Calibration Targets
(Notes on some calibration targets:)
- N132D
- Brightest X-ray SNR in the LMC. Emission-line dominated X-ray spectrum with strong O
lines at 573 and 652 eV. Constant
spectrum. Source has an extent of a few arcminutes in the PSPC bandpass.
- HZ43
- Bright DA white dwarf with T_e ~ 55,000 K, nearly pure H atmosphere
and very low N_H. Commonly used for calibration the soft X-ray response.
- Crab
- Power-law emission spectrum due to synchrotron radiation. Size
is approximately 1.25 arcmin x 1.75 arcmin. Embedded 33 ms pulsar produces
~10 percent of X-ray flux. Source is bright enough to use as a rate-gain
calibration for the PSPC.
- Vela
- 10,000 yr old remnant of size approximately 6 degrees diameter. Several
hundred counts/sec in PSPC and KT ~ 0.13 keV.
Contains an X-ray pulsar embedded in an extended synchrotron nebula. X-ray
pulsations are found only in the lowest PSPC channels (below 0.85 keV). The
spectrum of the pulsar is complex, with an underlying power-law of
Gamma ~2., a black body from the pulsar, and thermal emission from
the SNR.The synchrotron nebula has a power-law of Gamma ~2 also. The
column density to the pulsar is very low (~10^{19} cm^{-2}).
Pulsar is ~2 UFU with a power-law spectrum. There is a one arcminute nebula surrounding the pulsar.
- Meaty
- White dwarf discovered by WFC team and thereafter used a soft calibration
source.
- AR LAC
- Eclipsing RS CVn. Two temperature spectrum with very low $N_H$ value.
Bright, unabsorbed point source used for detector point spread function
calibrations.
- CYG X-2
- LMXB, shallow X-ray dips seen at optical period (9.8 days).
Shows oxygen edge at 0.533 keV. Dust halo makes this an extended X-ray
source at soft X-ray energies.
- CYG X-3
- LMXB with high and low states. Partial eclipses observed. Heavily obscured
at low energies. Smooth, quasi-sinusoidal modulation suggests the observed
X-rays are scattered from an accretion disk corona.
- A2256
- Nearby (z=0.060) cluster of galaxies. X-ray luminosity (2-10 keV)
~3 times 10^{44} erg \ cm^{-2} \ s^{-1}. Core radius is 0.5
MPC (5 arcmin) and the distribution is smooth. No cooling flow.
- LMC X-1
- Black hole candidate, soft X-ray spectrum. Embedded in optical nebula.
Soft X-ray halo.
- LMC X-3
- BV3 star and black hole candidate. 1.7 day optical period but no X-ray
eclipses seen. Soft X-ray spectrum. Boresight target.
- CAS A
- Diameter four arcmin SNR. Spectral variations seen across the remnant. SSS
found a complex spectrum dominated by strong lines from He-like ions.
- MKN421
- BL Lac used a spectral calibration source during its bright state. The
assumption of a featureless spectrum, and the 150 ct/sec brightness were
the reasons it was used for recalibration of the matrix. Unfortunately this
source was affected by the rate-gain and this was not known at the time of
recalibration.
- Also used to test the tail of the PSPC point spread function to high S/N, after these tests the Lorentzian tail of the psf was eventually rescaled (CAL/ROS/92-001a and CAL/ROS/93-015).
- Also used to test the tail of the PSPC point spread function to high S/N, after these tests the Lorentzian tail of the psf was eventually rescaled (CAL/ROS/92-001a and CAL/ROS/93-015).
- BETA CAR, BETA LEO and Vega
- UV leak tests. These stars are A type which are strong UV emitters, but
emit no X-rays.
- GD695, BPM97895, and EG 187
- Bright hot DA white dwarfs.
Bright UV point sources, flux and spectral calibration for WFC
- Delta Dor, BETA Aur, EPS Lyr
- HRI UV leak cal sources.
Calibration Tasks
Return to the ROSAT GOF
Last Update: Jan 11, 1995
Curator:Michael Arida (ADNET); arida@milkyway.gsfc.nasa.gov
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