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Register a new userSpecial supernova signature from BH-NS/BH progenitor systems
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The gravitational-wave detection by the LIGO-Virgo scientific collaboration shows that the black hole and neutron star (BH-NS) or BH-BH systems with a BH mass of tens of solar masses widely exist in the universe. Two main types of scenarios have been invoked for the formation of BH-NS/BH systems, including isolated binary evolution in galactic fields and dynamical interactions in dense environments. Here we propose that if the BH-NS/BH systems are formed from isolated binary evolution, the supernova (SN) signal associated with the second core collapse would show some identifiable features, due to the accretion feedback from the companion BH. Depending on the binary properties, we show that the SN lightcurve could present a sharp peak around $sim10$ days, with luminosity even at the level of the super luminous SNe ( e.g. $sim10^{44}~rm erg~s^{-1}$) or present a plateau feature lasting for several tens of days with regular luminosity of core collapse SNe. Comparing the event rate density of these special SN signals with the event rate density of LIGO-Virgo detected BH-NS/BH systems could help to distinguish the BH-NS/BH formation channel.
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We argue that the Black Hole-Neutron Star (BH-NS) binaries are the natural astrophysical probes of quantum gravity in the context of the new era of multi-messenger astronomy. In particular, we discuss the observable effect of enhanced black-hole mass loss in a BH-NS binary, due to the presence of an additional length scale tied to the intrinsic non-commutativity of quantum spacetime in quantum gravity.
The LIGO/Virgo collaboration has reported 50 BH-BH mergers and 8 additional candidates recovered from digging deeper into the detectors noise. Majority of these mergers have low effective spins pointing toward low BH spins and efficient angular momentum transport in massive stars as proposed by several models (e.g., Tayler-Spruit magnetic dynamo or Fuller model). However, out of these 58 mergers, 7 are consistent with having high effective spin parameter (chi_eff>0.3). Additionally, 2 out of these 7 events seem to have high effective spins sourced from the high spin of a primary (more massive) BH. The most extreme merger has very high primary BH dimensionless spin (a_1=0.9). These particular observations may be potentially used to discriminate between the isolated binary and dynamical globular cluster BH-BH formation channels. It may seem that high BH spins point to the dynamical origin if stars have efficient angular momentum transport and form low-spinning BHs. Then dynamical formation is required to produce second and third generations of BH-BH mergers that typically produce high-spinning BHs. Here we show that isolated binary BH-BH formation channel can naturally reproduce such highly spinning BHs. Our models start with efficient angular momentum transport in massive stars that is needed to reproduce majority of BH-BH mergers with low effective spins. However, some massive binaries are subject to strong tidal spin-up allowing for the formation of moderate fraction (~10%) of BH-BH mergers with high effective spins (chi_eff>0.4-0.5). Moreover, binary evolution can produce small fraction (~1%) of BH-BH mergers with almost maximally spinning primary BHs ($a_1>0.9$). Therefore, the formation scenario of those unusual BH-BH mergers remains unresolved.
In the population synthesis simulations of Pop III stars, many BH (Black Hole)-BH binaries with merger time less than the age of the Universe $(tau_{rm H})$ are formed, while NS (Neutron Star)-BH binaries are not. The reason is that Pop III stars have no metal so that no mass loss is expected. Then, in the final supernova explosion to NS, much mass is lost so that the semi major axis becomes too large for Pop III NS-BH binaries to merge within $tau_{rm H}$. However it is almost established that the kick velocity of the order of $200-500{rm~ km~s^{-1}}$ exists for NS from the observation of the proper motion of the pulsar. Therefore, the semi major axis of the half of NS-BH binaries can be smaller than that of the previous argument for Pop III NS-BH binaries to decrease the merging time. We perform population synthesis Monte Carlo simulations of Pop III NS-BH binaries including the kick of NS and find that the event rate of Pop III NS-BH merger rate is $sim 1 {rm Gpc^{-3} yr^{-1}}$. This suggests that there is a good chance of the detection of Pop III NS-BH mergers in O2 of Advanced LIGO and Advanced Virgo from this autumn.
While an axion-clouded black hole (BH) encounters a pulsar (PSR) or has a PSR companion, a gravitational molecule can be formed. In such a system, the axion cloud evolves at the binary hybrid orbitals, as it happens at microscopic level to electron cloud in a chemical molecule. To demonstrate this picture, we develop a semi-analytical formalism using the method of linear combination of atomic orbitals with an adiabatic approximation. An oscillating axion-cloud profile and a perturbed binary rotation, together with unique and novel detection signals, are then predicted. Remarkably, the proposed PSR timing and polarization observables, namely the oscillation of periastron time shift and the birefringence with multiple modulations, correlate in pattern, and thus can be properly combined to strengthen the detection.
Precessing black hole-neutron star (BH-NS) binaries produce a rich gravitational wave signal, encoding the binarys nature and inspiral kinematics. Using the lalinference_mcmc Markov-chain Monte Carlo parameter estimation code, we use two fiducial examples to illustrate how the geometry and kinematics are encoded into the modulated gravitational wave signal, using coordinates well-adapted to precession. Even for precessing binaries, we show the performance of detailed parameter estimation can be estimated by effective estimates: comparisons of a prototype signal with its nearest neighbors, adopting a fixed sky location and idealized two-detector network. We use detailed and effective approaches to show higher harmonics provide nonzero but small local improvement when estimating the parameters of precessing BH-NS binaries. That said, we show higher harmonics can improve parameter estimation accuracy for precessing binaries ruling out approximately-degenerate source orientations. Our work illustrates quantities gravitational wave measurements can provide, such as reliable component masses and the precise orientation of a precessing short gamma ray burst progenitor relative to the line of sight. Effective estimates may provide a simple way to estimate trends in the performance of parameter estimation for generic precessing BH-NS binaries in next-generation detectors. For example, our results suggest that the orbital chirp rate, precession rate, and precession geometry are roughly-independent observables, defining natural variables to organize correlations in the high-dimensional BH-NS binary parameter space.
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