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7 results on '"Shankar, N. U."'

1. Parametrising Epoch of Reionization foregrounds: A deep survey of low-frequency point-source spectra with the MWA

Author

Offringa, A. R., Trott, C. M., Hurley-Walker, N., Johnston-Hollitt, M., McKinley, B., Barry, N., Beardsley, A. P., Bowman, J. D., Briggs, F., Carroll, P., Dillon, J. S., Ewall-Wice, A., Feng, L., Gaensler, B. M., Greenhill, L. J., Hazelton, B. J., Hewitt, J. N., Jacobs, D. C., Kim, H. -S., Kittiwisit, P., Lenc, E., Line, J., Loeb, A., Mitchell, D. A., Morales, M. F., Neben, A. R., Paul, S., Pindor, B., Pober, J. C., Procopio, P., Riding, J., Sethi, S. K., Shankar, N. U., Subrahmanyan, R., Sullivan, I. S., Tegmark, M., Thyagarajan, N., Tingay, S. J., Wayth, R. B., Webster, R. L., and Wyithe, J. S. B.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Experiments that pursue detection of signals from the Epoch of Reionization (EoR) are relying on spectral smoothness of source spectra at low frequencies. This article empirically explores the effect of foreground spectra on EoR experiments by measuring high-resolution full-polarization spectra for the 586 brightest unresolved sources in one of the MWA EoR fields using 45 h of observation. A novel peeling scheme is used to subtract 2500 sources from the visibilities with ionospheric and beam corrections, resulting in the deepest, confusion-limited MWA image so far. The resulting spectra are found to be affected by instrumental effects, which limit the constraints that can be set on source-intrinsic spectral structure. The sensitivity and power-spectrum of the spectra are analysed, and it is found that the spectra of residuals are dominated by PSF sidelobes from nearby undeconvolved sources. We release a catalogue describing the spectral parameters for each measured source., Comment: Accepted for publication in MNRAS. 15 pages, 16 figures. Catalogue of sources externally available as CSV file

Published
2016
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2. Parametrizing Epoch of Reionization foregrounds: a deep survey of low-frequency point-source spectra with the Murchison Widefield Array

Author

Massachusetts Institute of Technology. Department of Physics, MIT Kavli Institute for Astrophysics and Space Research, Dillon, Joshua Shane, Ewall-Wice, Aaron Michael, Feng, Lu, Hewitt, Jacqueline N, Neben, Abraham Richard, Tegmark, Max Erik, Offringa, A. R., Trott, C. M., Hurley-Walker, N., Johnston-Hollitt, M., McKinley, B., Barry, N., Beardsley, A. P., Bowman, J. D., Briggs, F., Carroll, P., Gaensler, B. M., Greenhill, L. J., Hazelton, B. J., Jacobs, D. C., Kim, H.-S., Kittiwisit, P., Lenc, E., Line, J., Loeb, A., Mitchell, D. A., Morales, M. F., Paul, S., Pindor, B., Pober, J. C., Procopio, P., Riding, J., Sethi, S. K., Shankar, N. U., Subrahmanyan, R., Sullivan, I. S., Thyagarajan, N., Tingay, S. J., Wayth, R. B., Webster, R. L., Wyithe, J. S. B., Massachusetts Institute of Technology. Department of Physics, MIT Kavli Institute for Astrophysics and Space Research, Dillon, Joshua Shane, Ewall-Wice, Aaron Michael, Feng, Lu, Hewitt, Jacqueline N, Neben, Abraham Richard, Tegmark, Max Erik, Offringa, A. R., Trott, C. M., Hurley-Walker, N., Johnston-Hollitt, M., McKinley, B., Barry, N., Beardsley, A. P., Bowman, J. D., Briggs, F., Carroll, P., Gaensler, B. M., Greenhill, L. J., Hazelton, B. J., Jacobs, D. C., Kim, H.-S., Kittiwisit, P., Lenc, E., Line, J., Loeb, A., Mitchell, D. A., Morales, M. F., Paul, S., Pindor, B., Pober, J. C., Procopio, P., Riding, J., Sethi, S. K., Shankar, N. U., Subrahmanyan, R., Sullivan, I. S., Thyagarajan, N., Tingay, S. J., Wayth, R. B., Webster, R. L., and Wyithe, J. S. B.

Abstract

Experiments that pursue detection of signals from the Epoch of Reionization (EoR) are relying on spectral smoothness of source spectra at low frequencies. This article empirically explores the effect of foreground spectra on EoR experiments by measuring high-resolution full-polarization spectra for the 586 brightest unresolved sources in one of the Murchison Widefield Array (MWA) EoR fields using 45 h of observation. A novel peeling scheme is used to subtract 2500 sources from the visibilities with ionospheric and beam corrections, resulting in the deepest, confusion-limited MWA image so far. The resulting spectra are found to be affected by instrumental effects, which limit the constraints that can be set on source-intrinsic spectral structure. The sensitivity and power-spectrum of the spectra are analysed, and it is found that the spectra of residuals are dominated by point spread function sidelobes from nearby undeconvolved sources. We release a catalogue describing the spectral parameters for each measured source.

Published
2017

3. Parametrizing Epoch of Reionization foregrounds: a deep survey of low-frequency point-source spectra with the Murchison Widefield Array

Author

Offringa, A. R., primary, Trott, C. M., additional, Hurley-Walker, N., additional, Johnston-Hollitt, M., additional, McKinley, B., additional, Barry, N., additional, Beardsley, A. P., additional, Bowman, J. D., additional, Briggs, F., additional, Carroll, P., additional, Dillon, J. S., additional, Ewall-Wice, A., additional, Feng, L., additional, Gaensler, B. M., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hewitt, J. N., additional, Jacobs, D. C., additional, Kim, H.-S., additional, Kittiwisit, P., additional, Lenc, E., additional, Line, J., additional, Loeb, A., additional, Mitchell, D. A., additional, Morales, M. F., additional, Neben, A. R., additional, Paul, S., additional, Pindor, B., additional, Pober, J. C., additional, Procopio, P., additional, Riding, J., additional, Sethi, S. K., additional, Shankar, N. U., additional, Subrahmanyan, R., additional, Sullivan, I. S., additional, Tegmark, M., additional, Thyagarajan, N., additional, Tingay, S. J., additional, Wayth, R. B., additional, Webster, R. L., additional, and Wyithe, J. S. B., additional

Published
2016
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4. Limits on low-frequency radio emission from southern exoplanets with the Murchison Widefield Array

Author

Murphy, T., primary, Bell, M. E., additional, Kaplan, D. L., additional, Gaensler, B. M., additional, Offringa, A. R., additional, Lenc, E., additional, Hurley-Walker, N., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hewitt, J. N., additional, Johnston-Hollitt, M., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, D. A., additional, Shankar, N. U., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2014
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5. Assistive communication device for cognitive disability and spastic children

Author

Shankar, N. U., Velamuri, V. S., Venkatesan, P., Deo, Samarth, Shankar, N. U., Velamuri, V. S., Venkatesan, P., and Deo, Samarth

Abstract

Communication has been a major problem for children with cognitive disabilities and spastic children. They are unable to effectively communicate their needs to their parents and caretakers. Modern advancements in communication technology, with increased capabilities of mobile phones, provide scope to design assistive technologies for these children. In this paper, we describe the design of a smartphone based communication device for children with cognitive disabilities and spastic children. We also present early findings on how it was successful in increased engagement between the children and caretakers, along with further r capabilities that the device can cater to., QC 20140903

Published
2011
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6. The murchison widefield array

Author

Mitchell, D. A., Greenhill, L. J., Ord, S. M., Bernardi, G., Wayth, R. B., Edgar, R. G., Clark, M. A., Dale, K., Hanspeter Pfister, Gleadow, S. J., Arcus, W., Briggs, F. H., Benkevitch, L., Bowman, J. D., Bunton, J. D., Burns, S., Cappallo, R. J., Corey, B. E., Oliveira-Costa, A., Desouza, L., Doeleman, S. S., Derome, M. F., Emrich, D., Glossop, M., Goeke, R., Krishna, M. R. G., Hazelton, B., Herne, D. E., Hewitt, J. N., Kamini, P. A., Kaplan, D. L., Kasper, J. C., Kincaid, B. B., Kocz, J., Kowald, E., Kratzenberg, E., Kumar, D., Lonsdale, C. J., Lynch, M. J., Madhavi, S., Matejek, M., Mcwhirter, S. R., Morales, M. F., Morgan, E., Oberoi, D., Pathikulangara, J., Prabu, T., Rogers, A., Salah, J. E., Sault, R. J., Shankar, N. U., Srivani, K. S., Stevens, J., Tingay, S. J., Vaccarella, A., Waterson, M., Webster, R. L., Whitney, A. R., Williams, A., and Williams, C.

Subjects
Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

It is shown that the excellent Murchison Radio-astronomy Observatory site allows the Murchison Widefield Array to employ a simple RFI blanking scheme and still calibrate visibilities and form images in the FM radio band. The techniques described are running autonomously in our calibration and imaging software, which is currently being used to process an FM-band survey of the entire southern sky., Accepted for publication in Proceedings of Science [PoS(RFI2010)016]. 6 pages and 3 figures. Presented at RFI2010, the Third Workshop on RFI Mitigation in Radio Astronomy, 29-31 March 2010, Groningen, The Netherlands

7. Isospectrality in chaotic billiards.

Author

Dhar A, Madhusudhana Rao D, Shankar N U, and Sridhar S

Abstract

We consider a modification of isospectral cavities whereby the classical dynamics changes from pseudointegrable to chaotic. We construct an example where we can prove that isospectrality is retained. We then demonstrate this explicitly in microwave resonators.

Published
2003
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