A Pacemaker with P=2.48 hour Modulated the Generator of Flares in the X-ray Light Curve of Sgr A* in the year 2012

TL;DR

The paper identifies a 2.48-hour periodic modulation in the X-ray flare activity of Sgr A* during 2012, suggesting a possible orbital mechanism influencing flare timing.

Contribution

It reports the discovery of a statistically significant 2.48-hour periodicity in Sgr A*'s X-ray flares, linking it to a potential orbital process near the black hole.

Findings

Flares are grouped around a 0.10333-day period with 3.2σ significance.

The period corresponds to an orbit at 7.6 Schwarzschild radii.

No such periodicity was found in 2013-2014 data.

Abstract

In an intensive observational campaign in the 9 month duration of Chandra X-ray Visionary Project that was conducted in the year 2012, 39 large X-ray flares of Sgr A* were recorded. An analysis of the times of the observed flares reveals that the 39 flares are separated in time by intervals that are grouped around integer numbers times 0.10333 days. This time interval is thus the period of a uniform grid of equally spaced points on the time axis. The grouping of the flares around tic marks of this grid is derived from the data with at least a 3.2 {\sigma} level of statistical significance. No signal of any period can be found among 22 flares recorded by Chandra in the years 2013-2014. If the 0.10333 d period is that of a nearly circular Keplerian orbit around the blackhole at the center of the Galaxy, its radius is at 7.6 Schwarzschild radii. Large flares were more likely to be triggered when the agent responsible for their outbursts was near the peri-center phase of its slightly eccentric orbit.