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Robert P. Kirshner - One of the best experts on this subject based on the ideXlab platform.
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type ia supernova Light Curve inference hierarchical bayesian analysis in the near infrared
The Astrophysical Journal, 2009Co-Authors: Kaisey S Mandel, Michael W Woodvasey, Andrew S Friedman, Robert P. KirshnerAbstract:We present a comprehensive statistical analysis of the properties of Type Ia supernova (SN Ia) Light Curves in the near-infrared using recent data from Peters Automated InfraRed Imaging TELescope and the literature. We construct a hierarchical Bayesian framework, incorporating several uncertainties including photometric error, peculiar velocities, dust extinction, and intrinsic variations, for principled and coherent statistical inference. SN Ia Light-Curve inferences are drawn from the global posterior probability of parameters describing both individual supernovae and the population conditioned on the entire SN Ia NIR data set. The logical structure of the hierarchical model is represented by a directed acyclic graph. Fully Bayesian analysis of the model and data is enabled by an efficient Markov Chain Monte Carlo algorithm exploiting the conditional probabilistic structure using Gibbs sampling. We apply this framework to the JHKs SN Ia Light-Curve data. A new Light-Curve model captures the observed J-band Light-Curve shape variations. The marginal intrinsic variances in peak absolute magnitudes are ?(MJ ) = 0.17 ? 0.03, ?(MH ) = 0.11 ? 0.03, and ?(MKs ) = 0.19 ? 0.04. We describe the first quantitative evidence for correlations between the NIR absolute magnitudes and J-band Light-Curve shapes, and demonstrate their utility for distance estimation. The average residual in the Hubble diagram for the training set SNe at cz > 2000kms?1 is 0.10 mag. The new application of bootstrap cross-validation to SN Ia Light-Curve inference tests the sensitivity of the statistical model fit to the finite sample and estimates the prediction error at 0.15 mag. These results demonstrate that SN Ia NIR Light Curves are as effective as corrected optical Light Curves, and, because they are less vulnerable to dust absorption, they have great potential as precise and accurate cosmological distance indicators.
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improved distances to type ia supernovae with multicolor Light Curve shapes mlcs2k2
The Astrophysical Journal, 2007Co-Authors: Adam G. Riess, Robert P. KirshnerAbstract:We present an updated version of the multicolor Light-Curve shape method to measure distances to Type Ia supernovae (SNe Ia), incorporating new procedures for K-correction and extinction corrections. We also develop a simple model to disentangle intrinsic color variations and reddening by dust and expand the method to incorporate U-band Light Curves and to more easily accommodate prior constraints on any of the model parameters. We apply this method to 133 nearby SNe Ia, including 95 objects in the Hubble flow (cz ≥ 2500 km s-1), which give an intrinsic dispersion of less than 7% in distance. The Hubble flow sample, which is of critical importance to all cosmological uses of SNe Ia, is the largest ever presented with homogeneous distances. We find that the Hubble flow SNe with H0dSN ≥ 7400 km s-1 yield an expansion rate that is 6.5% ± 1.8% lower than the rate determined from SNe within that distance, and this can have a large effect on measurements of the dark energy equation of state with SNe Ia. Peculiar velocities of SN Ia host galaxies in the rest frame of the Local Group are consistent with the dipole measured in the cosmic microwave background. Direct fits of SNe Ia that are significantly reddened by dust in their host galaxies suggest that their mean extinction law may be described by RV 2.7, but optical colors alone provide weak constraints on RV.
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Improved Distances to Type Ia Supernovae with Multicolor Light‐Curve Shapes: MLCS2k2
The Astrophysical Journal, 2007Co-Authors: Saurabh Jha, Adam G. Riess, Robert P. KirshnerAbstract:We present an updated version of the Multicolor Light Curve Shape method to measure distances to type Ia supernovae (SN Ia), incorporating new procedures for K-correction and extinction corrections. We also develop a simple model to disentangle intrinsic color variations and reddening by dust, and expand the method to incorporate U-band Light Curves and to more easily accommodate prior constraints on any of the model parameters. We apply this method to 133 nearby SN Ia, including 95 objects in the Hubble flow (cz >= 2500 km/s), which give an intrinsic dispersion of less than 7% in distance. The Hubble flow sample, which is of critical importance to all cosmological uses of SN Ia, is the largest ever presented with homogeneous distances. We find the Hubble flow supernovae with Hd >= 7400 km/s yield an expansion rate that is 6.5 +/- 1.8% lower than the rate determined from supernovae within that distance, and this can have a large effect on measurements of the dark energy equation of state with SN Ia. Peculiar velocities of SN Ia host galaxies in the rest frame of the Local Group are consistent with the dipole measured in the Cosmic Microwave Background. Direct fits of SN Ia that are significantly reddened by dust in their host galaxies suggest their mean extinction law may be described by R_V ~= 2.7, but optical colors alone provide weak constraints on R_V.
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improved distances to type ia supernovae with multicolor Light Curve shapes mlcs2k2
arXiv: Astrophysics, 2006Co-Authors: Adam G. Riess, Robert P. KirshnerAbstract:We present an updated version of the Multicolor Light Curve Shape method to measure distances to type Ia supernovae (SN Ia), incorporating new procedures for K-correction and extinction corrections. We also develop a simple model to disentangle intrinsic color variations and reddening by dust, and expand the method to incorporate U-band Light Curves and to more easily accommodate prior constraints on any of the model parameters. We apply this method to 133 nearby SN Ia, including 95 objects in the Hubble flow (cz >= 2500 km/s), which give an intrinsic dispersion of less than 7% in distance. The Hubble flow sample, which is of critical importance to all cosmological uses of SN Ia, is the largest ever presented with homogeneous distances. We find the Hubble flow supernovae with Hd >= 7400 km/s yield an expansion rate that is 6.5 +/- 1.8% lower than the rate determined from supernovae within that distance, and this can have a large effect on measurements of the dark energy equation of state with SN Ia. Peculiar velocities of SN Ia host galaxies in the rest frame of the Local Group are consistent with the dipole measured in the Cosmic Microwave Background. Direct fits of SN Ia that are significantly reddened by dust in their host galaxies suggest their mean extinction law may be described by R_V ~= 2.7, but optical colors alone provide weak constraints on R_V.
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a precise distance indicator type ia supernova multicolor Light Curve shapes
The Astrophysical Journal, 1996Co-Authors: Adam G. Riess, William H Press, Robert P. KirshnerAbstract:We present an empirical method that uses multicolor Light-Curve shapes (MLCSs) to estimate the luminosity, distance, and total line-of-sight extinction of Type Ia supernovae (SNe Ia). The empirical correlation between the MLCSs and the luminosity is derived from a " training set" of nine SN Ia Light Curves with independent distance and reddening estimates. We find that intrinsically dim SN Ia's are redder and have faster Light Curves than the bright ones, which are slow and blue. By 35 days after maximum, the intrinsic color variations become negligible. A formal treatment of extinction employing Bayes's theorem is used to estimate the best value and its uncertainty. Applying the MLCS method to both Light Curves and to color Curves provides enough information to determine which supernovae are dim because they are distant, which are intrinsically dim, and which are dim because of extinction by dust. The precision of the MLCS distances is examined by constructing a Hubble diagram with an independent set of 20 SN Ia's. The dispersion of 0.12 mag indicates a typical distance accuracy of 5% for a single object, and the intercept yields a Hubble constant on the Sandage et al. Cepheid distance scale of H0 = 64 ± 3 (statistical) km s–1 Mpc–1 (±6 total error). The slope of 0.2010 ± 0.0035 mag over the distance interval 32.2 < μ < 38.3 yields the most precise confirmation of the linearity of the Hubble law.
A Derekas - One of the best experts on this subject based on the ideXlab platform.
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the kepler cepheid v1154 cyg revisited Light Curve modulation and detection of granulation
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: A Sodor, A Derekas, E Plachy, L Molnar, J M Benkő, Laszlo Szabados, Zs Bognar, B Csak, Gy M SzaboAbstract:We present a detailed analysis of the bright Cepheid-type variable star V1154 Cygni using 4 years of continuous observations by the Kepler space telescope. We detected 28 frequencies using standard Fourier transform method.We identified modulation of the main pulsation frequency and its harmonics with a period of ~159 d. This modulation is also present in the Fourier parameters of the Light Curve and the O-C diagram. We detected another modulation with a period of about 1160 d. The star also shows significant power in the low-frequency region that we identified as granulation noise. The effective timescale of the granulation agrees with the extrapolated scalings of red giant stars. Non-detection of solar-like oscillations indicates that the pulsation inhibits other oscillations. We obtained new radial velocity observations which are in a perfect agreement with previous years data, suggesting that there is no high mass star companion of V1154 Cygni. Finally, we discuss the possible origin of the detected frequency modulations.
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period and Light Curve fluctuations of the kepler cepheid v1154 cygni
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: A Derekas, Gy Szabo, L N Berdnikov, R Szabo, R Smolec, L L KissAbstract:We present a detailed period analysis of the bright Cepheid-type variable star V1154 Cygni (V1154 Cyg; V = 9.1 mag, P ≈ 4.9 d) based on almost 600 d of continuous observations by the Kepler space telescope. The data reveal significant cycle-to-cycle fluctuations in the pulsation period, indicating that classical Cepheids may not be as accurate astrophysical clocks as commonly believed: regardless of the specific points used to determine the O − C values, the cycle lengths show a scatter of 0.015–0.02 d over 120 cycles covered by the observations. A very sLight correlation between the individual Fourier parameters and the O − C values was found, suggesting that the O − C variations might be due to the instability of the Light-Curve shape. Random-fluctuation tests revealed a linear trend up to a cycle difference 15, but for long term, the period remains around the mean value. We compare the measurements with simulated Light Curves that were constructed to mimic V1154 Cyg as a perfect pulsator modulated only by the Light travel time effect caused by low-mass companions. We show that the observed period jitter in V1154 Cyg represents a serious limitation in the search for binary companions. While the Kepler data are accurate enough to allow the detection of planetary bodies in close orbits around a Cepheid, the astrophysical noise can easily hide the signal of the Light-time effect.
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period and Light Curve fluctuations of the kepler cepheid v1154 cyg
arXiv: Solar and Stellar Astrophysics, 2012Co-Authors: A Derekas, Laszlo Szabados, Gy Szabo, L N Berdnikov, R Szabo, R Smolec, L L Kiss, M Chadid, Nancy Remage Evans, Karen KinemuchiAbstract:We present a detailed period analysis of the bright Cepheid-type variable star V1154 Cygni (V =9.1 mag, P~4.9 d) based on almost 600 days of continuous observations by the Kepler space telescope. The data reveal significant cycle-to-cycle fluctuations in the pulsation period, indicating that classical Cepheids may not be as accurate astrophysical clocks as commonly believed: regardless of the specific points used to determine the O-C values, the cycle lengths show a scatter of 0.015-0.02 days over the 120 cycles covered by the observations. A very sLight correlation between the individual Fourier parameters and the O-C values was found, suggesting that the O - C variations might be due to the instability of the Light Curve shape. Random fluctuation tests revealed a linear trend up to a cycle difference 15, but for long term, the period remains around the mean value. We compare the measurements with simulated Light Curves that were constructed to mimic V1154 Cyg as a perfect pulsator modulated only by the Light travel time effect caused by low-mass companions. We show that the observed period jitter in V1154 Cyg represents a serious limitation in the search for binary companions. While the Kepler data are accurate enough to allow the detection of planetary bodies in close orbits around a Cepheid, the astrophysical noise can easily hide the signal of the Light-time effect.
Adam G. Riess - One of the best experts on this subject based on the ideXlab platform.
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improved distances to type ia supernovae with multicolor Light Curve shapes mlcs2k2
The Astrophysical Journal, 2007Co-Authors: Adam G. Riess, Robert P. KirshnerAbstract:We present an updated version of the multicolor Light-Curve shape method to measure distances to Type Ia supernovae (SNe Ia), incorporating new procedures for K-correction and extinction corrections. We also develop a simple model to disentangle intrinsic color variations and reddening by dust and expand the method to incorporate U-band Light Curves and to more easily accommodate prior constraints on any of the model parameters. We apply this method to 133 nearby SNe Ia, including 95 objects in the Hubble flow (cz ≥ 2500 km s-1), which give an intrinsic dispersion of less than 7% in distance. The Hubble flow sample, which is of critical importance to all cosmological uses of SNe Ia, is the largest ever presented with homogeneous distances. We find that the Hubble flow SNe with H0dSN ≥ 7400 km s-1 yield an expansion rate that is 6.5% ± 1.8% lower than the rate determined from SNe within that distance, and this can have a large effect on measurements of the dark energy equation of state with SNe Ia. Peculiar velocities of SN Ia host galaxies in the rest frame of the Local Group are consistent with the dipole measured in the cosmic microwave background. Direct fits of SNe Ia that are significantly reddened by dust in their host galaxies suggest that their mean extinction law may be described by RV 2.7, but optical colors alone provide weak constraints on RV.
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Improved Distances to Type Ia Supernovae with Multicolor Light‐Curve Shapes: MLCS2k2
The Astrophysical Journal, 2007Co-Authors: Saurabh Jha, Adam G. Riess, Robert P. KirshnerAbstract:We present an updated version of the Multicolor Light Curve Shape method to measure distances to type Ia supernovae (SN Ia), incorporating new procedures for K-correction and extinction corrections. We also develop a simple model to disentangle intrinsic color variations and reddening by dust, and expand the method to incorporate U-band Light Curves and to more easily accommodate prior constraints on any of the model parameters. We apply this method to 133 nearby SN Ia, including 95 objects in the Hubble flow (cz >= 2500 km/s), which give an intrinsic dispersion of less than 7% in distance. The Hubble flow sample, which is of critical importance to all cosmological uses of SN Ia, is the largest ever presented with homogeneous distances. We find the Hubble flow supernovae with Hd >= 7400 km/s yield an expansion rate that is 6.5 +/- 1.8% lower than the rate determined from supernovae within that distance, and this can have a large effect on measurements of the dark energy equation of state with SN Ia. Peculiar velocities of SN Ia host galaxies in the rest frame of the Local Group are consistent with the dipole measured in the Cosmic Microwave Background. Direct fits of SN Ia that are significantly reddened by dust in their host galaxies suggest their mean extinction law may be described by R_V ~= 2.7, but optical colors alone provide weak constraints on R_V.
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improved distances to type ia supernovae with multicolor Light Curve shapes mlcs2k2
arXiv: Astrophysics, 2006Co-Authors: Adam G. Riess, Robert P. KirshnerAbstract:We present an updated version of the Multicolor Light Curve Shape method to measure distances to type Ia supernovae (SN Ia), incorporating new procedures for K-correction and extinction corrections. We also develop a simple model to disentangle intrinsic color variations and reddening by dust, and expand the method to incorporate U-band Light Curves and to more easily accommodate prior constraints on any of the model parameters. We apply this method to 133 nearby SN Ia, including 95 objects in the Hubble flow (cz >= 2500 km/s), which give an intrinsic dispersion of less than 7% in distance. The Hubble flow sample, which is of critical importance to all cosmological uses of SN Ia, is the largest ever presented with homogeneous distances. We find the Hubble flow supernovae with Hd >= 7400 km/s yield an expansion rate that is 6.5 +/- 1.8% lower than the rate determined from supernovae within that distance, and this can have a large effect on measurements of the dark energy equation of state with SN Ia. Peculiar velocities of SN Ia host galaxies in the rest frame of the Local Group are consistent with the dipole measured in the Cosmic Microwave Background. Direct fits of SN Ia that are significantly reddened by dust in their host galaxies suggest their mean extinction law may be described by R_V ~= 2.7, but optical colors alone provide weak constraints on R_V.
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a precise distance indicator type ia supernova multicolor Light Curve shapes
The Astrophysical Journal, 1996Co-Authors: Adam G. Riess, William H Press, Robert P. KirshnerAbstract:We present an empirical method that uses multicolor Light-Curve shapes (MLCSs) to estimate the luminosity, distance, and total line-of-sight extinction of Type Ia supernovae (SNe Ia). The empirical correlation between the MLCSs and the luminosity is derived from a " training set" of nine SN Ia Light Curves with independent distance and reddening estimates. We find that intrinsically dim SN Ia's are redder and have faster Light Curves than the bright ones, which are slow and blue. By 35 days after maximum, the intrinsic color variations become negligible. A formal treatment of extinction employing Bayes's theorem is used to estimate the best value and its uncertainty. Applying the MLCS method to both Light Curves and to color Curves provides enough information to determine which supernovae are dim because they are distant, which are intrinsically dim, and which are dim because of extinction by dust. The precision of the MLCS distances is examined by constructing a Hubble diagram with an independent set of 20 SN Ia's. The dispersion of 0.12 mag indicates a typical distance accuracy of 5% for a single object, and the intercept yields a Hubble constant on the Sandage et al. Cepheid distance scale of H0 = 64 ± 3 (statistical) km s–1 Mpc–1 (±6 total error). The slope of 0.2010 ± 0.0035 mag over the distance interval 32.2 < μ < 38.3 yields the most precise confirmation of the linearity of the Hubble law.
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time dilation in the Light Curve of the distant type ia supernova sn 1995k
The Astrophysical Journal, 1996Co-Authors: Bruno Leibundgut, Adam G. Riess, R A Schommer, Mark M Phillips, B P Schmidt, J Spyromilio, J R Walsh, Nicholas B Suntzeff, M Hamuy, J MazaAbstract:The Light Curve of a distant Type Ia supernova acts like a clock that can be used to test the expansion of the universe. SN 1995K, at a spectroscopic redshift of z = 0.479, provides one of the first meaningful data sets for this test. We find that all aspects of SN 1995K resemble local Type Ia supernova events when the Light Curve is dilated by (1 + z), as prescribed by cosmological expansion. In a static, nonexpanding universe, SN 1995K would represent a unique object with a spectrum identifying it as a regular Type Ia supernova but with a Light-Curve shape and luminosity that do not follow the well-established relations for local events. We conclude that SN 1995K provides strong evidence for an interpretation of cosmological redshifts as being due to universal expansion. Theories in which photons dissipate their energy during travel are excluded as are age-redshift dependencies.
Gabriela Mallenornelas - One of the best experts on this subject based on the ideXlab platform.
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a unique solution of planet and star parameters from an extrasolar planet transit Light Curve
The Astrophysical Journal, 2003Co-Authors: Sara Seager, Gabriela MallenornelasAbstract:There is a unique solution of the planet and star parameters from a planet transit Light Curve with two or more transits if the planet has a circular orbit and the Light Curve is observed in a bandpass where limb darkening is negligible. The existence of this unique solution is very useful for current planet transit surveys for several reasons. First, there is an analytic solution that allows a quick parameter estimate, in particular of Rp. Second, the stellar density can be uniquely derived from the transit Light Curve alone. The stellar density can then be used to immediately rule out a giant star (and hence a much larger than planetary companion) and can also be used to put an upper limit on the stellar and planet radius even considering sLightly evolved stars. Third, the presence of an additional fully blended star that contaminates an eclipsing system to mimic a planet transit can be largely ruled out from the transit Light Curve given a spectral type for the central star. Fourth, the period can be estimated from a single-transit Light Curve and a measured spectral type. All of these applications can be used to select the best planet transit candidates for mass determination by radial velocity follow-up. To use these applications in practice, the photometric precision and time sampling of the Light Curve must be high (better than 0.005 mag precision and 5 minute time sampling for a two-transit Light Curve).
L L Kiss - One of the best experts on this subject based on the ideXlab platform.
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period and Light Curve fluctuations of the kepler cepheid v1154 cygni
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: A Derekas, Gy Szabo, L N Berdnikov, R Szabo, R Smolec, L L KissAbstract:We present a detailed period analysis of the bright Cepheid-type variable star V1154 Cygni (V1154 Cyg; V = 9.1 mag, P ≈ 4.9 d) based on almost 600 d of continuous observations by the Kepler space telescope. The data reveal significant cycle-to-cycle fluctuations in the pulsation period, indicating that classical Cepheids may not be as accurate astrophysical clocks as commonly believed: regardless of the specific points used to determine the O − C values, the cycle lengths show a scatter of 0.015–0.02 d over 120 cycles covered by the observations. A very sLight correlation between the individual Fourier parameters and the O − C values was found, suggesting that the O − C variations might be due to the instability of the Light-Curve shape. Random-fluctuation tests revealed a linear trend up to a cycle difference 15, but for long term, the period remains around the mean value. We compare the measurements with simulated Light Curves that were constructed to mimic V1154 Cyg as a perfect pulsator modulated only by the Light travel time effect caused by low-mass companions. We show that the observed period jitter in V1154 Cyg represents a serious limitation in the search for binary companions. While the Kepler data are accurate enough to allow the detection of planetary bodies in close orbits around a Cepheid, the astrophysical noise can easily hide the signal of the Light-time effect.
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period and Light Curve fluctuations of the kepler cepheid v1154 cyg
arXiv: Solar and Stellar Astrophysics, 2012Co-Authors: A Derekas, Laszlo Szabados, Gy Szabo, L N Berdnikov, R Szabo, R Smolec, L L Kiss, M Chadid, Nancy Remage Evans, Karen KinemuchiAbstract:We present a detailed period analysis of the bright Cepheid-type variable star V1154 Cygni (V =9.1 mag, P~4.9 d) based on almost 600 days of continuous observations by the Kepler space telescope. The data reveal significant cycle-to-cycle fluctuations in the pulsation period, indicating that classical Cepheids may not be as accurate astrophysical clocks as commonly believed: regardless of the specific points used to determine the O-C values, the cycle lengths show a scatter of 0.015-0.02 days over the 120 cycles covered by the observations. A very sLight correlation between the individual Fourier parameters and the O-C values was found, suggesting that the O - C variations might be due to the instability of the Light Curve shape. Random fluctuation tests revealed a linear trend up to a cycle difference 15, but for long term, the period remains around the mean value. We compare the measurements with simulated Light Curves that were constructed to mimic V1154 Cyg as a perfect pulsator modulated only by the Light travel time effect caused by low-mass companions. We show that the observed period jitter in V1154 Cyg represents a serious limitation in the search for binary companions. While the Kepler data are accurate enough to allow the detection of planetary bodies in close orbits around a Cepheid, the astrophysical noise can easily hide the signal of the Light-time effect.
