Discrete scale invariance in viscous fingering patterns

Roy, Aniruddha; Roy, Sayan Basu; Bhattacharyya, Abhijit; Banerjee, Sanjib; Tarafdar, Sujata

doi:10.1007/s100510050966

Cited by 34 publications

(32 citation statements)

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“…In this case the magnetosphere should be devoid of matter and the radio pulsar mechanism should turn on with a strong pulsar wind preventing further accretion (see e.g., Stella et al 1994;Burderi et al 2001). This is what is currently thought to occur in the radio-pulsar phase of the three transitional pulsars recently discovered (Archibald et al 2009;Papitto et al 2013;Bassa et al 2014;Patruno et al 2014;Roy et al 2014Roy et al , 2015Stappers et al 2014) and in the quiescence phase of SAX J1808.4−3658 (Homer et al 2001;Burderi et al 2003;). The fact that in SAX J1808.4 −3658 the X-ray luminosity increases by three orders of magnitude right after reaching the luminosity minima on a very fast timescale of 1-2 days (see Figures 2 and 3) suggests that the radio pulsar mechanism does not turn on, although a very rapid switch cannot be excluded at the moment.…”

Section: Accretion Flow Geometrymentioning

confidence: 96%

The Reflares and Outburst Evolution in the Accreting Millisecond Pulsar Sax J1808.4–3658: A Disk Truncated Near Co-Rotation?

Patruno

Maitra

Curran

et al. 2016

ApJ

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The accreting millisecond X-ray pulsar SAX J1808.4-3658 shows peculiar low luminosity states known as "reflares" after the end of the main outburst. During this phase the X-ray luminosity of the source varies by up to three orders of magnitude in less than 1-2 days. The lowest X-ray luminosity observed reaches a value of 10 erg s 32 1 -, only a factor of a few brighter than its typical quiescent level. We investigate the 2008 and 2005 reflaring state of SAX J1808.4-3658 to determine whether there is any evidence for a change in the accretion flow with respect to the main outburst. We perform a multiwavelength photometric and spectral study of the 2005 and 2008 reflares with data collected during an observational campaign covering the near-infrared, optical, ultra-violet and X-ray band. We find that the NIR/optical/UV emission, expected to come from the outer accretion disk, shows variations in luminosity over an order of magnitude. The corresponding X-ray luminosity variations are instead much deeper, spanning about 2-3 orders of magnitude. The X-ray spectral state observed during the reflares does not change substantially with X-ray luminosity, indicating a rather stable configuration of the accretion flow. We investigate the most likely configuration of the innermost regions of the accretion flow and we infer an accretion disk truncated at or near the co-rotation radius. We interpret these findings as due to either a strong outflow (due to a propeller effect) or a trapped disk (with limited/no outflow) in the inner regions of the accretion flow.

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Section: Accretion Flow Geometrymentioning

confidence: 96%

The Reflares and Outburst Evolution in the Accreting Millisecond Pulsar Sax J1808.4–3658: A Disk Truncated Near Co-Rotation?

Patruno

Maitra

Curran

et al. 2016

ApJ

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“…This variability reinforced the prediction, first made by Hill et al (2011), that the system could harbour an active radio MSP, sharing similar properties with J1023. Follow-up observations in the radio finally succeeded in detecting pulsations at a period of 1.69 ms (Roy et al 2014).…”

Section: Xss J12270-4859mentioning

confidence: 96%

“…A similar system is the LMXB XSS J12270−4859. In recent years, radio, optical, and X-ray observations of this system suggested that, since the end of 2012, it may have switched to a MSP phase (Bassa et al 2014;Bogdanov et al 2014;de Martino et al 2015), and the detection of 1.69 ms radio pulsations provided compelling evidence for the change of state (Roy et al 2014). …”

Section: Based On Observations Made With European Southern Observatormentioning

confidence: 97%

Different twins in the millisecond pulsar recycling scenario: Optical polarimetry of PSR J1023+0038 and XSS J12270-4859

Baglio

D’Avanzo

Campana

et al. 2016

A&A

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We present the first optical polarimetric study of the two transitional pulsars PSR J1023+0038 and XSS J12270-4859. This work is focused on the search for intrinsically linearly polarised optical emission from the two systems. To this aim, we carried out multiband optical (BVRi) and near-infrared (NIR; JHK) photo-polarimetric observations of the two systems using the ESO New Technology Telescope (NTT) at La Silla (Chile), equipped with the EFOSC2 and the SOFI instruments. The system XSS J12270-4859 was observed during its radio-pulsar state; we did not detect a significant degree of polarisation in any of the bands, with 3σ upper limits, for example, of 1.4% in the R-band. We built the NIR−optical averaged spectral energy distribution (SED) of the system, which could be described well by an irradiated black body with radius R * = 0.33 ± 0.03 R and albedo η = 0.32 ± 0.05, without the need for further components. Thus, we excluded the visible presence of an extended accretion disc and/or of relativistic jets. The case was different for PSR J1023+0038, which was in its accretion phase during our campaign. We measured a linear polarisation of 1.09 ± 0.27% and 0.90 ± 0.17% in the V and R bands, respectively. The phase-resolved polarimetric curve of the source in the R band reveals a hint of a sinusoidal modulation at the source 4.75 h orbital period, peaked at the same orbital phase as the light curve. The measured optical polarisation of PSR J1023+0038 could, in principle, be interpreted as electron scattering with free electrons, which can be found in the accretion disc of the system or even in the hot corona that sorrounds the disc itself, or as synchrotron emission from a jet of relativistic particles or an outflow. However, the NIR-optical SED of the system built from our dataset did not suggest the presence of a jet. We conclude that the optical linear polarisation observed for PSR J1023+0038 is possibly due to Thomson scattering with electrons in the disc, as is also suggested from the possible modulation of the R-band linear polarisation at the system orbital period.

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“…The swings between rotation and accretionpowered behaviour recently observed from IGR J18245-2452 (Papitto et al 2013;Pallanca et al 2013;Ferrigno et al 2014;Linares et al 2014) PSR J1023+0038 (Archibald et al 2009;Stappers et al 2013;Patruno et al 2014), and XSS J12270-4859 (Bassa et al 2014;Papitto et al 2014;Roy et al 2014;Bogdanov et al 2014) demonstrated that NSs in some LMXBs alternate cyclically between rotation and accretion-powered states on short time-scales of a few years, or shorter.…”

Section: Introductionmentioning

confidence: 93%

Spin frequency distributions of binary millisecond pulsars

Papitto

Torres

Rea

et al. 2014

A&A

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Rotation-powered millisecond radio pulsars have been spun up to their present spin period by a 10 8 −10 9 yr long X-ray-bright phase of accretion of matter and angular momentum in a low-to-intermediate mass binary system. Recently, the discovery of transitional pulsars that alternate cyclically between accretion and rotation-powered states on time scales of a few years or shorter, has demonstrated this evolutionary scenario. Here, we present a thorough statistical analysis of the spin distributions of the various classes of millisecond pulsars to assess the evolution of their spin period between the different stages. Accreting sources that showed oscillations exclusively during thermonuclear type I X-ray bursts (nuclear-powered millisecond pulsars) are found to be significantly faster than rotationpowered sources, while accreting sources that possess a magnetosphere and show coherent pulsations (accreting millisecond pulsars) are not. On the other hand, if accreting millisecond pulsars and eclipsing rotation-powered millisecond pulsars form a common class of transitional pulsars, these are shown to have a spin distribution intermediate between the faster nuclear-powered millisecond pulsars and the slower non-eclipsing rotation-powered millisecond pulsars. We interpret these findings in terms of a spin-down due to the decreasing mass-accretion rate during the latest stages of the accretion phase, and in terms of the different orbital evolutionary channels mapped by the various classes of pulsars. We summarize possible instrumental selection effects, showing that even if an unbiased sample of pulsars is still lacking, their influence on the results of the presented analysis is reduced by recent improvements in instrumentation and searching techniques.

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Discrete scale invariance in viscous fingering patterns

Abstract: PACS. 47.20.Ma Interfacial instability - 83.10.Ji Fluid dynamics (nonlinear fluids) - 68.10.-m Fluid surfaces and fluid-fluid interfaces,

Cited by 34 publications

References 0 publications

The Reflares and Outburst Evolution in the Accreting Millisecond Pulsar Sax J1808.4–3658: A Disk Truncated Near Co-Rotation?

The Reflares and Outburst Evolution in the Accreting Millisecond Pulsar Sax J1808.4–3658: A Disk Truncated Near Co-Rotation?

Different twins in the millisecond pulsar recycling scenario: Optical polarimetry of PSR J1023+0038 and XSS J12270-4859

Spin frequency distributions of binary millisecond pulsars

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