71 research outputs found
Uniqueness of the electrostatic solution in Schwarzschild space
In this Brief Report we give the proof that the solution of any static test
charge distribution in Schwarzschild space is unique. In order to give the
proof we derive the first Green's identity written with p-forms on (pseudo)
Riemannian manifolds. Moreover, the proof of uniqueness can be shown for either
any purely electric or purely magnetic field configuration. The spacetime
geometry is not crucial for the proof.Comment: 3 pages, no figures, uses revtex4 style file
Large size and slow rotation of the trans-Neptunian object (225088) 2007 OR10 discovered from Herschel and K2 observations
We present the first comprehensive thermal and rotational analysis of the
second most distant trans-Neptunian object (225088) 2007 OR10. We combined
optical light curves provided by the Kepler space telescope -- K2 extended
mission and thermal infrared data provided by the Herschel Space Observatory.
We found that (225088) 2007 OR10 is likely to be larger and darker than derived
by earlier studies: we obtained a diameter of d=1535^{+75}_{-225} km which
places (225088) 2007 OR10 in the biggest top three trans-Neptunian objects. The
corresponding visual geometric albedo is p_V=0.089^{+0.031}_{-0.009}. The light
curve analysis revealed a slow rotation rate of P_rot=44.81+/-0.37 h,
superseded by a very few objects only. The most likely light-curve solution is
double-peaked with a slight asymmetry, however, we cannot safely rule out the
possibility of having a rotation period of P_rot=22.40+/-0.18 h which
corresponds to a single-peaked solution. Due to the size and slow rotation, the
shape of the object should be a MacLaurin ellipsoid, so the light variation
should be caused by surface inhomogeneities. Its newly derived larger diameter
also implies larger surface gravity and a more likely retention of volatiles --
CH_4, CO and N_2 -- on the surface.Comment: Accepted for publication in AJ, 8 pages in emulateapj styl
Shocked Minerals in NWA 5011 L6 Chondritic Meteorite.
第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月18日(金) 国立国語研究所 2階講
Multi-wavelength study of the low-luminosity outbursting young star HBC 722
HBC 722 (V2493 Cyg) is a young eruptive star in outburst since 2010. It is an
FU Orionis-type object with an atypically low outburst luminosity. Because it
was well characterized in the pre-outburst phase, HBC 722 is one of the few
FUors where we can learn about the physical changes and processes associated
with the eruption. We monitored the source in the BVRIJHKs bands from the
ground, and at 3.6 and 4.5 m from space with the Spitzer Space Telescope.
We analyzed the light curves and the spectral energy distribution by fitting a
series of steady accretion disk models at many epochs. We also analyzed the
spectral properties of the source based on new optical and infrared spectra. We
also mapped HBC 722 and its surroundings at millimeter wavelengths. From the
light curve analysis we concluded that the first peak of the outburst in 2010
September was due to an abrupt increase of the accretion rate in the innermost
part of the system. This was followed by a long term process, when the
brightening was mainly due to a gradual increase of the accretion rate and the
emitting area. Our new observations show that the source is currently in a
constant plateau phase. We found that around the peak the continuum was bluer
and the H profile changed significantly between 2012 and 2013. The
source was not detected in the millimeter continuum, but we discovered a
flattened molecular gas structure with a diameter of 1700 au and mass of 0.3
M centered on HBC 722. While the first brightness peak could be
interpreted as a rapid fall of piled-up material from the inner disk onto the
star, the later monotonic flux rise suggests the outward expansion of a hot
component according to the theory of Bell & Lin (1994). Our study of HBC 722
demonstrated that accretion-related outbursts can occur in young stellar
objects even with very low mass disks, in the late Class II phase.Comment: 11 pages, 7 figures, 3 online tables. Accepted for publication in the
A&
Properties of the Irregular Satellite System around Uranus Inferred from K2, Herschel, and Spitzer Observations
In this paper, we present visible-range light curves of the irregular Uranian satellites Sycorax, Caliban, Prospero, Ferdinand, and Setebos taken with the Kepler Space Telescope over the course of the K2 mission. Thermal emission measurements obtained with the Herschel/PACS and Spitzer/MIPS instruments of Sycorax and Caliban were also analyzed and used to determine size, albedo, and surface characteristics of these bodies. We compare these properties with the rotational and surface characteristics of irregular satellites in other giant planet systems and also with those of main belt and Trojan asteroids and trans-Neptunian objects. Our results indicate that the Uranian irregular satellite system likely went through a more intense collisional evolution than the irregular satellites of Jupiter and Saturn. Surface characteristics of Uranian irregular satellites seem to resemble the Centaurs and trans-Neptunian objects more than irregular satellites around other giant planets, suggesting the existence of a compositional discontinuity in the young solar system inside the orbit of Uranus
Electrostatic boundary value problems in the Schwarzschild background
The electrostatic potential of any test charge distribution in Schwarzschild
space with boundary values is derived. We calculate the Green's function,
generalize the second Green's identity for p-forms and find the general
solution. Boundary value problems are solved. With a multipole expansion the
asymptotic property for the field of any charge distribution is derived. It is
shown that one produces a Reissner--Nordstrom black hole if one lowers a test
charge distribution slowly toward the horizon. The symmetry of the distribution
is not important. All the multipole moments fade away except the monopole. A
calculation of the gravitationally induced electrostatic self-force on a
pointlike test charge distribution held stationary outside the black hole is
presented.Comment: 18 pages, no figures, uses iopart.st
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