| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 14m 36.5051s[1] |
| Declination | −22° 30′ 31.081″[1] |
| Characteristics | |
| Spectral type | Pulsar |
| Astrometry | |
| Distance | 3,900 ly (1,200[1] pc) |
| Details | |
| Mass | 1.908[2] M☉ |
| Radius | 13 ± 2 km,[1] 1.87(29) × 10-5 R☉ |
| Rotation | 3.150807655690673ms[1] |
| Age | 5.2 Gyr |
| Other designations | |
| PSR J1614–22 | |
| Database references | |
| SIMBAD | data |
PSR J1614–2230 is apulsar in a binary system with awhite dwarf in the constellationScorpius. It was discovered in 2006 with theParkes telescope in a survey of unidentifiedgamma ray sources in theEnergetic Gamma Ray Experiment Telescope catalog.[3] PSR J1614–2230 is amillisecond pulsar, a type of neutron star, that spins on its axis roughly 317.37 times per second, corresponding to a period of 3.1508 milliseconds. Like all pulsars, it emits radiation in a beam, similar to alighthouse.[4] Emission from PSR J1614–2230 is observed as pulses at the spin period of PSR J1614–2230. The pulsed nature of its emission allows for the arrival of individual pulses to be timed. By measuring the arrival time of pulses,astronomers observed the delay of pulse arrivals from PSR J1614–2230 when it was passing behind its companion from the vantage point ofEarth. By measuring this delay, known as theShapiro delay, astronomers determined the mass of PSR J1614–2230 and its companion. The team performing the observations found that the mass of PSR J1614–2230 is1.97 ± 0.04 M☉. This mass made PSR J1614–2230 the most massive knownneutron star at the time of discovery, and rules out many neutron starequations of state that includeexotic matter such ashyperons andkaon condensates.[1]
In 2013, a slightly higher neutron star mass measurement was announced forPSR J0348+0432,2.01 ± 0.04 M☉.[5]This confirmed the existence of such massive neutron stars using a different measuring technique.
After further high-precision timing of the pulsar, the mass measurement for J1614–2230 was updated to1.908 ± 0.016 M☉ in 2018.[2]
Pulsars were discovered in 1967 byJocelyn Bell and her adviserAntony Hewish using theInterplanetary Scintillation Array.[6]Franco Pacini andThomas Gold quickly put forth the idea that pulsars are highlymagnetized rotatingneutron stars, which form as a result of asupernova at the end of the life ofstars more massive than about 10 M☉.[7][8] Theradiation emitted by pulsars is caused by interaction of theplasma surrounding the neutron star with its rapidly rotating magnetic field. This interaction leads to emission "in the pattern of a rotating beacon," as emission escapes along the magnetic poles of the neutron star.[8] The "rotating beacon" property of pulsars arises from the misalignment of their magnetic poles with their rotational poles. Historically, pulsars have been discovered atradio wavelengths where emission is strong, butspace telescopes that operate in thegamma ray wavelengths have also discovered pulsars.
TheEnergetic Gamma-Ray Experiment Telescope (EGRET) identified a half dozen known pulsars at gamma ray wavelengths. Many of the sources it detected had no known counterparts at other wavelengths. In order to see whether any of these sources were pulsars, Fronefield Crawfordet al. used theParkes telescope to conduct a survey of the EGRET sources located in the plane of theMilky Way that lacked a known counterpart. In the search, they discovered PSR J1614–2230, and concluded that it might be a counterpart to a gamma ray source near the same location.[3] The radio observations revealed that PSR J1614–2230 had a companion, likely awhite dwarf. The observed orbital parameters of the system indicated a minimum companion mass of 0.4 M☉, and an orbital period of 8.6866 days.[9]
Paul Demorestet al. used theGreen Bank Telescope at theNational Radio Astronomy Observatory to observe the system through a complete 8.68661942256 day orbit, recording the pulse arrival times from PSR J1614–2230 over this period. After accounting for factors that would alter pulse arrival times from exactly matching its period of 3.150807655690673 milliseconds, including theorbital parameters of the binary system, the spin of the pulsar, and the motion of the system, Demorestet al. determined the delay in the arrival of pulses that resulted from the pulse having to travel past the companion to PSR J1614–2230 on its way toEarth. This delay is a consequence ofgeneral relativity known as theShapiro delay, and the magnitude of the delay is dependent upon the mass of the white dwarf companion. The best fit companion mass was0.500 ± 0.006 M☉. Knowing the companion mass and orbital elements then provided enough information to determine the mass of PSR J1614–2230 to be1.97 ± 0.04 M☉.[1]
The measurement was later improved based on observations of the pulses over several years.[2]
The conditions in neutron stars are very different from those encountered on Earth, as a result of the highdensity andgravity of neutron stars; their masses are of order the mass of astar, but they have sizes around 10 to 13 kilometres (6 to 8 mi) in radius, which is comparable to the size of the center of large cities such asLondon.[4] Neutron stars also have the property that as they become more massive, their diameter decreases. The mass of PSR J1614–2230 is the second highest of all the knownneutron stars. The existence of a neutron star with such a high mass constrains the composition and structure of neutron stars, both of which are poorly understood. The reason for this is that the maximum mass of a neutron star is dependent upon its composition. A neutron star composed of matter such ashyperons orkaoncondensates would collapse to form ablack hole before it could reach the observed mass of PSR J1614–2230, meaning neutron star models that include such matter are strongly constrained by this result.[1][10]
