350 research outputs found
The PALFA Survey: Going to great depths to find radio pulsars
The on-going PALFA survey is searching the Galactic plane (|b| < 5 deg., 32 <
l < 77 deg. and 168 < l < 214 deg.) for radio pulsars at 1.4 GHz using ALFA,
the 7-beam receiver installed at the Arecibo Observatory. By the end of August
2012, the PALFA survey has discovered 100 pulsars, including 17 millisecond
pulsars (P < 30 ms). Many of these discoveries are among the pulsars with the
largest DM/P ratios, proving that the PALFA survey is capable of probing the
Galactic plane for millisecond pulsars to a much greater depth than any
previous survey. This is due to the survey's high sensitivity, relatively high
observing frequency, and its high time and frequency resolution. Recently the
rate of discoveries has increased, due to a new more sensitive spectrometer,
two updated complementary search pipelines, the development of online
collaborative tools, and access to new computing resources. Looking forward,
focus has shifted to the application of artificial intelligence systems to
identify pulsar-like candidates, and the development of an improved
full-resolution pipeline incorporating more sophisticated radio interference
rejection. The new pipeline will be used in a complete second analysis of data
already taken, and will be applied to future survey observations. An overview
of recent developments, and highlights of exciting discoveries will be
presented.Comment: Proceedings of IAUS 291 "Neutron Stars and Pulsars: Challenges and
Opportunities after 80 years", J. van Leeuwen (ed.); 6 pages, 4 figure
Applying hybrid clustering in pulsar candidate sifting with multi-modality for FAST survey
Pulsar search is always the basis of pulsar navigation, gravitational wave
detection and other research topics. Currently, the volume of pulsar candidates
collected by Five-hundred-meter Aperture Spherical radio Telescope (FAST) shows
an explosive growth rate that has brought challenges for its pulsar candidate
filtering System. Particularly, the multi-view heterogeneous data and class
imbalance between true pulsars and non-pulsar candidates have negative effects
on traditional single-modal supervised classification methods. In this study, a
multi-modal and semi-supervised learning based pulsar candidate sifting
algorithm is presented, which adopts a hybrid ensemble clustering scheme of
density-based and partition-based methods combined with a feature-level fusion
strategy for input data and a data partition strategy for parallelization.
Experiments on both HTRU (The High Time Resolution Universe Survey) 2 and FAST
actual observation data demonstrate that the proposed algorithm could
excellently identify the pulsars: On HTRU2, the precision and recall rates of
its parallel mode reach 0.981 and 0.988. On FAST data, those of its parallel
mode reach 0.891 and 0.961, meanwhile, the running time also significantly
decrease with the increment of parallel nodes within limits. So, we can get the
conclusion that our algorithm could be a feasible idea for large scale pulsar
candidate sifting of FAST drift scan observation
Predicting Pulsars from Imbalanced Dataset with Hybrid Resampling Approach
Pulsar stars, usually neutron stars, are spherical and compact objects containing a large quantity of mass. Each pulsar star possesses a magnetic field and emits a slightly different pattern of electromagnetic radiation which is used to identify the potential candidates for a real pulsar star. Pulsar stars are considered an important cosmic phenomenon, and scientists use them to study nuclear physics, gravitational waves, and collisions between black holes. Defining the process of automatic detection of pulsar stars can accelerate the study of pulsar stars by scientists. This study contrives an accurate and efficient approach for true pulsar detection using supervised machine learning. For experiments, the high time-resolution (HTRU2) dataset is used in this study. To resolve the data imbalance problem and overcome model overfitting, a hybrid resampling approach is presented in this study. Experiments are performed with imbalanced and balanced datasets using well-known machine learning algorithms. Results demonstrate that the proposed hybrid resampling approach proves highly influential to avoid model overfitting and increase the prediction accuracy. With the proposed hybrid resampling approach, the extra tree classifier achieves a 0.993 accuracy score for true pulsar star prediction
SETI science working group report
This report covers the initial activities and deliberations of a continuing working group asked to assist the SETI Program Office at NASA. Seven chapters present the group's consensus on objectives, strategies, and plans for instrumental R&D and for a microwave search for extraterrestrial in intelligence (SETI) projected for the end of this decade. Thirteen appendixes reflect the views of their individual authors. Included are discussions of the 8-million-channel spectrum analyzer architecture and the proof-of-concept device under development; signal detection, recognition, and identification on-line in the presence of noise and radio interference; the 1-10 GHz sky survey and the 1-3 GHz targeted search envisaged; and the mutual interests of SETI and radio astronomy. The report ends with a selective, annotated SETI reading list of pro and contra SETI publications
- …