Prospects of detection of subsolar mass primordial black hole and white dwarf binary mergers

The subsolar mass primordial black hole (PBH) attracts attention as robust evidence of its primordial origin against the astrophysical black hole. Not only with themselves, PBHs can also form binaries with ordinary astrophysical objects, catching them by gravitational wave (GW) bremsstrahlung. We discuss the detectability of the inspiral GWs from binaries consisting of a PBH and a white dwarf (WD) by using space-borne gravitational wave interferometers like DECIGO. The conservative assessment shows the expected event number in three years by DECIGO is $\mathcal{O}(10^{-6})$ for $M_\mathrm{PBH} \sim 0.1M_\odot$. Possible enhancement mechanisms of WD-PBH binary formation may amplify this event rate. We discuss how large enhancement associated with WDs is required to detect WD-PBH merger events without violating the existing constraints on the PBH-PBH merger by the ground-based detector.Comment: 13 pages, 10 figure

Primordial black holes and gravitational waves induced by exponential-tailed perturbations

Primordial black holes (PBHs) whose masses are in $\sim[10^{-15}M_\odot,10^{-11}M_{\odot}]$ have been extensively studied as a candidate of whole dark matter (DM). One of the probes to test such a PBH-DM scenario is scalar-induced stochastic gravitational waves (GWs) accompanied with the enhanced primordial fluctuations to form the PBHs with frequency peaked in the mHz band being targeted by the LISA mission. In order to utilize the stochastic GWs for checking the PBH-DM scenario, it needs to exactly relate the PBH abundance and the amplitude of the GWs spectrum. Recently in Kitajima et al., the impact of the non-Gaussianity of the enhanced primordial curvature perturbations on the PBH abundance has been investigated based on the peak theory, and they found that a specific non-Gaussian feature called the exponential tail significantly increases the PBH abundance compared with the Gaussian case. In this work, we investigate the spectrum of the induced stochastic GWs associated with PBH DM in the exponential-tail case. In order to take into account the non-Gaussianity properly, we employ the diagrammatic approach for the calculation of the spectrum. We find that the amplitude of the stochastic GW spectrum is slightly lower than the one for the Gaussian case, but it can still be detectable with the LISA sensitivity. We also find that the non-Gaussian contribution can appear on the high-frequency side through their complicated momentum configurations. Although this feature emerges under the LISA sensitivity, it might be possible to obtain information about the non-Gaussianity from GW observation with a deeper sensitivity such as the DECIGO mission.Comment: 33 pages, 19 figure

Associations between Supper Timing and Mortality from Cardiovascular Disease among People with and without Hypertension

Inui, Tomoki, Sakaniwa, Ryoto, Shirai, Kokoro, et al. Associations between Supper Timing and Mortality from Cardiovascular Disease among People with and without Hypertension : . Journal of Atherosclerosis and Thrombosis advpub, (2024); https://doi.org/10.5551/jat.64192 .Aim: Less is known about the impact of supper time on cardiovascular disease (CVD) risk among hypertensives and nonhypertensives. We aimed to explore this issue in a cohort study. Methods: We analyzed the data of 72,658 participants (15,386 hypertensives and 57,272 nonhypertensives) aged 40–79 years without a history of CVD at baseline (1988–1990) under the Japan Collaborative Cohort study. Supper time was assessed based on self-reported questionnaires categorized as before 17:00, between 17:00 and 20:00, after 20:00, irregular supper time, and reference supper time (17:00–20:00). Hazard ratios (HRs) and 95% confidence intervals (95% CI) of CVD mortality were calculated according to supper time after adjustment for potential confounders, stratified by hypertensive status and age group (＜65 and ≥ 65 years).Results: During a median of 19.4 years of follow-up, 4,850 CVD deaths were recorded. Compared with the reference time, the risk of CVD mortality was higher for irregular supper time for the total population, either hypertensives or nonhypertensives, more specifically hypertensives aged ≥ 65 years; the multivariable HR (95% CI) of CVD mortality in the total population was 1.28 (1.11–1.50, P＜0.01). The supper time of ＞20:00 tended to be associated with the higher risk only for hypertensives; the multivariable HR was 1.39 (0.98–1.96, P=0.06). Conclusion: Irregular supper time was associated with an increased risk of CVD mortality. Supper timing could be a surrogate marker for CVD risk