Rochester Institute of Technology

Site-wide links

A QPO in NGC 4945 from Archival RXTE Data
  • Speaker: Rebecca Robles
  • Start Time:
  • End Time:
  • Location: CCRG Lounge
  • Type: Lunch Talk

We report the discovery of a ∼ 6-week quasi-periodic oscillation (QPO)
in archival NGC 4945 data observed by the Rossi X-Ray Timing Explorer
(RXTE) satellite. QPOs are an important observable in accretion disks
and have been studied extensively in both neutron star (NS) and black

hole (BH) x-ray binaries (XRB). QPOs should be present in Active Galac-
tic Nuclei (AGN) if galactic black holes and supermassive black holes

(SMBH) are governed by a common set of physical processes. The search
for QPOs in AGN has proven difficult because the timescales would be

much longer, due to their higher mass. RXTE AGN light curves span-
ning 1996 to 2011 provide an excellent baseline to search for low-frequency

QPOs. We investigated the 533 RXTE observations made of the Seyfert-2
AGN, NGC 4945. During a large cluster of observations in 2006-2007 (194
observations, spanning 396 days), the Lomb-Scargle periodogram shows
a candidate QPO at 27.4 μ Hz (period = 42.2 days). A folded light

curve on this period shows a relatively smooth variation. We also inves-
tigate SWIFT BAT data for this source covering the same time period,

and estimate the uncertainties using the Continuous-time Auto-Regressive
Moving-Average (CARMA) method.