2,487 research outputs found
On the Variation of Fourier Parameters for Galactic and LMC Cepheids at Optical, Near-Infrared and Mid-Infrared Wavelengths
We present a light curve analysis of fundamental-mode Galactic and Large
Magellanic Cloud (LMC) Cepheids based on the Fourier decomposition technique.
We have compiled light curve data for Galactic and LMC Cepheids in optical
({\it VI}), near-infrared ({\it JHK}) and mid-infrared (3.6
4.5-m) bands from the literature and determined the variation of their
Fourier parameters as a function of period and wavelength. We observed a
decrease in Fourier amplitude parameters and an increase in Fourier phase
parameters with increasing wavelengths at a given period. We also found a
decrease in the skewness and acuteness parameters as a function of wavelength
at a fixed period. We applied a binning method to analyze the progression of
the mean Fourier parameters with period and wavelength. We found that for
periods longer than about 20 days, the values of the Fourier amplitude
parameters increase sharply for shorter wavelengths as compared to wavelengths
longer than the -band. We observed the variation of the Hertzsprung
progression with wavelength. The central period of the Hertzsprung progression
was found to increase with wavelength in the case of the Fourier amplitude
parameters and decrease with increasing wavelength in the case of phase
parameters. We also observed a small variation of the central period of the
progression between the Galaxy and LMC, presumably related to metallicity
effects. These results will provide useful constraints for stellar pulsation
codes that incorporate stellar atmosphere models to produce Cepheid light
curves in various bands.Comment: 22 pages, 19 figures, Accepted for publication in Monthly Notices of
the Royal Astronomical Society Main Journa
Collection of Cryptocurrency Customer-Information: Tax Enforcement Mechanism or Invasion of Privacy?
After granting permission to the Internal Revenue Service to serve a digital exchange company a summons for user information, the Federal District Court for the Northern District of California created some uncertainty regarding the privacy of cryptocurrencies. The IRS views this information gathering as necessary for monitoring compliance with Notice 2014-21, which classifies cryptocurrencies as property for tax purposes. Cryptocurrency users, however, view the attempt for information as an infringement on their privacy rights and are seeking legal protection. This Issue Brief investigates the future tax implications of Notice 2014-21 and considers possible routes the cryptocurrency market can take to avoid the burden of capital gains taxes. Further, this Issue Brief attempts to uncover the validity of the privacy claims made against the customer information summons and will recommend alternative actions for the IRS to take regardless of whether it succeeds in obtaining the information
Multiwavelength Light Curve Parameters of Cepheid Variables
We present a comparative analysis of theoretical and observed light curves of
Cepheid variables using Fourier decomposition. The theoretical light curves at
multiple wavelengths are generated using stellar pulsation models for chemical
compositions representative of Cepheids in the Galaxy and Magellanic Clouds.
The observed light curves at optical ({\it VI}), near-infrared ({\it JHK})
and mid-infrared (3.6 4.5-m) bands are compiled from the literature.
We discuss the variation of light curve parameters as a function of period,
wavelength and metallicity. Theoretical and observed Fourier amplitude
parameters decrease with increase in wavelength while the phase parameters
increase with wavelength. We find that theoretical amplitude parameters
obtained using canonical mass-luminosity levels exhibit a greater offset with
respect to observations when compared to non-canonical relations. We also
discuss the impact of variation in convective efficiency on the light curve
structure of Cepheid variables. The increase in mixing length parameter results
in a zero-point offset in bolometric mean magnitudes and reduces the systematic
large difference in theoretical amplitudes with respect to observations.Comment: 5 pages, 4 figures, proceedings for the 22nd Los Alamos Stellar
Pulsation Conference Series Meeting "Wide field variability surveys: a
21st-century perspective", held in San Pedro de Atacama, Chile, Nov. 28 -
Dec. 2, 201
Large Magellanic Cloud Near-Infrared Synoptic Survey. II. The Wesenheit relations and their application to the Distance scale
We present new near-infrared Cepheid Period-Wesenheit relations in the LMC
using time-series observations from the Large Magellanic Cloud Near-Infrared
Synoptic Survey. We also derive opticalnear-infrared P-W relations using
and ~magnitudes from OGLE-III. We employ our new data to determine
an independent distance to the LMC of ~mag, using an absolute calibration of the Galactic
relations based on several distance determination methods and accounting for
the intrinsic scatter of each technique. We also derive new near-infrared
Period-Luminosity and Wesenheit relations for Cepheids in M31 using
observations from the PHAT survey. We use the absolute calibrations of the
Galactic and LMC relations to determine the distance modulus of M31,
~mag. We apply a simultaneous fit to Cepheids in
several Local Group galaxies covering a range of metallicities
(~dex) to determine a global slope of
-~mag/dex for the relation and obtain robust
distance estimates. Our distances are in good agreement with recent TRGB based
distance estimates and we do not find any evidence for a metallicity dependence
in the near-infrared P-W relations.Comment: 16 pages, 8 figures, Accepted for publication in The Astronomical
Journa
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