Independent Black Hole Mass Estimation for the \gamma-ray Detected Archetypal Narrow-Line Seyfert 1 Galaxy 1H 0323+342 from X-ray Variability

TL;DR

This paper estimates the black hole mass of the gamma-ray detected NLS1 galaxy 1H 0323+342 using X-ray variability, confirming it has a lower mass similar to typical NLS1s rather than blazars, challenging previous estimates.

Contribution

It introduces an inclination-independent method to estimate black hole mass in gamma-ray NLS1s using X-ray variability, providing more accurate measurements.

Findings

Black hole mass of 1H 0323+342 is (2.8-7.9)×10^6 solar masses.

X-ray variability method confirms lower mass consistent with NLS1s.

Challenges previous virial method estimates for these galaxies.

Abstract

As a newly discovered class of radio-loud active galactic nuclei (AGNs), the \gamma-ray detected narrow-line Seyfert 1 galaxies (NLS1s) launch powerful jets which are generally found only in blazars and radio galaxies. However, their black hole (BH) masses as estimated from the broad emission lines are one order of magnitude or more lower than those in blazars. This brings new challenges for explaining the radio loudness triggering in AGNs. It is still under debate whether their BH masses from the commonly used virial method are underestimated. Here we present an estimate of the BH mass for the \gamma-ray detected NLS1 1H 0323+342, an archetype of this class, from the X-ray variability which is inclination independent. Our results independently confirm that this \gamma-ray detected NLS1 harbors a $(2.8-7.9)\times10^6\,M_{\odot}$ BH similar to those in normal NLS1s rather than those in blazars.