# On the morphology of outbursts of accreting millisecond X-ray pulsar Aquila X-1

## TL;DR

This paper analyzes the X-ray light curves of two outbursts of the accreting millisecond X-ray pulsar Aquila X-1, revealing that longer quiescent periods lead to more energetic outbursts, with the 2016 event being the most energetic observed.

## Contribution

It provides a detailed comparison of two outbursts of Aql X-1, classifies them based on their properties, and investigates the relationship between quiescent duration and outburst energy.

## Key findings

- 2016 outburst is the most energetic observed from Aql X-1.
- 2016 outburst belongs to the long-high class; 2014 to the short-low class.
- Longer quiescent periods tend to produce higher peak energy outbursts.

## Abstract

We present the X-ray light curves of the last two outbursts --2014 & 2016-- of the well known accreting millisecond X-ray pulsar (AMXP) Aquila X-1 using the monitor of all sky X-ray image (MAXI) observations in the $2-20$ keV band. After calibrating the (MAXI) count rates to the all-sky monitor (ASM) level, we report that the 2016 outburst is the most energetic event of Aql X-1, ever observed from this source. We show that 2016 outburst is a member of the long-high class according to the classification presented by G\"ung\"or et al. with $\sim68$ cnt/s maximum flux and $\sim60$ days duration time and the previous outburst, 2014, belongs to the short-low class with $\sim 25$ cnt/s maximum flux and $\sim 30$ days duration time. In order to understand differences between outbursts, we investigate the possible dependence of the peak intensity to the quiescent duration leading to the outburst and find that the outbursts following longer quiescent episodes tend to reach higher peak energetic.