The spin and orbit of the newly discovered pulsar IGR J17480-2446

Abstract

We present an analysis of the spin and orbital properties of the newly discovered accreting pulsar IGR J17480-2446, located in the globular cluster Terzan 5. Considering the pulses detected by the Rossi X-ray Timing Explorer at a period of 90.539645(2) ms, we derive a solution for the 21.27454(8) hr binary system. The binary mass function is estimated to be 0.021275(5) M , indicating a companion star with a mass larger than 0.4 M . The X-ray pulsar spins up while accreting at a rate of between 1.2 and 1.7 × 10 −12 Hz s −1 , in agreement with the accretion of disc matter angular momentum given the observed luminosity. We also report the detection of pulsations at the spin period of the source during a Swift observation performed ∼2 d before the beginning of the RXTE coverage. Assuming that the inner disc radius lies in between the neutron star radius and the corotation radius while the source shows pulsations, we estimate the magnetic field of the neutron star to be within ∼2 × 10 8 G and ∼2.4 × 10 10 G. From this estimate, the value of the spin period and of the observed spin-up rate, we associate this source with the still poorly sampled population of slow, mildly recycled, accreting pulsars.

A comparison of broad iron emission lines in archival data of neutron star LMXBs

“…Furthermore, magnetic field estimates based on the inner disk radius measured from the Fe lines in two pulsars, SAXJ1808.4−3658 (Cackett et al 2009;Papitto et al 2009) and IGR J17480-2446 in the globular cluster Terzan 5 (Miller et al 2011;Papitto et al 2011), are consistent with the magnetic field estimates determined from timing methods. Thus, the measured inner disk radii are consistent with expectations.…”

“…In many cases, relativistic line shapes are found with inner disk radii, measured using relativistic line models, close to expectations for the stellar radius. Moreover, neutron star magnetic field strength estimates based on the inner disk radius for two accreting pulsars are consistent with measurements from timing (Cackett et al 2009;Miller et al 2011;Papitto et al 2009Papitto et al , 2011. Gas spectrometer observations have also revealed relativistic lines in 4U 1705−44 (Piraino et al 2007;Lin et al 2010).…”

The Slowest Spinning X-Ray Pulsar in an Extragalactic Globular Cluster

“…For brevity we denote the pulsar XB091D after its host globular cluster designation. This is the first persistently accreting X-ray pulsar hosting a neutron star detected in M31 2 , and it also has the longest period among all known pulsars (rotation-powered and accreting) in globular clusters, being more than an order of magnitude slower than the mildly recycled accreting pulsar from Terzan 5 globular cluster (Papitto et al 2011). We note that this pulsar has also recently been detected by Esposito et al (2016), but these authors interpret the nature of this source quite differently.…”

“…We employ same approach as in Papitto et al (2011) to estimate the lower and upper limits for the magnetic field of the neutron star given that it persistently accretes matter from the companion. It is reasonable to assume in this case that the accretion disk is truncated at the radius R in between the radius of the neutron star R NS and the corotation radius R C :…”

Unbeamed tidal disruption events at hard X-rays

“…The flare onset occurred after 2010 Oct. 01, peaked on 2010 Oct. 14, and probably lasted for about 72 days (up to 108 days). The flare, with a position consistent with the centre of the globular cluster Terzan 5, was detected by INTEGRAL (Bordas et al 2010) and allowed the discovery of the new accreting pulsar IGR J17480-2446 (Papitto et al 2011). The second brightest flare in Terzan 5 peaked on 2012 July 18 and corresponds to a Type-I burst, which led to the discovery of the new accreting neutron star Terzan 5 X-3 (Bahramian et al 2014).…”