1,424 research outputs found
N II 5668-5712, a New Class of Spectral Features in Eta Carinae
We report on the N II 5668-5712 emission and absorption lines in the spectrum
of Eta Carinae. Spectral lines of the stellar wind regions can be classified
into four physically distinct categories: 1) low-excitation emission such as H
I and Fe II, 2) higher excitation He I features, 3) the N II lines discussed in
this paper, and 4) He II emission. These categories have different combinations
of radial velocity behavior, excitation processes, and dependences on the
secondary star. The N II lines are the only known features that originate in
"normal" undisturbed zones of the primary wind but depend primarily on the
location of the hot secondary star. N II probably excludes some proposed
models, such as those where He I lines originate in the secondary star's wind
or in an accretion disk.Comment: 4 figures, 1 tabl
Track, then Decide: Category-Agnostic Vision-based Multi-Object Tracking
The most common paradigm for vision-based multi-object tracking is
tracking-by-detection, due to the availability of reliable detectors for
several important object categories such as cars and pedestrians. However,
future mobile systems will need a capability to cope with rich human-made
environments, in which obtaining detectors for every possible object category
would be infeasible. In this paper, we propose a model-free multi-object
tracking approach that uses a category-agnostic image segmentation method to
track objects. We present an efficient segmentation mask-based tracker which
associates pixel-precise masks reported by the segmentation. Our approach can
utilize semantic information whenever it is available for classifying objects
at the track level, while retaining the capability to track generic unknown
objects in the absence of such information. We demonstrate experimentally that
our approach achieves performance comparable to state-of-the-art
tracking-by-detection methods for popular object categories such as cars and
pedestrians. Additionally, we show that the proposed method can discover and
robustly track a large variety of other objects.Comment: ICRA'18 submissio
Metal-Insulator Transition in a Generalized Hubbard Model with Correlated Hopping at Half-Filling
In the present paper metal-insulator transition is studied in a generalized
Hubbard model with correlated hopping at half-filling and zero temperature.
Single-particle Green function and energy spectrum of electron system are
calculated. The expressions for energy gap width and the concentration of polar
states (holes or doublons) are obtained. The conditions for metallic and
insulating states are found.Comment: 11 pages, 2 eps figures, Latex 2.09, submitted to Phys. Stat. Sol.
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Critical Differences and Clues in Eta Car's 2009 Event
We monitored Eta Carinae with HST WFPC2 and Gemini GMOS throughout the 2009
spectroscopic event, which was expected to differ from its predecessor in 2003
(Davidson et al. 2005). Here we report major observed differences between
events, and their implications. Some of these results were quite unexpected.
(1) The UV brightness minimum was much deeper in 2009. This suggests that
physical conditions in the early stages of an event depend on different
parameters than the "normal" inter-event wind. Extra mass ejection from the
primary star is one possible cause. (2) The expected He II 4687 brightness
maximum was followed several weeks later by another. We explain why this fact,
and the timing of the 4687 maxima, strongly support a "shock breakup"
hypothesis for X-ray and 4687 behavior as proposed 5-10 years ago. (3) We
observed a polar view of the star via light reflected by dust in the Homunculus
nebula. Surprisingly, at that location the variations of emission-line
brightness and Doppler velocities closely resembled a direct view of the star;
which should not have been true for any phenomena related to the orbit. This
result casts very serious doubt on all the proposed velocity interpretations
that depend on the secondary star's orbital motion. (4) Latitude-dependent
variations of H I, He I and Fe II features reveal aspects of wind behavior
during the event. In addition, we discuss implications of the observations for
several crucial unsolved problems.Comment: 45 pages, 9 figures, submitted to Ap
DGD Gallery: Storage, sharing, and publication of digital research data
We describe a project, called the "Discretization in Geometry and Dynamics
Gallery", or DGD Gallery for short, whose goal is to store geometric data and
to make it publicly available. The DGD Gallery offers an online web service for
the storage, sharing, and publication of digital research data.Comment: 19 pages, 8 figures, to appear in "Advances in Discrete Differential
Geometry", ed. A. I. Bobenko, Springer, 201
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