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4 results on '"Bell, M.R. (Michael)"'

1. Identifying transient and variable sources in radio images

Author

Rowlinson, A., Stewart, A.J., Broderick, J.W., Swinbank, J.D., Wijers, R.A.M.J. (Ralph), Carbone, D., Cendes, Y.N., Fender, R.P., Horst, A.J. van der, Molenaar, G.J., Scheers, L.H.A. (Bart), Staley, T.D., Farrell, S.A. (Sean), Grießmeier, J.-M., Bell, M.R. (Michael), Eislöffel, J., Law, C.J., Leeuwen, J. van, Zarka, P., Rowlinson, A., Stewart, A.J., Broderick, J.W., Swinbank, J.D., Wijers, R.A.M.J. (Ralph), Carbone, D., Cendes, Y.N., Fender, R.P., Horst, A.J. van der, Molenaar, G.J., Scheers, L.H.A. (Bart), Staley, T.D., Farrell, S.A. (Sean), Grießmeier, J.-M., Bell, M.R. (Michael), Eislöffel, J., Law, C.J., Leeuwen, J. van, and Zarka, P.

Abstract

With the arrival of a number of wide-field snapshot image-plane radio transient surveys, there will be a huge influx of images in the coming years making it impossible to manually analyse the datasets. Automated pipelines to process the information stored in the images are being developed, such as the LOFAR Transients Pipeline, outputting light curves and various transient parameters. These pipelines have a number of tuneable parameters that require training to meet the survey requirements. This paper utilises both observed and s

Published
2019
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2. Identifying transient and variable sources in radio images

Author

Rowlinson, A., Stewart, A.J., Broderick, J.W., Swinbank, J.D., Wijers, R.A.M.J. (Ralph), Carbone, D., Cendes, Y.N., Fender, R.P., Horst, A.J. van der, Molenaar, G.J., Scheers, L.H.A. (Bart), Staley, T.D., Farrell, S.A. (Sean), Grießmeier, J.-M., Bell, M.R. (Michael), Eislöffel, J., Law, C.J., Leeuwen, J. van, Zarka, P., Rowlinson, A., Stewart, A.J., Broderick, J.W., Swinbank, J.D., Wijers, R.A.M.J. (Ralph), Carbone, D., Cendes, Y.N., Fender, R.P., Horst, A.J. van der, Molenaar, G.J., Scheers, L.H.A. (Bart), Staley, T.D., Farrell, S.A. (Sean), Grießmeier, J.-M., Bell, M.R. (Michael), Eislöffel, J., Law, C.J., Leeuwen, J. van, and Zarka, P.

Abstract

With the arrival of a number of wide-field snapshot image-plane radio transient surveys, there will be a huge influx of images in the coming years making it impossible to manually analyse the datasets. Automated pipelines to process the information stored in the images are being developed, such as the LOFAR Transients Pipeline, outputting light curves and various transient parameters. These pipelines have a number of tuneable parameters that require training to meet the survey requirements. This paper utilises both observed and simulated datasets to demonstrate different machine learning strategies that can be used to train these parameters. We use a simple anomaly detection algorithm and a penalised logistic regression algorithm. The datasets used are from LOFAR observations and we process the data using the LOFAR Transients Pipeline; however the strategies developed are applicable to any light curve datasets at different frequencies and can be adapted to different automated pipelines. These machine learning strategies are publicly available as PYTHON tools that can be downloaded and adapted to different datasets (https://github.com/AntoniaR/TraP_ML_tools).

Published
2019
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3. LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A

Author

Asgekar, A., Oonk, J.B., Yatawatta, S., Weeren, R.J. van, McKean, J.P., White, G., Jackson, N., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Bell, M.E., Bell, M.R. (Michael), Bemmel, I. van, Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Braun, R., Breitling, F., Brink, R.H. van de, Broderick, J.W., Brouw, W.N., Brüggen, M., Butcher, H.R., Cappellen, W. van, Ciardi, B., Conway, J.E., De Gasperin, F., Geus, E. de, Jong, A. de, Vos, M. de, Duscha, S., Eislöffel, J., Falcke, H., Fellows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J.-M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Law, C.J., Leeuwen, J. van, Maat, P., Macario, G., Mann, G., Markoff, S., McKay-Bukowski, D., Mevins, M., Miller-Jones, J.C.A., Mol, J.D., Morganti, R., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N. (Varun), Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H.J.A., Scheers, L.H.A. (Bart), Schoenmakers, A., Sluman, J., Smirnov, O., Sobey, C.A., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Vocks, C., Wijers, R.A.M.J. (Ralph), Wise, M.W. (Michael), Wucknitz, O., Zarka, P., Leeuwen, J. (Joeri) van, Asgekar, A., Oonk, J.B., Yatawatta, S., Weeren, R.J. van, McKean, J.P., White, G., Jackson, N., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Bell, M.E., Bell, M.R. (Michael), Bemmel, I. van, Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Braun, R., Breitling, F., Brink, R.H. van de, Broderick, J.W., Brouw, W.N., Brüggen, M., Butcher, H.R., Cappellen, W. van, Ciardi, B., Conway, J.E., De Gasperin, F., Geus, E. de, Jong, A. de, Vos, M. de, Duscha, S., Eislöffel, J., Falcke, H., Fellows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J.-M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Law, C.J., Leeuwen, J. van, Maat, P., Macario, G., Mann, G., Markoff, S., McKay-Bukowski, D., Mevins, M., Miller-Jones, J.C.A., Mol, J.D., Morganti, R., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N. (Varun), Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H.J.A., Scheers, L.H.A. (Bart), Schoenmakers, A., Sluman, J., Smirnov, O., Sobey, C.A., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Vocks, C., Wijers, R.A.M.J. (Ralph), Wise, M.W. (Michael), Wucknitz, O., Zarka, P., and Leeuwen, J. (Joeri) van

Abstract

Cassiopeia A was observed using the low-band antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) along the line-of-sight to this source. Five carbon alpha RRLs were detected in absorption between 40 and 50 MHz with a signal-to-noise ratio of >5 from two independent LOFAR data sets. The derived line velocities (vLSR ~ - 50 km s-1) and integrated optical depths (~13 s-1) of the RRLs in our spectra, extracted over the whole supernova remnant, are consistent within each LOFAR data set and with those previously reported. For the first time, we are able to extract spectra against the brightest hotspot of the remnant at frequencies below 330 MHz. These spectra show significantly higher (15-80 percent) integrated optical depths, indicating that there is small-scale angular structure of the order of ~1 pc in the absorbing gas distribution over the face of the remnant. We also place an upper limit of 3 × 10-4 on the peak optical depths of hydrogen and helium RRLs. These results demonstrate that LOFAR has the desired spectral stability and sensitivity to study faint recombination lines in the decameter band.

Published
2013

4. LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A

Author

Asgekar, A., Oonk, J.B., Yatawatta, S., Weeren, R.J. van, McKean, J.P., White, G., Jackson, N., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Bell, M.E., Bell, M.R. (Michael), Bemmel, I. van, Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Braun, R., Breitling, F., Brink, R.H. van de, Broderick, J.W., Brouw, W.N., Brüggen, M., Butcher, H.R., Cappellen, W. van, Ciardi, B., Conway, J.E., De Gasperin, F., Geus, E. de, Jong, A. de, Vos, M. de, Duscha, S., Eislöffel, J., Falcke, H., Fellows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J.-M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Law, C.J., Leeuwen, J. van, Maat, P., Macario, G., Mann, G., Markoff, S., McKay-Bukowski, D., Mevins, M., Miller-Jones, J.C.A., Mol, J.D., Morganti, R., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N. (Varun), Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H.J.A., Scheers, L.H.A. (Bart), Schoenmakers, A., Sluman, J., Smirnov, O., Sobey, C.A., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Vocks, C., Wijers, R.A.M.J. (Ralph), Wise, M.W. (Michael), Wucknitz, O., Zarka, P., Leeuwen, J. (Joeri) van, Asgekar, A., Oonk, J.B., Yatawatta, S., Weeren, R.J. van, McKean, J.P., White, G., Jackson, N., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Bell, M.E., Bell, M.R. (Michael), Bemmel, I. van, Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Braun, R., Breitling, F., Brink, R.H. van de, Broderick, J.W., Brouw, W.N., Brüggen, M., Butcher, H.R., Cappellen, W. van, Ciardi, B., Conway, J.E., De Gasperin, F., Geus, E. de, Jong, A. de, Vos, M. de, Duscha, S., Eislöffel, J., Falcke, H., Fellows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J.-M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Law, C.J., Leeuwen, J. van, Maat, P., Macario, G., Mann, G., Markoff, S., McKay-Bukowski, D., Mevins, M., Miller-Jones, J.C.A., Mol, J.D., Morganti, R., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N. (Varun), Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H.J.A., Scheers, L.H.A. (Bart), Schoenmakers, A., Sluman, J., Smirnov, O., Sobey, C.A., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Vocks, C., Wijers, R.A.M.J. (Ralph), Wise, M.W. (Michael), Wucknitz, O., Zarka, P., and Leeuwen, J. (Joeri) van

Abstract

Cassiopeia A was observed using the low-band antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) along the line-of-sight to this source. Five carbon alpha RRLs were detected in absorption between 40 and 50 MHz with a signal-to-noise ratio of >5 from two independent LOFAR data sets. The derived line velocities (vLSR ~ - 50 km s-1) and integrated optical depths (~13 s-1) of the RRLs in our spectra, extracted over the whole supernova remnant, are consistent within each LOFAR data set and with those previously reported. For the first time, we are able to extract spectra against the brightest hotspot of the remnant at frequencies below 330 MHz. These spectra show significantly higher (15-80 percent) integrated optical depths, indicating that there is small-scale angular structure of the order of ~1 pc in the absorbing gas distribution over the face of the remnant. We also place an upper limit of 3 × 10-4 on the peak optical depths of hydrogen and helium RRLs. These results demonstrate that LOFAR has the desired spectral stability and sensitivity to study faint recombination lines in the decameter band.

Published
2013

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