We present a comparative study of the low-frequency eclipses of spider (compact, irradiating binary) PSRs B1957+20 and J1816+4510. Combining these data with those of three other eclipsing systems we study the frequency dependence of the eclipse duration. PSRs B1957+20 and J1816+4510 have similar orbital properties, but the companions to the pulsars have masses that differ by an order of magnitude. A dedicated campaign to simultaneously observe the pulsed and imaged continuum flux densities throughout the eclipses reveals many similarities between the excess material within the two binaries, irrespective of the companion star properties. The observations show that the pulsar fluxes are removed from the line of sight throughout the main body of the eclipses. For PSR J1816+4510 we present the first direct evidence of an eclipse mechanism that transitions from one that removes the pulsar flux from the line of sight to one that merely smears out pulsations, and claim that this is a consequence of scattering in a tail of material flowing behind the companion. Inferred mass loss rates from the companion stars are found to be $\dot{M}_{\text{C}} \sim 10^{-12}~M_\odot$~yr$^{-1}$ and $\dot{M}_{\text{C}} \sim 2 \times 10^{-13}~M_\odot$~yr$^{-1}$ for PSR B1957+20 and PSR J1816+4510, respectively; seemingly too low to evaporate the stars within Hubble time. Measurements of eclipse durations over a wide range of radio-frequencies show a significant dependence of eclipse duration on frequency for all pulsars, with wider eclipses at lower-frequencies. These results provide a marked improvement in the observational constraints available for theoretical studies of the eclipse mechanisms.
Reliable neutron star mass measurements are key to determining the equation-of-state of cold nuclear matter, but these are rare. "Black Widows" and "Redbacks" are compact binaries consisting of millisecond pulsars and semi-degenerate companion stars. Spectroscopy of the optically bright companions can determine their radial velocities, providing inclination-dependent pulsar mass estimates. While inclinations can be inferred from subtle features in optical light curves, such estimates may be systematically biased due to incomplete heating models and poorly-understood variability. Using data fro…
Radio eclipse of the slowest spinning Galactic-field spider pulsar PSR J1932+2121 and its X-ray emission prospect
Central China Normal University（华中师范大学）；Institute of Astrophysics, Central China Normal University（华中师范大学天体物理研究所）；Laboratory for Compact Object Astrophysics and Astronomical Technology, Central China Normal University（华中师范大学致密天体天文学与技术实验室）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；University of Chinese Academy of Sciences（中国科学院大学）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences（中国科学院射电天文与技术重点实验室）
Spider pulsars are compact binary systems composed of a millisecond pulsar and a low-mass companion. The relativistic magnetically-dominated pulsar wind impacts onto the companion, ablating it and slowly consuming its atmosphere. The interaction forms an intrabinary shock, a proposed site of particle acceleration. We perform global fully-kinetic particle-in-cell simulations of the intrabinary shock, assuming that the pulsar wind consists of plane-parallel stripes of alternating polarity and that the shock wraps around the companion. We find that particles are efficiently accelerated via shock-…
Gamma-ray Orbital Modulation in Spider Pulsars: Three Discoveries and a Universal Modulated Fraction
Norwegian University of Science and Technology（挪威科技大学）；Universitat Politècnica de Catalunya（加泰罗尼亚理工大学）；Shanghai Jiao Tong University（上海交通大学）；INAF Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切尔蒂天文台）
The discovery of transitional millisecond pulsars (tMSPs) provided conclusive proof that neutron star (NS) low-mass X-ray binaries (LMXBs) comprise part of the evolutionary pathway towards binary millisecond pulsars (MSPs). Redback and black widow `spider' pulsars are a sub-category of binary MSPs that `devour' their companions through ablation - the process through which material is lifted from the stellar surface by a pulsar wind. In addition to reducing the companion star's mass, ablation introduces observable characteristics like extended, energy-dependent and asymmetric eclipse profiles i…
The population of millisecond pulsars (MSPs) has been expanded considerably in the last decade. Not only is their number increasing, but also various classes of them have been revealed. Among different classes of MSPs, the behaviour of black widows and redbacks are particularly interesting. These systems consist of an MSP and a low-mass companion star in compact binaries with an orbital period of less than a day. In this article, we give an overview of the high energy nature of these two classes of MSPs. Updated catalogues of black widows and redbacks are presented and their X ray/$γ$-ray prop…
The GMRT High-Resolution Southern Sky Survey for pulsars and transients -- VII: Timing of Spider MSP J1242-4712, A Bridge Between Redback and Black Widow Pulsars
The frequency dependent eclipses of the radio emission from millisecond pulsars (MSPs) in compact binary systems provide an opportunity to understand the eclipse mechanism and to determine the nature of the eclipsing medium. We combine multifrequency observations from the upgraded Giant Metrewave Radio Telescope (uGMRT) and model the broadband radio spectrum in the optically thick to thin transition regime to constrain the eclipse mechanism. The best-fit model to the eclipse phase spectra favors synchrotron absorption by relativistic electrons. We are able to strongly constrain the frequency o…
On the Expected Orbitally-modulated TeV Signatures of Spider Binaries: The Effect of Intrabinary Shock Geometry
Centre for Space Research, North-West University（西北大学空间研究中心）；Department of Astronomy, University of Maryland（马里兰大学天文学系）；Astrophysics Science Division, NASA Goddard Space Flight Center（NASA戈达德太空飞行中心天体物理学科学部）；Center for Research and Exploration in Space Science and Technology, NASA/GSFC（NASA/GSFC空间科学与技术研究探索中心）
We report the discovery of X-ray eclipses in the recently discovered accreting millisecond X-ray pulsar Swift J1749.4-2807. This is the first detection of X-ray eclipses in a system of this type and should enable a precise neutron star mass measurement once the companion star is identified and studied. We present a combined pulse and eclipse timing solution that enables tight constraints on the orbital parameters and inclination and shows that the companion mass is in the range 0.6-0.8 M_sun for a likely range of neutron star masses, and that it is larger than a main sequence star of the same …
We have observed and analysed the eclipses of the black widow pulsar J1810+1744 at low radio frequencies. Using LOw-Frequency ARray (LOFAR) and Westerbork Synthesis Radio Telescope observations between 2011--2015 we have measured variations in flux density, dispersion measure and scattering around eclipses. High-time-resolution, simultaneous beamformed and interferometric imaging LOFAR observations show concurrent disappearance of pulsations and total flux from the source during the eclipses, with a $3σ$ upper limit of 36 mJy ($<10\%$ of the pulsar's averaged out-of-eclipse flux density). The …
We present a multi-frequency study of eclipse properties of a transitional redback millisecond pulsar J1227$-$4853 discovered in 2014 with the GMRT. Emission from this pulsar is eclipsed at 607 MHz for about 37% of its orbit around the superior conjunction. We observe eclipse ingress and egress transition which last 12% and 15% of its orbit respectively, resulting in only 36% of the orbit being unaffected by eclipsing material. We report an excess dispersion measure (DM) at eclipse boundaries of 0.079(3) pc cm$^{-3}$ and the corresponding electron column density (N$_e$) is 24.4(8) x 10$^{16}$ …
The eclipses of certain types of binary millisecond pulsars (i.e. `black widows' and `redbacks') are often studied using high-time-resolution, `beamformed' radio observations. However, they may also be detected in images generated from interferometric data. As part of a larger imaging project to characterize the variable and transient sky at radio frequencies <200 MHz, we have blindly detected the redback system PSR J2215+5135 as a variable source of interest with the Low-Frequency Array (LOFAR). Using observations with cadences of 2 weeks - 6 months, we find preliminary evidence that the ecli…
A Chandra X-ray study of millisecond pulsars in the globular cluster Omega Centauri: a correlation between spider pulsar companion mass and X-ray luminosity
Searching for Spider-Like Pulsars from TESS Ellipsoidal Lightcurves with X-ray counterparts
School of Physics and Astronomy, Sun Yat-Sen University（中山大学物理学院）；CSST Science Center for the Guangdong-Hongkong-Macau Greater Bay Area, Sun Yat-Sen University（中山大学CSST粤港澳大湾区科学中心）；Laboratory for Space Research, The University of Hong Kong（香港大学空间研究实验室）；Institute of Astronomy Space and Earth Science, P177, CIT Road, Scheme-7M, Kolkata, 700054, West Bengal, India（印度西孟加拉邦加尔各答CIT路P177号 scheme-7M 天体物理学、空间与地球科学研究所）
Pulsar winds interacting with sources of external pressure are well-established as efficient and prolific TeV accelerators in our Galaxy. Yet, enabled by observations from Fermi-LAT, a growing class of non-accreting pulsars in binaries has emerged and these are likely to become apparent as TeV emitters in the CTA era. This class consists of the black widows and redbacks, binaries in which a millisecond pulsar interacts with its low-mass companion. In such systems, an intrabinary shock can form as a site of particle acceleration and associated nonthermal emission. We motivate why these sources …
We present Keck spectroscopic measurements of the millisecond pulsar binary J2215+5135. These data indicate a neutron-star (NS) mass M_NS=1.6Mo, much less than previously estimated. The pulsar heats the companion face to T_D~9000K; the large heating efficiency may be mediated by the intrabinary shock dominating the X-ray light curve. At the best-fit inclination i=88.8deg, the pulsar should be eclipsed. We find weak evidence for such eclipses in the pulsed gamma-rays; an improved radio ephemeris allows use of up to 5 times more Fermi-LAT gamma-ray photons for a definitive test of this picture. …
Testing Magnetic Field Configurations in Spider Pulsar PSR J1723-2837 with IXPE
Louisiana State University（路易斯安那州立大学）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Stanford University（斯坦福大学）；Columbia University（哥伦比亚大学）；University of Maryland, College Park（马里兰大学帕克分校）；Center for Research and Exploration in Space Science and Technology, NASA/GSFC（NASA/戈达德太空飞行中心空间科学与技术研究探索中心）；University of Maryland, Baltimore County（马里兰大学巴尔的摩县分校）
Search for TeV emission from spider millisecond pulsars with HAWC
Instituto de Física, Universidad Nacional Autónoma de México（墨西哥国立自治大学物理研究所）；Instituto de Astronomía, Universidad Nacional Autónoma de México（墨西哥国立自治大学天文学研究所）；Universidad de Costa Rica（哥斯达黎加大学）；Universidad Michoacana de San Nicolás de Hidalgo（米却肯圣尼古拉斯德伊达尔戈大学）；Temple University（天普大学）；Department of Physics and Astronomy, Michigan State University（密歇根州立大学物理与天文系）；Laboratoire d’Annecy-le-Vieux de Physique Théorique (LAPTh), CNRS, USMB（法国国家科学研究中心/萨瓦大学安纳西勒沃旧理论物理实验室）；Università degli Studi di Torino（都灵大学）；Instituto Nacional de Astrofísica, Óptica y Electrónica（墨西哥国家天体物理学、光学和电子研究所）；Institute of Nuclear Physics Polish Academy of Sciences（波兰科学院核物理研究所）
Spider millisecond pulsars are, along with some eclipsing post-common envelope systems and cataclysmic variables, part of an expanding category of compact binaries with low-mass companions for which puzzling timing anomalies have been observed. The most prominent type of irregularities seen in them are orbital period variations, a phenomenon which has been proposed to originate from changes in the gravitational quadrupole moment of the companion star. A physically sound modelling of the timing of these systems is key to understanding their structure and evolution. In this paper we argue that a…
Recently, several eclipsing millisecond pulsars have been shown to experience strong and apparent weak lensing from the outflow of their ionized companions. Lensing can be a powerful probe of the ionized plasma, with the strongest lenses potentially resolving emission regions of pulsars. Understanding lensing in the `laboratory-like' conditions of an eclipsing pulsar may be analogously applied to fast radio bursts, many of which reside in dense, magnetized environments. We examined variable dispersion measure (DM), absorption, scattering, and flux density in the original Black Widow pulsar PSR…
We report on radio timing observations of the black widow binary pulsar J0610$-$2100 and optical observations of its binary companion. The radio timing observations extend the timing baseline to 16yr and reveal a marginal detection of the orbital period derivative, but they show no significant evidence of orbital variations such as those seen in other black widow pulsars. Furthermore, no eclipses are seen in the observations at observing frequencies ranging from 310 to 2700MHz. The optical VRI light curves were modulated with the orbital period, reaching maximum brightness of $V=26.8$, $R=25.4…
COBIPLANE: A Systematic Search for Compact Binary Millisecond Pulsars at Low Galactic Latitudes
Norwegian University of Science and Technology（挪威科技大学）；Universitat Politècnica de Catalunya（加泰罗尼亚理工大学）；Centro de Astrobiología, CSIC-INTA（西班牙国家航空航天技术研究所/西班牙国家研究委员会天体生物学中心）
The radio millisecond pulsar PSR J1023+0038 exhibits complex timing and eclipse behavior. Here we analyze four years' worth of radio monitoring observations of this object. We obtain a long-term timing solution, albeit with large residual timing errors as a result of apparent orbital period variations. We also observe variable eclipses when the companion passes near our line of sight, excess dispersion measure near the eclipses and at random orbital phases, and short-term disappearances of signal at random orbital phases. We interpret the eclipses as possibly due to material in the companion's…
Spider pulsars are binary systems containing an energetic millisecond pulsar that intensely irradiates a closely orbiting low-mass companion. Modelling their companion's optical light curves is essential to the study of the orbital properties of the binary, including the determination of the pulsar mass, characterising the pulsar wind and the star itself. We aim to generalise the traditional direct heating model of irradiation, whereby energy deposited by the pulsar wind into the stellar envelope is locally re-emitted, by introducing heat redistribution via diffusion and convection within the …
Observations with the Parkes radio telescope of the eclipsing millisecond binary pulsar PSR J1748$-$2446A, which is in the globular cluster Terzan 5, are presented. These include the first observations of this pulsar in the 3\,GHz frequency band, along with simultaneous observations in the 700\,MHz band and new observations around 1400\,MHz. We show that the pulsar signal is not eclipsed in the 3\,GHz band and observe the known eclipses in the lower frequency bands. We find that the observed pulse signal becomes depolarized during particular orbital phases and postulate that this depolarizatio…
We report on the latest six pulsars discovered through our standard pipeline in the intermediate-latitude region (|b| < 15 deg) of the Parkes High Time Resolution Universe Survey (HTRU). We also present timing solutions for the new discoveries and for 19 further pulsars for which only discovery parameters were previously published. Highlights of the presented sample include the isolated millisecond pulsar J1826-2415, the long-period binary pulsar J1837-0822 in a mildly eccentric 98-day orbit with a > 0.27 M_sun companion, and the nulling pulsar J1638-4233, detected only 10% of the time. Other …
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…
Over the last few years, the number of known eclipsing radio millisecond pulsar systems in the Galactic field has dramatically increased, with many being associated with Fermi gamma-ray sources. All are in tight binaries (orbital period < 24 hr) with many being classical "black widows" which have very low mass companions (companion mass Mc << 0.1 Msol) but some are "redbacks" with low mass (Mc ~ 0.2 - 0.4Msol) companions which are probably non-degenerate. These latter are systems where the mass transfer process may have only temporarily halted, and so are transitional systems between low mass …
