A Complete X-ray Spectral Survey of ISP BL Lac Objects in the 4LAC-DR3 High-Confidence Catalog: Evidence for a Rare Spectral Hardening Class

We present the first complete X-ray spectral survey of all 347 ISP BL Lac objects in the 4LAC-DR3 high-confidence catalog using archival Swift-XRT data. Of 347 targets, 242 had sufficient data, yielding 220 Class-S and 14 Class-H objects. Only 1WGA J0506.6-0857 exhibits statistically significant spectral hardening (p=0.037, beta=2.11). Results are interpreted under the delta-P_Ma Hypothesis (Katayama 2026). ORCID: 0009-0006-2290-6593 | TheYKHC Independent Research Institute

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Publication Details

Journal
Zenodo (CERN European Organization for Nuclear Research)
Published
2026-05-31
DOI
https://doi.org/10.5281/zenodo.20469861
Citations
2
Primary Topic
Astrophysical Phenomena and Observations
Type
preprint
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preprint

A Complete X-ray Spectral Survey of ISP BL Lac Objects in the 4LAC-DR3 High-Confidence Catalog: Evidence for a Rare Spectral Hardening Class

Yoshimitsu Katayama
2 citations
Zenodo (CERN European Organization for Nuclear Research)
Astrophysical Phenomena and Observations
preprint

A Complete X-ray Spectral Survey of ISP BL Lac Objects in the 4LAC-DR3 High-Confidence Catalog: Evidence for a Rare Spectral Hardening Class

Yoshimitsu Katayama
preprint en
2 citations

Abstract

We present the first complete X-ray spectral survey of all 347 ISP BL Lac objects in the 4LAC-DR3 high-confidence catalog using archival Swift-XRT data. Of 347 targets, 242 had sufficient data, yielding 220 Class-S and 14 Class-H objects. Only 1WGA J0506.6-0857 exhibits statistically significant spectral hardening (p=0.037, beta=2.11). Results are interpreted under the delta-P_Ma Hypothesis (Katayama 2026). ORCID: 0009-0006-2290-6593 | TheYKHC Independent Research Institute

Zenodo (CERN European Organization for Nuclear Research)
Oldham Council (GB)
Astrophysical Phenomena and Observations
DOIOpen Access PDFOpenAlex
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