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Peng Z.Y.,Yunnan Normal University | Yin Y.,Liupanshui Normal College | Bi X.W.,Honghe University | Zhao X.H.,CAS National Astronomical Observatories | And 3 more authors.
Astrophysical Journal | Year: 2010

In this paper, we have analyzed the temporal and spectral behavior of 52 fast rise and exponential decay (FRED) pulses in 48 long-duration gamma-ray bursts (GRBs) observed by the CGRO/BATSE, using a pulse model with two shape parameters and the Band model with three shape parameters, respectively. It is found that these FRED pulses are distinguished both temporally and spectrally from those in the long-lag pulses. In contrast to the long-lag pulses, only one parameter pair indicates an evident correlation among the five parameters, which suggests that at least four parameters are needed to model burst temporal and spectral behavior. In addition, our studies reveal that these FRED pulses have the following correlated properties: (1) long-duration pulses have harder spectra and are less luminous than short-duration pulses and (2) the more asymmetric the pulses are, the steeper are the evolutionary curves of the peak energy (Ep) in the ?f? spectrum within the pulse decay phase. Our statistical results give some constraints on the current GRB models. © 2010. The American Astronomical Society. All rights reserved.

Peng Z.Y.,Yunnan Normal University | Yin Y.,Liupanshui Normal College | Bi X.W.,Honghe University | Bao Y.Y.,Yuxi Normal College | Ma L.,Yunnan Normal University
Astronomische Nachrichten | Year: 2011

Assuming an intrinsic 'Band' shape spectrum and an intrinsic energy-independent emission profile we have investigated the connection between the evolution of the rest-frame spectral parameters and the spectral lags measured in gamma-ray burst (GRB) pulses by using a pulse model. We first focus our attention on the evolution of the peak energy, E0,p, and neglect the effect of the curvature effect. It is found that the evolution of E0,p alone can produce the observed lags. When E0,p varies from hard to soft only the positive lags can be observed. The negative lags would occur in the case of E0,p varying from soft to hard. When the evolution of E0,p and the low-energy spectral index α0 varying from soft to hard then to soft we can find the aforesaid two sorts of lags. We then examine the combined case of the spectral evolution and the curvature effect of fireball and find the observed spectral lags would increase. A sample including 15 single pulses whose spectral evolution follows hard to soft has been investigated. All the lags of these pulses are positive, which is in good agreement with our theoretical predictions. Our analysis shows that only the intrinsic spectral evolution can produce the spectral lags and the observed lags should be contributed by the intrinsic spectral evolution and the curvature effect. But it is still unclear what cause the spectral evolution. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Peng Z.-Y.,Yunnan Normal University | Peng Z.-Y.,Chinese Academy of Sciences | Zhao X.-H.,CAS National Astronomical Observatories | Yin Y.,Chinese Academy of Sciences | And 2 more authors.
Publications of the Astronomical Society of Japan | Year: 2013

Previous studies have shown that the dependence of the pulse temporal properties (pulse width, pulse rise width, pulse decay width, and pulse peak time) on energy is a power-law function. In this work we demonstrate that the power-law indices of the pulse width, pulse rise width, pulse decay width, and pulse peak time on energy are correlated with the spectral lag and the relative spectral lag, δt31 and w3 (where 4t31 and w3 are the spectral lag between BATSE channels 1 and 3 and the pulse width of BATSE channel 3, respectively), using a sample including 102 well-separated long-duration gamma-ray burst pulses. In addition, the correlations of the power-law indices with the relative spectral lags are much more tighter than those with the spectral lags. We further find that the power-law indices are also correlated with the pulse photon flux. The possible origins of these correlations are also discussed. We argue that the kinematic effect can explain the correlated properties. © 2013. Astronomical Society of Japan.

Peng Z.Y.,Yunnan Normal University | Yin Y.,Liupanshui Normal College | Yi T.F.,Yunnan Normal University | Bao Y.Y.,Yuxi Normal College | Wu H.,Yunnan Normal University
Astrophysics and Space Science | Year: 2014

We demonstrate that the optical flares, X-ray flares (XRFs), and the gamma-ray burst (GRB) pulses exhibit similar behaviors as evidenced by correlations among temporal properties and the temporal properties on energy by a comprehensive comparative analysis of 24 optical flares, 92 XRFs and 102 GRB pulses. The flare/pulse peak time, tpk, is correlated with their width, w, and with w/tpk for the three samples, but their slopes are very different. Both of the flares and GRB pulses bear the similar asymmetries and the asymmetry evolves neither with w nor with tpk. The spectral lags of the XRFs are much larger than those of the GRB pulses and almost follow the same lag versus width relation as that of the GRB pulse. In addition, the corresponding broadening of temporal properties (width, rise width and decay width) of the XRFs with energy decreasing follows the same power-law relation as those of the GRB pulses. The K-S tests show the distributions of the three corresponding power-law indices of the XRFs are the same as those of the GRB pulses at the 1 % significance level. All of our demonstrated relations and previous correlated relations seem to indicate that the XRFs as well as the optical flares should be belong to a extended class of the prompt GRBs that dominate the tail of the distribution function. Therefore, our analysis results place some constraints on the physical mechanism responsible for the pulsed emission properties. © 2014, Springer Science+Business Media Dordrecht.

Peng Z.Y.,Yunnan Normal University | Peng Z.Y.,Chinese Academy of Sciences | Zhao X.H.,Chinese Academy of Sciences | Zhao X.H.,CAS National Astronomical Observatories | And 3 more authors.
Astrophysical Journal | Year: 2012

Previous studies have found that the width of the gamma-ray burst (GRB) pulse is energy dependent and that it decreases as a power-law function with increasing photon energy. In this work we have investigated the relation between the energy dependence of the pulse and the so-called Band spectrum by using a sample including 51well-separated fast rise and exponential decay long-duration GRB pulses observed by BATSE (Burst and Transient Source Experiment on the Compton Gamma Ray Observatory). We first decompose these pulses into rise and decay phases and find that the rise widths and the decay widths also behave as a power-law function with photon energy. Then we investigate statistically the relations between the three power-law indices of the rise, decay, and total width of the pulse (denoted as δr, δd, and δw, respectively) and the three Band spectral parameters, high-energy index (α), low-energy index (β), and peak energy (E p ). It is found that (1) α is strongly correlated with δw and δd but seems uncorrelated with δr; (2) β is weakly correlated with the three power-law indices, and (3) Ep does not show evident correlations with the three power-law indices. We further investigate the origin of δd- α and δw-α. We show that the curvature effect and the intrinsic Band spectrum could naturally lead to the energy dependence of the GRB pulse width and also the δd-α and δw-α correlations. Our results hold so long as the shell emitting gamma rays has a curved surface and the intrinsic spectrum is a Band spectrum or broken power law. The strong δd-α correlation and inapparent correlations between δr and the three Band spectral parameters also suggest that the rise and decay phases of the GRB pulses have different origins. © 2012. The American Astronomical Society. All rights reserved..

Li H.Z.,Yunnan University | Li H.Z.,Yuxi Normal College | Xie G.Z.,Yunnan University | Xie G.Z.,CAS National Astronomical Observatories | And 8 more authors.
New Astronomy | Year: 2010

We have analyzed the radio light curves of the Seyfert galaxy III Zw 2 at 22 and 37 GHz taken from the database of Metsähovi Radio Observatory, and found evidence of quasi-periodic activity. The light curves show great activity, with very complicated non-sinusoidal variations. Period of Pobs = 5.14 ± 0.19 yr was consistently identified by three methods: the Jurkevich method, the power spectrum intensity estimation method and the discrete correlation function method. The variability period of about 5.14 yr in III Zw 2 is caused most likely by the helical motion of the jet. © 2009 Elsevier B.V. All rights reserved.

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