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تسجيل مستخدم جديدThe 26.3-hr orbit and multi-wavelength properties of the redback millisecond pulsar PSR J1306-40
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Manuel Linares
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We present the discovery of the variable optical and X-ray counterparts to the radio millisecond pulsar (MSP) PSR J1306-40, recently discovered by Keane et al. We find that both the optical and X-ray fluxes are modulated with the same period, which allows us to measure for the first time the orbital period P$_{rm orb}$=1.09716[6] d. The optical properties are consistent with a main sequence companion with spectral type G to mid K and, together with the X-ray luminosity (8.8$times$10$^{31}$ erg s$^{-1}$ in the 0.5-10 keV band, for a distance of 1.2 kpc), confirm the redback classification of this pulsar. Our results establish the binary nature of PSR J1306-40, which has the longest P$_{rm orb}$ among all known compact binary MSPs in the Galactic disk. We briefly discuss these findings in the context of irradiation and intrabinary shock emission in compact binary MSPs.
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PSR J1306--40 is a millisecond pulsar binary with a non-degenerate companion in an unusually long $sim$1.097 day orbit. We present new optical photometry and spectroscopy of this system, and model these data to constrain fundamental properties of the
binary such as the component masses and distance. The optical data imply a minimum neutron star mass of $1.75pm0.09,M_{odot}$ (1-sigma) and a high, nearly edge-on inclination. The light curves suggest a large hot spot on the companion, suggestive of a portion of the pulsar wind being channeled to the stellar surface by the magnetic field of the secondary, mediated via an intrabinary shock. The H$alpha$ line profiles switch rapidly from emission to absorption near companion inferior conjunction, consistent with an eclipse of the compact emission region at these phases. At our optically-inferred distance of $4.7pm0.5$ kpc, the X-ray luminosity is $sim$10$^{33}$ erg s$^{textrm{-1}}$, brighter than nearly all known redbacks in the pulsar state. The long period, subgiant-like secondary, and luminous X-ray emission suggest this system may be part of the expanding class of millisecond pulsar binaries that are progenitors to typical field pulsar--white dwarf binaries.
PSR J2129-0429 is a redback eclipsing millisecond pulsar binary with an unusually long 15.2 hour orbit. It was discovered by the Green Bank Telescope in a targeted search of unidentified Fermi gamma-ray sources. The pulsar companion is optically brig
ht (mean $m_R = 16.6$ mag), allowing us to construct the longest baseline photometric dataset available for such a system. We present ten years of archival and new photometry of the companion from LINEAR, CRTS, PTF, the Palomar 60-inch, and LCOGT. Radial velocity spectroscopy using the Double-Beam Spectrograph on the Palomar 200-inch indicates that the pulsar is massive: $1.74pm0.18 M_odot$. The G-type pulsar companion has mass $0.44pm0.04 M_odot$, one of the heaviest known redback companions. It is currently 95% Roche-lobe filling and only mildly irradiated by the pulsar. We identify a clear 13.1 mmag yr$^{-1}$ secular decline in the mean magnitude of the companion as well as smaller-scale variations in the optical lightcurve shape. This behavior may indicate that the companion is cooling. Binary evolution calculations indicate that PSR J2129-0429 has an orbital period almost exactly at the bifurcation period between systems that converge into tighter orbits as black widows and redbacks and those that diverge into wider pulsar--white dwarf binaries. Its eventual fate may depend on whether it undergoes future episodes of mass transfer and increased irradiation.
We present multi-wavelength observations of the unassociated gamma-ray source 3FGL J2039.6-5618 detected by the Fermi Large Area Telescope. The source gamma-ray properties suggest that it is a pulsar, most likely a millisecond pulsar, for which neith
er radio nor $gamma$-ray pulsations have been detected yet. We observed 3FGL J2039.6-5618 with XMM-Newton and discovered several candidate X-ray counterparts within/close to the gamma-ray error box. The brightest of these X-ray sources is variable with a period of 0.2245$pm$0.0081 d. Its X-ray spectrum can be described by a power law with photon index $Gamma_X =1.36pm0.09$, and hydrogen column density $N_{rm H} < 4 times 10^{20}$ cm$^{-2}$, which gives an unabsorbed 0.3--10 keV X-ray flux of $1.02 times 10^{-13}$ erg cm$^{-2}$ s$^{-1}$. Observations with the Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) discovered an optical counterpart to this X-ray source, with a time-average magnitude $gsim 19.5$. The counterpart features a flux modulation with a period of 0.22748$pm$0.00043 d that coincides, within the errors, with that of the X-ray source, confirming the association based on the positional coincidence. We interpret the observed X-ray/optical periodicity as the orbital period of a close binary system where one of the two members is a neutron star. The light curve profile of the companion star, with two asymmetric peaks, suggests that the optical emission comes from two regions at different temperatures on its tidally-distorted surface. Based upon its X-ray and optical properties, we consider this source as the most likely X-ray counterpart to 3FGL J2039.6-5618, which we propose to be a new redback system.
We have investigated the intrabinary shock emission from the redback millisecond pulsar PSR J2129-0429 with XMM-Newton and Fermi. Orbital modulation in X-ray and UV can be clearly seen. Its X-ray modulation has a double-peak structure with a dip in b
etween. The observed X-rays are non-thermal dominant which can be modeled by a power-law with a photon index of ~1.2. Intrabinary shock can be the origin of the observed X-rays. The UV light curve is resulted from the ellipsoidal modulation of the companion. Modeling the UV light curve prefers a large viewing angle. The heating effect of the UV light curve is found to be negligible which suggests the high energy radiation beam of PSR J2129-0429 does not direct toward its companion. On the other hand, no significant orbital modulation can be found in gamma-ray which suggests the majority of the gamma-rays come from the pulsar.
Linares et al. (2016) obtained quasi-simultaneous g, r and i-band light curves and an absorption line radial velocity curve of the secondary star in the redback system 3FGL J0212.1+5320. The light curves showed two maxima and minima primarily due to
the secondary stars ellipsoidal modulation, but with unequal maxima and minima. We fit these light curves and radial velocities with our X-ray binary model including either a dark solar-type star spot or a hot spot due to off-centre heating from an intrabinary shock, to account for the unequal maxima. Both models give a radial velocity semi-amplitude and rotational broadening that agree with the observations. The observed secondary stars effective temperature is best matched with the value obtained using the hot spot model, which gives a neutron star and secondary star mass of $M_{rm 1}$=1.85$^{+0.32}_{-0.26}$ $M_{odot}$and $M_{rm 2}$=0.50$^{+0.22}_{-0.19}$ $M_{odot}$, respectively.
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