Unveiling Sub-pc Supermassive Black Hole Binary Candidates in Active Galactic Nuclei

Journal
Date Issued
2020
Author(s)
•
•
•
•
Vignali, C
•
•
CICONE, CLAUDIA
•
Zaino, A
•
Dotti, M
•
Sesana, A
•
Gianolli, VE
•
Ballo, L
•
•
Matzeu, GA
DOI
Abstract
The elusive supermassive black hole binaries (SMBHBs) are thought to be the penultimate stage of galaxy mergers, preceding a final coalescence phase. SMBHBs are sources of continuous gravitational waves, possibly detectable by pulsar timing arrays; the identification of candidates could help in performing targeted gravitational wave searches. Due to SMBHBs’ origin in the innermost parts of active galactic nuclei (AGN), X-rays are a promising tool for unveiling their presence, by means of either double Fe Kα emission lines or periodicity in their light curve. Here we report on a new method for selecting SMBHBs by means of the presence of a periodic signal in their Swift Burst Alert Telescope (BAT) 105 month light curves. Our technique is based on Fisher’s exact g-test and takes into account the possible presence of colored noise. Among the 553 AGN selected for our investigation, only the Seyfert 1.5 galaxy Mrk 915 emerges as a candidate SMBHB; from subsequent analysis of its light curve we find a period P0 = 35 ± 2 months, and the null hypothesis is rejected at the 3.7σ confidence level. We also present a detailed analysis of the BAT light curve of the only previously X-ray-selected binary candidate source in the literature, the Seyfert 2 galaxy MCG+11-11-032. We find P0 = 26.3 ± 0.6 months, consistent with the one inferred from previously reported double Fe Kα emission lines.
Volume
902
Issue
1
Start page
10
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2020ApJ...902...10S
Rights
open.access
File(s)
Loading...
Thumbnail Image
Name

Serafinelli_2020_ApJ.pdf

Description
postprint
Size

794.91 KB

Format

Adobe PDF

Checksum (MD5)

289513f8674747f313d748c4e1e60faa

Loading...
Thumbnail Image
Name

Serafinelli_2020_ApJ_902_10.pdf

Description
[Administrators only]
Size

1.02 MB

Format

Adobe PDF

Checksum (MD5)

f890d5cdc947246e141d32a6f55cd4d9