4,480 research outputs found
Characterizing Some Gaia Alerts with LAMOST and SDSS
Gaia is regularly producing Alerts on objects where photometric variability
has been detected. The physical nature of these objects has often to be
determined with the complementary observations from ground-based facilities. We
have compared the list of Gaia Alerts (until 20181101) with archival LAMOST and
SDSS spectroscopic data. The date of the ground-based observation rarely
corresponds to the date of the Alert, but this allows at least the
identification of the source if it is persistent, or the host galaxy if the
object was only transient like a supernova. A list of Gaia Nuclear Transients
from Kostrzewa-Rutkowska et al. (2018) has been included in this search also.
We found 26 Gaia Alerts with spectra in LAMOST+SDSS labelled as stars (12 with
multi-epoch spectra). A majority of them are CVs. Similarly 206 Gaia Alerts
have associated spectra labelled as galaxies (49 with multi-epoch spectra).
Those spectra were generally obtained on a date different from the Alert date,
are mostly emission-line galaxies, leading to the suspicion that most of the
Alerts were due to a SN. As for the GNT list, we found 55 associated spectra
labelled as galaxies (13 with multi-epoch spectra). In two galaxies, Gaia17aal
and GNTJ170213+2543, was the date of the spectroscopic observation close enough
to the Alert date: we find a trace of the SN itself in their LAMOST spectrum,
both classified here as a type Ia SN. The GNT sample has a higher proportion of
AGNs, suggesting that some of the detected variations are also due to the AGN
itself. Similar for Quasars, we found 30 Gaia Alerts but 68 GNT cases have
single epoch quasar spectra, while 12 plus 23 have multi-epoch spectra. For ten
out of these 35, their multi-epoch spectra show appearance or disappearance of
the broad Balmer lines and also variations in the continuum, qualifying them as
"Changing Look Quasars".Comment: Accepted for publication in APSS, 14 pages, 8 figures, 2 table
Atomic Entanglement vs Photonic Visibility for Quantum Criticality of Hybrid System
To characterize the novel quantum phase transition for a hybrid system
consisting of an array of coupled cavities and two-level atoms doped in each
cavity, we study the atomic entanglement and photonic visibility in comparison
with the quantum fluctuation of total excitations. Analytical and numerical
simulation results show the happen of quantum critical phenomenon similar to
the Mott insulator to superfluid transition. Here, the contour lines
respectively representing the atomic entanglement, photonic visibility and
excitation variance in the phase diagram are consistent in the vicinity of the
non-analytic locus of atomic concurrences.Comment: 4 pages, 2 figure
HST and LAMOST discover a dual active galactic nucleus in J0038+4128
We report the discovery of a kiloparsec-scale dual active galactic nucleus
(AGN) in J0038+4128. From the Hubble Space Telescope (HST) Wide Field Planetary
Camera (WFPC2) images, we find two optical nuclei with a projection separation
of 4.7 kpc (3.44 arcsec). The southern component (J0038+4128S) is
spectroscopically observed with the HST Goddard High Resolution Spectrograph in
the UV range and is found to be a Seyfert 1 galaxy with a broad Ly alpha
emission line. The northern component (J0038+4128N) is spectroscopically
observed during the Large Sky Area Multi-Object Fibre Spectroscopic Telescope
(also named the Guoshoujing Telescope) pilot survey in the optical range. The
observed line ratios as well as the consistency of redshift of the nucleus
emission lines and the host galaxy's absorption lines indicate that J0038+4128N
is a Seyfert 2 galaxy with narrow lines only. These results thus confirm that
J0038+4128 is a Seyfert 1-Seyfert 2 AGN pair. The HST WFPC2 F336W/U-band image
of J0038+4128 also reveals for the first time for a dual AGN system two pairs
of bi-symmetric arms, as are expected from the numerical simulations of such
system. Being one of a few confirmed kiloparsec-scale dual AGNs exhibiting a
clear morphological structure of the host galaxies, J0038+4128 provides an
unique opportunity to study the co-evolution of the host galaxies and their
central supermassive black holes undergoing a merging process.Comment: 6 pages, 4 figures, 2 tables, Accepted for publication in MNRAS
Letter
Design of a five-axis ultra-precision micro-milling machine—UltraMill. Part 2: Integrated dynamic modelling, design optimisation and analysis
Using computer models to predict the dynamic performance of ultra-precision machine tools can help manufacturers to substantially reduce the lead time and cost of developing new machines. However, the use of electronic drives on such machines is becoming widespread, the machine dynamic performance depending not only on the mechanical structure and components but also on the control system and electronic drives. Bench-top ultra-precision machine tools are highly desirable for the micro-manufacturing of high-accuracy micro-mechanical components. However, the development is still at the nascent stage and hence lacks standardised guidelines. Part 2 of this two-part paper proposes an integrated approach, which permits analysis and optimisation of the entire machine dynamic performance at the early design stage. Based on the proposed approach, the modelling and simulation process of a novel five-axis bench-top ultra-precision micro-milling machine tool—UltraMill—is presented. The modelling and simulation cover the dynamics of the machine structure, the moving components, the control system and the machining process and are used to predict the entire machine performance of two typical configurations
Peierls distorted chain as a quantum data bus for quantum state transfer
We systematically study the transfer of quantum state of electron spin as the
flying qubit along a half-filled Peierls distorted tight-binding chain
described by the Su-Schrieffer-Heeger (SSH) model, which behaves as a quantum
data bus. This enables a novel physical mechanism for quantum communication
with always-on interaction: the effective hopping of the spin carrier between
sites and connected to two sites in this SSH chain can be induced by
the quasi-excitations of the SSH model. As we prove, it is the Peierls energy
gap of the SSH quasi-excitations that plays a crucial role to protect the
robustness of the quantum state transfer process. Moreover, our observation
also indicates that such a scheme can also be employed to explore the intrinsic
property of the quantum system.Comment: 10 pages, 6 figure
Facial expression cloning optimization method based Laplace operator.
In view of the reality of facial expression cloning and efficiency of expression reconstruction, a novel method based on motion capture data is proposed. After capturing the data of six fundamental expressions, it normalizes these data to make them in the same range. Then 41 points are chosen in critical areas of facial expression and it gets cloning expression using Laplace deformation algorithm with convex weight which can preserve the details of facial expression to avoid the low fidelity of uniform weights and unstable calculation of cotangent weights. Experimental results show that this method can generate realistic and natural expression animations and the efficiency of facial expression cloning is improved significantly
A cosmic ray super high multicore family event. 1: Experiment and general features
Information on the fragmentation region in super high energy hadronic interactions can be obtained through the observations of gamma-ray families produced by cosmic rays. Gamma-ray families with the sum of E sub gamma or 1000 TeV are receiving increasing interests in emulsion chamber experiments. There exist some complications caused by the superposition of nuclear and electromagnetic cascades and the uncertainty in the nature of the primary particles. These complications usually make the conclusions drawn from various interesting phenomena observed in family events not so definite. An interesting family event KO E19, which is likely to have suffered only very slight disturbances is described. It was found in the Mt. Kambala emulsion chamber experiment. The production height of the event is determined to be H=(70 + or - 30)m and some conclusions are given
Intensities of high-energy cosmic rays at Mount Kanbala
The energy spectra of atmospheric cosmic rays at Mt. Kanbala (520 g/sq cm.) are measured with emulsion chambers. The power indexes of the spectra are values of about 2.0 for both gamma-rays and hadrons. Those fluxes are consistent with the ones expected from the model of primary cosmic rays with heavy nuclei of high content in the energy around 10 to the 15th power eV
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