New Direct Observational Evidence for Kicks in SNe

We present an updated list of direct strong evidence in favour of kicks being imparted to newborn neutron stars. In particular we discuss the new cases of evidence resulting from recent observations of the X-ray binary Circinus X-1 and the newly discovered binary radio pulsar PSR J1141-6545. We conclude that the assumption that neutron stars receive a kick velocity at their formation is unavoidable (van den Heuvel & van Paradijs 1997).Comment: 2 pages, to appear in the proceedings of the IAU Colloq. 177 "Pulsar Astronomy - 2000 and beyond

Comment on "A non-interacting low-mass black hole -- giant star binary system"

Thompson et al. (Reports, 1 November 2019, p. 637, Science) interpreted the unseen companion of the red giant star 2MASS J05215658+4359220 as most likely a black hole. We argue that if the red giant is about one solar mass, its companion can be a close binary consisting of two main-sequence stars. This would explain why no X-ray emission is detected from the system.Comment: 3 pages, Author version of Technical Comment published in Science on 8 May, 202

Discovery of Two Relativistic Neutron Star-White Dwarf Binaries

We have discovered two recycled pulsars in relativistic orbits as part of the first high-frequency survey of intermediate Galactic latitudes. PSR J1157-5112 is a 44 ms pulsar and the first recycled pulsar with an ultra-massive (M > 1.14 Mo) white dwarf companion. Millisecond pulsar J1757-5322 is a relativistic circular-orbit system which will coalesce due to the emission of gravitational radiation in less than 9.5 Gyr. Of the ~40 known circular orbit pulsars, J1757-5322 and J1157-5112 have the highest projected orbital velocities. There are now three local neutron-star/white-dwarf binaries that will coalesce in less than a Hubble time, implying a large coalescence rate for these objects in the local Universe. Systems such as J1141-6545 (Kaspi et al. 2000) are potential gamma-ray burst progenitors and dominate the coalescence rate, whilst lighter systems make excellent progenitors of millisecond pulsars with planetary or ultra-low mass companions.Comment: 4 pages, to appear in ApJ Letters. Uses aastex v 5.0, emulateapj5.sty, apjfonts.st

The Peculiar Evolutionary History of IGR J17480-2446 in Terzan 5

The low mass X-ray binary (LMXB) IGR J17480-2446 in the globular cluster Terzan 5 harbors an 11 Hz accreting pulsar. This is the first object discovered in a globular cluster with a pulsar spinning at such low rate. The accreting pulsar is anomalous because its characteristics are very different from the other five known slow accreting pulsars in galactic LMXBs. Many features of the 11 Hz pulsar are instead very similar to those of accreting millisecond pulsars, spinning at frequencies >100 Hz. Understanding this anomaly is valuable because IGR J17480-2446 can be the only accreting pulsar discovered so far which is in the process of becoming an accreting millisecond pulsar. We first verify that the neutron star (NS) in IGR J17480-2446 is indeed spinning up by carefully analyzing X-ray data with coherent timing techniques that account for the presence of timing noise. We then study the present Roche lobe overflow epoch and the two previous spin-down epochs dominated by magneto dipole radiation and stellar wind accretion. We find that IGR J17480-2446 is very likely a mildly recycled pulsar and suggest that it has started a spin-up phase in an exceptionally recent time, that has lasted less than a few 10^7 yr. We also find that the total age of the binary is surprisingly low (<10^8 yr) when considering typical parameters for the newborn NS and propose different scenarios to explain this anomaly.Comment: Accepted by ApJ, in pres

The formation of the double neutron star pulsar J0737--3039

We find that the orbital period (2.4 hours), eccentricity (0.09), dipole magnetic field strength (6.9 x 10^9 Gauss) and spin period (22 ms) of the new highly relativistic double neutron star system PSR J0737-3039 can all be consistently explained if this system originated from a close helium star plus neutron star binary (HeS-NS) in which at the onset of the evolution the helium star had a mass in the range 4.0 to 6.5 M_sun and an orbital period in the range 0.1 to 0.2 days. Such systems are the post-Common-Envelope remnants of wide Be/X-ray binaries (orbital period ~ 100 to 1000 days) which consist of a normal hydrogen-rich star with a mass in the range 10 - 20 M_sun and a neutron star. The close HeS-NS progenitor system went through a phase of mass transfer by Roche-lobe overflow at a high rate lasting a few times 10^4 years; assuming Eddington-limited disk accretion onto the neutron star this star was spun up to its present rapid spin rate. At the moment of the second supernova explosion the He star had a mass in the range 2.3 to 3.3 M_sun and in order to obtain the present orbital parameters of PSR J0737-3039 a kick velocity in the range 70 - 230 km/s must have been imparted to the second neutron star at its birth.Comment: accepted by MNRA

Formation of Millisecond Pulsars with Heavy White Dwarf Companions: Extreme Mass Transfer on Sub-Thermal Timescales

We have performed detailed numerical calculations of the non-conservative evolution of close X-ray binary systems with intermediate-mass (2.0-6.0 M_sun) donor stars and a 1.3 M_sun accreting neutron star. We calculated the thermal response of the donor star to mass loss, in order to determine its stability and follow the evolution of the mass transfer. Under the assumption of the "isotropic re-emission model" we demonstrate that in many cases it is possible for the binary to prevent a spiral-in and survive a highly super-Eddington mass-transfer phase (1 << M_dot/M_Edd < 10^5) on a sub-thermal timescale, if the convective envelope of the donor star is not too deep. These systems thus provide a new formation channel for binary millisecond pulsars with heavy CO white dwarfs and relatively short orbital periods (3-50 days). However, we conclude that to produce a binary pulsar with a O-Ne-Mg white dwarf or P_orb ~1 day (e.g. PSR B0655+64) the above scenario does not work, and a spiral-in phase is still considered the most plausible scenario for the formation of such a system

Evolution of Neutron-Star, Carbon-Oxygen White-Dwarf Binaries

At least one, but more likely two or more, eccentric neutron-star, carbon-oxygen white-dwarf binaries with an unrecycled pulsar have been observed. According to the standard scenario for evolving neutron stars which are recycled in common envelope evolution we expect to observe \gsim 50 such circular neutron star-carbon oxygen white dwarf binaries, since their formation rate is roughly equal to that of the eccentric binaries and the time over which they can be observed is two orders of magnitude longer, as we shall outline. We observe at most one or two such circular binaries and from that we conclude that the standard scenario must be revised. Introducing hypercritical accretion into common envelope evolution removes the discrepancy by converting the neutron star into a black hole which does not emit radio waves, and therefore would not be observed.Comment: 25 pages, 1 figure, accepted in Ap

Different Aspects of Classical Pathway Overactivation in Patients With C3 Glomerulopathy and Immune Complex-Mediated Membranoproliferative Glomerulonephritis

The rare and heterogeneous kidney disorder C3 glomerulopathy (C3G) is characterized by dysregulation of the alternative pathway (AP) of the complement system. C3G is often associated with autoantibodies stabilizing the AP C3 convertase named C3 nephritic factors (C3NeF). The role of classical pathway (CP) convertase stabilization in C3G and related diseases such as immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) remains largely unknown. Here, we investigated the CP convertase activity in patients with C3G and IC-MPGN. Using a refined two-step hemolytic assay, we measured the stability of CP convertases directly in the serum of 52 patients and 17 healthy controls. In four patients, CP convertase activity was prolonged compared to healthy controls, i.e. the enzymatic complex was stabilized. In three patients (2 C3G, 1 IC-MPGN) the convertase stabilization was caused by immunoglobulins, indicating the presence of autoantibodies named C4 nephritic factors (C4NeFs). Importantly, the assay also enabled detection of non-immunoglobulin-mediated stabilization of the CP convertase in one patient with C3G. Prolonged CP convertase activity coincided with C3NeF activity in all patients and for up to 70 months of observation. Crucially, experiments with C3-depleted serum showed that C4NeFs stabilized the CP C3 convertase (C4bC2a), that does not contain C3NeF epitopes. All patients with prolonged CP convertase activity showed clear signs of complement activation, i.e. lowered C3 and C5 levels and elevated levels of C3d, C3bc, C3bBbP, and C5b-9. In conclusion, this work provides new insights into the diverse aspects and (non-)immunoglobulin nature of factors causing CP convertase overactivity in C3G/IC-MPGN.</p

A Theoretical Light-Curve Model for the 1999 Outburst of U Scorpii

A theoretical light curve for the 1999 outburst of U Scorpii is presented in order to obtain various physical parameters of the recurrent nova. Our U Sco model consists of a very massive white dwarf (WD) with an accretion disk and a lobe-filling, slightly evolved, main-sequence star (MS). The model includes a reflection effect by the companion and the accretion disk together with a shadowing effect on the companion by the accretion disk. The early visual light curve (t ~ 1-15 days after maximum) is well reproduced by a thermonuclear runaway model on a very massive WD close to the Chandrasekhar limit (M_{WD}= 1.37 \pm 0.01 M_\odot), in which optically thick winds blowing from the WD play a key role in determining the nova duration. The duration of the strong wind phase (t~0-17 days) is very consistent with the BeppoSAX supersoft X-ray detection at t~19-20 days because supersoft X-rays are self-absorbed by the massive wind. The envelope mass at the peak is estimated to be ~3x10^{-6} M_\odot, which is indicating an average mass accretion rate ~2.5x10^{-7} M_\odot yr^{-1} during the quiescent phase between 1987 and 1999. These quantities are exactly the same as those predicted in a new progenitor model of Type Ia supernovae.Comment: 7 pages, 3 figures, to appear in ApJL, vol. 52

On the mass distribution of neutron stars in HMXBs

We present the results of a monitoring campaign of three eclipsing high-mass X-ray binaries (HMXBs: SMC X-1, LMC X-4 and Cen X-3). High-resolution VLT/UVES spectra are used to measure the radial velocities of these systems with high accuracy. We show that the subsequent mass determination of the neutron stars in these systems is significantly improved and discuss the implications of this result.Comment: 6 pages, 5 figures, To appear in the proceedings of the International Workshop "Massive Stars in Interacting Binaries" in Montrea