Monitoring the Mass Accretion Rate in Scorpius X‐1 Using the Optical Johnson<i>B</i>Filter

McNamara, B. J.; Norwood, James; Harrison, T. E.; Holtzman, Jon A.; Dukes, R. J.; Barker, T.

doi:10.1086/428640

Cited by 8 publications

(16 citation statements)

References 20 publications

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“…The corresponding (near) simultaneous ASM photon count-rate corresponds to 956 s −1 . This estimation ofṀðtÞ of Sco X-1 from RXTE/PCA is in good agreement with (only 14% below) the corresponding estimation from the ASM countrate calibrated to McNamara et al [23]. This underestimate inṀðtÞ could, possibly, due to presence of some other emission mechanisms predominant outside this 2-10 keV band over which we modeled photon energy spectrum which can result in a small fraction of the flux falling outside this measured energy band.…”

Section: Fluctuating Torque On the Neutron Star And The Spin Wandsupporting

confidence: 88%

“…Therefore, we compute the 95% confidence level upper-limit and lower limit of the RXTE/ASM count-rate to be 1716 photons/s and 618 photons/s, respectively. Comparing the reported upper-limit of mass accretion rate from Sco X-1 by McNamara et al [23], we find the upper-limit (95% confidence level) of the flux corresponds to ≃0.42 × 10 −8 M ⊙ yr −1 and lower-limit (95% confidence level) of the flux corresponds to ≃1.2 × 10 −8 M ⊙ yr −1 . This corresponds to a conversion factor of 7.03 × 10 −10 M ⊙ yr −1 per 100 photon count-rate in RXTE/ASM.…”

Section: Fluctuating Torque On the Neutron Star And The Spin Wandsupporting

confidence: 75%

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Accretion-induced spin-wandering effects on the neutron star in Scorpius X-1: Implications for continuous gravitational wave searches

2018

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The LIGO's discovery of binary black hole mergers has opened up a new era of transient gravitational wave astronomy. The potential detection of gravitational radiation from another class of astronomical objects, rapidly spinning nonaxisymmetric neutron stars, would constitute a new area of gravitational wave astronomy. Scorpius X-1 (Sco X-1) is one of the most promising sources of continuous gravitational radiation to be detected with present-generation ground-based gravitational wave detectors, such as Advanced LIGO and Advanced Virgo. As the sensitivity of these detectors improve in the coming years, so will power of the search algorithms being used to find gravitational wave signals. Those searches will still require integration over nearly year long observational spans to detect the incredibly weak signals from rotating neutron stars. For low mass X-ray binaries such as Sco X-1 this difficult task is compounded by neutron star "spin wandering" caused by stochastic accretion fluctuations. In this paper, we analyze X-ray data from the RXTE satellite to infer the fluctuating torque on the neutron star in Sco X-1. We then perform a large-scale simulation to quantify the statistical properties of spin-wandering effects on the gravitational wave signal frequency and phase evolution. We find that there are a broad range of expected maximum levels of frequency wandering corresponding to maximum drifts of between 0.3-50 μHz/ sec over a year at 99% confidence. These results can be cast in terms of the maximum allowed length of a coherent signal model neglecting spin-wandering effects as ranging between 5-80 days. This study is designed to guide the development and evaluation of Sco X-1 search algorithms.

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Section: Fluctuating Torque On the Neutron Star And The Spin Wandsupporting

confidence: 88%

Section: Fluctuating Torque On the Neutron Star And The Spin Wandsupporting

confidence: 75%

Accretion-induced spin-wandering effects on the neutron star in Scorpius X-1: Implications for continuous gravitational wave searches

2018

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“…It is clearly seen that Sco X‐1 exhibits significant variations of its SED at the long‐wavelength end, while in the optical the changes are inessential (see e.g. McNamara et al 2005). This is not surprising because the source is known to be strongly variable at radio wavelengths (e.g.…”

Section: Datamentioning

confidence: 99%

Period-luminosity relation for persistent low-mass X-ray binaries in the near-infrared

Revnivtsev

Zolotukhin

Meshcheryakov

2012

Monthly Notices of the Royal Astronomical Society

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We study the relations between the X‐ray luminosity, orbital period and absolute near‐infrared magnitude of persistent low‐mass X‐ray binaries (LMXBs). We show that often the optical and near‐infrared spectral energy distributions of LMXBs can be adequately described by a simple model of an accretion disc and a secondary star reprocessing X‐ray emission from a central compact object. This gives us evidence that one can make a reliable estimate of the orbital period of a persistent LMXB using an X‐ray luminosity and an absolute infrared magnitude. Using a sample of well‐known LMXBs, we have constructed a correlation of LX, Porb and MK values that can be approximated by a straight line with root‐mean‐square scatter at the level of ∼0.3 mag. Such a correlation, being to some extent analogous to the correlation found by van Paradijs & McClintock, might be helpful for future population studies, especially in the light of forthcoming surveys of the Galaxy in the X‐ray and infrared spectral domains.

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“…The X-ray flux variation may result in the variation of optical flux. There have been some other claims since the discovery of the narrow emission components arising from the donor star [4-6].Mcnamara et al suggested a nearly linear relation between the B magnitude and the accretion rate on the normal and lower flaring branches [7]. Typically, a flux correlation between X-ray and optical occurs only when the object is brighter than the B magnitude around 12.7 [8-12], but there are some exceptions (e.g.…”

mentioning

confidence: 99%

“…Mcnamara et al suggested a nearly linear relation between the B magnitude and the accretion rate on the normal and lower flaring branches [7]. Typically, a flux correlation between X-ray and optical occurs only when the object is brighter than the B magnitude around 12.7 [8][9][10][11][12], but there are some exceptions (e.g.…”

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confidence: 99%

Optical observations of Scorpius X-1 in 2008: Evidence of rapid variability

Cao

Yan

et al. 2010

Sci. China Phys. Mech. Astron.

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Optical observations of Sco X-1 with exposure times around 0.5 s were performed with the 1.56 m telescope of the Shanghai Astronomical Observatory in 2008. With these observations, we studied the fluctuation of the optical flux on three short timescales (5, 10, 100 s). We found that the standard deviations of fluctuations on these three timescales differ from those of Gaussian distributions by 7 Sigma, 5 Sigma and 3 Sigma, respectively. The result suggests that the variations in the intensity on these short timescales differ from pure statistical fluctuations, which, we suggest, is due to the intrinsic variability in the optical emission.accretion disks, stars: individual (Scorpius X-1), optical: stars Sco X-1 is the brightest X-ray point source in the sky. It is a Z source, a subclass of low-mass X-ray binaries (LMXBs) [1], which traces out roughly a Z-shaped pattern in the X-ray color-color diagram. Its optical counterpart, V818 Sco, is a 13th magnitude star with excess UV emission. The optical emission is generally considered to originate mainly from the accretion disc rather than the donor star [2], and arises from the reprocessed X-ray emission of the accretion disk. The X-ray emission illuminates the accretion disk and heats the corona above the disk, and the optical emission arises from the hot plasma in the corona [3]. The X-ray flux variation may result in the variation of optical flux. There have been some other claims since the discovery of the narrow emission components arising from the donor star [4-6].Mcnamara et al. suggested a nearly linear relation between the B magnitude and the accretion rate on the normal and lower flaring branches [7]. Typically, a flux correlation between X-ray and optical occurs only when the object is brighter than the B magnitude around 12.7 [8-12], but there are some exceptions (e.g. refs. [13-15]). Several attempts have been made to study the erratic variability of Sco X-1 simultaneously in optical and X-ray, but there is no systematic understanding that has yet been achieved.Recent X-ray observations show X-ray variability on time scales as short as milliseconds (see a review in [16]). Some of the X-ray variability, such as the band-limited noise (BLN) on time scales from subseconds to tens of seconds, has been suggested to correspond to the variation of mass accretion rate in the disk [17]. The search for optical variability and the relation between optical and X-ray variability on short timescales would help reveal the origin of both the X-ray and optical variability. The study of optical variability on short timescales would open a new window for the study of the X-ray variability.In this paper, we show the optical behavior of Sco X-1 on short timescales of 5, 10 and 100 s and found evidence of rapid variability on these timescales in the optical emission of Sco X-1.

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Monitoring the Mass Accretion Rate in Scorpius X‐1 Using the Optical JohnsonBFilter

Cited by 8 publications

References 20 publications

Accretion-induced spin-wandering effects on the neutron star in Scorpius X-1: Implications for continuous gravitational wave searches

Accretion-induced spin-wandering effects on the neutron star in Scorpius X-1: Implications for continuous gravitational wave searches

Period-luminosity relation for persistent low-mass X-ray binaries in the near-infrared

Optical observations of Scorpius X-1 in 2008: Evidence of rapid variability

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