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

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 Güngör et al. with $\sim 68$ cnt/s maximum flux and $\sim 60$ 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.

5 pages, 3 figures, accepted for publication in New Astronomy

References in corpus (5)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Discovery of coherent millisecond X-ray pulsations in Aql X-1
• The return to quiescence of Aql X-1 following the 2010 outburst
• Outburst Morphology in the Soft X-ray Transient Aquila X-1
• Classification and Spectral Evolution of Outbursts of Aql X-1

Cited by in corpus (6)

• Partial accretion in the propeller stage of low mass X-ray binary Aql X--1
• The evolving jet spectrum of the neutron star X-ray binary Aql X-1 in transitional states during its 2016 outburst
• The connection between the UV/optical and X-ray emission in the neutron star low-mass X-ray binary Aql X-1
• Long-term temperature evolution of neutron stars undergoing episodic accretion outbursts
• Optical nebular emission following the most luminous outburst of Aquila X-1
• A Detailed Spectral Study of Intermittent-Accreting Millisecond X-ray Pulsar Aql X-1 during Pulse-on and Pulse-off Stages