arXiv subjects

Chin-Ping Hu

Publications and source records attributed to Chin-Ping Hu.

57 records · Page 4Linked to original sources

arXiv2013

Superorbital Phase-Resolved Analysis of SMC X-1

The high-mass X-ray binary SMC X-1 is an eclipsing binary with an orbital period of 3.89 d. This system exhibits a superorbital modulation with a period varying between ~40 d and ~65 d. The instantaneous frequency and the corresponding phase of the superorbital modulation can be obtained by a recently developed time-frequency analysis technique, the Hilbert-Huang transform (HHT). We present a phase-resolved analysis of both the spectra and the orbital profiles with the superorbital phase derived from the HHT. The X-ray spectra observed by the Proportional Counter Array onboard the Rossi X-ray Timing Explorer are fitted well by a blackbody plus a Comptonized component. The plasma optical depth, which is a good indicator of the distribution of material along the line of sight, is significantly anti-correlated with the flux detected at 2.5-25 keV. However, the relationship between the plasma optical depth and the equivalent width of the iron line is not monotonic: there is no significant correlation for fluxes higher than ~35 mCrab but clear positive correlation when the intensity is lower than ~20 mCrab. This indicates that the iron line production is dominated by different regions of this binary system in different superorbital phases. To study the dependence of the orbital profile on the superorbital phase, we obtained the eclipse profiles by folding the All Sky Monitor light curve with the orbital period for different superorbital states. A dip feature, similar to the pre-eclipse dip in Her X-1, lying at orbital phase ~0.6-0.85, was discovered during the superorbital transition state. This indicates that the accretion disk has a bulge that absorbs considerable X-ray emission in the stream-disk interaction region. The dip width is anti-correlated with the flux, and this relation can be interpreted by the precessing tilted accretion disk scenario.

astro-ph.HE↗

arXiv2011

Time-Frequency Analysis of Superorbital Modulation of X-ray Binary SMC X-1 by Hilbert-Huang Transform

The high-mass X-ray binary (HMXB) SMC X-1 exhibits a superorbital modulation with a dramatically varying period ranging between ~40 d and ~60 d. This research studies the time-frequency properties of the superorbital modulation of SMC X-1 based on the observations made by the All-Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE).We analyzed the entire ASM database collected since 1996. The Hilbert-Huang Transform (HHT), developed for non-stationary and nonlinear time series analysis, was adopted to derive the instantaneous superorbital frequency. The resultant Hilbert spectrum is consistent with the dynamic power spectrum while it shows more detailed information in both the time and frequency domains. The RXTE observations manifest that the superorbital modulation period was mostly betweenn ~50 d and ~65 d, whenas it changed to ~45 d around MJD 50,800 and MJD 54,000. Our analysis further indicates that the instantaneous frequency changed in a time scale of hundreds of days between ~MJD 51,500 and ~MJD 53,500. Based on the instantaneous phase defined by HHT, we folded the ASM light curve to derive a superorbital profile, from which an asymmetric feature and a low state with barely any X-ray emissions (lasting for ~0.3 cycles) were observed. We also calculated the correlation between the mean period and the amplitude of the superorbital modulation. The result is similar to the recently discovered relationship between the superorbital cycle length and the mean X-ray flux for Her X-1.

astro-ph.HE↗

arXiv2007

Parameterization studies of the properties of the X-ray dips for Low Mass X-ray binary X1916-053

The ultra-compact Low Mass X-ray Binary (LMXB) X1916-053, composed of a neutron star and a semi-degenerated white dwarf, exhibits periodic X-ray dips with variable width and depth. We have developed new methods to parameterize the dip to systematically study its variations. This helps to further understand binary and accretion disk behaviors. The RXTE 1998 observations clearly show a 4.87d periodic variation of the dip width. This is probably due to the nodal precession of the accretion disk, although there are no significant sidebands in the spectrum from the epoch folding search. From the negative superhump model (Larwood et. al. 1996), the mass ratio can be estimated as q = 0.045. Combined with more than 24 years of historical data, we found an orbital period derivative of $\dot{P}_{orb}/P_{orb}=(1.62 \pm 0.48)\times 10^{-7} yr^{-1}$ and established a quadratic ephemeris for the X-ray dips. The period derivative seems inconsistent with the prediction of the standard model of binary orbital evolution proposed by Rappaport et. al. (1987). On the other hand, the radiation-driven model (Tavani et. al. 1991) may properly interpret the period derivative even though the large mass outflow predicted by this model has never been observed in this system. With the best ephemeris, we obtained that the standard deviation of primary dips are smaller than that of secondary dips. This means that the primary dips are more stable than the secondary dips. Thus, we conclude that the primary dips of X1916-053 occur from the bulge at the rim instead of the ring of the disk proposed by Frank et. al. (1987).

astro-ph↗