Spin Evolution of the Magnetar SGR J1935+2154

Fast radio bursts(FRBs)are short pulses observed in radio frequencies usually originating from cosmological distances.The discovery of FRB 200428 and its X-ray counterpart from the Galactic magnetar SGR J1935+2154suggests that at least some FRBs can be generated by magnetars.However,the majority of X-ray bursts from magnetars are not associated with radio emission.The fact that only in rare cases can an FRB be generated raises the question regarding the special triggering mechanism of FRBs.Here we report long time spin evolution of SGR J1935+2154 until the end of 2022.According to v and v,the spin evolution of SGR J1935+2154 could be divided into two stages.The first stage evolves relatively steady evolution until 2020 April 27.After the burst activity in2020,the spin of SGR J1935+2154 shows strong variations,especially for v.After the burst activity in 2022October,a new spin-down glitch with△v/v=(-7.2±0.6)×10^(-6)is detected around MJD 59876,which is the second event in SGR J1935+2154.At the end,spin frequency and pulse profile do not show variations around the time of FRB 200428 and radio bursts 221014 and 221021,which supply strong clues to constrain the trigger mechanism of FRBs or radio bursts.

A Note on the Anti-glitch of Magnetar SGR 1935+2154

The magnetar SGR 1935+2154 is reported to have an anti-glitch,accompanied by fast radio bursts,and transient pulsed radio emission.In the wind braking model,this triplet event tells people that(1) SGR 1935+2154 does not have a strong particle wind and can be approximated by magnetic dipole braking in the persistent state;(2) its antiglitch is due to an enhanced particle wind,similar to the first anti-glitch in magnetars;(3) its transient pulsed radio emission may be due to a decreasing emission beam during the outburst;(4) the enhanced particle acceleration potential and pulsar death line may not be the dominate factor.

Single-pulse Emission Variation of Two Pulsars Discovered by FAST

We investigate the single-pulse emission variations of two pulsars,PSRs J0211+4235 and J0553+4111,observed with the Five-hundred-meter Aperture Spherical radio Telescope at the 1.25 GHz central frequency.The observation sessions span from 2020 December to 2021 July,with 21 and 22 observations for them respectively.The integrated pulse profile of PSR J0211+4235 shows that there is a weak pulse component following the main component,and PSR J0553+4111 displays a bimodal profile with a bridge component in the middle.PSR J0211+4235 presents significant nulling phenomenon with nulling duration lasting from 2 to 115 pulses and burst duration lasting from 2 to 113 pulses.The NF of each observation is determined to be 45%-55%.No emission greater than threeσis found in the mean integrated profile of all nulling pulses.In most cases,the pulse energy changes abruptly during the transition from null to burst,while in the transition from burst to null there are two trends:abrupt and gradual.We find that the nulling phenomenon of PSR J0211+4235 is periodic by the Fourier transform of the null and burst state.In addition,the single-pulse modulation characteristics of these two pulsars are investigated,and the distributions of modulation index,LRFS and 2DFS are analyzed with PSRSALSA.The left peak of PSR J0553+4111 has intensity modulation.Finally,the polarization properties of these two pulsars are obtained through polarization calibration,and their characteristics are analyzed.The possible physical mechanisms of these phenomena are discussed.

Detection of Quasi-periodic Oscillations in SGR 150228213

The detection of quasi-periodic oscillations(QPOs)in magnetar giant flares(GFs)has brought a new perspective to studies of the mechanism of magnetar bursts.Due to the scarcity of GFs,searching for QPOs in magnetar short bursts is reasonable.Here we report the detection of a narrow QPO at approximately 110 Hz and a wide QPO at approximately 60 Hz in the short magnetar burst SGR 150228213,with a confidence level of 3.35σ.This burst was initially attributed to 4U 0142+61 by Fermi/GBM on location,but we have not detected such QPOs in other bursts from this magnetar.We also found that there was a repeating fast radio burst associated with SGR 150228213 on location.Finally,we discuss the possible origins of SGR 150228213.

Constraining the Orbital Inclination and Companion Properties of Three Black Widow Pulsars Detected by FAST

Black widows(BWs)are millisecond pulsars ablating their companion stars.The out-flowing material from the companion can block the radio emission of the pulsar,resulting in eclipses.In this paper,we construct a model for the radio eclipse by calculating the geometry of the bow shock between the winds of the pulsar and companion,where the shock shapes the eclipsing medium but had not been described in detail in previous works.The model is further used to explain the variations of the flux density and dispersion measure of three BW pulsars(i.e.,PSR B1957+20,J2055+3829,and J2051-0827)detected by the Five-hundred-meter Aperture Spherical radio Telescope.Consequently,we constrained the parameters of the three BW systems such as the inclination angles and true anomalies of the observer as well as the mass-loss rates and wind velocity of the companion stars.With the help of these constraints,it is expected that magnetic fields of companion stars and even masses of pulsars could further be determined as some extra observation can be achieved in the future.

The RFI Fast Mitigation Algorithm Based on Block LMS Filter

The radio telescope possesses high sensitivity and strong signal collection capabilities.While receiving celestial radiation signals,it also captures Radio Frequency Interferences(RFIs)introduced by human activities.RFI,as signals originating from sources other than the astronomical targets,significantly impacts the quality of astronomical data.This paper presents an RFI fast mitigation algorithm based on block Least Mean Square(LMS)algorithm.It enhances the traditional adaptive LMS filter by grouping L adjacent time-sampled points into one block and applying the same filter coefficients for filtering within each block.This transformation reduces multiplication calculations and enhances algorithm efficiency by leveraging the time-domain convolution theorem.The algorithm is tested using baseband data from the Parkes 64 m radio telescope's pulsar observations and simulated data.The results confirm the algorithm's effectiveness,as the pulsar profile after RFI mitigation closely matches the original pulsar profile.

A Possible γ-Ray Pulsation from PSR J1740-5340B in the Globular Cluster NGC 6397

Recently, a new radio millisecond pulsar(MSP) J1740-5340B, hosted in the globular cluster(GC) NGC 6397,was reported with a 5.78 ms spin period in an eclipsing binary system with a 1.97 days orbital period. Based on a modified radio ephemeris updated by tool tempo2, we analyze the ~15 yr γ-ray data obtained from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope and detect PSR J1740-5340B's γ-ray pulsation at a confidence level of ~4σ with a weighted H-test value of ~26. By performing a phase-resolved analysis, the γ-ray luminosity in on-pulse interval of PSR J1740-5340B is L_(γ)~ 3.8 × 10^(33) erg s^(-1) using NGC 6397's distance of 2.48 kpc. And γ-rays from the on-pulse part of PSR J1740-5340B contribute ~90% of the total observed γ-ray emissions from NGC 6397. No significant γ-ray pulsation of another MSP J1740-5340A in the GC is detected.Considering that the previous four cases of MSPs in GCs, more data in γ-ray, X-ray, and radio are encouraged to finally confirm the γ-ray emissions from MSP J1740-5340B, especially starving for a precise ephemeris.

Resonant cyclotron scattering in pulsar magnetospheres and its application to isolated neutron stars

Resonant cyclotron scattering(RCS) in pulsar magnetospheres is considered.The photon diffusion equation(Kompaneets equation) for RCS is derived.The photon system is modeled three dimensionally.Numerical calculations show that there exist not only up scattering but also down scattering of RCS,depending on the parameter space.RCS's possible applications to spectral energy distributions of magnetar candidates and radio quiet isolated neutron stars(INSs) are pointed out.The optical/UV excess of INSs may be caused by the down scattering of RCS.The calculations for RX J1856.5-3754 and RX J0720.4-3125 are presented and compared with their observational data.In our model,the INSs are proposed to be normal neutron stars,although the quark star hypothesis is still possible.The low pulsation amplitude of INSs is a natural consequence in the RCS model.

Sgr B2中处于振动激发态的CH_3CN分子

使用BIMA的C位形混合波寻联结9元天线阵，对SgrB2（N）和SgrB2（M）观测了CH3CN分子振动激发态v8＝1的6k－5k线系.仅在SgrB2（N）的10＂×14＂区域里探测到上述发射线．在8．5kpe的距离下，该区域的相应线尺寸是0．41pc×0．58pc．对于SgrB2（M）没有探测到高于均方根噪音的发射流量密度．经粗略地估计，SgrB2（N）区的振动激发温度约为300K．针对此线系的激发机制以及SgrB2（N）区和SgrB2（M）区物理条件之间的差别进行了讨论．

A possible origin of the Galactic Center magnetar SGR 1745–2900

Since there is a large population of massive O/B stars and putative neutron stars(NSs) located in the vicinity of the Galactic Center(GC),intermediate-mass X-ray binaries(IMXBs) constituted by an NS and a B-type star probably exist there.We investigate the evolutions of accreting NSs in IMXBs(similar to M82 X-2) with a ~ 5.2 M⊙companion and orbital period■ 2.53 d.By adopting a mildly super-Eddington rate M= 6 × 10^(-8) M⊙yr^(-1) for the early Case B Roche-lobe overflow(RLOF)accretion,we find that only in accreting NSs with quite elastic crusts(slippage factor s = 0.05) can the toroidal magnetic fields be amplified within 1 Myr,which is assumed to be the longest duration of the RLOF.These IMXBs will evolve into NS+white dwarf(WD) binaries if they are dynamically stable.However,before the formation of NS+WD binaries,the high stellar density in the GC will probably lead to frequent encounters between the NS+ evolved star binaries(in post-early Case B mass transfer phase)and NSs or exchange encounters with other stars,which may produce single NSs.These NSs will evolve into magnetars when the amplified poloidal magnetic fields diffuse out to the NS surfaces.Consequently,our results provide a possible explanation for the origin of the GC magnetar SGR 1745–2900.Moreover,the accreting NSs with s > 0.05 will evolve into millisecond pulsars(MSPs).Therefore,our model reveals that the GC magnetars and MSPs could both originate from a special kind of IMXB.

A note on the puzzling spindown behavior of the Galactic center magnetar SGR J1745-2900

SGR J1745-2900 is a magnetar near the Galactic center. X-ray observations of this source found a decreasing X-ray luminosity accompanied by an enhanced spindown rate. This negative correlation between X-ray luminosity and spindown rate is hard to understand. The wind braking model of magnetars is employed to explain this puzzling spindown behavior. During the release of magnetic energy of magnetars,a system of particles may be generated. Some of these particles remain trapped in the magnetosphere and may contribute to the X-ray luminosity. The rest of the particles can flow out and take away the rotational energy of the central neutron star. A smaller polar cap angle will cause the decrease of X-ray luminosity and enhanced spindown rate of SGR J1745-2900. This magnetar is shortly expected to have a maximum spindown rate.

Understanding the X-ray spectrum of anomalous X-ray pulsars and soft gamma-ray repeaters

Hard X-rays above 10 ke V are detected from several anomalous X-ray pulsars(AXPs)and soft gamma-ray repeaters(SGRs),and different models have been proposed to explain the physical origin within the frame of either a magnetar model or a fallback disk system.Using data from Suzaku and INTEGRAL,we study the soft and hard X-ray spectra of four AXPs/SGRs:1RXS J170849–400910,1E 1547.0–5408,SGR 1806–20 and SGR 0501+4516.It is found that the spectra could be well reproduced by the bulk-motion Comptonization(BMC)process as was first suggested by Tr¨umper et al.,showing that the accretion scenario could be compatible with Xray emission from AXPs/SGRs.Simulated results from the Hard X-ray Modulation Telescope using the BMC model show that the spectra would have discrepancies from the power-law,especially the cutoff at～200 ke V.Thus future observations will allow researchers to distinguish different models of the hard X-ray emission and will help us understand the nature of AXPs/SGRs.

Observational characteristics of SiO masers around VX Sgr

SiO maser VLBA observations toward VX Sgr are performed at five epochs, and lots of maser spots are obtained. We make a statistical analysis on these spots. It is shown that the apparent sizes and the fluxes of maser spots decrease with increasing the distance from the central star. In addition, the similarity between the v = 1,2(J =1–0) spectrums increases with epochs, consistent with the full width at half maximum(FWHM), while the total fluxes increase. The results may be related to the changeable pumping mechanisms.

Radio pulsars with expected gamma radiation and gamma-ray pulsars as pulsating radio emitters

Pulsars play a crucial astrophy sical role as highly energetic compact radio, X-ray and gammaray sources. Our previous works show that radio pulsars identified as pulsing gamma-ray sources by the Large Area Telescope(LAT) on board the Fermi Gamma-Ray Space Telescope have high values of magnetic field near the light cylinder, two-three orders of magnitude stronger compared with the magnetic fields of radio pulsars: log B_(lc)(G) are 3.60-3.95 and 1.75 correspondingly. Moreover,their losses of rotational energy are also three orders higher than the corresponding values for the main group of radio pulsars on average: log E(erg s^(-1)) = 35.37-35.53 and 32.64. The correlation between gammaray luminosities and radio luminosities is found. It allows us to select those objects from all sets of known radio pulsars that can be detected as gamma-ray pulsars with high probability. We provide a list of such radio pulsars and propose to search for gamma emission from these objects. On the other hand,the known catalog of gamma-ray pulsars contains some sources which are not currently identified as radio pulsars. Some of them have large values of gamma-ray luminosities and according to the obtained correlation, we can expect marked radio emission from these objects. We give the list of such pulsars and expected flux densities to search for radiation at frequencies 1400 and 111 MHz.

Near-infrared studies of nova V5584 Sgr in the pre-maximum and early decline phase

We present near-infrared spectroscopic and photometric observations of nova V5584 Sgr taken during the first 12 d following its discovery on Oct. 26.439 UT2009. The evolution of the spectra is shown from the initial P Cygni phase to an emission line phase. The prominent carbon lines seen in the JHK spectra closely match those observed in an Fe II class nova outburst. The spectra show first-overtone CO bands in emission between 2.29–2.40 μm. By examining WISE and other publicly available data, we show that the nova underwent a pronounced dust formation phase between February- April 2010.

On the magnetic fields of ultraluminous X-ray pulsars

So far quite a few ultraluminous X-ray(ULX) pulsars have been discovered.In this work,we construct a super-Eddington,magnetic accretion disk model to estimate the dipole magnetic field of eight ULX pulsars based on their observed spin-up variations and luminosities.We obtain two branches of dipole magnetic field solutions.They are distributed in the range of B-(0.156-64.5) × 10^(10) G and-(0.275-79.0) × 10^(13) G corresponding to the low-and high-B solutions respectively.The low magnetic field solutions correspond to the state that the neutron stars are far away from the spin equilibrium,and the high magnetic field solutions are close to the spin equilibrium.The ultra-strong magnetic fields derived in Be-type ULX pulsars imply that the accretion mode in Be-type ULX pulsars could be more complicated than in the persistent ULX pulsars and may not be accounted for by the magnetized accretion disk model.We suggest that the transition between the accretor and the propeller regimes may be used to distinguish between the low-and high-B magnetic field solutions in addition to the detection of the cyclotron resonance scattering features.

Search for giant pulses of radio pulsars at frequency 111 MHz with LPA radio telescope

We have used the unique low frequency sensitivity of the Large Phased Array(LPA) radio telescope of Pushchino Radio Astronomy Observatory to collect a dataset consisting of single pulse observations of second period pulsars in the Northern Hemisphere. During observation sessions in 2011–2017, we collected data on 71 pulsars at a frequency of 111 MHz using a digital pulsar receiver. We have discovered Giant Radio Pulses(GRPs) from pulsars B0301+09 and B1237+25, and confirmed earlier reported generation of anomalously strong(probable giant) pulses from B1133+16 in a statistically significant dataset. Data for these pulsars and from B0950+08 and B1112+50, earlier reported as pulsars generating GRPs, were analyzed to evaluate their behavior over long time intervals. It was found that the statistical criterion(power-law spectrum of GRP distribution of energy and peak flux density) seems not to be strict for pulsars with a low magnetic field at their light cylinder. Moreover, spectra of some of these pulsars demonstrate unstable behavior with time and have a complex multicomponent shape. In the dataset for B0950+08, we have detected the strongest GRP from a pulsar with a low magnetic field at its light cylinder ever reported, having a peak flux density as strong as 16.8 kJy.

Fallback Disk-Involved Spin-Down of Young Radio Pulsars

Disks originating from supernova fallback have been suggested to surround young neutron stars. Interaction between the disk and the magnetic field of the neutron star may considerably influence the evolution of the star through the so called propeller effect. There are many controversies about the efficiency of the propeller mechanism proposed in the literature. We investigate the fallback diskinvolved spin-down of young pulsars. By comparing the simulated and measured results of pulsar evolution, we present some possible constraints on the propeller torques exerted by the disks on neutron stars.

The optical/ultraviolet excess of isolated neutron stars in the resonant cyclotron scattering model

X-ray dim isolated neutron stars are peculiar pulsar-like objects,characterized by their Planck-like spectrum.In studying their spectral energy distributions,optical/ultraviolet(UV) excess is a long standing problem.Recently Kaplan et al.measured the optical/UV excess for all seven sources,which is understandable in the resonant cyclotron scattering(RCS) model previously addressed.The RCS model calculations show that the RCS process can account for the observed optical/UV excess for most sources.The ?at spectrum of RX J2143.0+0654 may be due to contributions from the bremsstrahlung emission of the electron system in addition to the RCS process.

On the Nature of Long Period Radio Pulsar GPM J1839-10:Death Line and Pulse Width

Recently another long period radio pulsar GPM J1839-10 has been reported,similar to GLEAM-X J162759.5-523504.3.Previously,the energy budget and rotational evolution of long period radio pulsars had been considered.This time,the death line and pulse width for neutron star and white dwarf pulsars are investigated.The pulse width is included as the second criterion for neutron star and white dwarf pulsars.It is found that:(1)PSR J0250+5854 and PSR J0901-4046 etc.should be normal radio pulsars.They have narrow pulse width and they lie near the radio emission death line.(2)The two long period radio pulsars GLEAM-X J162759.5-523504.3 and GPM J1839-10 are unlikely to be normal radio pulsars.Their possible pulse width is relatively large.They lie far below the fiducial death line on the P-P^(·)diagram.(3)GLEAM-X J162759.5-523504.3 and GPM J1839-10 may be magnetars or white dwarf radio pulsars.At present,there are many parameters and uncertainties in both of these possibilities.