Class transitions and two component accretion flow in GRS 1915+105

Chakrabarti, Sandip K.; Nandi, Anuj; Chatterjee, Arka; Choudhury, A. K.; Chatterjee, U. K.

doi:10.1051/0004-6361:20041662

Cited by 18 publications

(20 citation statements)

References 15 publications

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“…In case of intermediate classes we have taken the hardness ratio of the harder portions. This sequence obtained from this Figure does not seem to have any special significance in that it does not support the observed class transitions reported in Chakrabarti et al (2004Chakrabarti et al ( , 2005. .…”

Section: Comptonizing Efficiency In Different Classes: An Unifying Viewcontrasting

confidence: 68%

“…Accepting the class XIII to be anomalous, we find from Fig. 4 that the observed transitions reported in Chakrabarti et al (2004Chakrabarti et al ( , 2005; Naik et al (2002b) are 'naturally' explained. For instance, χ → ρ (θ and β being anomalous and intermediate α has been reported by Naik et al (2002b)), ρ → α (β being anomalous) and κ → ρ, are expected from our analysis.…”

Section: Comptonizing Efficiency In Different Classes: An Unifying Viewmentioning

confidence: 74%

“…In Chakrabarti et al (2004Chakrabarti et al ( , 2005, it was mentioned that although many RXTE observations were made of GRS 1915+105, only in a few cases, direct transitions were observed. In particular, using Indian X-ray Astronomy Experiment (IXAE) it was shown that the direct transitions of κ → ρ (VIII → IX), χ → ρ (XIV → IX), χ → θ (XIV→ XIII) and ρ → α (IX→ XII) do take place in a matter of hours.…”

Section: Comptonizing Efficiency In Different Classes: An Unifying Viewmentioning

confidence: 99%

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Comptonization efficiencies of the variability classes of GRS 1915+105

Pal

Chakrabarti

Nandi

2013

Advances in Space Research

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The Galactic microquasar GRS 1915+105 exhibits at least seventeen types of variability classes. Intra and inter class transitions are reported to be observed within seconds to hours. Since the observation was not continuous, these classes appeared to be exhibited in a random order. Our goal is to predict a sequence of these classes. In this paper, we compute the ratio of the photon counts obtained from the power-law component and the blackbody component of each class and call this ratio as the 'Comptonizing efficiency' (CE) of that class. We sequence the classes in the ascending order of CE and find that this sequence matches with a few class transitions observed by RXTE satellite and IXAE instruments on board IRS-P3. A change in CE corresponds to a change in the optical depth of the Compton cloud. Our result implies that the optical depth of the Compton cloud gradually rises as the variability class becomes harder.

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Section: Comptonizing Efficiency In Different Classes: An Unifying Viewcontrasting

confidence: 68%

Section: Comptonizing Efficiency In Different Classes: An Unifying Viewmentioning

confidence: 74%

Section: Comptonizing Efficiency In Different Classes: An Unifying Viewmentioning

confidence: 99%

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Comptonization efficiencies of the variability classes of GRS 1915+105

Pal

Chakrabarti

Nandi

2013

Advances in Space Research

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“…It is suggested that these LFQPOs must be linked to the properties of the accretion disk since their centroid frequencies are correlated with the disk flux (Markwardt et al 1999) while the emitted luminosity itself varies, for example due to changes in mass accretion rate (Tagger & Pellat 1999;Cabanac et al 2010). In Chakrabarti & Manickam (2000); Vadawale et al (2001); Rao et al (2000); Chakrabarti et al (2005) it was shown that the Comptonized photons produce QPOs and thus they are intrinsically related to spectral states.…”

Section: Introductionmentioning

confidence: 99%

Evolution of accretion disc geometry of GRS 1915+105 during its χ state as revealed by TCAF solution

Dutta

Pal

Chakrabarti

2018

Monthly Notices of the Royal Astronomical Society

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The evolution of the C-type low frequency quasi-periodic oscillations (LFQPOs) and associated time lag in transient black hole sources as a function of time can be explained by variation of the Compton cloud size in a Two Component Advective Flow solution (TCAF). A similar study of a persistent source, GRS 1915+105, has not been attempted. We fit the evolution of QPOs with propagatory oscillating shock (POS) solution for two sets of so-called χ-state observations and find that the shock steadily recedes with almost constant velocity when QPO frequency is decreasing and the spectrum is hardening. The shock moves inward with a constant velocity v 0 = 473.0 cm s −1 and v 0 = 400.0 cm s −1 respectively in these two cases, when the QPO frequency is increasing and the spectrum softens. This behavior is similar to what was observed in XTE J1550-564 during the 1998 outburst. The time lag measured at the QPO frequency varies in a similar way as the size of the Compton cloud. Most interestingly, in both the cases, the lag switches sign (hard lag to soft lag) at a QPO frequency of ∼ 2.3 − 2.5 Hz irrespective of the energy of photons. We find, at very low frequencies < 1 Hz, the Comptonizing Efficiency (CE) increases with QPO frequency and at higher QPO frequencies the trend is opposite. The time lags become mostly positive at all energies when CE is larger than ∼ 0.85% for both the sources.

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“…On that occasion the source was in the ρ class for about five days, then changed to the κ class in which it remained for a similar time and afterwards returned to the former one. Transitions from/to the ρ class to/from other classes were described by Naik et al (2002), Chakrabarti et al (2004Chakrabarti et al ( , 2005, and Rodriguez et al (2008).…”

Section: Introductionmentioning

confidence: 99%

The complex behaviour of the microquasar GRS 1915+105 in theρclass observed with BeppoSAX

Massaro¹,

Ventura

Massa

et al. 2010

A&A

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GRS 1915+105 was observed byBeppoSAX for about 10 days in October 2000. For about 80% of the time, the source was in the variability class ρ, characterised by a series of recurrent bursts. We describe the results of the timing analysis performed on the MECS (1.6-10 keV) and PDS (15-100 keV) data. The X-ray count rate from GRS 1915+105 showed an increasing trend with different characteristics in the various energy bands: in the bands (1.6-3 keV) and (15-100 keV), it was nearly stable in the first part of the pointing and increased in a rather short time by about 20%, while in the energy range (3-10 keV) the increase had a smoother trend. Fourier and wavelet analyses detect a variation in the recurrence time of the bursts, from 45-50 s to about 75 s, which appear well correlated with the count rate. From the power distribution of peaks in Fourier periodograms and wavelet spectra, we distinguished between the regular and irregular variability modes of the ρ class, which are related to variations in the count rate in the 3-10 keV range. We identified two components in the burst structure: the slow leading trail, and the pulse, superimposed on a rather stable level. Pulses are generally structured in a series of peaks and their number is related to the regularity modes: the mean number of peaks is lower than 2 in the regular mode and increases up to values higher than 3 in the irregular mode. We found that the change in the recurrence time of the regular mode is caused by the slow leading trails, while the duration of the pulse phase remains far more stable. The evolution in the mean count rates shows that the time behaviour of both the leading trail and the baseline level are very similar to those observed in the 1.6-3 and 15-100 keV ranges, while that of the pulse follows the peak number. These differences in the time behaviour and count rates at different energies indicate that the process responsible for the pulses must produce the strongest emission between 3 and 10 keV, while that associated with both the leading trail and the baseline dominates at lower and higher energies.

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Class transitions and two component accretion flow in GRS 1915+105

Cited by 18 publications

References 15 publications

Comptonization efficiencies of the variability classes of GRS 1915+105

Comptonization efficiencies of the variability classes of GRS 1915+105

Evolution of accretion disc geometry of GRS 1915+105 during its χ state as revealed by TCAF solution

The complex behaviour of the microquasar GRS 1915+105 in theρclass observed with BeppoSAX

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