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Published January 2017 | Published
Journal Article Open

On the black hole mass of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342

Abstract

Narrow-line Seyfert 1 galaxies have been identified by the Fermi Gamma-Ray Space Telescope as a rare class of γ-ray emitting active galactic nuclei. The lowest redshift candidate among them is the source 1H 0323+342. Here we present quasi-simultaneous Gemini near-infrared and Keck optical spectroscopy for it, from which we derive a black hole mass based on both the broad Balmer and Paschen emission lines. We supplement these observations with a Nuclear Spectroscopic Telescope Array X-ray spectrum taken about two years earlier, from which we constrain the black hole mass based on the short time-scale spectral variability. Our multiwavelength observations suggest a black hole mass of ∼2 × 10^7 M_⊙, which agrees well with previous estimates. We build the spectral energy distribution and show that it is dominated by the thermal and reprocessed emission from the accretion disc rather than the non-thermal jet component. A detailed spectral fitting with the energy-conserving accretion disc model of Done et al. constrains the Eddington ratio to L/LEdd ∼ 0.5 for a (non-rotating) Schwarzschild black hole and to L/LEdd ∼ 1 for a Kerr black hole with dimensionless spin of a^★ = 0.8. Higher spin values and so higher Eddington ratios are excluded, since they would strongly overpredict the observed soft X-ray flux.

Additional Information

© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 September 23. Received 2016 September 20; in original form 2016 August 25. MJW and DK would like to thank the Observatoire de Paris for its hospitality and support during some months of this work in the framework of the Laboratoire Européen Associé (LEA) ELGA (European Laboratory for Gamma-ray Astronomy). We thank Maria Marchã for kindly making their optical spectrum available to us in electronic format. HL is supported by a European Union COFUND/Durham Junior Research Fellowship (under EU grant agreement number 267209). MB acknowledges support from the National Aeronautics and Space Administration (NASA) Headquarters under the NASA Earth and Space Science Fellowship Program grant no. NNX14AQ07H. DK acknowledges the receipt of an STFC studentship. This work is partly based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and NASA. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. This work made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory and funded by NASA.

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Created:
August 19, 2023
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October 25, 2023