56 research outputs found
Stellar explosion in the weak field approximation of the Brans-Dicke theory
We treat a very crude model of an exploding star, in the weak field
approximation of the Brans-Dicke theory, in a scenario that resembles some
characteristics data of a Type Ia Supernova. The most noticeable feature, in
the electromagnetic component, is the relationship between the absolute
magnitude at maximum brightness of the star and the decline rate in one
magnitude from that maximum. This characteristic has become one of the most
accurate method to measure luminosity distances to objects at cosmological
distances. An interesting result is that the active mass associated with the
scalar field is totally radiated to infinity, representing a mass loss in the
ratio of the "tensor" component to the scalar component of 1 to ( is the Brans-Dicke parameter), in agreement with a general result
of Hawking. Then, this model shows explicitly, in a dynamical case, the
mechanism of radiation of scalar field, which is necessary to understand the
Hawking result.Comment: 11 pages, no figures. Published in Class. Quantum Gravity V22 (2005
The Stony Brook / SMARTS Atlas of mostly Southern Novae
We introduce the Stony Brook / SMARTS Atlas of (mostly) Southern Novae. This
atlas contains both spectra and photometry obtained since 2003. The data
archived in this atlas will facilitate systematic studies of the nova
phenomenon and correlative studies with other comprehensive data sets. It will
also enable detailed investigations of individual objects. In making the data
public we hope to engender more interest on the part of the community in the
physics of novae. The atlas is on-line at
\url{http://www.astro.sunysb.edu/fwalter/SMARTS/NovaAtlas/} .Comment: 11 figures; 5 table
Nova light curves from the Solar Mass Ejection Imager (SMEI) - II. The extended catalogue
We present the results from observing nine Galactic novae in eruption with the Solar Mass Ejection Imager (SMEI) between 2004 and 2009. While many of these novae reached peak magnitudes that were either at or approaching the detection limits of SMEI, we were still able to produce light curves that in many cases contained more data at and around the initial rise, peak, and decline than those found in other variable star catalogs. For each nova, we obtained a peak time, maximum magnitude, and for several an estimate of the decline time (t2). Interestingly, although of lower quality than those found in Hounsell et al. (2010a), two of the light curves may indicate the presence of a pre-maximum halt. In addition the high cadence of the SMEI instrument has allowed the detection of low amplitude variations in at least one of the nova light curves
Rate of Period Change as a Diagnostic of Cepheid Properties
Rate of period change for a Cepheid is shown to be a parameter that
is capable of indicating the instability strip crossing mode for individual
objects, and, in conjunction with light amplitude, likely location within the
instability strip. Observed rates of period change in over 200 Milky Way
Cepheids are demonstrated to be in general agreement with predictions from
stellar evolutionary models, although the sample also displays features that
are inconsistent with some published models and indicative of the importance of
additional factors not fully incorporated in models to date.Comment: Published in PASP (March 2006); TeX source & figures now provide
Association of Lipidome Remodeling in the Adipocyte Membrane with Acquired Obesity in Humans
The authors describe a new approach to studying cellular lipid profiles and
propose a compensatory mechanism that may help maintain the normal membrane
function of adipocytes in the context of obesity
Multiwavelength observations of V407 Lupi (ASASSN-16kt) --- a very fast nova erupting in an intermediate polar
We present a detailed study of the 2016 eruption of nova V407 Lupi (ASASSN-16kt), including optical, near-infrared, X-ray, and ultraviolet data from SALT, SMARTS, SOAR, Chandra, Swift, and XMM-Newton. Timing analysis of the multiwavelength light-curves shows that, from 168 days post-eruption and for the duration of the X-ray supersoft source phase, two periods at 565 s and 3.57 h are detected. We suggest that these are the rotational period of the white dwarf and the orbital period of the binary, respectively, and that the system is likely to be an intermediate polar. The optical light-curve decline was very fast ( 2.9 d), suggesting that the white dwarf is likely massive ( M). The optical spectra obtained during the X-ray supersoft source phase exhibit narrow, complex, and moving emission lines of He II, also characteristics of magnetic cataclysmic variables. The optical and X-ray data show evidence for accretion resumption while the X-ray supersoft source is still on, possibly extending its duration
Binary systems and their nuclear explosions
Peer ReviewedPreprin
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