Eight New Millisecond Pulsars in NGC 6440 and NGC 6441

By P. Freire, S. Ransom, S. Bégin, Ingrid Stairs, Jason W. T. Hessels, L. Frey, F. Camilo. 2007

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Motivated by the recent discovery of 30 new millisecond pulsars in Terzan 5, made using the Green Bank Telescope's S-band receiver and the Pulsar Spigot spectrometer, we have set out to use the same observing system in a systematic search for pulsars in other globular clusters. Here we report on the discovery of five new pulsars in NGC 6440 and three in NGC 6441; each cluster previously had one known pulsar. Using the most recent distance estimates to these clusters, we conclude that there are as many potentially observable pulsars in NGC 6440 and NGC 6441 as in Terzan 5. We present timing solutions for all of the pulsars in these globular clusters. Four of the new discoveries are in binary systems; one of them, PSR J1748–2021B (NGC 6440B), has a wide (Pb = 20.5 days) and eccentric (e = 0.57) orbit. This allowed a measurement of its rate of advance of periastron, ω̇ = 0.00391(18)° yr−1. If this is a purely relativistic effect, the total mass of this binary system is 2.92 ± 0.20 M☉ (1 σ) implying a median pulsar mass of 2.74 ± 0.21 M☉. There is a 1% probability that the inclination is low enough that pulsar mass is below 2 M☉, and 0.10% probability that it is between 1.20 and 1.44 M☉. If confirmed, this anomalously large mass would strongly constrain the equation of state for dense matter. The other highly eccentric binary, PSR J1750–37A, has e = 0.71, and ω̇ = 0.0055(3)° yr−1, implying a total system mass of 1.97 ± 0.15 M☉ and, along with the mass function, maximum and median pulsar masses of 1.65 and 1.26 M☉, respectively.

Subfields: Astronomy and Astrophysics, Oceanography

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Citations in the corpus

• Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo (2018, background): “While the existence and nature of this gap are still uncertain(Kreidberg et al. 2012), it is proposed to exist between the most massive neutron stars (Freire et al. 2008; Özel & Freire 2016; Margalit & Metzger 2017; 2.1–2.5 M ) and the lightest BHs (∼5 M ).”
• Testing Relativistic Gravity with Radio Pulsars (2014, background): “46M , which can also account for the high-mass candidates of [86, 87, 88].”
• Evidence for a maximum mass cut-off in the neutron star mass distribution and constraints on the equation of state (2017, background): “The other high-mass NS that one might suspect has a disproportionate impact on the inferred mmax is J17482021B6 (Freire et al. 2008a).”
• THE NEUTRON STAR MASS DISTRIBUTION (2010, background): “Many of NSs in globular clusters also show systematically higher masses (see Freire et al. 2008b).”
• Detecting gravitational wave emission from the known accreting neutron stars (2008, background): “The current record stands at 716 Hz (Hessels et al. 2006) and surveys in nearby globular clusters continue to reveal a paucity of rapid rotators (Ransom et al. 2005; Hessels et al. 2007; Freire et al. 2008).”
• NEUTRON STAR MASSES AND RADII FROM QUIESCENT LOW-MASS X-RAY BINARIES (2013, background): “…2 M⊙ , as perhaps indicated by the two black widow pulsar systems PSR B1957+20 (van Kerkwijk, Breton and Kulkarni 2011) and PSR J1311-3430 (Romani et al. 2012), as well as the binary pulsar J1748-2021B in NGC 6440 (Freire et al. 2008), the possibility of strange quark stars is strongly disfavored.”
• A population of gamma-ray emitting globular clusters seen with the Fermi Large Area Telescope (2010, background): “For NGC 6440, Freire et al. (2008) estimate that it may house as many pulsars as Terzan 5, a prediction that is compatible with our observations.”
• EARLY X-RAY AND OPTICAL AFTERGLOW OF GRAVITATIONAL WAVE BURSTS FROM MERGERS OF BINARY NEUTRON STARS (2012, background): “For example, the NS candidate in the X-ray binary 4U 1700-377 has a mass 2.44± 0.27M⊙ (Rawls et al. 2011), and the NS in the NS-WD binary PSR B1516+02B has a mass 2.08±0.19M⊙ (Freire et al. 2008).”
• Strange star equation of state fits the refined mass measurement of 12 pulsars and predicts their radii (2013, background): “1 IN T RO D U C T I O N High masses were found in different types of pulsar binaries, starting with some in globular clusters (Ransom et al. 2005; Freire et al. 2008a,b).”
• Precision Timing of PSR J0437–4715: An Accurate Pulsar Distance, a High Pulsar Mass, and a Limit on the Variation of Newton’s Gravitational Constant (2008, background): “Presently, only the pulsars NGC 6440B, Terzan 5 I and Terzan 5 J have predictedmasses higher than the typical value of 1.4M (Freire et al. 2008; Ransom et al. 2005); however, as discussed in more detail in x 5, such predictions do not represent objective mass estimates.”
• Shapiro delay measurement of a two solar mass neutron star (2010, methodology): “In addition, unlike statistical pulsar mass determinations based on measurement of the advance of periastron[19, 20, 21], pure Shapiro delay mass measurements involve no assumptions about classical contributions to periastron advance or the distribution of orbital inclinations.”
• ON THE MASS DISTRIBUTION AND BIRTH MASSES OF NEUTRON STARS (2012, unknown): “Freire et al. 2008a; 5.”