Hypercritical accretion scenario in central compact objects accompanied with an expected neutrino burst

Abstract

The measurement of the period and period derivative, and the canonical model of dipole radiation have provided a method to estimate the low superficial magnetic fields in the so-called Central Compact Objects (CCOs). In the present work, a scenario is introduced in order to explain the magnetic behavior of such CCOs. Based on magnetohydrodynamic simulations of the post core-collapse supernova phase during the hypercritical accretion episode, we argue that the magnetic field of a newborn neutron star could have been early buried. During this phase, thermal neutrinos are created mainly by the pair annihilation, plasmon decay, photo-neutrino emission and other processes. We study the dynamics of these neutrinos in this environment and also estimate the number expected of the neutrino events with their flavor ratios on Earth. The neutrino burst is the only viable observable that could provide compelling evidence of the hypercritical phase and therefore, the hidden magnetic field mechanism as the most favorable scenario to explain the anomalous low magnetic fields estimated for CCOs.

X-ray bounds on cooling, composition, and magnetic field of the Cassiopeia A neutron star and young central compact objects

“…One can also consider the three (older) CCOs with a measured spin period and spin period derivative that indicate a global dipolar magnetic field strength of 3 × 10 10 − 10 11 G. Two of these three have hot spot emission that might indicate much stronger localized fields (Gotthelf et al 2010;Shabaltas & Lai 2012;Bogdanov 2014), while the third undergoes spin frequency glitches, which are phenomena seen in many young pulsars with stronger fields (Gotthelf & Halpern 2020). Magnetic field evolution in the above CCOs can follow from a scenario where a strong global magnetic field at birth is submerged below the neutron star surface and gradually diffuses to the surface with an emergence timescale that depends on burial depth and can be ∼ 1000 yr (Ho 2011(Ho , 2015Viganò & Pons 2012;Torres-Forné et al 2016;Fraija et al 2018;Gourgouliatos et al 2020) Previous and future searches for CCOs and their descendants (Gotthelf et al 2013b;Bogdanov et al 2014;Luo et al 2015;Pires 2018) will be important for revealing where the CCO class sits within the general population of neutron stars. As we show here, studies of CCOs can potentially provide valuable insights into the surface composition, magnetic field, and evolution of neutron stars.…”

Gravitational Wave Radiation from Newborn Accreting Magnetars

“…The fall-back matter accreted onto a newborn NS may also result in the decrease of the NS's dipole magnetic field by burying it into the stellar crust (Muslimov & Page 1995;Geppert et al 1999). The burial processes of dipole field have been investigated through MHD simulations of fall-back accretion onto NSs produced in core-collapse supernovae (e.g., Bernal et al 2013;Torres-Forné et al 2016;Fraija et al 2018). The results show that the accretion rate plays a crucial role in determining whether the dipole field of a newborn NS could be completely submerged into the crust (Bernal et al 2013;Torres-Forné et al 2016) The second phenomenological model (Model II) is accreted mass-dominated, which is established by analogy to the case of NSs in XRBs.…”

“…It is also possible that fall-back accretion may lead to decay of the surface dipole magnetic field of the newborn magnetar, as the dipole field would be buried into the NS crust by the accreted matter (Muslimov & Page 1995;Geppert et al 1999;Shabaltas & Lai 2012;Bernal et al 2013;Torres-Forné et al 2016;Fraija et al 2018). The field burial scenario has been invoked to explain the low dipole magnetic fields of central compact objects (CCOs) in supernova remnants (Shabaltas & Lai 2012;Bernal et al 2013;Torres-Forné et al 2016;Fraija et al 2018) and NSs in X-ray binaries (XRBs) (e.g., Shibazaki et al 1989;Melatos & Phinney 2001;Payne & Melatos 2004;Zhang & Kojima 2006;Priymak et al 2011;Haskell et al 2015;Mukherjee 2017;Suvorov & Melatos 2019), though the accretion rates in the two cases differ remarkably.…”

“…It is also possible that fall-back accretion may lead to decay of the surface dipole magnetic field of the newborn magnetar, as the dipole field would be buried into the NS crust by the accreted matter (Muslimov & Page 1995;Geppert et al 1999;Shabaltas & Lai 2012;Bernal et al 2013;Torres-Forné et al 2016;Fraija et al 2018). The field burial scenario has been invoked to explain the low dipole magnetic fields of central compact objects (CCOs) in supernova remnants (Shabaltas & Lai 2012;Bernal et al 2013;Torres-Forné et al 2016;Fraija et al 2018) and NSs in X-ray binaries (XRBs) (e.g., Shibazaki et al 1989;Melatos & Phinney 2001;Payne & Melatos 2004;Zhang & Kojima 2006;Priymak et al 2011;Haskell et al 2015;Mukherjee 2017;Suvorov & Melatos 2019), though the accretion rates in the two cases differ remarkably. Interestingly, the observed multiband electromagnetic (EM) counterparts (the kilonova AT2017gfo and the candidate X-ray flare detected at 155 days after the merger) of the first BNS merger event detected, GW170817 (Abbott et al 2017a;2017b), indicate that the merger remnant is probably a long-lived massive NS with strong toroidal field and weak dipole field (Li et al 2018;Geng et al 2018;Yu et al 2018;Piro et al 2019;Lü et al 2019b), which may be simply the result of field burial caused by fallback accretion (Yu et al 2018).…”

On the overall properties of young neutron stars: an application to the Crab pulsar

“…In addition, Shabaltas and Lai (2012) explored the idea that a substantial sub-surface magnetic field exists in the crust of the young neutron star in Kes 79, which produces diffuse hot spots on the stellar surface due to anisotropic heat conduction, giving rise to the observed X-ray pulsations. Recently, Bernal et al (2010), Bernal et al (2013), Fraija et al (2014), Fraija and Bernal (2015), Fraija et al (2018), and Dehman et al (2023) performed 2D-3D magnetohydrodynamic (MHD) simulations with detailed physical components, showing that the magnetic field is indeed submerged under the stellar surface of such objects, regardless of their initial configuration or its strength.…”