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Title: Radio Pulse Search and X-Ray Monitoring of SAX J1808.4−3658: What Causes Its Orbital Evolution?

Abstract

The accreting millisecond X-ray pulsar SAX J1808.4−3658 shows a peculiar orbital evolution that proceeds at a very fast pace. It is important to identify the underlying mechanism responsible for this behavior because it can help to understand how this system evolves and which physical processes (such as mass loss or spin–orbit coupling) are occurring in the binary. It has also been suggested that, when in quiescence, SAX J1808.4−3658 turns on as a radio pulsar, a circumstance that might provide a link between accreting millisecond pulsars and black-widow (BW) radio pulsars. In this work, we report the results of a deep radio pulsation search at 2 GHz using the Green Bank Telescope in 2014 August and an X-ray study of the 2015 outburst with Chandra , Swift XRT, and INTEGRAL . In quiescence, we detect no radio pulsations and place the strongest limit to date on the pulsed radio flux density of any accreting millisecond pulsar. We also find that the orbit of SAX J1808.4−3658 continues evolving at a fast pace. We compare the orbital evolution of SAX J1808.4−3658 to that of several other accreting and nonaccreting binaries, including BWs, redbacks, cataclysmic variables, black holes, and neutron stars in low-mass X-raymore » binaries. We discuss two possible scenarios: either the neutron star has a large moment of inertia and is ablating the donor, generating mass loss with an efficiency of 40%, or the donor star has a strong magnetic field of at least 1 kG and is undergoing quasi-cyclic variations due to spin–orbit coupling.« less

Authors:
;  [1]; ;  [2];  [3]; ; ;  [4];  [5]
  1. Leiden Observatory, Leiden University, Neils Bohrweg 2, 2333 CA, Leiden (Netherlands)
  2. ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7900 AA, Dwingeloo (Netherlands)
  3. SRON-National Institute for Space Research, Sorbonnelaan 2, NL-3584 CA, Utrecht (Netherlands)
  4. Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam (Netherlands)
  5. University of Southampton, School of Physics and Astronomy, Southampton SO17 1BJ (United Kingdom)
Publication Date:
OSTI Identifier:
22663559
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 841; 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; BLACK HOLES; FLUX DENSITY; GHZ RANGE; L-S COUPLING; MAGNETIC FIELDS; MASS TRANSFER; MOMENT OF INERTIA; NEUTRON STARS; NEUTRONS; ORBITS; PULSARS; PULSATIONS; ROTATION; SMALL ANGLE SCATTERING; STELLAR WINDS; TELESCOPES; X RADIATION; X-RAY DIFFRACTION

Citation Formats

Patruno, Alessandro, King, Andrew R., Jaodand, Amruta, Hessels, Jason W. T., Kuiper, Lucien, Bult, Peter, Wijnands, Rudy, Van der Klis, Michiel, and Knigge, Christian. Radio Pulse Search and X-Ray Monitoring of SAX J1808.4−3658: What Causes Its Orbital Evolution?. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA6F5B.
Patruno, Alessandro, King, Andrew R., Jaodand, Amruta, Hessels, Jason W. T., Kuiper, Lucien, Bult, Peter, Wijnands, Rudy, Van der Klis, Michiel, & Knigge, Christian. Radio Pulse Search and X-Ray Monitoring of SAX J1808.4−3658: What Causes Its Orbital Evolution?. United States. doi:10.3847/1538-4357/AA6F5B.
Patruno, Alessandro, King, Andrew R., Jaodand, Amruta, Hessels, Jason W. T., Kuiper, Lucien, Bult, Peter, Wijnands, Rudy, Van der Klis, Michiel, and Knigge, Christian. Thu . "Radio Pulse Search and X-Ray Monitoring of SAX J1808.4−3658: What Causes Its Orbital Evolution?". United States. doi:10.3847/1538-4357/AA6F5B.
@article{osti_22663559,
title = {Radio Pulse Search and X-Ray Monitoring of SAX J1808.4−3658: What Causes Its Orbital Evolution?},
author = {Patruno, Alessandro and King, Andrew R. and Jaodand, Amruta and Hessels, Jason W. T. and Kuiper, Lucien and Bult, Peter and Wijnands, Rudy and Van der Klis, Michiel and Knigge, Christian},
abstractNote = {The accreting millisecond X-ray pulsar SAX J1808.4−3658 shows a peculiar orbital evolution that proceeds at a very fast pace. It is important to identify the underlying mechanism responsible for this behavior because it can help to understand how this system evolves and which physical processes (such as mass loss or spin–orbit coupling) are occurring in the binary. It has also been suggested that, when in quiescence, SAX J1808.4−3658 turns on as a radio pulsar, a circumstance that might provide a link between accreting millisecond pulsars and black-widow (BW) radio pulsars. In this work, we report the results of a deep radio pulsation search at 2 GHz using the Green Bank Telescope in 2014 August and an X-ray study of the 2015 outburst with Chandra , Swift XRT, and INTEGRAL . In quiescence, we detect no radio pulsations and place the strongest limit to date on the pulsed radio flux density of any accreting millisecond pulsar. We also find that the orbit of SAX J1808.4−3658 continues evolving at a fast pace. We compare the orbital evolution of SAX J1808.4−3658 to that of several other accreting and nonaccreting binaries, including BWs, redbacks, cataclysmic variables, black holes, and neutron stars in low-mass X-ray binaries. We discuss two possible scenarios: either the neutron star has a large moment of inertia and is ablating the donor, generating mass loss with an efficiency of 40%, or the donor star has a strong magnetic field of at least 1 kG and is undergoing quasi-cyclic variations due to spin–orbit coupling.},
doi = {10.3847/1538-4357/AA6F5B},
journal = {Astrophysical Journal},
number = 2,
volume = 841,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}