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1. chinaXiv:201609.01022 [pdf]

Versatile Directional Searches for Gravitational Waves with Pulsar Timing Arrays

D. R. Madison(1; 2); X.-J. Zhu(3; 4); G. Hobbs; W. Coles; R. M. Shannon(4; 6); J. Wang; C. Tiburzi(8; 9; 10; 11); R. N. Manchester; M. Bailes; N. D. R. Bhat; S. Burke-Spolaor; S.Dai; J. Dempsey; M. Keith
分类: 物理学 >> 核物理学

By regularly monitoring the most stable millisecond pulsars over many years, pulsar timing arrays (PTAs) are positioned to detect and study correlations in the timing behaviour of those pulsars. Gravitational waves (GWs) from supermassive black hole binaries (SMBHBs) are an exciting potentially detectable source of such correlations. We describe a straight-forward technique by which a PTA can be "phased-up" to form time series of the two polarisation modes of GWs coming from a particular direction of the sky. Our technique requires no assumptions regarding the time-domain behaviour of a GW signal. This method has already been used to place stringent bounds on GWs from individual SMBHBs in circular orbits. Here, we describe the methodology and demonstrate the versatility of the technique in searches for a wide variety of GW signals including bursts with unmodeled waveforms. Using the first six years of data from the Parkes Pulsar Timing Array, we conduct an all-sky search for a detectable excess of GW power from any direction. For the lines of sight to several nearby massive galaxy clusters, we carry out a more detailed search for GW bursts with memory, which are distinct signatures of SMBHB mergers. In all cases, we find that the data are consistent with noise.

提交时间: 2016-09-14 点击量218下载量126 评论 0

2. chinaXiv:201605.00849 [pdf]

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope Quasar Survey: Quasar Properties From The First Data Release

YanLi Ai
分类: 天文学 >> 天体物理学

We present preliminary results of the quasar survey in the Large Sky Area Multi-Object Fiber SpectroscopicTelescope (LAMOST) first data release (DR1), which includes the pilot survey and the first year of the regularsurvey. There are 3921 quasars reliably identified, among which 1180 are new quasars discovered in the survey.These quasars are at low to median redshifts, with a highest z of 4.83. We compile emission line measurementsaround the Hα, Hβ, Mg II, and C IV regions for the new quasars. The continuum luminosities are inferred fromSDSS photometric data with model fitting, as the spectra in DR1 are non-flux-calibrated. We also compile the virialblack hole mass estimates, with flags indicating the selection methods, and broad absorption line quasars. Thecatalog and spectra for these quasars are also available. Of the 3921 quasars, 28% are independently selected withop

提交时间: 2016-05-05 点击量1230下载量399 评论 0

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