Gravitational waves from an SMBH binary in M87

In this paper, we study gravitational-wave (GW) emission from a hypothetical supermassive black-hole (SMBH) binary at the center of M87. The existence of a SMBH other than that usually identified with the central AGN is a possible explanation for the observed displacement ($\sim O(1)~{\rm pc}$) between the AGN and the galactic centroid, and it is reasonable to assume consid- ering the evolution of SMBHs through galaxy mergers. Because the period of the binary and the resulting GWs is much longer than the observational time span, we calculate the variation of the GW amplitude, rather than the amplitude itself. We investigate the dependence on the orbital elements and the second BH mass taking the observational constraints into account. The frequency of the GWs is too low to be detected with the conventional pulsar timing array and we propose a new method to detect such low-frequency GWs with the distribution func- tion of pulsar spin-down rates. Although the GWs from a SMBH binary which explains the observed displacement is extremely hard to be detected even with the new method, GWs are still a useful way to probe the M87 center.Comment: 5 pages, 6 figures. Accepted for Publications of the Astronomical Society of Japa

Artificial neural networks for selection of pulsar candidates from the radio continuum surveys

Pulsar search with time-domain observation is very computationally expensive and data volume will be enormous with the next generation telescopes such as the Square Kilometre Array. We apply artificial neural networks (ANNs), a machine learning method, for efficient selection of pulsar candidates from radio continuum surveys, which are much cheaper than time-domain observation. With observed quantities such as radio fluxes, sky position and compactness as inputs, our ANNs output the "score" that indicates the degree of likeliness of an object to be a pulsar. We demonstrate ANNs based on existing survey data by the TIFR GMRT Sky Survey (TGSS) and the NRAO VLA Sky Survey (NVSS) and test their performance. Precision, which is the ratio of the number of pulsars classified correctly as pulsars to that of any objects classified as pulsars, is about 96$\%$. Finally, we apply the trained ANNs to unidentified radio sources and our fiducial ANN with five inputs (the galactic longitude and latitude, the TGSS and NVSS fluxes and compactness) generates 2,436 pulsar candidates from 456,866 unidentified radio sources. These candidates need to be confirmed if they are truly pulsars by time-domain observations. More information such as polarization will narrow the candidates down further.Comment: 11 pages, 13 figures, 3 tables, accepted for publication in MNRA

Discovery of Millisecond Pulsars in the Globular Cluster Omega Centauri

The globular cluster Omega Centauri is the most massive and luminous cluster in the Galaxy. The $\gamma$-ray source FL8Y J1326.7$-$4729 is coincident with the core of the cluster, leading to speculation that hitherto unknown radio pulsars or annihilating dark matter may be present in the cluster core. Here we report on the discovery of five millisecond pulsars in Omega Centauri following observations with the Parkes radio telescope. Four of these pulsars are isolated with spin periods of 4.1, 4.2, 4.6 and 6.8 ms. The fifth has a spin period of 4.8 ms and is in an eclipsing binary system with an orbital period of 2.1 hours. Deep radio continuum images of the cluster centre with the Australian Telescope Compact Array reveal a small population of compact radio sources making it likely that other pulsars await discovery. We consider it highly likely that the millisecond pulsars are the source of the $\gamma$-ray emission. The long-term timing of these pulsars opens up opportunities to explore the dynamics and interstellar medium of the cluster.Comment: 8 pages, 2 figures, accepted for publication in the Astrophysical Journal Letter

CPAPアドヒランスの予測因子としてのCPAP装着下覚醒時の呼吸不規則性

BACKGROUND AND OBJECTIVE: The standard therapy for obstructive sleep apnoea (OSA) is continuous positive airway pressure (CPAP) therapy. However, long-term adherence remains at ~50% despite improvements in behavioural and educational interventions. Based on prior work, we explored whether regularity of breathing during wakefulness might be a physiologic predictor of CPAP adherence. METHODS: Of the 117 consecutive patients who were diagnosed with OSA and prescribed CPAP, 79 CPAP naïve patients were enrolled in this prospective study. During CPAP initiation, respiratory signals were collected using respiratory inductance plethysmography while wearing CPAP during wakefulness in a seated position. Breathing regularity was assessed by the coefficient of variation (CV) for breath-by-breath estimated tidal volume (VT ) and total duration of respiratory cycle (Ttot). In a derivation group (n = 36), we determined the cut-off CV value which predicted poor CPAP adherence at the first month of therapy, and verified the validity of this predetermined cut-off value in the remaining participants (validation group; n = 43). RESULTS: In the derivation group, the CV for estimated VT was significantly higher in patients with poor adherence than with good adherence (median (interquartile range): 44.2 (33.4-57.4) vs 26.0 (20.4-33.2), P 34.0 confirmed to be predicting poor CPAP adherence (sensitivity, 0.78; specificity, 0.83). CONCLUSION: At the initiation of therapy, breathing regularity during wakefulness while wearing CPAP is an objective predictor of short-term CPAP adherence.博士（医学）・乙第1391号・平成29年3月15日© 2016 Asian Pacific Society of RespirologyThis is the peer reviewed version of the following article: Respirology Vol.22 No.2 p.386-393 (2017 Feb), which has been published in final form at http://dx.doi.org/10.1111/resp.12900. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving