1,212 research outputs found
A Spectrophotometric Method to Determine the Inclination of Class I Objects
A new method which enables us to estimate the inclination of Class I young
stellar objects is proposed. Since Class I objects are not spherically
symmetric, it is likely that the observed feature is sensitive to the
inclination of the system. Thus, we construct a protostar model by carefully
treating two-dimensional (2D) radiative transfer and radiative equilibrium. We
show from the present 2D numerical simulations that the emergent luminosity
L_SED,which is the frequency integration of spectral energy distribution (SED),
depends strongly on the inclination of the system i, whereas the peak flux is
insensitive to i. Based on this result, we introduce a novel indicator f_L,
which is the ratio of L_SED to the peak flux, as a good measure for the
inclination. By using f_L, we can determine the inclination regardless of the
other physical parameters. The inclination would be determined by f_L within
the accuracy of +- 5 degree, if the opening angle of bipolar outflows is
specified by any other procedure. Since this spectrophotometric method is
easier than a geometrical method or a full SED fitting method, this method
could be a powerful tool to investigate the feature of protostars statistically
with observational data which will be provided by future missions, such as
SIRTF, ASTRO-F, and ALMA.Comment: 14 pages, 9 figures, accepted by Ap
The Reionization History and Early Metal Enrichment inferred from the Gamma-Ray Burst Rate
Based on the gamma-ray burst (GRB) event rate at redshifts of , which is assessed by the spectral peak energy-to-luminosity relation
recently found by Yonetoku et al., we observationally derive the star formation
rate (SFR) for Pop III stars in a high redshift universe. As a result, we find
that Pop III stars could form continuously at . Using the
derived Pop III SFR, we attempt to estimate the ultraviolet (UV) photon
emission rate at in which redshift range no observational
information has been hitherto obtained on ionizing radiation intensity. We find
that the UV emissivity at can make a noticeable contribution
to the early reionization. The maximal emissivity is higher than the level
required to keep ionizing the intergalactic matter at .
However, if the escape fraction of ionizing photons from Pop III objects is
smaller than 10%, then the IGM can be neutralized at some redshift, which may
lead to the double reionization. As for the enrichment, the ejection of all
metals synthesized in Pop III objects is marginally consistent with the IGM
metallicity, although the confinement of metals in Pop III objects can reduce
the enrichment significantly.Comment: 12 pages, 2 figures, ApJL accepte
A generalization of determinant formulas for the solutions of Painlev\'e II and XXXIV equations
A generalization of determinant formulas for the classical solutions of
Painlev\'e XXXIV and Painlev\'e II equations are constructed using the
technique of Darboux transformation and Hirota's bilinear formalism. It is
shown that the solutions admit determinant formulas even for the transcendental
case.Comment: 20 pages, LaTeX 2.09(IOP style), submitted to J. Phys.
Formation of Large-Scale Obscuring Wall and AGN Evolution Regulated by Circumnuclear Starbursts
By considering the radiative force by a circumnuclear starburst as well as an
AGN, we analyze the equilibrium configuration and the stability of dusty gas in
the circumnuclear regions. It is found that the radiative force by an intensive
starburst can support a stable gaseous wall with a scale-height of several
hundred parsecs. Moreover, by taking the simple stellar evolution in the
starburst into account, we find that the covering factor of the wall decreases
on a time-scale of several yr. The large-scale wall, if formed, works to
obscure the nucleus due to the dust opacity. Hence, it is anticipated that the
index of AGN type tends to shift from higher to lower in several yr
according as the circumnuclear starburst becomes dimmer. On the other hand, if
the AGN itself is brighter than the circumnuclear starburst (e.g. quasar case),
no stable large-scale wall forms. In that case, the AGN is highly probably
identified as type 1. The present mechanism may provide a physical explanation
for the putative correlation between AGN type and host properties that Sy2's
are more frequently associated with circumnuclear starbursts than Sy1's,
whereas quasars are mostly observed as type 1 regardless of star-forming
activity in the host galaxies.Comment: 10 pages, 3 figures, ApJ Letters in pres
Existence and Uniqueness of Tri-tronqu\'ee Solutions of the second Painlev\'e hierarchy
The first five classical Painlev\'e equations are known to have solutions
described by divergent asymptotic power series near infinity. Here we prove
that such solutions also exist for the infinite hierarchy of equations
associated with the second Painlev\'e equation. Moreover we prove that these
are unique in certain sectors near infinity.Comment: 13 pages, Late
Rational Solutions of the Painleve' VI Equation
In this paper, we classify all values of the parameters , ,
and of the Painlev\'e VI equation such that there are
rational solutions. We give a formula for them up to the birational canonical
transformations and the symmetries of the Painlev\'e VI equation.Comment: 13 pages, 1 Postscript figure Typos fixe
Imprint of Gravitational Lensing by Population III Stars in Gamma Ray Burst Light Curves
We propose a novel method to extract the imprint of gravitational lensing by
Pop III stars in the light curves of Gamma Ray Bursts (GRBs). Significant
portions of GRBs can originate in hypernovae of Pop III stars and be
gravitationally lensed by foreground Pop III stars or their remnants. If the
lens mass is on the order of and the lens redshift is
greater than 10, the time delay between two lensed images of a GRB is s and the image separation is as. Although it is difficult to
resolve the two lensed images spatially with current facilities, the light
curves of two images are superimposed with a delay of s. GRB light
curves usually exhibit noticeable variability, where each spike is less than
1s. If a GRB is lensed, all spikes are superimposed with the same time delay.
Hence, if the autocorrelation of light curve with changing time interval is
calculated, it should show the resonance at the time delay of lensed images.
Applying this autocorrelation method to GRB light curves which are archived as
the {\it BATSE} catalogue, we demonstrate that more than half light curves can
show the recognizable resonance, if they are lensed. Furthermore, in 1821 GRBs
we actually find one candidate of GRB lensed by a Pop III star, which may be
located at redshift 20-200. The present method is quite straightforward and
therefore provides an effective tool to search for Pop III stars at redshift
greater than 10. Using this method, we may find more candidates of GRBs lensed
by Pop III stars in the data by the {\it Swift} satellite.Comment: 13 pages, 13 figures, accepted for publication in Ap
An X-Ray Microlensing Test of AU-Scale Accretion Disk Structure in Q2237+0305
The innermost regions of quasars can be resolved by a gravitational-lens
{\lq}telescope{\rq} on scales down to a few AU. For the purpose, X-ray
observations are most preferable, because X-rays originating from the innermost
regions, can be selectively amplified by microlensing due to the so-called
`caustic crossing'. If detected, X-ray variations will constrain the size of
the X-ray emitting region down to a few AU. The maximum attainable resolution
depends mainly on the monitoring intervals of lens events, which should be much
shorter than the crossing time. On the basis of this idea, we performe
numerical simulations of microlensing of an optically-thick, standard-type disk
as well as an optically-thin, advection-dominated accretion flow (ADAF).
Calculated spectral variations and light curves show distinct behaviors,
depending on the photon energy. X-ray radiation which is produced in optically
thin region, exhibits intensity variation over a few tens of days. In contrast,
optical-UV fluxes, which are likely to come from optically thick region,
exhibit more gradual light changes, which is consistent with the microlensing
events so far observed in Q2237+0305.
Currently, Q2237+0305 is being monitored in the optical range at Apache Point
Observatory. Simultaneous multi-wavelength observations by X-ray sattelites
(e.g., ASCA, AXAF, XMM) as well as HST at the moment of a microlens event
enable us to reveal an AU scale structure of the central accretion disk around
black hole.Comment: 10 pages LaTeX, 3 figures, accepted to ApJ Letter. e-mail:
[email protected]
Tabulation of PVI Transcendents and Parametrization Formulas (August 17, 2011)
The critical and asymptotic behaviors of solutions of the sixth Painlev\'e
equation PVI, obtained in the framework of the monodromy preserving deformation
method, and their explicit parametrization in terms of monodromy data, are
tabulated.Comment: 30 pages, 1 figure; Nonlinearity 201
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