Spectro-temporal and type I X-ray burst analysis of GX 3+1 using AstroSat observations

GX 3 + 1, an atoll type neutron star low-mass X-ray binary, was observed four times by Soft X-ray Telescope and The Large Area X-ray Proportional Counter on-board AstroSat between 2017 October 5 and 2018 August 9. The hardness-intensity-diagram of the source showed it to be in the soft spectral state during all the four observations. The spectra of the source could be adequately fit with a model consisting of blackbody (bbody) and power-law (powerlaw) components. This yielded the blackbody radius and mass accretion rate to be similar to 8 km and similar to 2 x 10(-9) M-? y(-1), respectively. In one of the observations, a type I X-ray burst having a rise and e-folding time of 0.6 and 5.6 s, respectively, was detected. Time-resolved spectral analysis of the burst showed that the source underwent a photospheric radius expansion. The radius of the emitting blackbody in GX 3 + 1 and its distance were estimated to be 9.19 (+0.97)(-0.82) km and 10.17 (+0.07)(-0.18) kpc, respectively. Temporal analysis of the burst yielded upper limits of the fractional root mean square amplitude of 7 per cent , 5 per cent , and 6 per cent during burst start, burst maximum, and right after the radius expansion phase, respectively.

Automated summary

GX 3 + 1, an atoll type neutron star low-mass X-ray binary, was observed four times between 2017 October 5 and 2018 August 9. The source was in the soft spectral state during all four observations. The spectra could be fitted with a model consisting of blackbody and power-law components, giving the blackbody radius and mass accretion rate as approximately 8 km and approximately 2 x 10(-9) M-? y(-1), respectively. One of the observations detected a type I X-ray burst with a rise time of 0.6 s and an e-folding time of 5.6 s. Time-resolved spectral analysis showed a photospheric radius expansion during the burst. The radius and distance of the emitting blackbody in GX 3 + 1 were estimated to be 9.19 (+0.97)(-0.82) km and 10.17 (+0.07)(-0.18) kpc, respectively. Temporal analysis of the burst revealed upper limits of the fractional root mean square amplitude of 7%, 5%, and 6% at different phases of the burst.