We report new simultaneous X-ray and radio continuum observations of 3FGL J0427.9-6704, a candidate member of the enigmatic class of transitional millisecond pulsars. These XMM-Newton and Australia Telescope Compact Array observations of this nearly edge-on, eclipsing low-mass X-ray binary were taken in the sub-luminous disk state at an X-ray luminosity of ~10^33(d/2.3kpc)^2 erg/s. Unlike the few well-studied transitional millisecond pulsars, which spend most of their disk state in a characteristic high or low accretion mode with occasional flares, 3FGL J0427.9-6704 stayed in the flare mode for the entire X-ray observation of ~20 hours, with the brightest flares reaching ~2*10^34 erg/s. The source continuously exhibited flaring activity on time-scales of ~10-100 sec in both the X-ray and optical/UV. No measurable time delay between the X-ray and optical/UV flares is observed, but the optical/UV flares last longer, and the relative amplitudes of the X-ray and optical/UV flares show a large scatter. The X-ray spectrum can be well-fit with a partially-absorbed power-law (Gamma~1.4-1.5), perhaps due to the edge-on viewing angle. Modestly variable radio continuum emission is present at all epochs, and is not eclipsed by the secondary, consistent with the presence of a steady radio outflow or jet. The simultaneous radio/X-ray luminosity ratio of 3FGL J0427.9-6704 is higher than any known transitional millisecond pulsars and comparable to that of stellar-mass black holes of the same X-ray luminosity, providing additional evidence that some neutron stars can be as radio-loud as black holes.
Millisecond pulsars in tight binaries have recently opened new challenges in our understanding of physical processes governing the evolution of binaries and the interaction between astrophysical plasma and electromagnetic fields. Transitional systems that showed changes from rotation-powered to accretion powered states and vice versa have bridged the populations of radio and accreting millisecond pulsars, eventually demonstrating the tight evolutionary link envisaged by the recycling scenario. A decade of discoveries and theoretical efforts have just grasped the complex phenomenology of transi…
Transitional millisecond pulsars (tMSPs), which are systems that harbor a pulsar in the throes of the recycling process, have emerged as a new source class since the discovery of the first such system a decade ago. These systems switch between accretion-powered low-mass X-ray binary (LMXB) and rotation-powered radio millisecond pulsar (RMSP) states, and provide exciting avenues to understand the physical processes that spin-up neutron stars to millisecond periods. During the last decade, three tMSPs, as well as a candidate source, have been extensively probed using systematic, multi-wavelength…
Transitional millisecond pulsars are accreting millisecond pulsars that switch between accreting X-ray binary and millisecond radio pulsar states. Only a handful of these objects have been identified so far. Terzan 5 CX1 is a variable hard X-ray source in the globular cluster Terzan 5. In this paper, we identify a radio counterpart to CX1 in deep Very Large Array radio continuum data. Chandra observations over the last fourteen years indicate that CX1 shows two brightness states: in 2003 and 2016 the source was the brightest X-ray source in the cluster (at L$_X \sim 10^{33}$ erg s$^{-1}$), whi…
We present a timing analysis of the transitional millisecond pulsar PSR J1023+0038 using observations taken between January 2018 and January 2020 with the high time resolution photon counter Aqueye+ mounted at the 1.82 m Copernicus telescope in Asiago. We report the first measurement of the timing solution and the frequency derivative of PSR J1023+0038 based entirely on optical data. The spin-down rate of the pulsar is $(-2.53 \pm 0.04) \times 10^{-15}$ Hz$^2$, which is $\sim$20% slower than that measured from the X-ray observations taken in 2013-2016 and $\sim$5% faster than that measured in …
Multiwavelength Evidence for Two New Candidate Transitional Millisecond Pulsars in the Sub-luminous Disk State: 4FGL J0639.1--8009 and 4FGL J1824.2+1231
We present the orbital solution for the donor star of the candidate transitional millisecond pulsar 3FGL J1544.6-1125, currently observed as an accreting low-mass X-ray binary. The orbital period is $0.2415361(36)$ days, entirely consistent with the spectral classification of the donor star as a mid to late K dwarf. The semi-amplitude of the radial velocity curve is exceptionally low at $K_2=39.3\pm1.5$ km s$^{-1}$, implying a remarkably face-on inclination in the range 5--8$^{\circ}$, depending on the neutron star and donor masses. After determining the veiling of the secondary, we derive a d…
Weakly magnetic, millisecond spinning neutron stars attain their very fast rotation through a 1E8-1E9 yr long phase during which they undergo disk-accretion of matter from a low mass companion star. They can be detected as accretion-powered millisecond X-ray pulsars if towards the end of this phase their magnetic field is still strong enough to channel the accreting matter towards the magnetic poles. When mass transfer is much reduced or ceases altogether, pulsed emission generated by particle acceleration in the magnetosphere and powered by the rotation of the neutron star is observed, prefer…
We report the discovery of a variable optical and X-ray source within the error ellipse of the previously unassociated Fermi Large Area Telescope $γ$-ray source 4FGL J0407.7--5702. A 22 ksec observation from XMM-Newton/EPIC shows an X-ray light curve with rapid variability and flaring. The X-ray spectrum is well-fit by a hard power law with $Γ= 1.7$. Optical photometry taken over several epochs is dominated by aperiodic variations of moderate amplitude. Optical spectroscopy with SOAR and Gemini reveals a blue continuum with broad and double-peaked H and He emission, as expected for an accretio…
We report on the first simultaneous XMM-Newton, NuSTAR and Swift observations of the transitional millisecond pulsar PSR J1023+0038 in the X-ray active state. Our multi-wavelength campaign allowed us to investigate with unprecedented detail possible spectral variability over a broad energy range in the X-rays, as well as correlations and lags among emissions in different bands. The soft and hard X-ray emissions are significantly correlated, with no lags between the two bands. On the other hand, the X-ray emission does not correlate with the UV emission. We refine our model for the observed mod…
I present a 40 kilosecond Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the recently identified low-luminosity X-ray binary and transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4-112820, which is associated with the high-energy gamma-ray source 3FGL J1544.6--1125. The system is detected up to ~30 keV with an extension of the same power-law spectrum and rapid large-amplitude variability between two flux levels observed in soft X-rays. These findings provide further evidence that 1RXS J154439.4-112820 belongs to the same class of objects as the nearby bona fide tMSPs…
Transitional millisecond pulsars are millisecond pulsars that switch between a rotation-powered millisecond pulsar state and an accretion-powered X-ray binary state, and are thought to be an evolutionary stage between neutron star low-mass X-ray binaries and millisecond pulsars. So far, only three confirmed systems have been identified in addition to a handful of candidates. We present the results of a multi-wavelength study of the low-mass X-ray binary NGC 6652B in the globular cluster NGC 6652, including simultaneous radio and X-ray observations taken by the Karl G. Jansky Very Large Array a…
We present X-ray, ultraviolet, and optical observations of 1RXS J154439.4-112820, the most probable counterpart of the unassociated Fermi LAT source 3FGL J1544.6-1125. The optical data reveal rapid variability, which is a feature of accreting systems. The X-rays exhibit large-amplitude variations in the form of fast switching (within ~10 s) between two distinct flux levels that differ by a factor of $\approx$10. The detailed optical and X-ray behavior is virtually identical to that seen in the accretion-disk-dominated states of the transitional millisecond pulsar binaries PSR J1023+0038 and XS…
We report the discovery of a new low-mass X-ray binary near the center of the unassociated Fermi GeV gamma-ray source 4FGL J0540.0-7552. The source shows the persistent presence of an optical accretion disk and exhibits extreme X-ray and optical variability. It also has an X-ray spectrum well-fit by a hard power law with a Gamma = 1.8 and a high ratio of X-ray to gamma-ray flux. Together, these properties are consistent with the classification of the binary as a transitional millisecond pulsar (tMSP) in the sub-luminous disk state. Uniquely among the candidate tMSPs, 4FGL J0540.0-7552 shows co…
The spin-down rate of PSR J1023+0038, one of the three confirmed transitional millisecond pulsars, was measured in both radio pulsar (RMSP) and X-ray pulsar (LMXB) states. The spin-down rate in the LMXB state is only about 27 % greater than in the RMSP state (Jaodand et al. 2016). The inner disk radius, r_in, obtained recently by Ertan (2017) for the propeller phase, which is close to the co-rotation radius, r_co, and insensitive to the mass-flow rate, can explain the observed torques together with the X-ray luminosities, Lx . The X-ray pulsar and radio pulsar states correspond to accretion wi…
In the last 25 years, a new generation of X-ray satellites imparted a significant leap forward in our knowledge of X-ray pulsars. The discovery of accreting and transitional millisecond pulsars proved that disk accretion can spin up a neutron star to a very high rotation speed. The detection of MeV-GeV pulsed emission from a few hundreds of rotation-powered pulsars probed particle acceleration in the outer magnetosphere, or even beyond. Also, a population of two dozens of magnetars has emerged. INTEGRAL played a central role to achieve these results by providing instruments with high temporal …
We present an optical, X-ray, and $γ$-ray study of 1SXPS J042749.2-670434, an eclipsing X-ray binary which has an associated $γ$-ray counterpart, 4FGL J0427.8-6704. This association has led to the source being classified as a transitional millisecond pulsar (tMSP) in an accreting state. We analyse 10.5 years of Fermi LAT data, and detect a $γ$-ray eclipse at the same phase as optical and X-ray eclipses at the >5$σ$ level, a significant improvement on the 2.8$σ$level of the previous detection. The confirmation of this eclipse solidifies the association between the X-ray source and the $γ$-ray s…
The discovery of millisecond pulsars switching between states powered either by the rotation of their magnetic field or by the accretion of matter, has recently proved the tight link shared by millisecond radio pulsars and neutron stars in low-mass X-ray binaries. Transitional millisecond pulsars also show an enigmatic intermediate state in which the neutron star is surrounded by an accretion disk, it emits coherent X-ray pulsations, but is sub-luminous in X-rays with respect to accreting neutron stars, and is brighter in gamma-rays than millisecond pulsars in the rotation-powered state. Here,…
We present the first detection of X-ray coherent pulsations from the transitional millisecond pulsar XSS J12270-4859, while it was in a sub-luminous accretion disk state characterized by a 0.5-10 keV luminosity of 5E33 erg/s (assuming a distance of 1.4 kpc). Pulsations were observed by XMM-Newton at an rms amplitude of (7.7 +/- 0.5)% with a second harmonic stronger than the the fundamental frequency, and were detected when the source is neither flaring nor dipping. The most likely interpretation of this detection is that matter from the accretion disk was channelled by the neutron star magneto…
We present coordinated Chandra X-ray Observatory and Karl G. Jansky Very Large Array observations of the transitional millisecond pulsar PSR J1023+0038 in its low-luminosity accreting state. The unprecedented five hours of strictly simultaneous X-ray and radio continuum coverage for the first time unambiguously show a highly reproducible, anti-correlated variability pattern. The characteristic switches from the X-ray high mode into a low mode are always accompanied by a radio brightening with duration that closely matches the X-ray low mode interval. This behavior cannot be explained by a cano…
IGR~J18245--2452/PSR J1824--2452I is one of the rare transitional accreting millisecond X-ray pulsars, showing direct evidence of switches between states of rotation powered radio pulsations and accretion powered X-ray pulsations, dubbed transitional pulsars. IGR~J18245--2452 is the only transitional pulsar so far to have shown a full accretion episode, reaching an X-ray luminosity of $\sim10^{37}$~erg~s$^{-1}$ permitting its discovery with INTEGRAL in 2013. In this paper, we report on a detailed analysis of the data collected with the IBIS/ISGRI and the two JEM-X monitors on-board INTEGRAL at…
Properties of the population of millisecond extragalactic radio bursts discovered by Thornton et al. (2013) are in good correspondence with the hypothesis that such events are related to hyperflares of magnetars, as was proposed by us after the first observation of an extragalactic millisecond radio burst by Lorimer et al. (2007). We also point that some of multiple millisecond radio bursts from M31 discovered by Rubio-Herrera et al. (2013) also can be related to weaker magnetar bursts.
Detection of giant pulses from the transitional millisecond pulsar J1227$-$4853
National Centre for Radio Astrophysics, Tata Institute of Fundamental Research（国家射电天文中心，塔塔基础研究所）；Space Science Division, U.S. Naval Research Laboratory（空间科学处，美国海军研究实验室）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester（曼彻斯特大学物理与天文学系乔德雷尔银行天体物理学中心）
We report on the first continuous, 80 day optical monitoring of the transitional millisecond pulsar PSR J1023+0038 carried out in mid-2017 with Kepler in the K2 configuration, when an X-ray subluminous accretion disk was present in the binary. Flares lasting from minutes to 14 hr were observed for 15.6% of the time, which is a larger fraction than previously reported on the basis of X-ray and past optical observations, and more frequently when the companion was at the superior conjunction of the orbit. A sinusoidal modulation at the binary orbital period was also present with an amplitude of ~…
The transitional millisecond pulsar PSR\,J1023+0038 is the first millisecond pulsar discovered to emit UV and optical pulses. Here we present the results of the UV and X-ray phase-resolved timing analysis of observations performed with the Hubble Space Telescope, \textit{XMM-Newton} and NuSTAR satellites between 2014 and 2021. Ultraviolet pulsations are detected in the high luminosity mode and disappear during low and flaring modes, similar to what is observed in the X-ray band. In the high mode, we find variability in both the UV and X-ray pulse amplitudes. The root mean square pulsed amplitu…
PSR J1023+0038 is a rapidly-spinning neutron star with a low-mass-binary companion that switches between a radio pulsar and low-luminosity disk state. In 2013, it transitioned to its current disk state accompanied by brightening at all observed wavelengths. In this state, PSR J1023+0038 now shows optical and X-ray pulsations and abrupt X-ray luminosity switches between discrete 'low' and 'high' modes. Continuum radio emission, denoting an outflow, is also present and brightens during the X-ray low modes. Here, we present a simultaneous optical, ultraviolet (UV) and X-ray campaign comprising Ke…
Transitional millisecond pulsars (tMSPs) have emerged in the last decade as a unique class of neutron stars at the crossroads between accretion- and rotation-powered phenomena. In their (sub-luminous) accretion disk state, with X-ray luminosities of order $10^{33}-10^{34}$ erg s$^{-1}$, they switch rapidly between two distinct X-ray modes: the disk-high (DH) and disk-low (DL) states. We present a systematic XMM-Newton and Chandra analysis of the aperiodic X-ray variability of all three currently known tMSPs, with a main focus on their disk state and separating DH and DL modes. We report the di…
3FGL J1544.6-1125 is a candidate transitional millisecond pulsar (tMSP). Similar to the well-established tMSPs - PSR J1023+0038, IGR J18245-2452, and XSS J12270-4859 -- 3FGL J1544.6-1125 shows $γ$-ray emission and discrete X-ray "low" and "high" modes during its low-luminosity accretion-disk state. Coordinated radio/X-ray observations of PSR J1023+0038 in its current low-luminosity accretion-disk state showed rapidly variable radio continuum emission-possibly originating from a compact, self-absorbed jet, the "propellering" of accretion material, and/or pulsar moding. 3FGL J1544.6-1125 is curr…
We present an analysis of X-ray, Ultraviolet and optical/near-IR photometric data of the transitional millisecond pulsar binary XSSJ12270-4859, obtained at different epochs after the transition to a rotation-powered radio pulsar state. The observations, while confirming the large-amplitude orbital modulation found in previous studies after the state change, also reveal an energy dependence of the amplitudes as well as variations on time scale of months. The amplitude variations are anti-correlated in the X-ray and the UV/optical bands. The average X-ray spectrum is described by a power law wit…
We present the results of simultaneous observations of the transitional millisecond pulsar (tMSP) candidate CXOU J110926.4-650224 with the XMM-Newton satellite and the MeerKAT telescope. The source was found at an average X-ray luminosity of $L_{\rm X}\simeq7\times10^{33}$ erg s$^{-1}$ over the 0.3-10 keV band (assuming a distance of 4 kpc) and displayed a peculiar variability pattern in the X-ray emission, switching between high, low and flaring modes on timescales of tens of seconds. A radio counterpart was detected at a significance of 7.9$σ$ with an average flux density of $\simeq$33$μ$Jy …
This chapter provides a phenomenological appraisal of the high-energy emission of millisecond pulsars. We comment on some of their properties as a population, as well as consider the especial cases of transitional pulsars, other redbacks, and black widow systems.
We report on the first NuSTAR observation of the transitional millisecond pulsar binary XSS J12270-4859 during its current rotation-powered state, complemented with a 2.5yr-long radio monitoring at Parkes telescope and archival XMM-Newton and Swift X-ray and optical data. The radio pulsar is mainly detected at 1.4GHz displaying eclipses over about 40% of the 6.91h orbital cycle. We derive a new updated radio ephemeris to study the 3-79keV light curve that displays a significant orbital modulation with fractional amplitude of 28+/-3%, a structured maximum centred at the inferior conjunction of …
We present ULTRACAM multiband optical photometry of two transitional millisecond pulsars, PSR J1023+0038 and PSR J1227$-$4853, taken while both were in their radio pulsar states. The light curves show significant asymmetry about the flux maxima in all observed bands, suggesting an asymmetric source of heating in the system. We model the light curves using the Icarus binary code, using models with an additional "hot spot" heating contribution and an anisotropic heat redistribution model to treat the asymmetry. Our modelling reveals companion stars with under-filled Roche lobes in both PSRs J102…
For 80 days in 2017, the Kepler Space Telescope continuously observed the transitional millisecond pulsar system PSR J1023+0038 in its accreting state. We present analyses of the 59 second cadence data, focusing on investigations of the orbital light curve of the irradiated companion star, and of flaring activity in the neutron star's accretion disc. The underlying orbital modulation from the companion star retains a similar amplitude and asymmetric heating profile as seen in previous photometric observations of the system in its radio pulsar state, suggesting that the heating mechanism has no…
Evolution of the transitional millisecond pulsar PSR J1023+0038 from Aqueye+ and NICER observations
University of Padova（帕多瓦大学）；INAF - Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；Department of Physics and Astronomy, University of Padova（帕多瓦大学物理与天文学系）；Università di Firenze（佛罗伦萨大学）；INAF - Osservatorio Astrofisico di Torino（意大利国家天体物理研究所都灵天文台）
Transitional millisecond pulsars (tMSPs) switch between an accretion-powered state without radio pulsations and a rotation-powered state with radio pulsations. In the former state, they are X-ray bright, in the latter X-ray dim. Soft X-ray transients (SXTs) undergo similar switches in X-ray, between "high" states with bright X-ray outbursts and a "low" state of quiescence. The upper limit on the quiescent X-ray luminosity of SXT 1H 1905+000 suggests that its luminosity might be similar to that of the known tMSPs. A detection of radio pulsations would link SXTs more strongly with tMSPs; and thu…
Modes in Transitional Millisecond Pulsars: Evidence of Pulsar Wind-Induced Disk Heating from GRMHD and Radiative Transfer
Norwegian University of Science and Technology（挪威科技大学）；University of Valladolid UVA（巴利亚多利德大学）；Aix Marseille Univ, CNRS, CNES, LAM（艾克斯-马赛大学）；Universitat Politècnica de Catalunya（加泰罗尼亚理工大学）；Princeton Plasma Physics Laboratory（普林斯顿等离子体物理实验室）；Northwestern University（西北大学）；University of Toronto（多伦多大学）
PSR J1023+0038 is the first millisecond pulsar discovered to pulsate in the visible band; such a detection took place when the pulsar was surrounded by an accretion disk and also showed X-ray pulsations. We report on the first high time resolution observational campaign of this transitional pulsar in the disk state, using simultaneous observations in the optical (TNG, NOT, TJO), X-ray (XMM-Newton, NuSTAR, NICER), infrared (GTC) and UV (Swift) bands. Optical and X-ray pulsations were detected simultaneously in the X-ray high intensity mode in which the source spends $\sim$ 70% of the time, and …
We present the discovery of IGR J18245-2452, the first millisecond pulsar observed to swing between a rotation-powered, radio pulsar state, and an accretion-powered X-ray pulsar state (Papitto et al. 2013, Nature, 501, 517). This transitional source represents the most convincing proof of the evolutionary link shared by accreting neutron stars in low mass X-ray binaries, and radio millisecond pulsars. It demonstrates that swings between these two states take place on the same time-scales of luminosity variations of X-ray transients, and are therefore most easily interpreted in terms of changes…
Rotation-powered millisecond radio pulsars have been spun up to their present spin period by a $10^8$ - $10^9$ yr long X-ray-bright phase of accretion of matter and angular momentum in a low-to-intermediate mass binary system. Recently, the discovery of transitional pulsars that alternate cyclically between accretion and rotation-powered states on time scales of a few years or shorter, has demonstrated this evolutionary scenario. Here, we present a thorough statistical analysis of the spin distributions of the various classes of millisecond pulsars to assess the evolution of their spin period …
Transitional millisecond pulsars provide a unique set of observational data for understanding accretion at low rates onto magnetized neutron stars. In particular, PSR~J1023+0038 exhibits a remarkable bimodality of the X-ray luminosity (low and high modes), pulsations extending from the X-ray to the optical band, GeV emission, and occasional X-ray flares. We discuss a scenario for the pulsar interaction with the accretion disk capable of explaining the observed behavior. We suggest that during the high mode the disk is truncated outside the light cylinder, allowing the pulsar wind to develop ne…
GRO J1744-28 (the Bursting Pulsar) is a neutron star LMXB which shows highly structured X-ray variability near the end of its X-ray outbursts. In this letter we show that this variability is analogous to that seen in Transitional Millisecond Pulsars such as PSR J1023+0038: 'missing link' systems consisting of a pulsar nearing the end of its recycling phase. As such, we show that the Bursting Pulsar may also be associated with this class of objects. We discuss the implications of this scenario; in particular, we discuss the fact that the Bursting Pulsar has a significantly higher spin period an…
Using high-resolution optical spectroscopy we determine the chemical abundance of the secondary star in the binary millisecond pulsar PSR J1023+0038. We measure a metallicity of [Fe/H] = 0.48 +/- 0.04 which is higher than the Solar value and in general find that the element abundances are different compared to the secondary stars in X-ray binaries and stars in the solar neighbourhood of similar Fe content. Our results suggest that the pulsar was formed in a supernova explosion. We find that supernova models, where matter that has been processed in the supernova is captured by the secondary sta…
We report mid-UV (MUV) observations taken with HST/WFC3, Swift/UVOT and GALEX/NUV of the transitional millisecond pulsars XSS J12270-4859 and PSR J1023+0038 during their radio pulsar states. Both systems were detected in our images and showed MUV variability. At similar orbital phases, the MUV luminosities of both pulsars are comparable. This suggests that the emission processes involved in both objects are similar. We estimated limits on the mass ratio, companion's temperature, inclination, and distance to XSS J12270-4859 by using a Markov Chain Monte Carlo algorithm to fit published folded o…
A number of low-mass millisecond pulsar (MSP) binaries in their rotation-powered state exhibit double-peaked X-ray orbital modulation centered at inferior pulsar conjunction. This state, which has been known to persist for years, has recently been interpreted as emission from a shock that enshrouds the pulsar. However, the pressure balance for such a configuration is a crucial unresolved issue. We consider two scenarios for pressure balance: a companion magnetosphere and stellar mass loss with gas dominance. It is found that the magnetospheric scenario requires several kilogauss poloidal field…
PSR J1023+0038 is the first millisecond pulsar that was ever observed as an optical and UV pulsar. So far, it is the only optical transitional millisecond pulsar. The rotation- and accretion-powered emission mechanisms hardly individually explain the observed characteristics of optical pulsations. A synergistic model, combining these standard emission processes, was proposed to explain the origin of the X-ray/UV/optical pulsations. We study the phase lag between the pulses in the optical and X-ray bands to gain insight into the physical mechanisms that cause it. We performed a detailed timing …
We present simultaneous optical and near-infrared (IR) photometry of the millisecond pulsar PSR J1023+0038 during its low-mass X-ray binary phase. The r'- and K_s-band light curves show rectangular, flat-bottomed dips, similar to the X-ray mode-switching (active-passive state transitions) behaviour observed previously. The cross-correlation function (CCF) of the optical and near-IR data reveals a strong, broad negative anti-correlation at negative lags, a broad positive correlation at positive lags, with a strong, positive narrow correlation superimposed. The shape of the CCF resembles the CCF…
4FGL J0935.5+0901, a $γ$-ray source recently identified as a candidate redback-type millisecond pulsar binary (MSP), shows an interesting feature of having double-peaked emission lines in its optical spectrum. The feature would further suggest the source as a transitional MSP system in the sub-luminous disk state. We have observed the source with \xmm\ and Five-hundred-meter Aperture Spherical radio Telescope (FAST) at X-ray and radio frequencies respectivelyfor further studies. From the X-ray observation, a bimodal count-rate distribution, which is a distinctive feature of the transitional MS…
