1,060 research outputs found
Partial-Matching RMS Distance Under Translation: Combinatorics and Algorithms
We consider the problem of minimizing the RMS distance (sum of squared distances between pairs of points) under translation between two point sets A and B, in the plane, with (Formula presented.), in the partial-matching setup, in which each point in B is matched to a distinct point in A. Although the problem is not known to be polynomial, we establish several structural properties of the underlying subdivision (Formula presented.) of the plane and derive improved bounds on its complexity. Specifically, we show that this complexity is (Formula presented.), so it is only quadratic in |A|. These results lead to the best known algorithm for finding a translation for which the partial-matching RMS distance between the point sets is minimized. In addition, we show how to compute a local minimum of the partial-matching RMS distance under translation, in polynomial time. © 2017 Springer Science+Business Media New Yor
Film calibration for the Skylab/ATM S-056 X-ray telescope
The sensitometry and film calibration effort for the Skylab/ATM S-056 X-ray telescope is summarized. The apparatus and procedures used are described together with the two types of flight film used, Kodak SO-212 and SO-242. The sensitometry and processing of the flight film are discussed, and the results are presented in the form of the characteristic curves and related data. The use of copy films is also discussed
Prospek Jawawut (Pennisetum Spp. ) sebagai Tanaman Pangan Serealia Alternatif
Untuk meningkatkan ketahanan pangan dan diversifikasi pangan, Indonesia dapatmemanfaatkan lahan kering yang cukup luas jumlahnya. Jawawut (Pennisetumspp.) memiliki potensi yang sangat baik sebagai tanaman pangan alternatifditinjau dari aspek kandungan gizi, dan kemampuan tumbuhnya di daerahberiklim kering. Dilihat dari segi kandungan gizinya, jawawut berpotensi sebagaisumber energi, protein, kalsium, vitamin B1, riboflavin (vitamin B2), sedangkannutrisi lainnya setara dengan beras. Potensi hasil yang dapat dicapai di Indonesiaadalah 4 ton per ha pada kondisi agroekologi yang marginal, dimanapertumbuhan serealia lainnya kurang berhasil. Jawawut dipanen sebagai tanamanpangan semusim
A phenomenological model for the X-ray spectrum of Nova V2491 Cygni
The X-ray flux of Nova V2491 Cyg reached a maximum some forty days after
optical maximum. The X-ray spectrum at that time, obtained with the RGS of
XMM-Newton, shows deep, blue-shifted absorption by ions of a wide range of
ionization. We show that the deep absorption lines of the X-ray spectrum at
maximum, and nine days later, are well described by the following
phenomenological model with emission from a central blackbody and from a
collisionally ionized plasma (CIE). The blackbody spectrum (BB) is absorbed by
three main highly-ionized expanding shells; the CIE and BB are absorbed by cold
circumstellar and interstellar matter that includes dust. The outflow density
does not decrease monotonically with distance. The abundances of the shells
indicate that they were ejected from an O-Ne white dwarf. We show that the
variations on time scales of hours in the X-ray spectrum are caused by a
combination of variation in the central source and in the column density of the
ionized shells. Our phenomenological model gives the best description so far of
the supersoft X-ray spectrum of nova V2491 Cyg, but underpredicts, by a large
factor, the optical and ultraviolet flux. The X-ray part of the spectrum must
originate from a very different layer in the expanding envelope, presumably
much closer to the white dwarf than the layers responsible for the
optical/ultraviolet spectrum. This is confirmed by absence of any correlation
between the X-ray and UV/optical observed fluxes.Comment: 11 pages, 6 figure
Discovery of a new photometric sub-class of faint and fast classical novae
We present photometric and spectroscopic follow-up of a sample of
extragalactic novae discovered by the Palomar 60-inch telescope during a search
for "Fast Transients In Nearest Galaxies" (P60-FasTING). Designed as a fast
cadence (1-day) and deep (g < 21 mag) survey, P60-FasTING was particularly
sensitive to short-lived and faint optical transients. The P60-FasTING nova
sample includes 10 novae in M31, 6 in M81, 3 in M82, 1 in NGC2403 and 1 in
NGC891. This significantly expands the known sample of extragalactic novae
beyond the Local Group, including the first discoveries in a starburst
environment. Surprisingly, our photometry shows that this sample is quite
inconsistent with the canonical Maximum Magnitude Rate of Decline (MMRD)
relation for classical novae. Furthermore, the spectra of the P60-FasTING
sample are indistinguishable from classical novae. We suggest that we have
uncovered a sub-class of faint and fast classical novae in a new phase space in
luminosity-timescale of optical transients. Thus, novae span two orders of
magnitude in both luminosity and time. Perhaps, the MMRD, which is
characterized only by the white dwarf mass, was an over-simplification. Nova
physics appears to be characterized by quite a rich four-dimensional parameter
space in white dwarf mass, temperature, composition and accretion rate.Comment: Submitted to ApJ, 12 pages. High resolution version at
http://www.astro.caltech.edu/~mansi/msFasting.pd
Geometrical constraints on the origin of timing signals from black holes
We present a systematic study of the orbital inclination effects on black hole transients fast time-variability properties. We have considered all the black hole binaries that have been densely monitored by the Rossi X-ray Timing Explorer satellite. We find that the amplitude of low-frequency quasi-periodic oscillations (QPOs) depends on the orbital inclination. type-C QPOs are stronger for nearly edge-on systems (high inclination), while type-B QPOs are stronger when the accretion disc is closer to face-on (low inclination). Our results also suggest that the noise associated with type-CQPOs is consistent with being stronger for low-inclination sources, while the noise associated with type-B QPOs seems inclination independent. These results are consistent with a geometric origin of the type-C QPOs - for instance arising from relativistic precession of the inner flow within a truncated disc - while the noise would correspond to intrinsic brightness variability from mass accretion rate fluctuations in the accretion flow. The opposite behaviour of type-B QPOs - stronger in low-inclinations sources supports the hypothesis that type-B QPOs are related to the jet, the power of which is the most obvious measurable parameter expected to be stronger in nearly face-on sources
Measuring Transit Signal Recovery in the Kepler Pipeline. III. Completeness of the Q1-Q17 DR24 Planet Candidate Catalogue, with Important Caveats for Occurrence Rate Calculations
With each new version of the Kepler pipeline and resulting planet candidate
catalogue, an updated measurement of the underlying planet population can only
be recovered with an corresponding measurement of the Kepler pipeline detection
efficiency. Here, we present measurements of the sensitivity of the pipeline
(version 9.2) used to generate the Q1-Q17 DR24 planet candidate catalog
(Coughlin et al. 2016). We measure this by injecting simulated transiting
planets into the pixel-level data of 159,013 targets across the entire Kepler
focal plane, and examining the recovery rate. Unlike previous versions of the
Kepler pipeline, we find a strong period dependence in the measured detection
efficiency, with longer (>40 day) periods having a significantly lower
detectability than shorter periods, introduced in part by an incorrectly
implemented veto. Consequently, the sensitivity of the 9.2 pipeline cannot be
cast as a simple one-dimensional function of the signal strength of the
candidate planet signal as was possible for previous versions of the pipeline.
We report on the implications for occurrence rate calculations based on the
Q1-Q17 DR24 planet candidate catalog and offer important caveats and
recommendations for performing such calculations. As before, we make available
the entire table of injected planet parameters and whether they were recovered
by the pipeline, enabling readers to derive the pipeline detection sensitivity
in the planet and/or stellar parameter space of their choice.Comment: 8 pages, 5 figures, full electronic version of Table 1 available at
the NASA Exoplanet Archive; accepted by ApJ May 2nd, 201
Securing the legacy of TESS through the care and maintenance of TESS planet ephemerides
Much of the science from the exoplanets detected by the TESS mission relies
on precisely predicted transit times that are needed for many follow-up
characterization studies. We investigate ephemeris deterioration for simulated
TESS planets and find that the ephemerides of 81% of those will have expired
(i.e. 1 mid-transit time uncertainties greater than 30 minutes) one
year after their TESS observations. We verify these results using a sample of
TESS planet candidates as well. In particular, of the simulated planets that
would be recommended as JWST targets by Kempton et al. (2018), 80% will
have mid-transit time uncertainties 30 minutes by the earliest time JWST
would observe them. This rapid deterioration is driven primarily by the
relatively short time baseline of TESS observations. We describe strategies for
maintaining TESS ephemerides fresh through follow-up transit observations. We
find that the longer the baseline between the TESS and the follow-up
observations, the longer the ephemerides stay fresh, and that 51% of simulated
primary mission TESS planets will require space-based observations. The
recently-approved extension to the TESS mission will rescue the ephemerides of
most (though not all) primary mission planets, but the benefits of these new
observations can only be reaped two years after the primary mission
observations. Moreover, the ephemerides of most primary mission TESS planets
(as well as those newly discovered during the extended mission) will again have
expired by the time future facilities such as the ELTs, Ariel and the possible
LUVOIR/OST missions come online, unless maintenance follow-up observations are
obtained.Comment: 16 pages, 10 figures, accepted to AJ; main changes are cross-checking
results against the sample of real TOIs, and addressing the impact of the
TESS extended missio
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