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Luminosity of a radio pulsar and its new emission death line 被引量:1
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作者 Qing-Dong Wu Qi-Jun Zhi +2 位作者 cheng-min zhang De-Hua Wang Chang-Qing Ye 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2020年第11期325-332,共8页
We investigated the pulsar radio luminosity(L),emission efficiency(ratio of radio luminosity to its spin-down powerE),and death line in the magnetic field(B)versus spin period(P)diagram.We found that the dependence of... We investigated the pulsar radio luminosity(L),emission efficiency(ratio of radio luminosity to its spin-down powerE),and death line in the magnetic field(B)versus spin period(P)diagram.We found that the dependence of pulsar radio luminosity on its spin-down power(L-E)is very weak,shown as L^E0.06,which deduces an equivalent inverse correlation between emission efficiency and spin-down power asξ~E-0.94.Furthermore,we examined the distributions of radio luminosity of millisecond and normal pulsars and found that for the similar spin-down powers,the radio luminosity of millisecond pulsars is about one order of magnitude lower than that of the normal pulsars.The analysis of pulsar radio flux suggests that these correlations are not due to a selective effect but are intrinsic to the pulsar radio emission physics.Their radio radiations may be dominated by the different radiation mechanisms.The cutoff phenomenon of currently observed radio pulsars in B-P diagram is usually referred as the"pulsar death line",which corresponds toE≈1030 erg s-1 and is obtained by the cut-off voltage of electron acceleration gap in the polar cap model of pulsar proposed by Ruderman and Sutherland.Observationally,this death line can be inferred by the actual observed pulsar flux S≥1 mJy and 1 kpc distance,together with the maximum radio emission efficiency of 1%.However,the observation data show that the 37 pulsars pass over the death line,including the recently observed two pulsars with long periods of 23.5 s and 12.1 s,which violate the prediction of the polar cap model.At present,the actual observed pulsar flux can reach0.01 mJy by FAST telescope.This will arise the observational limit of spin-down power of pulsars as low as E˙≈1028 erg s-1.This means that the new death line is downward shifted two orders of magnitude,which might be favorably referred as the"observational limit–line".Accordingly,the pulsar theoretical model for the cut-off voltage of gap should be heavily modified. 展开更多
关键词 STARS NEUTRON PULSARS general STARS fundamental parameters
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X-ray Spectroscopy of Dips of Cir X-1 被引量:1
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作者 Ya-Juan Lei Fang-Jun Lu +2 位作者 Jin-Lu Qu Li-Ming Song cheng-min zhang 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2007年第5期693-704,共12页
We present X-ray spectral analyses of the low-mass X-ray binary Cir X-1 during X-ray dips, using the Rossi X-ray Timing Explorer (RXTE) data. Each dip was divided into several segments, and the spectrum of each segm... We present X-ray spectral analyses of the low-mass X-ray binary Cir X-1 during X-ray dips, using the Rossi X-ray Timing Explorer (RXTE) data. Each dip was divided into several segments, and the spectrum of each segment was fitted with a three-component blackbody model, in which the first two components are affected by partial covering and the third one is unaffected. A Gaussian emission line is also included in the spectral model to represent the Fe Kα line at - 6.4 keV. The fitted temperatures of the two partially covered components are about 2 keV and 1 keV, while the uncovered component has a temperature of -0.5-0.6 keV. The equivalent blackbody emission radius of the hottest component is the smallest and that of the coolest component is the largest. During the dips the fluxes of the two hot components are linearly correlated, while that of the third component does not show any significant variation. The Fe line flux remains constant, within the errors, during the short dips. However, during the long dips the line flux varies significantly and is positively correlated with the fluxes of the two hot components. These results suggest; (1) that the temperature of the X-ray emitting region decreases with radius, (2) that the Fe Kα line emitting region is close to the hot continuum emitting region, and (3) that the size of the Fe line emitting region is larger than that of the obscuring matter causing the short dips but smaller than the region of that causing the long dips. 展开更多
关键词 STARS individual (Circinus X-1) -- stars neutron -- X-rays STARS
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Exploring the Accretion Disk Structure and X-ray Radiation of GX 17+2 Based on kHz QPOs and Cross-correlations
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作者 De-Hua Wang cheng-min zhang Ya-Juan Lei 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2022年第12期239-248,共10页
Applying the timing tools of kilohertz quasi-periodic oscillations(k Hz QPOs)and cross-correlations,we study the influence of the magnetosphere-disk relation on the X-ray radiation process of GX 17+2.First,as the spec... Applying the timing tools of kilohertz quasi-periodic oscillations(k Hz QPOs)and cross-correlations,we study the influence of the magnetosphere-disk relation on the X-ray radiation process of GX 17+2.First,as the spectral state track of X-ray emission evolves along the horizontal branch(HB),the magnetosphere-disk radii of the source derived by k Hz QPOs shrink from r~24 km to r~18 km,while its average X-ray intensities in≤10 ke V and in≥10 ke V show the opposite evolutional trends.Moreover,this branch has been detected with the anti-correlations between the low-/high-energy(e.g.,2–5 ke V/16–30 ke V)X-rays.We suggest that in HB there may exist an X-ray radiation transfer process at the disk radii near the neutron star(NS),i.e.,~5–10 km away from the surface,which probably originates from the interaction between the corona or jet with high-energy X-rays and accretion disk with low-energy X-rays.Second,as the source evolves along the normal branch(NB)and along the flaring branch(FB),their average X-ray intensities in all~2–30 ke V show the monotonously decreasing and monotonously increasing trends,respectively.In addition,these two branches are both dominated by the positive correlations between the low-and high-energy(e.g.,2–5 ke V/16–30 ke V)X-rays.Moreover,the evolution along NB is accompanied by the shrinking of the magnetosphere-disk radii from r~18 km to r~16 km.We ascribe these phenomena to that as the shrinking of the accretion disk radius,the piled up accretion matter around the NS surface may trigger the radiation that produces both the low-and high-energy X-rays simultaneously,and then form the branches of NB and FB. 展开更多
关键词 X-rays:binaries stars:neutron stars:individual(GX 17+2) ACCRETION accretion disks
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Constraints on the kinetic energy of type-Ic supernova explosion from young PSR J1906+0746 in a double neutron star candidate
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作者 Yi-Yan Yang cheng-min zhang +1 位作者 Jian-Wei zhang De-Hua Wang 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第6期721-726,共6页
So far among the nineteen pairs of detected double neutron star(DNS) systems, it is a usual fact that the first-born recycled pulsar is detected, however the youngest DNS system PSR J1906+0746, with the characteristic... So far among the nineteen pairs of detected double neutron star(DNS) systems, it is a usual fact that the first-born recycled pulsar is detected, however the youngest DNS system PSR J1906+0746, with the characteristic age of 113 kyr, is one of the three detected DNS as a non-recycled and second-born NS, which is believed to be formed by an electron capture or a low energy ultra-stripped iron core-collapse supernova(SN) explosion. The SN remnant around PSR J1906+0746 is too dim to be observed by optical telescopes, then its x-ray flux limit has been given by Chandra. A reference pulsar PSR J1509-5850 with the young characteristic age of 154 kyr was chosen as an object of comparison, which has an SN remnant observed by Chandra and is believed to be formed by iron core SN explosion. We impose a restriction on the maximum kinetic energy of electron-capture(EC) SN explosion that induces the formation of PSR J1906+0746. The estimated result is(4–8)×10^(50) erg(1 erg= 10-7 J), which is consistent with that of the published simulations of the EC process, i.e., a lower value than that of the conventional iron core SN explosion of(1–2)×10^(51) erg. As suggested, EC process for NS formation is pertained to the subluminous type Ic SN by the helium star with ONeMg core, thus for the first time we derived the kinetic energy of EC SN explosion of DNS, which may be reconciled with the recent observation of type Ic SN 2014 ft with kinetic energy of 2 × 10^(50) erg. 展开更多
关键词 neutron star pulsar ASTROPHYSICS high energy astrophysical phenomena
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A Detailed Study of Mode Changing and Modulation of PSR B1237+25 with FAST
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作者 Zheng-Wu Wang Mao Yuan +2 位作者 Lin Wang cheng-min zhang Bo Peng 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2022年第7期73-83,共11页
PSR B1237+25,whose mean pulse profile has five components,is a well-known star to study pulsar emission geometries.We conducted mode changing and modulation analysis on this pulsar using FAST data at 1.25 GHz with a b... PSR B1237+25,whose mean pulse profile has five components,is a well-known star to study pulsar emission geometries.We conducted mode changing and modulation analysis on this pulsar using FAST data at 1.25 GHz with a bandwidth of 400 MHz.We observed and identified three emission modes of this pulsar:a quiet normal mode that has little or no core activity with distinctive 2.8-period subpulse modulation on its outer cone,a flare normal mode in which the core is highly active and an abnormal mode in which the core is active and the last component is weak.We found that the core activity cuts off the position angle traverse in flare normal mode and leads to a position angle jumping in abnormal mode.We also found that there exists a quasi-periodical modulation on the outer conal components.Such modulation shows an irregular wave-like pattern,and has a weak correlation with the core component.We discuss the likely origin of such a modulation,and argue that this modulation can be interpreted as precession of the emission cones around the magnetic axis. 展开更多
关键词 (stars:)pulsars:individual(PSR B1237+25) radiation mechanisms:non-thermal magnetic fields polarization
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A Study on the Correlations between the Twin kHz QPO Frequencies in Sco X-1
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作者 Hong-Xing Yin cheng-min zhang +2 位作者 Yong-Heng Zhao Li-Ming Song Fan zhang 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2005年第6期595-600,共6页
For the bright neutron star low-mass X-ray binary Sco X-l, we analyzed all updated frequencies of the twin kilohertz quasi-periodic oscillations (kHz QPOs), their correlations and distributions. We found that the fr... For the bright neutron star low-mass X-ray binary Sco X-l, we analyzed all updated frequencies of the twin kilohertz quasi-periodic oscillations (kHz QPOs), their correlations and distributions. We found that the frequency separation of the kHz QPO peaks appears not to be a constant, rather, it decreases with increasing inferred mass accretion rate. We show that the currently available data of Sco X-1 by Rossi X-ray Timing Explorer are inconsistent with the proposals of the beat model that the frequency separation is a constant. Our conclusions are consistent with those of some previous researchers and we discuss further implications for the kilohertz QPO models. 展开更多
关键词 X-rays accretion disks - stars neutron - X-rays STARS
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Statistical properties of fast radio bursts elucidate their origins:magnetars are favored over gamma-ray bursts
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作者 Xiang-Han Cui cheng-min zhang +11 位作者 Shuang-Qiang Wang Jian-Wei zhang Di Li Bo Peng Wei-Wei Zhu Richard Strom Na Wang Qingdong Wu Chang-Qing Ye De-Hua Wang Yi-Yan Yang Zhen-Qi Diao 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第8期285-292,共8页
Fast radio bursts(FRBs) are extremely strong radio flares lasting several milliseconds,most of which come from unidentified objects at a cosmological distance.They can be apparently repeating or not.In this paper,we a... Fast radio bursts(FRBs) are extremely strong radio flares lasting several milliseconds,most of which come from unidentified objects at a cosmological distance.They can be apparently repeating or not.In this paper,we analyzed 18 repeaters and 12 non-repeating FRBs observed in the frequency bands of 400–800 MHz from Canadian Hydrogen Intensity Mapping Experiment(CHIME).We investigated the distributions of FRB isotropic-equivalent radio luminosity,considering the K correction.Statistically,the luminosity distribution can be better fitted by Gaussian form than by power-law.Based on the above results,together with the observed FRB event rate,pulse duration,and radio luminosity,FRB origin models are evaluated and constrained such that the gamma-ray bursts(GRBs) may be excluded for the non-repeaters while magnetars or neutron stars(NSs) emitting the supergiant pulses are preferred for the repeaters.We also found the necessity of a small FRB emission beaming solid angle(about 0.1 sr) from magnetars that should be considered,and/or the FRB association with soft gamma-ray repeaters(SGRs) may lie at a low probability of about 10%.Finally,we discussed the uncertainty of FRB luminosity caused by the estimation of the distance that is inferred by the simple relation between the redshift and dispersion measure(DM). 展开更多
关键词 transients:fast radio bursts methods:statistical stars:magnetars
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Could bright γ-ray burst optical transients have been recorded historically?
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作者 Richard G. Strom Fu-Yuan Zhao cheng-min zhang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第3期260-268,共9页
The brightest optical flash from a γ-ray burst (GRB) was, briefly, a naked- eye object. Several other GRBs have produced optical transients only slightly fainter. We argue that, based upon the recently accumulated ... The brightest optical flash from a γ-ray burst (GRB) was, briefly, a naked- eye object. Several other GRBs have produced optical transients only slightly fainter. We argue that, based upon the recently accumulated data from hundreds of GRB transients, many such optical events should have been visible to the unaided eye in the course of human history. The most likely repositories of such observations are histor- ical records from the Orient, and we have located and discuss a number of candidates. We also consider the value of such observations, should any very likely ones be uncovered, to modern astrophysics. 展开更多
关键词 γ-rays: bursts—optical transients—historical records
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