Classification and spectral evolution of outbursts of Aql X-1

Can Güngör*, Tolga Güver, K. Yavuz Ekşi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

We present a broad classification of all outbursts detected with the All-Sky Monitor on the Rossi X-Ray Timing Explorer (RXTE) and the Monitor of All Sky X-Ray Image (MAXI) of Aql X-1.We identify three types of outbursts: long high, medium low and short low, based on the duration and maximum flux. We analyse the trends in the 'phase space' of flux derivative versus flux to demonstrate the differences in the three identified outburst types. We present a spectral analysis of the observations of Aql X-1 performed by the Proportional Counter Array on board RXTE during the 2000 and 2011 outbursts of the long high class and the 2010 outburst of the medium low class. We model the source spectrum with a hybrid thermal/non-thermal hot plasma emission model (EQPAIR in XSPEC) together with a Gaussian component to model the Fe Ka emission line. We construct time histories of the source flux, the optical depth of the corona (τ), the seed photon temperature (kTbb) and the hard state compactness (lh) for these three outbursts. We show that the physical parameters of either classes reach the same values throughout the outbursts, the only difference being the maximum flux. We discuss our results in the terms of modes of interaction of the star with the disc and the size of the disc kept hot by irradiation. We conclude that irradiation is the dominant physical process leading to the different classes of outbursts.

Original languageEnglish
Pages (from-to)2717-2727
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume439
Issue number3
DOIs
Publication statusPublished - Apr 2014

Keywords

  • Aql X-1
  • Binaries-X-rays
  • Individual
  • X-rays

Fingerprint

Dive into the research topics of 'Classification and spectral evolution of outbursts of Aql X-1'. Together they form a unique fingerprint.

Cite this