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TOPIC: SDSS J102347.68+003841.2
Blobrana


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RE: SDSS J102347.68+003841.2
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Title: NuSTAR observations and broadband spectral energy distribution modeling of the millisecond pulsar binary PSR J1023+0038
Author: K.L. Li, A.K.H. Kong, J. Takata, K.S. Cheng, P.H.T. Tam, C.Y. Hui, Ruolan Jin

We report the first hard X-ray (3-79 keV) observations of the millisecond pulsar (MSP) binary PSR J1023+0038 using NuSTAR. This system has been shown transiting between a low-mass X-ray binary (LMXB) state and a rotation-powered MSP state. The NuSTAR observations were taken in both LMXB state and rotation-powered state. The source is clearly seen in both states up to ~79 keV. During the LMXB state, the 3-79 keV flux is about a factor of 10 higher that in the rotation-powered state. The hard X-rays show clear orbital modulation during the X-ray faint rotation-powered state but the X-ray orbital period is not detected in the X-ray bright LMXB state. In addition, the X-ray spectrum changes from a flat power-law spectrum during the rotation-powered state to a steeper power-law spectrum in the LMXB state. We suggest that the hard X-rays are due to the intra-binary shock from the interaction between the pulsar wind and the injected material from the low-mass companion star. During the rotation-powered MSP state, the X-ray orbital modulation is due to Doppler boosting of the shocked pulsar wind. At the LMXB state, the evaporating matter of the accretion disk due to the gamma-ray irradiation from the pulsar stops almost all the pulsar wind, resulting the disappearance of the X-ray orbital modulation.

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Blobrana


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NASA's Fermi Finds A 'Transformer' Pulsar

In late June 2013, an exceptional binary containing a rapidly spinning neutron star underwent a dramatic change in behavior never before observed. The pulsar's radio beacon vanished, while at the same time the system brightened fivefold in gamma rays, the most powerful form of light, according to measurements by NASA's Fermi Gamma-ray Space Telescope.
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Blobrana


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Title: Infrared Observations of The Millisecond Pulsar Binary J1023+0038: Evidence for Short-Term Nature of Its Interacting Phase in 2000--2001
Authors: Xuebing Wang, Zhongxiang Wang (SHAO, China), Nidia Morrell

We report our multi-band infrared (IR) imaging of the transitional millisecond pulsar system J1023+0038, a rare pulsar binary known to have an accretion disk in 2000--2001. The observations were carried out with ground-based and space telescopes from near-IR to far-IR wavelengths. We detected the source in near-IR JH bands and Spitzer 3.6 and 4.5 µm mid-IR channels. Combined with the previously-reported optical spectrum of the source, the IR emission is found to arise from the companion star, with no excess emission detected in the wavelength range. Because our near-IR fluxes are nearly equal to those obtained by the 2MASS all-sky survey in 2000 Feb., the result indicates that the binary did not contain the accretion disk at the time, whose existence would have raised the near-IR fluxes to 2-times larger values. Our observations have thus established the short-term nature of the interacting phase seen in 2000--2001: the accretion disk at most existed for 2.5 yrs. The binary was not detected by the WISE all-sky survey carried out in 2010 at its 12 and 22 µm bands and our Herschel far-IR imaging at 70 and 160 µm. Depending on the assumed properties of the dust, the resulting flux upper limits provide a constraint of <3x10^{22}--3x10^{25} g on the mass of the dust grains that possibly exist as the remnant of the previously-seen accretion disk.

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Blobrana


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PSR J1023+0038
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Title: A Chandra X-ray Observation of the Binary Millisecond Pulsar PSR J1023+0038
Authors: Slavko Bogdanov (McGill), Anne M. Archibald, Jason W. T. Hessels, Victoria M. Kaspi, Duncan Lorimer, Maura A. McLaughlin, Scott M. Ransom, Ingrid H. Stairs

We present a Chandra X-ray Observatory ACIS-S variability, spectroscopy, and imaging study of the peculiar binary containing the millisecond pulsar J1023+0038. The X-ray emission from the system exhibits highly significant (12.5 sigma) large-amplitude (factor of 2-3) orbital variability over the five consecutive orbits covered by the observation, with a pronounced decline in the flux at all energies at superior conjunction. This can be naturally explained by a partial geometric occultation by the secondary star of an X-ray--emitting intrabinary shock, produced by the interaction of outflows from the two stars. The depth and duration of the eclipse imply that the intrabinary shock is localised near or at the surface of the companion star and close to the inner Lagrangian point. The energetics of the shock favour a magnetically dominated pulsar wind that is focused into the orbital plane, requiring close alignment of the pulsar spin and orbital angular momentum axes. The X-ray spectrum consists of a dominant non-thermal component and at least one thermal component, likely originating from the heated pulsar polar caps, although a portion of this emission may be from an optically-thin "corona". We find no evidence for extended emission due to a pulsar wind nebula or bow shock down to a limiting luminosity of L_X<3.6x10^29 ergs s^-1 (0.3-8 keV), <7x10^-6 of the pulsar spin-down luminosity, for a distance of 1.3 kpc and an assumed power-law spectrum with photon index Gamma=1.5.

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Blobrana


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SDSS J102347.6+003841
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Title: SDSS J102347.6+003841: A Millisecond Radio Pulsar Binary That Had A Hot Disk During 2000-2001
Authors: Zhongxiang Wang, Anne M. Archibald, John R. Thorstensen, Victoria M. Kaspi, Duncan R. Lorimer, Ingrid Stairs, Scott M. Ransom
(Version v2)

The Sloan Digital Sky Survey (SDSS) source J102347.6+003841 was recently revealed to be a binary 1.69 millisecond radio pulsar with a 4.75 hr orbital period and a ~0.2 M_sun companion. Here we analyse the SDSS spectrum of the source in detail. The spectrum was taken on 2001 February 1, when the source was in a bright state and showed broad, double-peaked hydrogen and helium lines -- dramatically different from the G-type absorption spectrum seen from 2003 onward. The lines are consistent with emission from a disk around the compact primary. We derive properties of the disk by fitting the SDSS continuum with a simple disk model, and find a temperature range of 2000--34000 K from the outer to inner edge of the disk. The disk inner and outer radii were approximately 10^9 and 5.7x10^10 cm, respectively. These results further emphasise the unique feature of the source: it is likely a system at the end of its transition from an X-ray binary to a recycled radio pulsar. The disk mass is estimated to have been ~10^23 g, most of which would have been lost due to pulsar wind ablation (or due to the propeller effect if the disk had extended inside the light cylinder of the pulsar) before the final disk disruption event. The system could undergo repeated episodes of disk formation. Close monitoring of the source is needed to catch the system in its bright state again, so that this unusual example of a pulsar-disk interaction can be studied in much finer detail

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Blobrana


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Title: SDSS J102347.6+003841: A Millisecond Radio Pulsar Binary That Had A Hot Disk
Authors: Zhongxiang Wang, Anne M. Archibald, John R. Thorstensen, Victoria M. Kaspi, Duncan R. Lorimer, Ingrid Stairs, Scott M. Ransom

The Sloan Digital Sky Survey (SDSS) source J102347.6+003841 is a binary star with a 4.75 hr orbital period. A recent radio pulsar survey showed that its primary is a millisecond pulsar (MSP). Here we analyse the SDSS spectrum of the source in detail. The spectrum was taken on 2001 February 1, when the source was in a bright state and showed broad, double-peaked hydrogen and helium lines -- dramatically different from the G-type absorption spectrum seen from 2003 onward. The lines are consistent with emission from a disk around the compact primary. We derive properties of the disk by fitting the SDSS continuum with a simple disk model, and find a temperature range of 2000--34000 K from the outer to inner edge of the disk. The disk inner and outer radii were approximately 10^9 and 5.7x10^10 cm, respectively. These results further emphasize the unique feature of the source: it is evidently a system at the beginning of its life as a recycled radio pulsar. The disk mass is estimated to have been ~10^23 g, most of which would have been lost due to the pulsar wind ablation (or due to the propeller effect if the disk had extended inside the light cylinder of the pulsar) before the final disk disruption event. The system could undergo repeated episodes of disk formation. Close monitoring of the source is needed to catch the system in its bright state again, so that this unusual example of a pulsar-disk interaction can be studied in much detail.

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Blobrana


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Millisecond pulsars
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Astronomers have shed light on the mysterious origins of the fastest spinning stars known to science - millisecond pulsars.
Pulsars are dense, highly magnetised dead stars that emit radio waves along their magnetic poles.
These waves sweep around as the star rotates, a bit like lighthouse beams.
Writing in the journal Science, a team has worked out how millisecond pulsars might evolve from a type of binary star system which spews out X-rays.

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Blobrana


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PSR J1023+0038
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Title: A Radio Pulsar/X-ray Binary Link
Authors: Anne M. Archibald, Ingrid H. Stairs, Scott M. Ransom, Victoria M. Kaspi, Vladislav I. Kondratiev, Duncan R. Lorimer, Maura A. McLaughlin, Jason Boyles, Jason W. T. Hessels, Ryan Lynch, Joeri van Leeuwen, Mallory S. E. Roberts, Frederick Jenet, David J. Champion, Rachel Rosen, Brad N. Barlow, Bart H. Dunlap, Ronald A. Remillard

Radio pulsars with millisecond spin periods are thought to have been spun up by transfer of matter and angular momentum from a low-mass companion star during an X-ray-emitting phase. The spin periods of the neutron stars in several such low-mass X-ray binary (LMXB) systems have been shown to be in the millisecond regime, but no radio pulsations have been detected. Here we report on detection and follow-up observations of a nearby radio millisecond pulsar (MSP) in a circular binary orbit with an optically identified companion star. Optical observations indicate that an accretion disk was present in this system within the last decade. Our optical data show no evidence that one exists today, suggesting that the radio MSP has turned on after a recent LMXB phase.

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Blobrana


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J1023
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Astronomers have discovered a unique double-star system that represents a "missing link" stage in what they believe is the birth process of the most rapidly-spinning stars in the Universe -- millisecond pulsars.

"We've thought for some time that we knew how these pulsars get 'spun up' to rotate so swiftly, and this system looks like it's showing us the process in action" - Anne Archibald, of McGill University in Montreal, Canada.

Pulsars are superdense neutron stars, the remnants left after massive stars have exploded as supernovae. Their powerful magnetic fields generate lighthouse-like beams of light and radio waves that sweep around as the star rotates. Most rotate a few to tens of times a second, slowing down over thousands of years.
However, some, dubbed millisecond pulsars, rotate hundreds of times a second. Astronomers believe the fast rotation is caused by a companion star dumping material onto the neutron star and spinning it up. The material from the companion would form a flat, spinning disk around the neutron star, and during this period, the radio waves characteristic of a pulsar would not be seen coming from the system. As the amount of matter falling onto the neutron star decreased and stopped, the radio waves could emerge, and the object would be recognized as a pulsar.
This sequence of events is apparently what happened with a binary-star system some 4000 light-years from Earth. The millisecond pulsar in this system, called J1023, was discovered by the National Science Foundation's (NSF) Robert C. Byrd Green Bank Telescope (GBT) in West Virginia in 2007 in a survey led by astronomers at West Virginia University and the National Radio Astronomy Observatory (NRAO).

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Blobrana


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Posts: 131433
Date:
SDSS J102347.68+003841.2
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A dying star has been caught in the act of resurrecting itself by eating its neighbour.
Together, the stars represent a previously unseen stage in the lifecycle of millisecond pulsars, the fastest-spinning objects in the universe.

"It's really a missing link in the chain from young pulsar to old pulsar" - Anne Archibald, a McGill University graduate student and lead author of the study published in Science Thursday.

Pulsars are a special class of neutron stars, the corpses of massive stars that exploded as supernovae. They're born spinning quickly, up to tens of times per second, and sweep the sky with a beam of radio energy as they rotate. Eventually, they slow down to the point where they can no longer emit radio waves and die a second death.
But until now, scientists couldn't explain how some old, dead pulsars become millisecond pulsars, which rotate hundreds of times a second. The new discovery of an intermediate step between the two appears to be the missing link.

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