# A deceleration search for magnetar pulsations in the X-ray plateaus of Short GRBs

## TL;DR

This study searches for pulsations from newly formed magnetars in short GRBs during X-ray plateau phases using Swift data, setting constraints on their emission and informing future detection strategies.

## Contribution

It introduces a targeted deceleration search method for detecting magnetar pulsations in short GRBs and applies it to Swift data, establishing upper limits on detectable periodic signals.

## Key findings

- No periodic signals detected in the 10-285 Hz band.
- Detectability threshold for pulsations is approximately 15-30% rms.
- Results suggest reprocessing or alignment may hide pulsations.

## Abstract

A newly formed magnetar has been proposed as the central engine of short GRBs to explain on-going energy injection giving observed plateau phases in the X-ray lightcurves. These rapidly spinning magnetars may be capable of emitting pulsed emission comparable to known pulsars and magnetars. In this paper we show that, if present, a periodic signal would be detectable during the plateau phases observed using the Swift X-Ray Telescope recording data in Window Timing mode. We conduct a targeted deceleration search for a periodic signal from a newly formed magnetar in 2 Swift short GRBs and rule out any periodic signals in the frequency band 10-285 Hz to $\approx$15-30% rms. These results demonstrate that we would able to detect pulsations from the magnetar central engine of short GRBs if they contribute to 15-30% of the total emission. We consider these constraints in the context of the potential emission mechanisms. The non-detection is consistent with the emission being reprocessed in the surrounding environment or with the rotation axis being highly aligned with the observing angle. As the emission may be reprocessed, the expected periodic emission may only constitute a few percent of the total emission and be undetectable in our observations. Applying this strategy to future observations of the plateau phases with more sensitive X-ray telescopes may lead to the detection of the periodic signal.