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It is very controversial whether radio–X-ray correlation as defined in low-hard state of X-ray binaries (XRBs) can extend to quiescent state (e.g. X-ray luminosity less than a critical value of LX,c ~ 10−5.5LEdd) or not. In this work, we collect a sample of XRBs and low-luminosity active galactic nuclei (LLAGNs) with wide distribution of Eddington ratios (LX/LEdd ~ 10−9–10−3) to re-explore the Fundamental Plane between 5 GHz radio luminosity, LR, 2–10 keV X-ray luminosity, LX, and black hole (BH) mass, MBH, namely log LR = ξXlog LX + ξMlog MBH + constant. For the whole sample, we confirm the former Fundamental Plane of Merloni et al. and Falcke et al. that ξX ~ 0.6 and ξM ~ 0.8 even after including more quiescent BHs. The quiescent BHs follow the Fundamental Plane very well, and, however, FR I radio galaxies follow a steeper track comparing other BH sources. After excluding FR Is, we investigate the Fundamental Plane for BHs in quiescent state with LX < LX,c and sub-Eddington BHs with LX > LX,c, respectively, and both sub-samples have a similar slope, ξX ~ 0.6, which support that quiescent BHs may behave similar to those in low-hard state. We further select two sub-samples of AGNs with BH mass in a narrow range (FR Is with MBH = 108.8±0.4 and other LLAGNs with MBH = 108.0±0.4) to simulate the behaviour of a single supermassive BH evolving from sub-Eddington to quiescent state. We find that the highly sub-Eddington sources with LX/LEdd ~ 10−6–10−9 still roughly stay on the extension of radio–X-ray correlation as defined by other sub-Eddington BHs. Our results are consistent with several recent observations in XRBs that the radio–X-ray correlation as defined in low-hard state can extend to highly sub-Eddington quiescent state. [ABSTRACT FROM AUTHOR]

The mass of the neutron star PSR J1614-2230 is calculated in the framework of relativistic mean field theory. In our calculations, we choose nine nucleon coupling constants (i.e. CZ11, DD-MEI, GL85, GL97, NL1, NL2, NLSH, TM1 and TM2), assuming that the neutron star only consists of neutrons, protons and electrons. It is found that the NLSH set give the hardest equation of state and the largest mass of neutron star. It is also found that, corresponding to the CZ11 set, the neutron star mass is 1.9702 M⊙ which is approximate the mass of the neutron star PSR J1614-2230. Thus, we may obtain a possible model for it. [ABSTRACT FROM AUTHOR]

Abstract: Using the public material of the Rosse X-ray Timing Explorer (RXTE) satellite from January 1996 to May 2005, the periodicity of the light curve of the X-ray binary Cyg X-1 as a black hole candidate is studied and some interesting periods (T =1.0±0.2 d and T = 18.0±3.0 d) are found. In the hard state, both the periods T = 1.0±0.2 d and T = 18.0±3.0 d simultaneously appear in the light curve, while in the soft state only the period T = 1.0±0.2 d exists. For analyzing the same material, a new method (i.e., the “derivative” method) is introduced and, in order to check the validity of this method, two traditional methods (the fast Fourier transform and period folding method) are also applied. Identical results are obtained. Besides, the orbital period of Cyg X-1 is also probed. It is discovered that the orbital period T = 5.6 d appears not only in the hard state, but also in the soft state, while it is more obvious in the former. [Copyright &y& Elsevier]

Highlights • We presented and analyzed the four-color light curves of NSVS 10441882 for the first time. • The photometric solutions reveal that NSVS 10441882 is a short-period detached eclipsing binary with strong magnetic activity. • We discovered that the (O–C) diagram of the system shows an cyclic oscillation due to the presence of an unseen third body. Abstract NSVS 10441882 is a newly discovered eclipsing binary system with strong magnetic activity and an orbital period of ∼ 0.5166 days. In order to study this eclipsing binary system, we analyzed its first four-color (BVR c I c) light curves. The observed light curves were asymmetric, so we used the 2013 version of the Wilson–Devinney (W–D) program with cool star-spots to analyze these data. We discovered that NSVS 10441882 is a detached total eclipsing binary system with an orbit inclination of 85°.34 ± 0.07 and a mass ratio of q = 0.94 ± 0.03. Based on the CCD times of the light minima according to our observations and those reported previously, the orbital period changes of NSVS 10441882 were studied using the traditional O–C method for the first time. The O–C diagram of the target exhibited a cyclic oscillation with a period of 16.7 ± 0.20 years and an amplitude of 0.00349 ± 0.00029 days, probably due to the presence of an unseen third body. If we assume that the total mass of NSVS 10441882 is 1.3M ⊙ (according to our calculated results for the average color index and mass ratio), then the mass of the third body is no less than 0.12 ± 0.01 M ⊙. Moreover, the orbital evolution of the central system will be accelerated due to the presence of this additional component. [ABSTRACT FROM AUTHOR]

• The ratio of the two peak intensities and the evolution of the phase separation with the energy of Crab pulsar are studied. • We simulate the eight-wavelength X-ray light curves of Crab pulsar by joint the core gap and annular gap. • The evolution of the Crab pulsar light curve with frequency provides a stronger constraint for the theoretical model. • By simulating the light curve of crab pulsar, the region of each radiation component is deduced. • This research has certain scientific significance for studying the geometry of the pulsar radiation area and discussing the timing noise of pulsar. Multiwavelength observation is an effective way to test and constrain theoretical models of pulsars. X-ray observations reveal that the light curve of the Crab pulsar has two sharp peaks, with a phase separation of ~ 0.4 spin periods between its first peak (P1) and second peak (P2). Using observations from the Hard X-ray Modulation Telescope (Insight -HXMT) of China, we studied eight-wavelength (from 11 keV to 250 keV) X-ray light curves of the Crab pulsar and found that the phase separation has no significant trend with the energy, while the total intensity ratios of the P2 and bridge emission components to the P1 component have a significant increasing trend with increasing energy. We used three-dimensional magnetospheric models for the core gap (CG) and annular gap (AG) to simulate the eight-wavelength X-ray light curves. It was found that the P1, P2 and bridge emission components at each band can be well reproduced by the two models and that the P1 and P2 emissions could be generated in the AG region, whereas the bridge emission could be generated in the CG region. [ABSTRACT FROM AUTHOR]

The hyperluminous X-ray source (HLX-1, peak X-ray luminosity ) near the spiral galaxy ESO 243-49, which underwent recurrent outbursts within a period of ∼400 days, is possibly the best candidate for an intermediate mass black hole (IMBH). The physical reason for this quasiperiodic variability is still unclear. We explore the possibility of radiation-pressure instability in the accretion disk by modeling the light curve of HLX-1, and find that it can roughly reproduce the duration, period, and amplitude of the recurrent outbursts in HLX-1 with an IMBH of . Our result provides a possible mechanism to explain the recurrent outbursts in HLX-1. We further find a universal correlation between the outburst duration and the bolometric luminosity for the black hole (BH) sources with a very broad mass range (e.g., X-ray binaries, HLX-1, and active galactic nuclei), which is roughly consistent with the prediction of radiation-pressure instability of the accretion disk. These results imply that “heartbeat” oscillations triggered by radiation-pressure instability may appear in different-scale BH systems. [ABSTRACT FROM AUTHOR]