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

GX 3$+$1, an atoll type neutron star low-mass X-ray binary, was observed four times by Soft X-ray Telescope and The Large Area X-ray Proportional Counters on-board \textit{AstroSat} between October 5, 2017 and August 9, 2018. The hardness-intensity-diagram of the source showed it to be in the soft spectral state during all the four observations. The spectra of the source could be adequately fit with a model consisting of blackbody ($\mathtt{bbody}$) and power-law ($\mathtt{powerlaw}$) components. This yielded the blackbody radius and mass accretion rate to be $\sim$8 km and $\sim$2 $\times$ $10^{-9}$ M$_{\odot}$ 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 $\substack{+0.97\\-0.82}$ km and 10.17 $\substack{+0.07\\-0.18}$ kpc, respectively. Temporal analysis of the burst yielded upper limits of the fractional RMS amplitude of 7$\%$, 5$\%$ and 6$\%$ during burst start, burst maximum and right after the radius expansion phase, respectively

NuSTAR and AstroSat observations of GX 9++1: Spectral and temporal studies

We have studied the spectro-temporal properties of the neutron star low mass X-ray binary GX 9$+$1 using data from \textit{NuSTAR/FPM} and \textit{AstroSat/SXT} and \textit{LAXPC}. The hardness-intensity diagram of the source showed it to be in the soft spectral state during both observations. \textit{NuSTAR} spectral analysis yielded an inclination angle ($\theta$) $=$ 29$\substack{+3\\-4}^{\circ}$ and inner disk radius ($R_{in}$) $\leq$ 19.01 km. Assuming that the accretion disk was truncated at the Alfv\'en radius during the observation, the upper limit of the magnetic dipole moment ($\mu$) and the magnetic field strength ($B$) at the poles of the neutron star in GX 9$+$1 were calculated to be 1.45$\times$$10^{26}$ G cm$^3$ and 2.08$\times$$10^8$ G, respectively (for $k_A$ $=$ 1). Flux resolved spectral analysis with \textit{AstroSat} data showed the source to be in the soft spectral state ($F_{disk}$/$F_{total}$ $\sim$0.9) with a monotonic increase in mass accretion rate ($\dot{m}$) along the banana branch. The analysis also showed the presence of absorption edges at $\sim$1.9 and $\sim$2.4 keV, likely due to Si XIII and S XV, respectively. Temporal analysis with \textit{LAXPC-20} data in the 0.02 $-$ 100 Hz range revealed the presence of noise components, which could be characterized with broad Lorentzian components