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Title: Swift Detection of a 65 Day X-Ray Period from the Ultraluminous Pulsar NGC 7793 P13

Abstract

NGC 7793 P13 is an ultraluminous X-ray source harboring an accreting pulsar. We report on the detection of a ∼65 day period X-ray modulation with Swift observations in this system. The modulation period found in the X-ray band is P = 65.05 ± 0.10 days and the profile is asymmetric with a fast rise and a slower decay. On the other hand, the u -band light curve collected by Swift UVOT confirmed an optical modulation with a period of P = 64.24 ± 0.13 days. We explored the phase evolution of the X-ray and optical periodicities and propose two solutions. A superorbital modulation with a period of ∼2700–4700 days probably caused by the precession of a warped accretion disk is necessary to interpret the phase drift of the optical data. We further discuss the implication if this ∼65 day periodicity is caused by the superorbital modulation. Estimated from the relationship between the spin-orbital and orbital-superorbital periods of known disk-fed high-mass X-ray binaries, the orbital period of P13 is roughly estimated as 3–7 days. In this case, an unknown mechanism with a much longer timescale is needed to interpret the phase drift. Further studies on the stability of these two periodicitiesmore » with a long-term monitoring could help us to probe their physical origins.« less

Authors:
;  [1];  [2];  [3];  [4]
  1. Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong)
  2. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
  3. Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)
  4. Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan (China)
Publication Date:
OSTI Identifier:
22654562
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 835; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ASYMMETRY; DETECTION; EVOLUTION; GALAXIES; MASS; MATHEMATICAL SOLUTIONS; MODULATION; NEUTRONS; PERIODICITY; PRECESSION; PULSARS; SPIN; STABILITY; STARS; VISIBLE RADIATION; X RADIATION; X-RAY SOURCES

Citation Formats

Hu, Chin-Ping, Ng, C.-Y., Li, K. L., Kong, Albert K. H., and Lin, Lupin Chun-Che, E-mail: cphu@hku.hk, E-mail: liliray@pa.msu.edu. Swift Detection of a 65 Day X-Ray Period from the Ultraluminous Pulsar NGC 7793 P13. United States: N. p., 2017. Web. doi:10.3847/2041-8213/835/1/L9.
Hu, Chin-Ping, Ng, C.-Y., Li, K. L., Kong, Albert K. H., & Lin, Lupin Chun-Che, E-mail: cphu@hku.hk, E-mail: liliray@pa.msu.edu. Swift Detection of a 65 Day X-Ray Period from the Ultraluminous Pulsar NGC 7793 P13. United States. doi:10.3847/2041-8213/835/1/L9.
Hu, Chin-Ping, Ng, C.-Y., Li, K. L., Kong, Albert K. H., and Lin, Lupin Chun-Che, E-mail: cphu@hku.hk, E-mail: liliray@pa.msu.edu. Fri . "Swift Detection of a 65 Day X-Ray Period from the Ultraluminous Pulsar NGC 7793 P13". United States. doi:10.3847/2041-8213/835/1/L9.
@article{osti_22654562,
title = {Swift Detection of a 65 Day X-Ray Period from the Ultraluminous Pulsar NGC 7793 P13},
author = {Hu, Chin-Ping and Ng, C.-Y. and Li, K. L. and Kong, Albert K. H. and Lin, Lupin Chun-Che, E-mail: cphu@hku.hk, E-mail: liliray@pa.msu.edu},
abstractNote = {NGC 7793 P13 is an ultraluminous X-ray source harboring an accreting pulsar. We report on the detection of a ∼65 day period X-ray modulation with Swift observations in this system. The modulation period found in the X-ray band is P = 65.05 ± 0.10 days and the profile is asymmetric with a fast rise and a slower decay. On the other hand, the u -band light curve collected by Swift UVOT confirmed an optical modulation with a period of P = 64.24 ± 0.13 days. We explored the phase evolution of the X-ray and optical periodicities and propose two solutions. A superorbital modulation with a period of ∼2700–4700 days probably caused by the precession of a warped accretion disk is necessary to interpret the phase drift of the optical data. We further discuss the implication if this ∼65 day periodicity is caused by the superorbital modulation. Estimated from the relationship between the spin-orbital and orbital-superorbital periods of known disk-fed high-mass X-ray binaries, the orbital period of P13 is roughly estimated as 3–7 days. In this case, an unknown mechanism with a much longer timescale is needed to interpret the phase drift. Further studies on the stability of these two periodicities with a long-term monitoring could help us to probe their physical origins.},
doi = {10.3847/2041-8213/835/1/L9},
journal = {Astrophysical Journal Letters},
number = 1,
volume = 835,
place = {United States},
year = {Fri Jan 20 00:00:00 EST 2017},
month = {Fri Jan 20 00:00:00 EST 2017}
}