255 research outputs found
Pushing the limits, episode 2: K2 observations of extragalactic RR Lyrae stars in the dwarf galaxy Leo IV
We present the first observations of extragalactic pulsating stars in the K2
ecliptic survey of the Kepler space telescope. Variability of all three RR
Lyrae stars in the dwarf spheroidal galaxy Leo IV were successfully detected,
at a brightness of Kp~21.5 mag, from data collected during Campaign 1. We
identified one modulated star and another likely Blazhko candidate with periods
of 29.8+-0.9 d and more than 80 d, respectively. EPIC 210282473 represents the
first star beyond the Magellanic Clouds for which the Blazhko period and
cycle-to-cycle variations in the modulation were unambiguously measured.The
photometric [Fe/H] indices of the stars agree with earlier results that Leo IV
is a very metal-poor galaxy. Two out of three stars blend with brighter
background galaxies in the K2 frames. We demonstrate that image subtraction can
be reliably used to extract photometry from faint confused sources that will be
crucial not only for the K2 mission but for future space photometric missions
as well.Comment: 8 pages, 6 figures, accepted for publication in the Astrophysical
Journal. Light curves can be downloaded from http://konkoly.hu/KIK/data.htm
First observations of W Virginis stars with K2: detection of period doubling
We present the first analysis of W Vir stars observed by the Kepler space
telescope in the K2 mission. Clear cycle-to-cycle variation were detected in
the light curves of KT Sco and the globular cluster member M80-V1. While the
variations in the former star seems to be irregular on the short time scale of
the K2 data, the latter appears to experience period doubling in its pulsation.
Ground-based colour data confirmed that both stars are W Vir-type pulsators,
while a comparison with historical photometric time-series data revealed
drastic period changes in both stars. For comparison we reexamine ground-based
observations of W Vir, the prototype of the class, and conclude that it shows
period doubling instead of mode beating. These results support the notion that
nonlinear dynamics plays an important role in the pulsation of W Virginis-type
stars.Comment: 8 pages, 7 figures, accepted for publication in MNRA
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
Identification of Pyroxene-Akimotoite Phase Transformation in NWA 5011 L6 Chondrite: Confirmation of the Preliminary Optical Observations
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17日(木) 国立国語研究所 2階講
Quarkyonic matter from hydro and rapid freeze out
Quarkyonic matter is a predicted phase between deconfined ideal QGP and Hadronic matter where the dominant degrees of freedom are quarks. Collective flow measurements indicate that the flow developed in QGP, as flow measurements scale with the constituent quark numbers. The possible reasons for the observed constituent quark number scaling were analyzed, arriving to the conclusion that collective flow must have frozen out early when quarks were the dominant constituents of matter.publishedVersio
The heart of the swarm: K2 photometry and rotational characteristics of 56 Jovian Trojan asteroids
We present fully covered phased light curves for 56 Jovian Trojan asteroids as acquired by the K2 mission of the Kepler space telescope. This set of objects has been monitored during Campaign 6 and represents a nearly unbiased subsample of the population of small Solar System bodies. We derived precise periods and amplitudes for all Trojans, and found their distributions to be compatible with the previous statistics. We point out, however, that ground-based rotation periods are often unreliable above 20h, and we find an overabundance of rotation periods above 60h compared with other minor planet populations. From amplitude analysis we derive a rate of binarity of 20 ±± 5%. Our spin rate distribution confirms the previously obtained spin barrier of ~5h and the corresponding ~0.5 g cm −3−3 cometary-like density limit, also suggesting a high internal porosity for Jovian Trojans. One of our targets, asteroid 65227 exhibits a double rotation period, which can either be due to binarity or the outcome of a recent collision
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&
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
The Kepler Cepheid V1154 Cyg revisited: light curve modulation and detection of granulation
We present a detailed analysis of the bright Cepheid-type variable star V1154 Cygni using 4 years of continuous observations by the Kepler space telescope. We detected 28 frequencies using standard Fourier transform method.We identified modulation of the main pulsation frequency and its harmonics with a period of ~159 d. This modulation is also present in the Fourier parameters of the light curve and the O-C diagram. We detected another modulation with a period of about 1160 d. The star also shows significant power in the low-frequency region that we identified as granulation noise. The effective timescale of the granulation agrees with the extrapolated scalings of red giant stars. Non-detection of solar-like oscillations indicates that the pulsation inhibits other oscillations. We obtained new radial velocity observations which are in a perfect agreement with previous years data, suggesting that there is no high mass star companion of V1154 Cygni. Finally, we discuss the possible origin of the detected frequency modulations
Celadonite and smectite formation in the Úrkút Mn-carbonate ore deposit (Hungary)
Synsedimentary and early diagenetic oxygen levels are estimated by evaluating celadonitesmectite formation in marine Jurassic black shale-hosted manganese-carbonates. Celadonite formed under suboxic-dysaerobic conditions, Al-rich Fe-smectite formed at suboxic-anaerobic conditions, and nontronite formed at anoxic-anaerobic conditions during sedimentary burial. A genetic pathway by direct precipitation from solution is proposed for the enormous mass of celadonite, based on mineral and textural evidence. Lamination of the manganese ore is independent of clay-mineral composition and was given by a series of mineralized microbial Ferich biomats
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