QPOs and Orbital elements of X-ray binary 4U 0115+63 during the 2017 outburst observed by Insight-HXMT. (arXiv:2102.09498v1 [astro-ph.HE])

QPOs and Orbital elements of X-ray binary 4U 0115+63 during the 2017 outburst observed by Insight-HXMT. (arXiv:2102.09498v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Ding_Y/0/1/0/all/0/1">Y. Z. Ding</a> (1,2), <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_W/0/1/0/all/0/1">W. Wang</a> (1,3), <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_P/0/1/0/all/0/1">P. Zhang</a> (1,3), <a href="http://arxiv.org/find/astro-ph/1/au:+Bu_Q/0/1/0/all/0/1">Q.C. Bu</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Cai_C/0/1/0/all/0/1">C. Cai</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Cao_X/0/1/0/all/0/1">X.L.Cao</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Zhi_C/0/1/0/all/0/1">C. Zhi</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_L/0/1/0/all/0/1">L. Chen</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_T/0/1/0/all/0/1">T. X. Chen</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Y/0/1/0/all/0/1">Y. B. Chen</a> (6) <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Y/0/1/0/all/0/1">Y. Chen</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Y/0/1/0/all/0/1">Y. P. Chen</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Cui_W/0/1/0/all/0/1">W. W. Cui</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Du_Y/0/1/0/all/0/1">Y. Y. Du</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Gao_G/0/1/0/all/0/1">G. H. Gao</a> (4,7), <a href="http://arxiv.org/find/astro-ph/1/au:+Gao_H/0/1/0/all/0/1">H. Gao</a> (4,7), <a href="http://arxiv.org/find/astro-ph/1/au:+Ge_M/0/1/0/all/0/1">M. Y. Ge</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Gu_Y/0/1/0/all/0/1">Y. D. Gu</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Guan_J/0/1/0/all/0/1">J. Guan</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Guo_C/0/1/0/all/0/1">C. C. Guo</a> (4,7), <a href="http://arxiv.org/find/astro-ph/1/au:+Han_D/0/1/0/all/0/1">D. W. Han</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Huang_Y/0/1/0/all/0/1">Y. Huang</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Huo_J/0/1/0/all/0/1">J. Huo</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Jia_S/0/1/0/all/0/1">S. M. Jia</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Jiang_W/0/1/0/all/0/1">W. C. Jiang</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Jin_J/0/1/0/all/0/1">J. Jin</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Kong_L/0/1/0/all/0/1">L. D. Kong</a> (4,7), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_B/0/1/0/all/0/1">B. Li</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_C/0/1/0/all/0/1">C. K. Li</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_G/0/1/0/all/0/1">G. Li</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_T/0/1/0/all/0/1">T. P. Li</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_W/0/1/0/all/0/1">W. Li</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_X/0/1/0/all/0/1">X. Li</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_X/0/1/0/all/0/1">X. B. Li</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_X/0/1/0/all/0/1">X. F. Li</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Li_Z/0/1/0/all/0/1">Z. W. Li</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Liang_X/0/1/0/all/0/1">X. H. Liang</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Liao_J/0/1/0/all/0/1">J. Y. Liao</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_B/0/1/0/all/0/1">B. S. Liu</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_C/0/1/0/all/0/1">C. Z. Liu</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_H/0/1/0/all/0/1">H. X. Liu</a> (4,7), <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_H/0/1/0/all/0/1">H. W. Liu</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Liu_X/0/1/0/all/0/1">X. J. Liu</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Lu_F/0/1/0/all/0/1">F. J. Lu</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Lu_X/0/1/0/all/0/1">X. F. Lu</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+L%2E_Q/0/1/0/all/0/1">Q. L.</a> (4,7), <a href="http://arxiv.org/find/astro-ph/1/au:+T%2E_L/0/1/0/all/0/1">L. T.</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Ma_R/0/1/0/all/0/1">R. C. Ma</a> (4,7), <a href="http://arxiv.org/find/astro-ph/1/au:+Ma_X/0/1/0/all/0/1">X. Ma</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Meng_B/0/1/0/all/0/1">B. Meng</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Nang_Y/0/1/0/all/0/1">Y. Nang</a> (4,7), <a href="http://arxiv.org/find/astro-ph/1/au:+Nie_J/0/1/0/all/0/1">J. Y. Nie</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Qu_J/0/1/0/all/0/1">J. L. Qu</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Ren_X/0/1/0/all/0/1">X. Q. Ren</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Sai_N/0/1/0/all/0/1">N. Sai</a> (4,7), <a href="http://arxiv.org/find/astro-ph/1/au:+Song_L/0/1/0/all/0/1">L. M. Song</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Song_X/0/1/0/all/0/1">X. Y. Song</a> (4), et al. (37 additional authors not shown)

In this paper, we presented a detailed timing analysis of a prominent
outburst of 4U 0115+63 detected by textit{Insight}-HXMT in 2017 August. The
spin period of the neutron star was determined to be $3.61398pm 0.00002$ s at
MJD 57978. We measured the period variability and extract the orbital elements
of the binary system. The angle of periastron evolved with a rate of
$0.048pm0.003$ $yr^{-1}$. The light curves are folded to sketch the pulse
profiles in different energy ranges. A multi-peak structure in 1-10 keV is
clearly illustrated. We introduced wavelet analysis into our data analysis
procedures to study QPO signals and perform a detailed wavelet analysis in many
different energy ranges. Through the wavelet spectra, we report the discovery
of a QPO at the frequency $sim 10$ mHz. In addition, the X-ray light curves
showed multiple QPOs in the period of $sim 16-32 $ s and $sim 67- 200 $ s. We
found that the $sim100$ s QPO was significant in most of the observations and
energies. There exist positive relations between X-ray luminosity and their
Q-factors and S-factors, while the QPO periods have no correlation with X-ray
luminosity. In wavelet phase maps, we found that the pulse phase of $sim 67-
200 $ s QPO drifting frequently while the $sim 16-32 $ s QPO scarcely
drifting. The dissipation of oscillations from high energy to low energy was
also observed. These features of QPOs in 4U 0115+63 provide new challenge to
our understanding of their physical origins.

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