Swift Observations of NGC 1275 Find Historically High UV and X-ray Fluxes

ATel #18085; Jon M. Miller, Tianyin Hu, Sarah Ketchum, Missagh Mehdipour, Veronica Tananko, Xin Xiang (Univ. of Michigan)
on 1 Oct 2026; 23:18 UT
Credential Certification: Jon Miller (jonmm@umich.edu)

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NGC 1275 is the bright central galaxy within the Perseus cluster. It harbors a black hole that launches powerful radio jets that ultimately reshape the intracluster medium (e.g., Fabian et al. 2003). Although it is also known as 3C 84, a very strong and potentially (misaligned) blazar-like radio source, neutral Fe K lines in the X-ray spectra of NGC 1275 suggest that the accretion flow may see the hard X-ray corona (e.g., Hitomi Collaboration 2018). This would signal that the central engine is visible and traceable. A recent analysis of X-ray monitoring with the Neil Gehrels Swift Observatory found an especially bright flaring near MJD 59956 (Ketchum et al. 2026). More recently, NGC 1275 has shown historically high flux in gamma-ray and radio bands (ATEL #18060 #18062 #18064 #18079). We therefore requested new, dense monitoring with Swift, to understand the nature of flaring events on shorter time scales.

The UVOT M2 filter has the smallest red leak of the UV filters aboard Swift, and affords the best measure of UV emission. In an observation starting on MJD 61297.3 (14 Sept. 2026), the M2 flux density was the highest yet observed over 20 years of Swift monitoring, at F_nu = 1.35 +/- 0.01 E-14 erg/s/cm^2/A (m_M2 = 15.53 +/- 0.04 in the AB system). Contemporaneously, the unabsorbed 0.3-10 keV flux reached the highest level yet detected, F = 1.4 +/- 0.1 E-10 erg/s/cm^2. The flux in both bands varies significantly between days, and potentially within single days. For a plot of the M2 lightcurve from the full Swift mission, see:

https://sites.lsa.umich.edu/jonmm/2026/10/01/ngc-1275-in-uv/

We will continue monitoring NGC 1275 with Swift, and we will report more developments. We thank the Swift team for making this possible.

References

Fabian, A., et al., 2003, MNRAS, 344, L43
Hitomi Collaboration, 2018, PASJ, 70, 13
Ketchum, S., et al., 2026, ApJ, 1008, L28