Light curves

We present a relativistic-MHD numerical study of axisymmetric, magnetically driven jets with parameters applicable to gamma-ray burst (GRB) flows. We also present analytic expressions for the asymptotic jet shape and other flow parameters that agree very well with the numerical results. All current-carrying outflows exhibit self-collimation and consequent acceleration near the rotation axis, but unconfined outflows lose causal connectivity across

This paper presents the first photometric solution of CPD-79 92 (GSC 09370-00140 = TYC 9370-140-1 = ASAS J030739-7856.5, V=10.32 mag). The ASAS V light curve of the system was analyzed using Wilson and Devinney code. The photometric mass ratio of the system was derived with q-search method. Then, the absolute parameters of system were estimated.

We have identified an extremely luminous radio and X-ray source with an optically variable emission-line object in the outskirts of the nearby barred spiral galaxy NGC 1313. Archival data show that the object (officially designated SN 1978K) had a major optical outburst (MB < -12.3) in mid-1978 and that a radio and X-ray outburst followed this event. The light curve, optical spectra, radio data, and the X-ray data all indicate that the event was a very unusual Type II supernova, with many similar properties to the so-called Type V supernovae SN 1961V in NGC 1058 and SN 1986J in NGC 891. The currently bright Doppler-broadened Balmer lines, the forbidden lines and the extremely high radio and X-ray luminosities (among the brightest of known supernovae in both regimes) are believed to be powered by the shock driving through a dense circumstellar medium created by extreme mass-loss (˜4 × 10-5 Msun yr-1) from a massive progenitor. Some of the optical properties may be explained by the super outburst of an ?I Carinae-type object, but such an event would fail to explain the radio and X-ray luminosity. The closeness, low extinction and low confusion toward SN 1978K will allow for a detailed study of a class of peculiar supernovae which is possibly much more common than previously supposed.

We consider the problem of fitting a parametric model to time-series data that are afflicted by correlated noise. The noise is represented by a sum of two stationary Gaussian processes: one that is uncorrelated in time, and another that has a power spectral density varying as $1/f^\gamma$. We present an accurate and fast [O(N)] algorithm for parameter estimation based on computing the likelihood in a wavelet basis. The method is illustrated and tested using simulated time-series photometry of exoplanetary transits, with particular attention to estimating the midtransit time. We compare our method to two other methods that have been used in the literature, the time-averaging method and the residual-permutation method. For noise processes that obey our assumptions, the algorithm presented here gives more accurate results for midtransit times and truer estimates of their uncertainties.

There is a difficulty which is inherent in photometric analysis of supernovae in that as a supernova fades, it becomes more and more difficult to detect and measure what little light is still being produced from the event. Though it lies at the end of a light curve, this data is still important, and so methods must be considered which will facilitate accurate collection. Standard methods of aperture photometry in the Image Reduction and Analysis Facility (IRAF) involve reading pixel-by-pixel flux measurements across a circular aperture and fitting a curve to define the centroid of this flux, which in turn should designate the center of the object. However, once a supernova is sufficiently faint, this process may fail due to low flux from the supernova, contribtions from the underlying galaxy, and instrumental and sky noise. Therefore, this paper explores the use of a user-defined template as a rigid designator of the centers of objects rather than the result of an automated centroid calculation. This method was tested on SN 1991M in the galaxy IC 1151, and the light curves produced compared to previously
published results.