Spectral and timing properties of atoll source 4U 1705-44: LAXPC/AstroSat results

Agrawal, V. K.; Nandi, Anuj; Girish, V.; Ramadevi, M. C.

doi:10.1093/mnras/sty1005

Cited by 40 publications

(34 citation statements)

References 52 publications

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“…The errors on the data points are smaller than the marker size. in overall fitting to account for the uncertainty in the spectral response (Agrawal et al 2018).…”

Section: Spectral Analysismentioning

confidence: 99%

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AstroSat/LAXPC view of GX 17+2: spectral evolution along the Z-track

Agrawal

Nandi

Ramadevi

2020

Astrophys Space Sci

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In this paper, we present the first results obtained using ∼ 50 ks observations of the bright low-mass X-ray binary (LMXB) GX 17+2 with Large Area X-ray Proportional Counter (LAXPC) onboard AstroSat. The source traced out a complete Z-track in the hardness intensity diagram (HID). The spectra at different sections of the Z-diagram are well described by either a combination of a thermal Comptonization component, a power-law and a relativistic iron line or a model consisting of a thermal disk component, a single temperature blackbody, a powerlaw and a relativistic iron line. Fitting the spectra with both phenomenological models suggests that the power-law component is strong in the horizontal branch (HB), becomes weaker as the source moves down the normal branch (NB) and then again becomes stronger as the sources moves up the flaring branch (FB). However, we find that the strength of the power-law component is model dependent, although the trend in the variation of the power-law strength along the Z-track is similar. A simple model composed by a Comptonized emission and power-law component, convolved with the ionized reflection, also describes the spectra very well.A normal branch oscillation (NBO) with a centroid frequency 7.42±0.23 Hz, quality factor (Q) ∼ 4.88, rms 1.41±0.29% and significance 5.1σ is detected

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“…The errors on the data points are smaller than the marker size. in overall fitting to account for the uncertainty in the spectral response (Agrawal et al 2018).…”

Section: Spectral Analysismentioning

confidence: 99%

“…Figure 5a shows the evolution of the best fit spectral parameters as a function of the position on the HID. The optical depth τ is calculated using formula given in Agrawal et al (2018) and the Comptonization parameter y is calculated using the formula,…”

Section: Spectral Propertiesmentioning

confidence: 99%

AstroSat/LAXPC view of GX 17+2: spectral evolution along the Z-track

Agrawal

Nandi

Ramadevi

2020

Astrophys Space Sci

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“…For the BH sources (see Table 3), the observations covered the 2002 and 2010 outbursts for GX339-4 (see Sonbas et al (2020)), the 1999 outburst for XTE J1859+226, 2010 outburst for MAXI J1659-152, and the 2003 outburst for H1743-322. These sources are good test candidates because they are well studied and the majority are known to exhibit a range of spectral transitions (Phillipson et al (2018), Agrawal et al (2018), Gardenier & Uttley (2018), Agrawal et al (2020), Mancuso et al (2021), Sreehari & Nandi (2021), and references therein).…”

Section: Data Reduction and Methodologymentioning

confidence: 99%

A Temporal Scale to Track the Spectral Transitions in Low-Mass X-ray Binaries

Sonbas,

Mohamed,

Dhuga

et al. 2021

Preprint

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The results of a temporal analysis of observations for a sample of nine low-mass X-ray binaries (LMXBs) are presented. Of these sources, five host a neutron star (NS) primary (4U1608-52, Aql X-1, 4U1705-44, GX17+2 and Cyg X-2), and four host a black hole (BH) (GX339-4, XTE J1859+226, H1743-322 and MAXI J1659-152). The NS group includes three Atolls and two Z-type sources. We utilized archival Proportional Counter Array (PCA)/RXTE data to construct high-resolution lightcurves. A wavelet transform of the lightcurves is deployed to extract a minimal time scale (MTS) associated with the spectral state of the sources. The MTS, together with the fractional root-mean-square (RMS) and hardness ratios, is used to construct RMS-MTS and hardness-MTS diagrams that enable a direct comparison of the evolution of spectral transitions in the target sources. Observations with high fractional RMS and high hardness cluster in a broad region occupied jointly by BH and NS sources. For low fractional RMS observations the Atolls exhibit large MTS whereas Z-type sources exhibit small MTS. This new feature raises the possibility of discriminating between these two types of sources. Moreover, in the hardness-MTS plane, BH sources are the sole occupiers of the low-hardness and small-MTS domain thus potentially signaling a unique property for distinguishing BH and NS hosts in LMXBs.

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“…The PDSs were normalized according to Leahy et al (1983), and the variability power was converted to the square fractional rms (Belloni & Hasinger 1990). Further, we subtracted the dead-time corrected Poisson noise level from each PDS (see Zhang et al 1995;Yadav et al 2016b;Agrawal et al 2018). Figure 2 shows the PDSs derived in the 3 − 15 keV and 15 − 30 keV bands in the left and right panels, respectively.…”

Section: Timing Analysismentioning

confidence: 99%

AstroSat view of the newly discovered X-ray transient MAXI~J1803--298 in the Hard-intermediate state

Chand,

Dewangan,

Thakur

et al. 2021

Preprint

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We perform comprehensive temporal and spectral analysis of the newly discovered X-ray transient MAXI J1803-298 using an AstroSat target of opportunity observation on May 11, 2021 during its outburst. The source was found to be in the hard intermediate state. We detect type C quasi-periodic oscillations (QPOs) at the frequencies of ∼ 5.4 Hz and ∼ 6.3 Hz along with a sub-harmonic at ∼ 2.8 Hz in the 3 − 15 keV band. The frequency and fractional rms amplitude of the QPO in the 15 − 30 keV band are found to be higher than those in the 3 − 15 keV band. We find soft lags of ∼ 3.8 ms and ∼ 6.8 ms for the respective QPOs at ∼ 5.4 Hz and ∼ 6.3 Hz, whereas soft lag of ∼ 4.7 ms is found at the sub-harmonic frequency. The increase in the soft lags at the QPO frequencies with energy is also observed in other black hole transients and is attributed to the inclination dependence of the lags. The rms-energy spectra indicate the power-law component to be more variable than the disk and the reflection components. We find a broad iron line with an equivalent width of ∼ 174 − 193 eV and a reflection hump above ∼ 12 keV in the energy spectrum. The estimated mass of the black hole (∼ 11 − 14 M ⊙ ) and the spin parameter suggest the source likely to be a stellar mass Kerr black hole X-ray binary.

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Spectral and timing properties of atoll source 4U 1705-44: LAXPC/AstroSat results

Cited by 40 publications

References 52 publications

AstroSat/LAXPC view of GX 17+2: spectral evolution along the Z-track

AstroSat/LAXPC view of GX 17+2: spectral evolution along the Z-track

A Temporal Scale to Track the Spectral Transitions in Low-Mass X-ray Binaries

AstroSat view of the newly discovered X-ray transient MAXI~J1803--298 in the Hard-intermediate state

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