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Register a new userHeated Poles on the Companion of Redback PSR J2339$-$0533
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We analyze photometry and spectra of the redback millisecond pulsar binary J2339$-$0533. These observations include new measurements from Keck and GROND, as well as archival measurements from the OISTER, WIYN, SOAR, and HET telescopes. The parameters derived from GROND, our primary photometric data, describe well the rest of the datasets, raising our confidence in our fitted binary properties. Our fit requires hot-spots (likely magnetic poles) on the surface of the companion star, and we see evidence that these spots move over the 8 yr span of our photometry. The derived binary inclination $i = 69.3^circpm 2.3^circ$, together with the center-of-mass velocity (from the radial-velocity fits) $K_{rm C} = 347.0pm 3.7,$ $mathrm{km,s}^{-1}$, give a fairly typical neutron star mass of $1.47pm 0.09,M_odot$.
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We report on orbital modulation of the 100-600 MeV gamma-ray emission of the $P_{rm B}=4.6$ hr millisecond pulsar binary PSR J2339$-$0533 using 11 yr of Fermi Large Area Telescope data. The modulation has high significance (chance probability $papprox 10^{-7}$), is approximately sinusoidal, peaks near pulsar superior conjunction, and is detected only in the low-energy 100-600 MeV band. The modulation is confined to the on-pulse interval, suggesting that the variation is in the 2.9-ms pulsed signal itself. This contrasts with the few other known systems exhibiting GeV orbital modulations, as these are unpulsed and generally associated with beamed emission from an intrabinary shock. The origin of the modulated pulsed signal is not yet clear, although we describe several scenarios, including Compton upscattering of photons from the heated companion. This would require high coherence in the striped pulsar wind.
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.
We report on the identification of a near-infrared counterpart to the massive (>11 Msun) binary companion of pulsar J1740-3052. An accurate celestial position of PSR J1740-3052 is determined from interferometric radio observations. Adaptive optics corrected near-infrared imaging observations show a counterpart at the interferometric position of the pulsar. The counterpart has Ks=15.87+-0.10 and J-Ks>0.83. Based on distance and absorption estimates from models of the Galactic electron and dust distributions these observed magnitudes are consistent with those of a main-sequence star as the binary companion. We argue that this counterpart is the binary companion to PSR J1740-3052 and thus rule out a stellar mass black hole as the pulsar companion.
We study the present evolutionary status of the binary system containing the 2.66 ms pulsar PSR J1417-4402 in a 5.4 day orbit. This is the pulsar in the original source 3FGL J1417.5-4402, that has undergone a transition from X-ray state to a pulsar state, just like some redbacks did. The system has many characteristics similar to redback pulsars family, but is on a much wider orbit. We show that close binary evolution including irradiation feedback driven by the luminosity due to accretion onto the neutron star component of the pair, and evaporation due to pulsar emission, is able to account for the masses of the components and the photometric data of the donor star. The tracks leading to the present PSR J1417-4402 are degenerate within a range of parameters, suggesting that the {it same} physics invoked to explain the redback/black widows groups leads to the formation of much wider orbit systems, outside the redback region limits.
The 1.69 ms spin period of PSR J1227-4853 was recently discovered in radio observations of the low-mass X-ray binary XSS J12270-4859 following the announcement of a possible transition to a rotation-powered millisecond pulsar state, inferred from decreases in optical, X-ray, and gamma-ray flux from the source. We report the detection of significant (5$sigma$) gamma-ray pulsations after the transition, at the known spin period, using ~1 year of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The gamma-ray light curve of PSR J1227-4853 can be fit by one broad peak, which occurs at nearly the same phase as the main peak in the 1.4 GHz radio profile. The partial alignment of light-curve peaks in different wavebands suggests that at least some of the radio emission may originate at high altitude in the pulsar magnetosphere, in extended regions co-located with the gamma-ray emission site. We folded the LAT data at the orbital period, both pre- and post-transition, but find no evidence for significant modulation of the gamma-ray flux. Analysis of the gamma-ray flux over the mission suggests an approximate transition time of 2012 November 30. Continued study of the pulsed emission and monitoring of PSR J1227-4853, and other known redback systems, for subsequent flux changes will increase our knowledge of the pulsar emission mechanism and transitioning systems.
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