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Register a new userThermal X-ray emission identified from the millisecond pulsar PSR J1909-3744
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Pulsating thermal X-ray emission from millisecond pulsars can be used to obtain constraints on the neutron star equation of state, but to date only five such sources have been identified. Of these five millisecond pulsars, only two have well constrained neutron star masses, which improve the determination of the radius via modelling of the X-ray waveform. We aim to find other millisecond pulsars that already have well constrained mass and distance measurements that show pulsed thermal X-ray emission in order to obtain tight constraints on the neutron star equation of state. The millisecond pulsar PSR~J1909--3744 has an accurately determined mass, M = 1.54$pm$0.03 M$_odot$ (1 $sigma$ error) and distance, D = 1.07$pm$0.04 kpc. We analysed {em XMM-Newton} data of this 2.95 ms pulsar to identify the nature of the X-ray emission. We show that the X-ray emission from PSR~J1909--3744 appears to be dominated by thermal emission from the polar cap. Only a single component model is required to fit the data. The black-body temperature of this emission is kT=0.26ud{0.03}{0.02} keV and we find a 0.2--10 keV un-absorbed flux of 1.1 $times$ 10$^{-14}$ erg cm$^{-2}$ s$^{-1}$ or an un-absorbed luminosity of 1.5 $times$ 10$^{30}$ erg s$^{-1}$. Thanks to the previously determined mass and distance constraints of the neutron star PSR~J1909--3744, and its predominantly thermal emission, deep observations of this object with future X-ray facilities should provide useful constraints on the neutron star equation of state.
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We extend the recently introduced Bayesian framework `Generative Pulsar Timing Analysis to incorporate both pulse jitter (high frequency variation in the arrival time of the pulse) and epoch to epoch stochasticity in the shape of the pulse profile. This framework allows for a full timing analysis to be performed on the folded profile data, rather than the site arrival times as is typical in most timing studies. We apply this extended framework both to simulations, and to an 11 yr, 10 cm data set for PSR J1909$-$3744. Using simulations, we show that temporal profile variation can induce timing noise in the residuals that when performing a standard timing analysis is highly covariant with the signal expected from a gravitational wave (GW) background. When working in the profile domain, these variations are de-correlated from the expected GW signal, resulting in significant improvement in the obtained upper limits. Using the PSR J1909$-$3744 data set from the Parkes Pulsar Timing Array project, we find significant evidence for systematic high-frequency profile variation resulting from non-Gaussian noise in the oldest observing system, but no evidence for either detectable pulse jitter, or low-frequency profile shape variation. Using our profile domain framework we therefore obtain upper limits on a red noise process with a spectral index of $gamma = 13/3$ of $1times10^{-15}$, consistent with previously published limits.
We report on a high-precision timing analysis and an astrophysical study of the binary millisecond pulsar, PSR J1909$-$3744, motivated by the accumulation of data with well improved quality over the past decade. Using 15 years of observations with the Nanc{c}ay Radio Telescope, we achieve a timing precision of approximately 100 ns. We verify our timing results by using both broad-band and sub-band template matching methods to create the pulse time-of-arrivals. Compared with previous studies, we improve the measurement precision of secular changes in orbital period and projected semi-major axis. We show that these variations are both dominated by the relative motion between the pulsar system and the solar system barycenter. Additionally, we identified four possible solutions to the ascending node of the pulsar orbit, and measured a precise kinetic distance of the system. Using our timing measurements and published optical observations, we investigate the binary history of this system using the stellar evolution code MESA, and discuss solutions based on detailed WD cooling at the edge of the WD age dichotomy paradigm. We determine the 3-D velocity of the system and show that it has been undergoing a highly eccentric orbit around the centre of our Galaxy. Furthermore, we set up a constraint over dipolar gravitational radiation with the system, which is complementary to previous studies given the mass of the pulsar. We also obtain a new limit on the parameterised post-Newtonian parameter, $alpha_1<2.1 times 10^{-5}$ at 95 % confidence level, which is fractionally better than previous best published value and achieved with a more concrete method.
The predicted nature of the candidate redback pulsar 3FGL,J2039.6$-$5618 was recently confirmed by the discovery of $gamma$-ray millisecond pulsations (Clark et al. 2020, hereafter Paper,I), which identify this $gamma$-ray source as msp. We observed this object with the Parkes radio telescope in 2016 and 2019. We detect radio pulsations at 1.4,GHz and 3.1,GHz, at the 2.6ms period discovered in $gamma$-rays, and also at 0.7,GHz in one 2015 archival observation. In all bands, the radio pulse profile is characterised by a single relatively broad peak which leads the main $gamma$-ray peak. At 1.4,GHz we found clear evidence of eclipses of the radio signal for about half of the orbit, a characteristic phenomenon in redback systems, which we associate with the presence of intra-binary gas. From the dispersion measure of $24.57pm0.03$,pc,cm$^{-3}$ we derive a pulsar distance of $0.9pm 0.2$,kpc or $1.7pm0.7$,kpc, depending on the assumed Galactic electron density model. The modelling of the radio and $gamma$-ray light curves leads to an independent determination of the orbital inclination, and to a determination of the pulsar mass, qualitatively consistent to the results in Paper,I.
PSR J0218+4232 is one of the most energetic millisecond pulsars known and has long been considered as one of the best candidates for very high-energy (VHE; >100 GeV) gamma-ray emission. Using 11.5 years of Fermi Large Area Telescope (LAT) data between 100 MeV and 870 GeV, and ~90 hours of MAGIC observations in the 20 GeV to 20 TeV range, we have searched for the highest energy gamma-ray emission from PSR J0218+4232. Based on the analysis of the LAT data, we find evidence for pulsed emission above 25 GeV, but see no evidence for emission above 100 GeV (VHE) with MAGIC. We present the results of searches for gamma-ray emission, along with theoretical modeling, to interpret the lack of VHE emission. We conclude that, based on the experimental observations and theoretical modeling, it will remain extremely challenging to detect VHE emission from PSR J0218+4232 with the current generation of Imaging Atmospheric Cherenkov Telescopes (IACTs), and maybe even with future ones, such as the Cherenkov Telescope Array (CTA).
We report the detection of X-ray pulsations from the rotation-powered millisecond-period pulsars PSR J0740+6620 and PSR J1614-2230, two of the most massive neutron stars known, using observations with the Neutron Star Interior Composition Explorer (NICER). We also analyze X-ray Multi-Mirror Mission (XMM-Newton) data for both pulsars to obtain their time-averaged fluxes and study their respective X-ray fields. PSR J0740+6620 exhibits a broad double-peaked profile with a separation of ~0.4 in phase. PSR J1614-2230, on the other hand, has a broad single-peak profile. The broad modulations with soft X-ray spectra of both pulsars are indicative of thermal radiation from one or more small regions of the stellar surface. We show the NICER detections of X-ray pulsations for both pulsars and also discuss the phase relationship to their radio pulsations. In the case of PSR J0740+6620, this paper documents the data reduction performed to obtain the pulsation detection and prepare for pulse profile modeling analysis.
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