A millisecond pulsar in a stellar triple system

Abstract

Gravitationally bound three-body systems have been studied for hundreds of years 1, 2 and are common in our Galaxy 3, 4 . They show complex orbital interactions, which can constrain the compositions, masses, and interior structures of the bodies 5 and test theories of gravity 6 , if sufficiently precise measurements are available. A triple system containing a radio pulsar could provide such measurements, but the only previously known such system, B1620−26 7, 8 (with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of several decades), shows only weak interactions. Here we report precision timing and multiwavelength observations of PSR J0337+1715, a millisecond pulsar in a hierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar (1.4378(13) M , where M is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15) M and 0.4101(3) M ), as well as the inclinations of the orbits (both ∼39.2• ). The unexpectedly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from those of known stellar systems. The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity. Millisecond pulsars (MSPs) are neutron stars that rotate hundreds of times per second and emit radio waves in a lighthouse-like fashion. They are thought to form in binary systems 9 and their rotation rates and orbital properties can be measured with exquisite precision via the unambiguous pulse-counting methodology known as pulsar timing. As part of a large-scale pulsar survey 10, 11 with the Green Bank Telescope (GBT), we have discovered the only known MSP in a stellar triple system. The pulsar has a spin period of 2.73 ms, is relatively bright (∼2 mJy at 1.4 GHz), and has a complex radio pulse profile with multiple narrow components.Though initial timing observations showed a seemingly typical binary MSP system with a 1.6-day circular orbit and a 0.1−0.2 M white dwarf (WD) companion, large timing systematics quickly appeared, strongly suggesting the presence of a third body. There are two other MSPs known to have multiple companions: the famous pulsar B1257+12 which hosts at least 3 low-mass planets 12,13 , and the MSP triple system B1620−26 in globular cluster M4 with a WD inner companion and a roughly Jupiter-mass outer companion 7, 8 . The timing perturbations from J0337+1715 were much too large to be caused by a planetary mass companion.We began an intensive multi-frequency radio timing campaign (Methods) using the GBT, the Arecibo telescope, and the Westerbork Synthesis Radio Telescope (WSRT) to constrain the system's position, orbital parameters, and the nature of the third body. At Arecibo, we achieve median arrival time uncertainties of 0.8 µs...

Understanding the Neutron Star Population with the SKA

“…However, their eccentricities and orbital periods have led to the suggestion of an alternative hypothesis of direct MSP formation via a rotationally delayed accretion-induced collapse of a massive WD (Freire & Tauris 2014). Whereas the origin of these systems remains unclear, a triple system MSP with two WD companions (PSR J0337+1715) was announced earlier this year by Ransom et al (2014). This amazing system must have survived at least 3 phases of mass transfer and one SN explosion and challenges current knowledge of multiple stellar system evolution (Tauris & van den Heuvel 2014).…”

Radio emissions from pulsar companions: a refutable explanation for galactic transients and fast radio bursts

“…Article published by EDP Sciences A86, page 1 of 11 (Ransom et al 2014). Five planets, distributed within three planetary systems, are known to orbit pulsars (Wolszczan & Frail 1992;Thorsett et al 1993;Bailes et al 2011).…”

A double white dwarf with a paradoxical origin?

“…Perhaps the lowmass white dwarf is in a close binary with an unseen massive companion such as a neutron star, while the hotter, massive white dwarf is a wide companion. Recently, Ransom et al (2014) discovered a triple system in the Galactic disk consisting of a neutron star and two white dwarfs, of which one is very low mass, and hence nature is apparently producing such triple compact star systems (Tauris & van den Heuvel 2014). However, in this scenario the problem with the incompatible cooling ages and masses remains, unless the hot white dwarf was captured as the third component later on and did not form at the same time as the close binary.…”

“…New dedicated searches such as the ELM Survey have significantly increased the known population in recent years (Brown et al 2010Kilic et al 2011Kilic et al , 2012. The majority of ELM white dwarfs are companions to other white dwarfs (Kaplan et al 2014, this paper) or millisecond pulsars (see for example van Kerkwijk et al 1996;Bassa et al 2006;Antoniadis et al 2013) and a few have been found in hierarchical triple systems (Ransom et al 2014;Kilic et al 2014aKilic et al , 2015 or orbiting A-or F-type mainsequence stars (Maxted et al 2014;Breton et al 2012). The subject of this paper, SDSS J1257+5428, is a binary that likely belongs to the first of these classes, but, as we shall see, how it evolved into the system we see today is a mystery.…”