations
500ks OBS_IDs: 00113 03380 03381 03382 03399
120ks OBS_IDs: 14418 15293
- 172ks OBS_IDs: 21693 21896 (will be obvserved in the context of eROSITA calibration)
Chandra LETG + ACIS-S
- Models
RX J1856.5-3754 based on the CHANDRA LETGS + HRCS Data
delchisqr = 1 ( = 1 sigma for 1 parameter)
tbabs*bbodyrad
chiqs = 692.6
dof =1251
chired = 0.55367
nh = (7.24 +/- 0.34 ) * 1e19 cm-2
kT = ( 62.38 +/- 0.38 ) eV
norm = (1.580 +/- 0.064) * 1e5phabs*bbodyrad
chiqs = 696.0
dof =1251
chired = 0.55636
nh = (7.37 +/- 0.35 ) * 1e19 cm-2
kT = ( 62.43 +/- 0.38 ) eV
norm = (1.576 +/- 0.065) * 1e5
White Dwarfs
- Objects
HZ 43, Sirius B, GD 153
- Missions
EUVE, ROSAT, Chandra, XMM-Newton
- Data
- Chandra
- HZ 43
- Sirius B
- GD 153
- Chandra
- Results
see papers
HZ43 Fitting Function
The Beuermann et al 2006 paper uses the TMAP white dwarf atmosphere model of Werner et al for fitting. For the purposes of calibration efforts, C. Markwardt developed a fitting function that can be used in place of the full atmosphere model. The fit was done in the 0.1 - 1 keV range. Note that Beuermann et al INCLUDE interstellar absorption in their model, so it is not necessary to provide an additional absorption component.
The model can be used in XSPEC using "mdefine" statements. The model is a modified blackbody spectrum, whose "energy" is a polynomial of several terms. The kT value is the white dwarf temperature in keV, and the norm is the expected norm. (Note that a 2021 version of XSPEC or later is required)
mdefine poly_hz43 e*(0.955968 + e*(-0.699684 + e*(0.555432 + e*(-0.292088 + e*0.069582))))+dummy
mdefine hz43 8.0525*poly_hz43(0.0)**2/kT**4/(exp(poly_hz43(0.0)/kT)-1.0)
and then defined as
model hz43
0.0130643 -0.0001(0.000130643) 0.01 0.01 0.02 0.02
0.0395467 0.001(0.000395467) 0 0 1e+20 1e+24
Here the temperature of ~0.013 keV is the best-fit temperature using this fitting function, and does not represent the true white dwarf temperature. The norm of ~0.039 is the best-fit norm, and again is physically meaningless other than as a fitting coefficient. Using this model results in the following curve in the photon spectrum. Solid is the Beuermann et al curve and dashed is the model. The residual panel below demonstrates that the worst-case error in this fitting function approximation is 1%.
Papers
- http://cdsads.u-strasbg.fr/abs/2006A%26A...458..541B Beuermann, K., Burwitz, V., Rauch, T. 2006: ''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'', A&A 458,541
- http://cdsads.u-strasbg.fr/abs/2008HEAD...10.0406K Kaastra, J. S., Lanz, T., Hubeny, I., Paerels, F. 2008: ''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'', HEAD 10.0406
- http://cdsads.u-strasbg.fr/abs/2008A%26A...481..807R Rauch, T. 2008, ''Uncertainties in (E)UV model atmosphere fluxes'', A&A 481, 807
- http://cdsads.u-strasbg.fr/abs/2006A%26A...458..541B Kaastra, J. S., Lanz, T.. Hubeny, I.. Paerels, F. B. S. 2009, ''Effective area calibration of the reflection grating spectrometers of XMM-Newton. II. X-ray spectroscopy of DA white dwarfs'', A&A 497, 311
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