Astronomy:PSR J0952–0607

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Short description: Massive millisecond pulsar in the Milky Way
PSR J0952–0607
PSR J0952-0607 Fermi.jpg
PSR J0952–0607 (center crosshair) imaged by the Fermi Gamma-ray Space Telescope
Observation data
Equinox J2000.0]] (ICRS)
Constellation Sextans
Right ascension  09h 52m 08.319s[1]
Declination −06° 07′ 23.49″[1]
Characteristics
Spectral type Pulsar
Apparent magnitude (i) 22.0–24.4[2]
Astrometry
Distance970+1160
−530 pc[3]
or 1740+1570
−820 pc[3]
or 6260+360
−400 (optical) pc
Details
PSR J0952–0607 A
Mass2.35±0.17[4] M☉
Rotation1.41379836 ms[3]
Age4.9[3] Gyr
PSR J0952–0607 B
Mass0.032±0.002[4] M☉
Luminosity9.96+1.20
−1.12[lower-alpha 1] L☉
Temperature3085+85
−80[4] K
Orbit[3]
PrimaryPSR J0952–0607 A
CompanionPSR J0952–0607 B
Period (P)0.267461035 d
(6.41906484 h)
Semi-major axis (a)1600000 km[lower-alpha 2]
Eccentricity (e)<0.004
Inclination (i)59.8+2.0
−1.9[4]°
Semi-amplitude (K2)
(secondary)		376.1±5.1[4] km/s
Other designations
PSR J0952–0607, 4FGL J0952.1–0607
Database references
SIMBADdata

PSR J0952–0607 is a massive millisecond pulsar in a binary system, located between 3,200–5,700 light-years (970–1,740 pc) away from Earth in the constellation Sextans.[5] It holds the record for being the most massive neutron star known (As of 2022), with a mass 2.35±0.17 times as much as the Sun—potentially close to the Tolman–Oppenheimer–Volkoff mass upper limit for neutron stars.[4][6] The pulsar rotates at a frequency of 707 Hz (1.41 ms period), making it the second-fastest-spinning pulsar known, and the fastest-spinning pulsar known within the Milky Way.[7][5]

PSR J0952–0607 was discovered by the Low-Frequency Array (LOFAR) radio telescope during a search for pulsars in 2016.[5] It is classified as a black widow pulsar, a type of pulsar harboring a closely-orbiting substellar-mass companion that is being ablated by the pulsar's intense high-energy solar winds and gamma-ray emissions.[4][8] The pulsar's high-energy emissions have been detected in gamma-ray and X-ray wavelengths.[9][3][10]

Discovery

PSR J0952–0607 was first identified as an unassociated gamma-ray source detected during the first seven years of the Fermi Gamma-ray Space Telescope's all-sky survey since 2008.[7](p2) Because of its optimal location away from the crowded Galactic Center and its pulsar-like[11](p8) gamma-ray emission peak at 1.4 GeV, it was deemed a prime millisecond pulsar candidate for follow-up.[7](p2) The pulsar was reobserved and confirmed by the Low-Frequency Array (LOFAR) radio telescope in the Netherlands on 25 December 2016, which revealed a 707-Hz radio pulsation frequency alongside radial acceleration by an unseen binary companion.[7](p3) Further LOFAR observations took place from January to February 2017, alongside radio observations by the Green Bank Telescope in Green Bank, West Virginia in March 2017.[7](p3) Optical observations by the 2.54-meter Isaac Newton Telescope on La Palma detected and confirmed the pulsar's companion at a faint apparent magnitude of 23 in January 2017.[7](p3) The discovery was published in The Astrophysical Journal Letters and was announced in a NASA press release in September 2017.[7][5]

Distance and location

The distance of PSR J0952–0607 from Earth is highly uncertain.[2][3][4]

Binary system

The PSR J0952–0607 binary system comprises a massive pulsar and a substellar-mass (<0.1 M☉)[8](p127) companion in close orbit around it.[4] Because of this configuration, this system falls under the category of black widow pulsars that "consume" their companion, by analogy with the mating behavior of the eponymous black widow spider.[6] The companion is continuously losing mass through ablation by intense high-energy solar winds and gamma-ray emissions from the pulsar, which then accretes some of the companion's lost material onto itself.[8](p127)[4](p1)

Companion

Artist's impression of a black widow pulsar system, where a stellar-mass companion is being ablated by the intense radiation of its host pulsar

The companion orbits the pulsar at a distance of 1.6 million km (1 million mi)[lower-alpha 2] with an orbital period of 6.42 hours.[4] Because it orbits so closely, the companion is presumably tidally locked, with one hemisphere always facing the pulsar.[3](p8) The companion does not appear to eclipse the pulsar,[7](p1)[3](p12) indicating that its orbit is oriented nearly face-on with an inclination of 60° with respect to the plane perpendicular to Earth's line of sight.[4](p4) The companion's orbital motion also does not appear to modulate the pulsar's pulsations, signifying a circular orbit with negligible orbital eccentricity.[3](p4)

The companion was likely a former star that had been reduced to the size of a large gas giant planet or brown dwarf,[6][3](p12) with a present-day mass of 0.032±0.002 M☉ or 34±2 Jupiter mass according to radial velocity measurements.[4](p4) Due to intense irradiation and heating by the host pulsar, the companion's radius is bloated up to 80% of its Roche lobe[3](p8)[4](p4) and brightly glows with a thermal luminosity of about 10 solar luminosity,[lower-alpha 1] thereby accounting for much of the system's optical brightness.[4](pp1, 4)[2](p1) As a result of bloating, the companion attains a low density likely around 10 g/cm3 (with significant uncertainty due to the system's unknown distance from Earth),[2](p11) making it susceptible to tidal deformation by the pulsar.[3](p12)

The companion's pulsar-facing irradiated hemisphere is continuously heated up to a temperature of 6,200 K, whereas the companion's unirradiated hemisphere experiences a uniform[2](p4) temperature of 3,000 K.[4](p4) This hemispherical temperature difference corresponds to a difference in hemisphere luminosities, which in turn causes significant variability in apparent brightness as the companion rotates around the pulsar.[7](p4)[3](p8) This brightness variability is demonstrated in PSR J0952–0607's optical light curve, which exhibits an amplitude greater than one magnitude.[2](p4)

Mass

PSR J0952–0607 has a mass of 2.35±0.17 M☉, making it the most massive neutron star known (As of 2022).[4] The pulsar likely acquired most of its mass by accreting up to 1 M☉ of lost material from its companion.[4](p5)

Rotation and age

PSR J0952–0607 rotates at a frequency of 707 Hz (1.41 ms period), making it the second-fastest-spinning pulsar known, and the fastest-spinning pulsar that is located in the Milky Way.[7][5] Assuming a standard neutron star radius of 10 km (6.2 mi),[3](p11) the equator of PSR J0952–0607 rotates at a tangential velocity over 44,400 km/s (27,600 mi/s)—about 14% the speed of light.[12] Based on 7 years of precise pulsation timing data from gamma-ray and radio observations, the pulsar's rotation period is estimated to be slowing down at a spin-down rate less than 4.6×10−21 seconds per second, corresponding to a characteristic age of 4.9 billion years.[3](p11)

Magnetic field

Measurements of PSR J0952–0607's spin-down rate show that the pulsar has a remarkably weak surface magnetic field strength of 6.1×107 gauss (6.1×103 T), placing it among the 10 weakest pulsar magnetic fields known (As of 2022).[4](p1) For context, ordinary pulsar magnetic fields usually lie on the order of teragauss (1×1012 G, 1.0×108 T), over 10,000 times greater than that of PSR J0952–0607.[13][4](p1) Other millisecond pulsars exhibit similarly weak magnetic fields, hinting at a common albeit unknown mechanism in these types of systems;[3](p2) possible explanations range from accreted matter burying the pulsar's surface magnetic field to heat-driven evolution of the pulsar's solid crust.[13](pp1–2)[4](p1)

Gamma-ray emissions

PSR J0952–0607 appears very faint in gamma-rays and was not detected in July 2011.[10][3](p2)

See also

Notes

  1. ↑ 1.0 1.1 Luminosity converted from erg/s to L☉, given 3.81+0.46
    −0.43    ×1034 erg/s     from Romani et al. (2022)[4] and the solar luminosity L☉ = 3.826×1033 erg/s.
  2. ↑ 2.0 2.1 Orbital semi-major axis calculated with Kepler's Third Law: [math]\displaystyle{ a = \sqrt[3]{\frac{GMT^2}{4\pi^2}} }[/math] given primary mass [math]\displaystyle{ M }[/math] = 2.35 M☉ and orbital period [math]\displaystyle{ T }[/math] = 6.42 h.[4] Nieder et al. (2019) determined a minimum projected semi-major axis of 0.0626670 light seconds (18787 km) from gamma-ray and radio pulsation timing.[3](p6)

References

  1. ↑ 1.0 1.1 "PSR J0952-0607 -- Pulsar". SIMBAD. Centre de données astronomiques de Strasbourg. https://simbad.u-strasbg.fr/simbad/sim-id?Ident=PSR+J0952-0607. Retrieved 26 July 2022. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Draghis, Paul; Romani, Roger W.; Filippenko, Alexei V.; Brink, Thomas G.; Zheng, WeiKang; Halpern, Jules P.; Fernando, Camilo (September 2019). "Multiband Optical Light Curves of Black-widow Pulsars". The Astrophysical Journal 883 (1): 13. doi:10.3847/1538-4357/ab378b. 108. Bibcode: 2019ApJ...883..108D. 
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 Nieder, L.Expression error: Unrecognized word "etal". (September 2019). "Detection and Timing of Gamma-Ray Pulsations from the 707 Hz Pulsar J0952-0607". The Astrophysical Journal 883 (1): 17. doi:10.3847/1538-4357/ab357e. 42. Bibcode: 2019ApJ...883...42N. 
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 Romani, Roger W.; Kandel, D.; Filippenko, Alexei V.; Brink, Thomas G.; Zheng, WeiKang (August 2022). "PSR J0952-0607: The Fastest and Heaviest Known Galactic Neutron Star". The Astrophysical Journal Letters 934 (2): 6. doi:10.3847/2041-8213/ac8007. L18. Bibcode: 2022ApJ...934L..17R. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 Reddy, Francis (5 September 2017). "'Extreme' Telescopes Find the Second-fastest-spinning Pulsar". NASA. https://www.nasa.gov/feature/goddard/2017/extreme-telescopes-find-second-fastest-pulsar. Retrieved 26 July 2022. 
  6. ↑ 6.0 6.1 6.2 Sanders, Robert (26 July 2022). "Heaviest neutron star to date is a 'black widow' eating its mate". Berkeley News (University of California Berkeley). https://news.berkeley.edu/2022/07/26/heaviest-neutron-star-to-date-is-a-black-widow-eating-its-mate/. Retrieved 26 July 2022. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 Bassa, C. G.Expression error: Unrecognized word "etal". (September 2017). "LOFAR Discovery of the Fastest-spinning Millisecond Pulsar in the Galactic Field". The Astrophysical Journal Letters 846 (2): 7. doi:10.3847/2041-8213/aa8400. L20. Bibcode: 2017ApJ...846L..20B. 
  8. ↑ 8.0 8.1 8.2 Roberts, Mallory S. E. (March 2013). "Surrounded by spiders! New black widows and redbacks in the Galactic field". Proceedings of the International Astronomical Union 291: 127–132. doi:10.1017/S174392131202337X. Bibcode: 2013IAUS..291..127R. https://articles.adsabs.harvard.edu/pdf/2013IAUS..291..127R. 
  9. ↑ Ho, Wynn C. G.; Heinke, Craig O.; Chugunov, Andrey I. (September 2019). "XMM-Newton Detection and Spectrum of the Second Fastest Spinning Pulsar PSR J0952-0607". The Astrophysical Journal 882 (2): 7. doi:10.3847/1538-4357/ab3578. 128. Bibcode: 2019ApJ...882..128H. 
  10. ↑ 10.0 10.1 Kohler, Susanna (11 December 2019). "An Extreme Pulsar Seen in Gamma Rays". AAS Nova Highlights (American Astronomical Society). Bibcode: 2019nova.pres.6048K. https://aasnova.org/2019/12/11/an-extreme-pulsar-seen-in-gamma-rays/. Retrieved 26 July 2022. 
  11. ↑ Abdollahi, S.Expression error: Unrecognized word "etal". (March 2020). "Fermi Large Area Telescope Fourth Source Catalog". The Astrophysical Journal Supplement Series 247 (1): 37. doi:10.3847/1538-4365/ab6bcb. 33. Bibcode: 2020ApJS..247...33A. 
  12. ↑ Starr, Michelle (24 September 2019). "Astronomers Detect Gamma Rays From an Extreme Pulsar Spinning 707 Times Per Second". ScienceAlert. https://www.sciencealert.com/this-extreme-pulsar-spins-707-times-per-second-and-it-s-spitting-out-gamma-rays. Retrieved 27 July 2022. 
  13. ↑ 13.0 13.1 Mukherjee, Dipanjan (September 2017). "Revisiting Field Burial by Accretion onto Neutron Stars". Journal of Astrophysics and Astronomy 38 (3): 10. doi:10.1007/s12036-017-9465-6. 48. Bibcode: 2017JApA...38...48M. https://www.ias.ac.in/article/fulltext/joaa/038/03/0048. 



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