NuSTAR spectral analysis beyond 79 keV with stray light
arXiv:2209.14325 · doi:10.3847/1538-4357/ac8c94
Abstract
Due to the structure of the NuSTAR telescope, photons at large off-axis (> 1deg) can reach the detectors directly (stray light), without passing through the instrument optics. At these off-axis angles NuSTAR essentially turns into a collimated instrument and the spectrum can extend to energies above the Pt k-edge (79 keV) of the multi-layers, which limits the effective area bandpass of the optics. We present the first scientific spectral analysis beyond 79 keV using a Cygnus X-1 observation in StrayCats, the catalog of stray light observations. This serendipitous stray light observation occurred simultaneously with an INTEGRAL observation. When the spectra are modeled together in the 30-120 keV energy band, we find that the NuSTAR stray light flux is well calibrated and constrained to be consistent with the INTEGRAL flux at the 90% confidence level. Furthermore, we explain how to treat the background of the stray light spectral analysis, which is especially important at high energies.
Accepted for publication in ApJ
References in corpus (6)
- NuSTAR Observations of the Bullet Cluster: Constraints on Inverse Compton Emission
- Jet contributions to the broad-band spectrum of Cyg X-1 in the hard state
- StrayCats: A catalog of NuSTAR Stray Light Observations
- Observations of Cygnus X-1 in the MeV band by the INTEGRAL imager
- Extending the baseline for SMC X-1's spin and orbital behavior with NuSTAR stray light
- StrayCats II: An Updated Catalog of NuSTAR Stray Light Observations