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6 results on '"Nada Jevtic"'

1. Nonlinear time series analysis of Kepler Space Telescope data: Mutually beneficial progress

Author

Peter Stine, J. S. Schweitzer, and Nada Jevtic

Subjects
Physics, Nonlinear system, Quality (physics), Series (mathematics), Spitzer Space Telescope, Space and Planetary Science, Noise (signal processing), Harmonics, Noise reduction, Astronomy and Astrophysics, Astrophysics, Mutual information, Algorithm
Abstract

Nonlinear time series analysis, though a powerful tool, has not been used widely in astronomy and astro-physics because the principle requirements that the data be sampled uniformly and continuous are rarely met. Kepler Space Telescope variable-star light curves satisfy these and almost all other requirements. These data have allowed a more systematic study of the methodology and yielded new information. Nonlinear noise reduction is the aspect we focus on here. Nonlinear time series power spectra often have relevant information across all the frequencies in a spectrum. As opposed to traditional filtering that results in a loss of information at the high frequencies, nonlinear local projective noise reduction allows us to significantly reduce noise while keeping high-frequency information. Nonlinear noise reduction is discussed for a number of Kepler Space Telescope targets with different power-spectral characteristics. The extremely high quality of the Kepler data has also allowed us to explore the novel use of average mutual information (AMI) for distinguishing signal from noise in broadband spectra. We report on noise reduction for targets with power spectra that contain a fundamental and harmonics, power spectra with no such lines and spectra with high-frequency lines (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Published
2012
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2. Nonlinear Time Series Analysis of the DB White Dwarf PG 1351+489 Light Intensity Curves

Author

Hope Feldman, J. S. Schweitzer, Cynthia W. Peterson, Nada Jevtic, and Sarah Zelechoski

Subjects
Physics, business.industry, Mathematical analysis, Spectral density, Astronomy and Astrophysics, Torus, White noise, Fundamental frequency, Light intensity, Amplitude, Optics, Space and Planetary Science, Harmonics, business, Poincaré map
Abstract

A nonlinear time series analysis is performed on light intensity data for the variable DB white dwarf PG 1351+489. The data were collected during the XCov12 campaign of the Whole Earth Telescope. Two data sets integrated to 30 and 10 s, taken at different times during the campaign, were analyzed. The power spectrum of PG 1351+489 is broadband, with a dominant fundamental frequency f0, and its harmonics, subharmonics, and other lower amplitude peaks. Our time delay phase-space portrait in 3 dimensions is a rhombohedral shape wrapped around a torus with triangular projections. This differs from earlier reports of a more circular two-dimensional representation. We show that the difference is due to binning and subsequent filtering in the earlier work. A circular phase-space portrait is obtained if only the fundamental frequency is used, the reconstruction subsequently growing in complexity as more and more of the power spectrum is included. Poincare section return times for the 30 s integrated data correspond to the fundamental period. For the 10 s integrated data, other return times are observed. These are shown to be due to dynamical resetting. An example of dynamical resetting on a theoretical model is given. Since resetting takes the phase-space point off the trajectory, locally projective nonlinear noise reduction was used. Locally projective nonlinear noise reduction results in lower white noise by a factor of ~50. Thus, three more harmonics of the fundamental frequency f0, four more (n + 0.47)f0 subharmonics, and at least 12 other peaks are identified.

Published
2005
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3. Detection of Solar-like Oscillations from Kepler Photometry of the Open Cluster NGC 6819

Author

Yveline Lebreton, Charles S. Baldner, Jørgen Christensen-Dalsgaard, Juan Carlos Suárez, Andrea Miglio, J. Molenda-Zakowicz, Nada Jevtic, Achim Weiss, Savita Mathur, Marie-Jo Goupil, L. Esch, Saskia Hekker, William J. Borucki, Caroline Barban, Hans Bruntt, Rafael A. García, Daniel Huber, Aldo Serenelli, Ian R. Stevens, Victor Silva Aguirre, Frank Grundah, Vinothini Sangaralingam, Katia Biazzo, Hans Kjeldsen, Torben Arentoft, Christiaan Sterken, Søren Meibom, Ian W. Roxburgh, Jérôme Ballot, Yvonne Elsworth, Karsten Brogaard, Francesca D'Antona, Dennis Stello, Ning Gai, Josefina Montalbán, Christoffer Karoff, Biwei Jiang, Timothy R. Bedding, Sarbani Basu, William J. Chaplin, Ronald L. Gilliland, Timothy M. Brown, B. Mosser, Kevin Belkacem, Róbert Szabó, Jon M. Jenkins, Pierre Demarque, Arlette Noels, Teodoro Roca Cortés, Peter Stine, Reza Samadi, David G. Koch, Sydney Institute for Astronomy (SIfA), The University of Sydney, Department of Astronomy, Yale University [New Haven], Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), School of Physics and Astronomy, University of Birmingham [Birmingham], Las Cumbres Observatory Global Telescope, Danish AsteroSeismology Centre (DASC), Aarhus University [Aarhus], Space Telescope Science Institute (STSci), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Indian Institute of Astrophysics (IIA), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Département des Sciences et Gestion de l'Environnement/Océanologie [Liège], Université de Liège, INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), INAF - Osservatorio Astronomico di Roma (OAR), Beijing Normal University (BNU), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Engineering Technology, Bloomsburg University, Astronomical Institute [Wroclaw], University of Wrocław [Poland] (UWr), Instituto de Astrofisica de Canarias (IAC), Departmento de Astrofísica, Universidad de La Laguna [Tenerife - SP] (ULL), Department of Computer Science (Queen Mary University of London), Queen Mary University of London (QMUL), Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, Vrije Universiteit Brussel (VUB), Konkoly Observatory, Research Centre for Astronomy and Earth Sciences [Budapest], Hungarian Academy of Sciences (MTA)-Hungarian Academy of Sciences (MTA), NASA Ames Research Center (ARC), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Consejo Superior de Investigaciones Científicas [Spain] (CSIC), Beijing Normal University, University of Wrocław [Poland], Vrije Universiteit [Brussels] (VUB), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Harvard University-Smithsonian Institution, and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, stars: interiors, 01 natural sciences, Asteroseismology, Luminosity, open clusters and associations: individual: NGC 6819, techniques: photometric, Frequency separation, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Solar-like oscillations, 010303 astronomy & astrophysics, Stellar evolution, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Radial velocity, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, stars: fundamental parameters, stars: oscillations, Open cluster
Abstract

Asteroseismology of stars in clusters has been a long-sought goal because the assumption of a common age, distance and initial chemical composition allows strong tests of the theory of stellar evolution. We report results from the first 34 days of science data from the Kepler Mission for the open cluster NGC 6819 -- one of four clusters in the field of view. We obtain the first clear detections of solar-like oscillations in the cluster red giants and are able to measure the large frequency separation and the frequency of maximum oscillation power. We find that the asteroseismic parameters allow us to test cluster-membership of the stars, and even with the limited seismic data in hand, we can already identify four possible non-members despite their having a better than 80% membership probability from radial velocity measurements. We are also able to determine the oscillation amplitudes for stars that span about two orders of magnitude in luminosity and find good agreement with the prediction that oscillation amplitudes scale as the luminosity to the power of 0.7. These early results demonstrate the unique potential of asteroseismology of the stellar clusters observed by Kepler., Comment: 5 pages, 4 figures, accepted by ApJ (Lett.)

Published
2010
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5. STOCHASTIC BRIGHTNESS VARIATIONS IN THE CENTRAL STAR OF PLANETARY NEBULA NGC 6826

Author

Peter Stine, Todd C. Klaus, J. S. Schweitzer, Ji Lie, Jon M. Jenkins, Wayne Nilsen, Nada Jevtic, and Sean McCauliff

Subjects
Physics, Brightness, Astronomy, Astronomy and Astrophysics, Astrophysics, Light curve, Planetary nebula, Spectral line, Common envelope, Spitzer Space Telescope, Space and Planetary Science, Phase space, Astrophysics::Solar and Stellar Astrophysics, Coherence (physics)
Abstract

One year of continuous Kepler Space Telescope data for the central object of planetary nebula NGC?6826 (KIC 12071221) were analyzed. KIC 12071221 has long-cadence light curves with stochastic brightness variations and broadband power spectra. The exception is a one-month long period during which variability was detected with a period of 14.8?hr. In search of the origin of this periodicity and in an attempt to better understand the complex NGC?6826 system, long-cadence KIC 12071221 data were analyzed using nonlinear time series methods. Nonlinear projective noise reduction from a phase-space dimension of six lowered the tail of the power spectra at the higher frequencies by factors of 38-133, an unexpected result for light curves with no obvious dominant frequencies. Even more notable is the identification of a structured distribution of trajectories, or coherence, in the reconstructed phase space for vectors spanning an interval of 1.5?hr. Organization weakens as the delay increases and is lost for phase-space vectors spanning times longer than 10?hr. This may be indicative of a binary object which shares a common envelope and/or pulsations but for a complete understanding one or both may have to be combined with wind structure. Thus, an estimate is made of the timescale of the response to what we propose is stochastic driving. This estimate of the timescale of the organized response is made by monitoring the loss of structure in the distribution of trajectories in phase space, a novel application of nonlinear methodology that may be used on data sampled with any sampling time.

Published
2012
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6. Extracting Asteroseismology from TESS FFIs

Author

Buzasi, Derek L., Lindsey Carboneau, Ashley Chontos, Oliver Hall, Rasmus Handberg, Nada Jevtic, Johnson, Jennifer A., Mikkel Nørup Lund, Dennis Stello, and Joel Zinn

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