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Title: A NuSTAR Observation of the Gamma-Ray Emitting Millisecond Pulsar PSR J1723–2837

Abstract

We report on the first NuSTAR observation of the gamma-ray emitting millisecond pulsar binary PSR J1723–2837. X-ray radiation up to 79 keV is clearly detected, and the simultaneous NuSTAR and Swift spectrum is well described by an absorbed power law with a photon index of ∼1.3. We also find X-ray modulations in the 3–10, 10–20, 20–79, and 3–79 keV bands at the 14.8 hr binary orbital period. All of these are entirely consistent with previous X-ray observations below 10 keV. This new hard X-ray observation of PSR J1723–2837 provides strong evidence that the X-rays are from the intrabinary shock via an interaction between the pulsar wind and the outflow from the companion star. We discuss how the NuSTAR observation constrains the physical parameters of the intrabinary shock model.

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)
  2. Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of)
  3. Institute of Particle Physics and Astronomy, Huazhong University of Science and Technology (China)
  4. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
  5. School of Physics and Astronomy, Sun Yat-sen University, Zhuhai 519082 (China)
Publication Date:
OSTI Identifier:
22663675
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 839; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMIC GAMMA SOURCES; GAMMA RADIATION; HARD X RADIATION; INTERACTIONS; KEV RANGE; PULSARS; SPECTRA; STARS; STELLAR WINDS

Citation Formats

Kong, A. K. H., Hui, C. Y., Takata, J., Li, K. L., and Tam, P. H. T., E-mail: akong@phys.nthu.edu.tw, E-mail: cyhui@cnu.ac.kr. A NuSTAR Observation of the Gamma-Ray Emitting Millisecond Pulsar PSR J1723–2837. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA6AA2.
Kong, A. K. H., Hui, C. Y., Takata, J., Li, K. L., & Tam, P. H. T., E-mail: akong@phys.nthu.edu.tw, E-mail: cyhui@cnu.ac.kr. A NuSTAR Observation of the Gamma-Ray Emitting Millisecond Pulsar PSR J1723–2837. United States. doi:10.3847/1538-4357/AA6AA2.
Kong, A. K. H., Hui, C. Y., Takata, J., Li, K. L., and Tam, P. H. T., E-mail: akong@phys.nthu.edu.tw, E-mail: cyhui@cnu.ac.kr. Thu . "A NuSTAR Observation of the Gamma-Ray Emitting Millisecond Pulsar PSR J1723–2837". United States. doi:10.3847/1538-4357/AA6AA2.
@article{osti_22663675,
title = {A NuSTAR Observation of the Gamma-Ray Emitting Millisecond Pulsar PSR J1723–2837},
author = {Kong, A. K. H. and Hui, C. Y. and Takata, J. and Li, K. L. and Tam, P. H. T., E-mail: akong@phys.nthu.edu.tw, E-mail: cyhui@cnu.ac.kr},
abstractNote = {We report on the first NuSTAR observation of the gamma-ray emitting millisecond pulsar binary PSR J1723–2837. X-ray radiation up to 79 keV is clearly detected, and the simultaneous NuSTAR and Swift spectrum is well described by an absorbed power law with a photon index of ∼1.3. We also find X-ray modulations in the 3–10, 10–20, 20–79, and 3–79 keV bands at the 14.8 hr binary orbital period. All of these are entirely consistent with previous X-ray observations below 10 keV. This new hard X-ray observation of PSR J1723–2837 provides strong evidence that the X-rays are from the intrabinary shock via an interaction between the pulsar wind and the outflow from the companion star. We discuss how the NuSTAR observation constrains the physical parameters of the intrabinary shock model.},
doi = {10.3847/1538-4357/AA6AA2},
journal = {Astrophysical Journal},
number = 2,
volume = 839,
place = {United States},
year = {Thu Apr 20 00:00:00 EDT 2017},
month = {Thu Apr 20 00:00:00 EDT 2017}
}
  • We present X-ray observations of the 'redback' eclipsing radio millisecond pulsar (MSP) and candidate radio pulsar/X-ray binary transition object PSR J1723-2837. The X-ray emission from the system is predominantly non-thermal and exhibits pronounced variability as a function of orbital phase, with a factor of ∼2 reduction in brightness around superior conjunction. Such temporal behavior appears to be a defining characteristic of this variety of peculiar MSP binaries and is likely caused by a partial geometric occultation by the main-sequence-like companion of a shock within the binary. There is no indication of diffuse X-ray emission from a bow shock or pulsarmore » wind nebula associated with the pulsar. We also report on a search for point source emission and γ-ray pulsations in Fermi Large Area Telescope data using a likelihood analysis and photon probability weighting. Although PSR J1723-2837 is consistent with being a γ-ray point source, due to the strong Galactic diffuse emission at its position a definitive association cannot be established. No statistically significant pulsations or modulation at the orbital period are detected. For a presumed detection, the implied γ-ray luminosity is ≲5% of its spin-down power. This indicates that PSR J1723-2837 is either one of the least efficient γ-ray producing MSPs or, if the detection is spurious, the γ-ray emission pattern is not directed toward us.« less
  • We have investigated the X-ray and γ-ray properties of the redback millisecond pulsar PSR J1723–2837 with XMM-Newton, Chandra, and Fermi. We have discovered the X-ray orbital modulation of this binary system with a minimum that coincides with the phases of radio eclipse. The X-ray emission is clearly non-thermal in nature, which can be described well by a simple power law with a photon index of ∼1.2. The phase-averaged luminosity is ∼9 × 10{sup 31} erg s{sup –1} in 0.3-10 keV, which consumes ∼0.2% of the spin-down power. We have detected the γ-ray emission in 0.1-300 GeV from this system at amore » significance of ∼6σ for the first time. The γ-rays in this energy range consume ∼2% of the spin-down power and can be modeled by a power law with a photon index of ∼2.6. We discuss the high energy properties of the new redback in the context of an intrabinary shock model.« less
  • We present a study of PSR J1723–2837, an eclipsing, 1.86 ms millisecond binary radio pulsar discovered in the Parkes Multibeam survey. Radio timing indicates that the pulsar has a circular orbit with a 15 hr orbital period, a low-mass companion, and a measurable orbital period derivative. The eclipse fraction of ∼15% during the pulsar's orbit is twice the Roche lobe size inferred for the companion. The timing behavior is significantly affected by unmodeled systematics of astrophysical origin, and higher-order orbital period derivatives are needed in the timing solution to account for these variations. We have identified the pulsar's (non-degenerate) companionmore » using archival ultraviolet, optical, and infrared survey data and new optical photometry. Doppler shifts from optical spectroscopy confirm the star's association with the pulsar and indicate a pulsar-to-companion mass ratio of 3.3 ± 0.5, corresponding to a companion mass range of 0.4 to 0.7 M{sub ☉} and an orbital inclination angle range of between 30° and 41°, assuming a pulsar mass range of 1.4-2.0 M{sub ☉}. Spectroscopy indicates a spectral type of G for the companion and an inferred Roche-lobe-filling distance that is consistent with the distance estimated from radio dispersion. The features of PSR J1723–2837 indicate that it is likely a 'redback' system. Unlike the five other Galactic redbacks discovered to date, PSR J1723–2837 has not been detected as a γ-ray source with Fermi. This may be due to an intrinsic spin-down luminosity that is much smaller than the measured value if the unmeasured contribution from proper motion is large.« less
  • I present a 40 ks Nuclear Spectroscopic Telescope Array observation of the recently identified low-luminosity X-ray binary and transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4 112820, which is associated with the high-energy γ -ray source 3FGL J1544.6 1125. The system is detected up to ∼30 keV with an extension of the same power-law spectrum and rapid large-amplitude variability between two flux levels observed in soft X-rays. These findings provide further evidence that 1RXS J154439.4 112820 belongs to the same class of objects as the nearby bona fide tMSPs PSR J1023+0038 and XSS J12270 4859 and therefore almost certainly hosts amore » millisecond pulsar accreting at low luminosity. I also examine the long-term accretion history of 1RXS J154439.4 112820 based on archival optical, ultraviolet, X-ray, and γ -ray light curves covering approximately the past decade. Throughout this period, the source has maintained similar flux levels at all wavelengths, which is an indication that it has not experienced prolonged episodes of a non-accreting radio pulsar state but may spontaneously undergo such events in the future.« less
  • 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 two to three) 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 themore » intrabinary shock is localized near or at the surface of the companion star and close to the inner Lagrangian point. The energetics of the shock favor 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{sub X} {approx}< 3.6 Multiplication-Sign 10{sup 29} erg s{sup -1} (0.3-8 keV), {approx}< 7 Multiplication-Sign 10{sup -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.« less