Did NANOGrav see a signal from primordial black hole formation?

We revisit the system consisting of a neutron star that harbors a small, possibly primordial, black hole at its center, focusing on a nonspinning black hole embedded in a nonrotating neutron star. Extending earlier treatments, we provide an analytical treatment describing the rate of secular accretion of the neutron star matter onto the black hole, adopting the relativistic Bondi accretion formalism for stiff equations of state that we presented elsewhere. We use these accretion rates to sketch the evolution of the system analytically until the neutron star is completely consumed. We also perform numerical simulations in full general relativity for black holes with masses up to nine orders of magnitude smaller than the neutron star mass, including a simulation of the entire evolution through collapse for the largest black hole mass. We construct relativistic initial data for these simulations by generalizing the black hole puncture method to allow for the presence of matter, and evolve these data with a code that is optimally designed to resolve the vastly different length scales present in this problem. We compare our analytic and numerical results, and provide expressions for the lifetime of neutron stars harboring such endoparasitic black holes.

show abstract

“…where we have used (17) in the last equality. The corresponding accretion timescale is then given by…”

Section: Case Ii: M(ra) ∼ Mbh -Dynamical Accretionmentioning

confidence: 99%

“…In particular, these arguments have been used to establish limits in the mass range of 10 −15 M M BH 10 −9 M [5], which is otherwise only poorly constrained (cf. [13][14][15]; see also [16,17] and references therein for constraints arising from gravitational wave observations).…”

Section: Introductionmentioning

confidence: 99%

Accretion onto a small black hole at the center of a neutron star

2021

View full text Add to dashboard Cite

show abstract

“…Assuming that this signal is due to a stochastic background of GW, there have been various suggestions for their origin. These include mergers of super-massive black holes [41][42][43] or scenarios involving cosmic string [44][45][46][47], primordial black holes [48][49][50][51][52][53], phase transitions [54][55][56] and magneto-hydrodynamics turbulence during the QCD phase transition [57] and others [58][59][60][61][62][63]. In this work, we focus on the GW spectrum produced in our model of inflationary magnetogenesis where reheating takes place around QCD epoch ( 150 MeV) and compare the predicted signals with those reported by NANOGrav Collaboration.…”

Section: Introductionmentioning

confidence: 99%

Constraining models of inflationary magnetogenesis with NANOGrav data

Sharma

2022

Phys. Rev. D

View full text Add to dashboard Cite

Generation of magnetic field during inflation can explain its presence over a wide range of scales in the Universe. In Ref. [1], we proposed a model to generate these fields during inflation. These fields have nonzero anisotropic stress which lead to the generation of a stochastic background of gravitational waves (GW) in the early universe. Here we show that for a scenario of magnetogenesis where reheating takes place around QCD epoch, this stochastic GW background lies in the 95% confidence region of the GW signal probed by NANOGrav collaboration. This is the case when the generated electromagnetic field (EM) energy density is 3 − 10% of the background energy density at the end of reheating. For this case, the values of magnetic field strength B0 ∼ (3.8 − 6.9) × 10 −11 G and its coherence length ∼ 30 kpc at the present epoch. These values are for the models in which EM fields are of nonhelical nature. For the helical nature of the fields, these values are B0 ∼ (1.1 − 1.9) × 10 −9 G and its coherence length ∼ 0.8 Mpc.

show abstract

“…In Refs. [59][60][61][62][63] the connection between the NANOGrav results and the primordial blackholes is investigated. The future gravitational wave experiments such as LISA [64,65], DECIGO [66,67], and BBO [68][69][70], may probe smaller mass ranges of primordial blackholes.…”

Section: Introductionmentioning

confidence: 99%

Primordial blackholes from Gauss-Bonnet-corrected single field inflation

Kawai,

Kim

2021

Preprint

View full text Add to dashboard Cite

Primordial blackholes formed in the early Universe via gravitational collapse of over-dense regions may contribute a significant amount to the present dark matter relic density. Inflation provides a natural framework for the production mechanism of primordial blackholes. For example, single field inflation models with a fine-tuned scalar potential may exhibit a period of ultra-slow-roll, during which the curvature perturbation may be enhanced to become seeds of the primordial blackholes formed as the corresponding scales reenter the horizon. In this work we propose an alternative mechanism for the primordial blackhole formation. We consider a model in which a scalar field is coupled to the Gauss-Bonnet term, and show that primordial blackholes may be seeded when a scalar potential term and the Gauss-Bonnet coupling term are nearly balanced. Large curvature perturbation in this model not only leads to the production of primordial blackholes but it also sources gravitational waves at the second order. We calculate the present density parameter of the gravitational waves and discuss the detectability of the signals by comparing them with sensitivity bounds of future gravitational wave experiments.

show abstract

Did NANOGrav see a signal from primordial black hole formation?

Cited by 33 publications

References 73 publications

Accretion onto a small black hole at the center of a neutron star

Accretion onto a small black hole at the center of a neutron star

Constraining models of inflationary magnetogenesis with NANOGrav data

Primordial blackholes from Gauss-Bonnet-corrected single field inflation

Contact Info

Product

Resources

About