PEARLS: NuSTAR and XMM-Newton Extragalactic Survey of the JWST North Ecliptic Pole Time-Domain Field V:…

Abstract

As one of the first deep time-domain surveys in the hard X-ray band, the NuSTAR campaign in the JWST North Ecliptic Pole Time Domain Field (NEP-TDF) offers a prime opportunity to measure variability in a faint population of Active Galactic Nuclei (AGN) in the medium-to-high redshift universe. In the X-ray band, AGN variability is generally caused by changes in the brightness of the corona (F_int variability) or changes in the column density of obscuring material near the SMBH (N_H variability). Broad-band spectroscopy (∼0.5-24 keV) is required to reliably disentangle these two phenomena. With simultaneous NuSTAR and XMM-Newton coverage---as well as 1.8 Ms of Chandra monitoring---the X-ray surveys in the NEP-TDF are ideally situated for this purpose. This work presents the first spectral modeling of the 52 NuSTAR-identified sources discovered in the latter half of the campaign, as well as a spectroscopic variability study of the entire 112-source NuSTAR NEP-TDF catalog. Seven variable candidates are identified. We find that ≳ 1000 total counts split across many (≳ 10) epochs are needed in order to detect variability. Additionally, variable sources are compared to the survey sensitivity in order to inform population synthesis models of how variations can affect the detectability of faint AGN, which dominate the SMBH accretion history. Lastly, the timescale of N_H variability is investigated as a probe for the obscurer location. Significant variability is slightly more common on > 100 day timescales, suggesting that the torus may have only slight dominance in driving N_H variability in faint AGN.

PEARLS: NuSTAR and XMM-Newton Extragalactic Survey of the JWST North Ecliptic Pole Time-Domain Field IV: X-Ray Variability Analysis
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BibTeX RIS

BibTeX

@misc{creech2026pearls,
  title = {{PEARLS: NuSTAR and XMM-Newton Extragalactic Survey of the JWST North Ecliptic Pole Time-Domain Field V: Unraveling X-ray Spectral Variability}},
  author = {Samantha Creech and Francesca Civano and Daniel Wik and Núria Torres-Alba and Ross Silver and Xiurui Zhao and Tonima Ananna and Gibson Bowling and Norman A. Grogin and Anton M. Koekemoer and Peter Maksym and Sylvia Mesicek and Rafael Ortiz III and Payaswini Saikia and Steven Willner and Rogier Windhorst},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.08920},
  eprint = {2610.08920},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.08920},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - PEARLS: NuSTAR and XMM-Newton Extragalactic Survey of the JWST North Ecliptic Pole Time-Domain Field V: Unraveling X-ray Spectral Variability
AU  - Samantha Creech
AU  - Francesca Civano
AU  - Daniel Wik
AU  - Núria Torres-Alba
AU  - Ross Silver
AU  - Xiurui Zhao
AU  - Tonima Ananna
AU  - Gibson Bowling
AU  - Norman A. Grogin
AU  - Anton M. Koekemoer
AU  - Peter Maksym
AU  - Sylvia Mesicek
AU  - Rafael Ortiz III
AU  - Payaswini Saikia
AU  - Steven Willner
AU  - Rogier Windhorst
PY  - 2026
DA  - 2026/10/08
PB  - arXiv
DO  - 10.48550/arxiv.2610.08920
UR  - https://arxiv.org/abs/2610.08920
AB  - As one of the first deep time-domain surveys in the hard X-ray band, the NuSTAR campaign in the JWST North Ecliptic Pole Time Domain Field (NEP-TDF) offers a prime opportunity to measure variability in a faint population of Active Galactic Nuclei (AGN) in the medium-to-high redshift universe. In the X-ray band, AGN variability is generally caused by changes in the brightness of the corona (F_int variability) or changes in the column density of obscuring material near the SMBH (N_H variability). Broad-band spectroscopy (∼0.5-24 keV) is required to reliably disentangle these two phenomena. With simultaneous NuSTAR and XMM-Newton coverage---as well as 1.8 Ms of Chandra monitoring---the X-ray surveys in the NEP-TDF are ideally situated for this purpose. This work presents the first spectral modeling of the 52 NuSTAR-identified sources discovered in the latter half of the campaign, as well as a spectroscopic variability study of the entire 112-source NuSTAR NEP-TDF catalog. Seven variable candidates are identified. We find that ≳ 1000 total counts split across many (≳ 10) epochs are needed in order to detect variability. Additionally, variable sources are compared to the survey sensitivity in order to inform population synthesis models of how variations can affect the detectability of faint AGN, which dominate the SMBH accretion history. Lastly, the timescale of N_H variability is investigated as a probe for the obscurer location. Significant variability is slightly more common on > 100 day timescales, suggesting that the torus may have only slight dominance in driving N_H variability in faint AGN.
ER  -

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