Matched-filtering line search methods applied to Suzaku data
Abstract
A detailed search for emission and absorption lines and an assessment of their upper limits are performed for Suzaku data. The method utilizes a matched-filtering approach to maximize the signal-to-noise ratio for a given energy resolution, which could be applicable to many types of line search. We first applied it to well-known active galactic nuclei spectra that have been reported to have ultra-fast outflows, and find that our results are consistent with previous findings at the ∼3σ level. We proceeded to search for emission and absorption features in two bright magnetars 4U 0142+61 and 1RXS J1708-4009, applying the filtering method to Suzaku data. We found that neither source showed any significant indication of line features, even using long-term Suzaku observations or dividing their spectra into spin phases. The upper limits on the equivalent width of emission/absorption lines are constrained to be a few eV at ∼1 keV and a few hundreds of eV at ∼10 keV. This strengthens previous reports that persistently bright magnetars do not show proton cyclotron absorption features in soft X-rays and, even if they exist, they would be broadened or much weaker than below the detection limit of X-ray CCD.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- December 2016
- DOI:
- 10.1093/pasj/psw091
- arXiv:
- arXiv:1609.06177
- Bibcode:
- 2016PASJ...68..100M
- Keywords:
-
- line: identification;
- methods: statistical;
- stars: magnetars;
- X-rays: general;
- X-rays: individual (4U 0142+61;
- 1RXS J1708-4009);
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 10 pages, 8 figures, accepted for publication in PASJ