article published yes M. Lynne Saade author Murray Brightman author Daniel Stern author Thomas Connor author S. G. Djorgovski author Daniel J. D’Orazio author K. E. S. Ford author Matthew J. Graham author Zoltán Haiman author 7c006e8c-cc0d-11ee-8322-cb904ef76f36 Hyunsung D. Jun author Elias Kammoun author Ralph P. Kraft author Barry McKernan author Alexei Vikhlinin author Dominic J. Walton author We present an analysis of NuSTAR X-ray observations of three active galactic nuclei (AGN) that were identified as candidate subparsec binary supermassive black hole (SMBH) systems in the Catalina Real-Time Transient Survey based on apparent periodicity in their optical light curves. Simulations predict that close-separation accreting SMBH binaries will have different X-ray spectra than single accreting SMBHs. We previously observed these AGN with Chandra and found no differences between their low-energy X-ray properties and the larger AGN population. However, some models predict differences to be more prominent at energies higher than probed by Chandra. We find that even at the higher energies probed by NuSTAR, the spectra of these AGN are indistinguishable from the larger AGN population. This could rule out models predicting large differences in the X-ray spectra in the NuSTAR bands. Alternatively, it might mean that these three AGN are not binary SMBHs. American Astronomical Society2024 eng 0004-637X 1538-435710.3847/1538-4357/ad372e 9661 yes Saade ML, Brightman M, Stern D, et al. NuSTAR observations of candidate subparsec binary supermassive black holes. <i>The Astrophysical Journal</i>. 2024;966(1). doi:<a href="https://doi.org/10.3847/1538-4357/ad372e">10.3847/1538-4357/ad372e</a> M. L. Saade <i>et al.</i>, “NuSTAR observations of candidate subparsec binary supermassive black holes,” <i>The Astrophysical Journal</i>, vol. 966, no. 1. American Astronomical Society, 2024. Saade, M. Lynne, et al. “NuSTAR Observations of Candidate Subparsec Binary Supermassive Black Holes.” <i>The Astrophysical Journal</i>, vol. 966, no. 1, 104, American Astronomical Society, 2024, doi:<a href="https://doi.org/10.3847/1538-4357/ad372e">10.3847/1538-4357/ad372e</a>. M.L. Saade, M. Brightman, D. Stern, T. Connor, S.G. Djorgovski, D.J. D’Orazio, K.E.S. Ford, M.J. Graham, Z. Haiman, H.D. Jun, E. Kammoun, R.P. Kraft, B. McKernan, A. Vikhlinin, D.J. Walton, The Astrophysical Journal 966 (2024). Saade ML, Brightman M, Stern D, Connor T, Djorgovski SG, D’Orazio DJ, Ford KES, Graham MJ, Haiman Z, Jun HD, Kammoun E, Kraft RP, McKernan B, Vikhlinin A, Walton DJ. 2024. NuSTAR observations of candidate subparsec binary supermassive black holes. The Astrophysical Journal. 966(1), 104. Saade, M. L., Brightman, M., Stern, D., Connor, T., Djorgovski, S. G., D’Orazio, D. J., … Walton, D. J. (2024). NuSTAR observations of candidate subparsec binary supermassive black holes. <i>The Astrophysical Journal</i>. American Astronomical Society. <a href="https://doi.org/10.3847/1538-4357/ad372e">https://doi.org/10.3847/1538-4357/ad372e</a> Saade, M. Lynne, Murray Brightman, Daniel Stern, Thomas Connor, S. G. Djorgovski, Daniel J. D’Orazio, K. E. S. Ford, et al. “NuSTAR Observations of Candidate Subparsec Binary Supermassive Black Holes.” <i>The Astrophysical Journal</i>. American Astronomical Society, 2024. <a href="https://doi.org/10.3847/1538-4357/ad372e">https://doi.org/10.3847/1538-4357/ad372e</a>. 175172024-09-05T08:57:37Z2024-09-10T14:31:31Z