5,308 research outputs found
The Dwarf Nova Outbursts of Nova Her 1960 (=V446 Her)
V446 Her is the best example of an old nova which has developed dwarf nova
eruptions in the post-nova state. We report on observed properties of the
long-term light curve of V446 Her, using photometry over 19 years. Yearly
averages of the outburst magnitudes shows a decline of ~0.013 mag/yr,
consistent with the decline of other post-novae that do not have dwarf nova
outbursts. Previous suggestions of bimodal distributions of the amplitudes and
widths of the outbursts are confirmed. The outbursts occur at a mean spacing of
18 days but the range of spacings is large (13-30 days). From simulations of
dwarf nova outbursts it has been predicted that the outburst spacing in V446
Her will increase as M-dot from the red dwarf companion slowly falls following
the nova; however the large intrinsic scatter in the spacings serves to hide
any evidence of this effect. We do find a systematic change in the outburst
pattern in which the brighter, wider type of outbursts disappeared after late
2003, and this phenomenon is suggested to be due to falling M-dot following the
nova.Comment: To appear at the Astronomical Journal; 7 pages, 1 table, 11 figure
Effectively Closed Infinite-Genus Surfaces and the String Coupling
The class of effectively closed infinite-genus surfaces, defining the
completion of the domain of string perturbation theory, can be included in the
category , which is characterized by the vanishing capacity of the ideal
boundary. The cardinality of the maximal set of endpoints is shown to be
2^{\mit N}. The product of the coefficient of the genus-g superstring
amplitude in four dimensions by in the limit is an
exponential function of the genus with a base comparable in magnitude to the
unified gauge coupling. The value of the string coupling is consistent with the
characteristics of configurations which provide a dominant contribution to a
finite vacuum amplitude.Comment: TeX, 33 page
Distance Measurement of Galaxies to Redshift of 0.1 using the CO-Line Tully-Fisher Relation
We report on the first results of a long-term project to derive distances of
galaxies at cosmological distances by applying the CO-line width-luminosity
relation. We have obtained deep CO-line observations of galaxies at redshifts
up to 29,000 km/s using the Nobeyama 45-m mm-wave Telescope, and some
supplementary data were obtained by using the IRAM 30-m telescope. We have
detected the CO line emission for several galaxies, and used their CO line
widths to estimate the absolute luminosities using the line-width-luminosity
relation. In order to obtain photometric data and inclination correction, we
also performed optical imaging observations of the CO-detected galaxies using
the CFHT 3.6-m telescope at high resolution. The radio and optical data have
been combined to derive the distance moduli and distances of the galaxies, and
Hubble ratios were estimated for these galaxies. We propose that the CO line
width-luminosity relation can be a powerful method to derive distances of
galaxies to redfhift of z = 0.1 and to derive the Hubble ratio in a significant
volume of the universe.
Key words: Cosmology - Galaxies: general - Distance scale - CO lineComment: To appear in PASJ, Plain Tex, 3 figures (in 10 ps files
The Origin of the Young Stars in the Nucleus of M31
The triple nucleus of M31 consists of a population of old red stars in an
eccentric disk (P1 and P2) and another population of younger A stars in a
circular disk (P3) around M31's central supermassive black hole (SMBH). We
argue that P1 and P2 determine the maximal radial extent of the younger A star
population and provide the gas that fueled the starburst that generated P3. The
eccentric stellar disk creates an non-axisymmetric perturbation to the
potential. This perturbed potential drives gas into the inner parsec around the
SMBH, if the pattern speed of the eccentric stellar disk is . We show that stellar mass loss from P1 and P2 is
sufficient to create a gravitationally unstable gaseous disk of \sim
10^5\Msun every Gyrs, consistent with the 200 Myr age of P3. Similar
processes may act in other systems to produce very compact nuclear starbursts.Comment: 10 pages, 7 figures, accepted by ApJ, changes made from referee
suggestion
The Cosmic Neutrino Background and the Age of the Universe
We discuss the cosmological degeneracy between the age of the Universe, the
Hubble parameter and the effective number of relativistic particles N_eff. We
show that independent determinations of the Hubble parameter H(z) as those
recently provided by Simon,Verde, Jimenez (2006), combined with other
cosmological data sets can provide the most stringent constraint on N_eff,
yielding N_eff=3.7 (-1.2) (+1.1) at 95% confidence level. A neutrino background
is detected with high significance: N_eff >1.8 at better than 99% confidence
level. Constraints on the age of the universe in the framework of an extra
background of relativistic particles are improved by a factor 3.Comment: JCAP, in pres
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