973 research outputs found
A plethora of new, magnetic chemically peculiar stars from LAMOST DR4
Magnetic chemically peculiar (mCP) stars are important to astrophysics
because their complex atmospheres lend themselves perfectly to the
investigation of the interplay between such diverse phenomena as atomic
diffusion, magnetic fields, and stellar rotation. The present work is aimed at
identifying new mCP stars using spectra collected by the Large Sky Area
Multi-Object Fiber Spectroscopic Telescope (LAMOST). Suitable candidates were
selected by searching LAMOST DR4 spectra for the presence of the characteristic
5200A flux depression. Spectral classification was carried out with a modified
version of the MKCLASS code and the accuracy of the classifications was
estimated by comparison with results from manual classification and the
literature. Using parallax data and photometry from Gaia DR2, we investigated
the space distribution of our sample stars and their properties in the
colour-magnitude diagram. Our final sample consists of 1002 mCP stars, most of
which are new discoveries (only 59 previously known). Traditional mCP star
peculiarities have been identified in all but 36 stars, highlighting the
efficiency of the code's peculiarity identification capabilities. The derived
temperature and peculiarity types are in agreement with manually derived
classifications and the literature. Our sample stars are between 100 Myr and 1
Gyr old, with the majority having masses between 2M(Sun) and 3M(Sun). Our
results could be considered as strong evidence for an inhomogeneous age
distribution among low-mass (M < 3M(Sun)) mCP stars. We identified several
astrophysically interesting objects: two mCP stars have distances and
kinematical properties in agreement with halo stars; an eclipsing binary system
hosting an mCP star component; and an SB2 system likely comprising of an mCP
star and a supergiant component.Comment: 62 pages, 24 figures, 10 tables, corrected some typos and minor
mistakes; corrected wrong number of stars with absolute parallax errors less
than 25
Open Cluster Characterization via Cross-Correlation with Spectral Library
We present a characterization method based on spectral cross-correlation to
obtain the physical parameters of the controversial stellar aggregate
ESO442-SC04. The data used was obtained with GMOS at Gemini-South telescope
including 17 stars in the central region of the ob ject and 6 standard-stars.
FXCOR was used in an iterative process to obtain self-consistent radial
velocities for the standard-stars and averaged radial velocities for the
science spectra. Spectral types, effective temperature, suface gravity and
metallicities parameters were determined using FXCOR to correlate cluster
spectra with ELODIE spectral library and selecting the best correlation matches
using the Tonry and Davis Ratio (TDR). Analysis of the results suggests that
the stars in ESO442-SC04 are not bound and therefore they do not constitute a
physical system.Comment: 4-page paper from IAU symposium 266. Contains 3 eps figures and IAU
document class file 'iau.cls
RACE-OC Project: Rotation and variability in the open cluster M11 (NGC6705)
Rotation and magnetic activity are intimately linked in main-sequence stars
of G or later spectral types. The presence and level of magnetic activity
depend on stellar rotation, and rotation itself is strongly influenced by
strength and topology of the magnetic fields. Open clusters represent
especially useful targets to investigate the rotation/activity/age connection.
The open cluster M11 has been studied as a part of the RACE-OC project
(Rotation and ACtivity Evolution in Open Clusters), which is aimed at exploring
the evolution of rotation and magnetic activity in the late-type members of
open clusters with different ages. Photometric observations of the open cluster
M11 were carried out in June 2004 using LOAO 1m telescope. The rotation periods
of the cluster members are determined by Fourier analysis of photometric data
time series. We further investigated the relations between the surface
activity, characterized by the light curve amplitude, and rotation. We have
discovered a total of 75 periodic variables in the M11 FoV, of which 38 are
candidate cluster members. Specifically, among cluster members we discovered 6
early-type, 2 eclipsing binaries and 30 bona-fide single periodic late-type
variables. Considering the rotation periods of 16 G-type members of the almost
coeval 200-Myr M34 cluster, we could determine the rotation period distribution
from a more numerous sample of 46 single G stars at an age of about 200-230 Myr
and determine a median rotation period P=4.8d. A comparison with the younger
M35 cluster (~150 Myr) and with the older M37 cluster (~550 Myr) shows that G
stars rotate slower than younger M35 stars and faster than older M37 stars. The
measured variation of the median rotation period is consistent with the
scenario of rotational braking of main-sequence spotted stars as they age.Comment: Accepted by Astronomy and Astrophysics on Dec 15, 200
A Process for Producing Ice Coverage Marine Information Objects (MIOs) in IHO S-57 Format
While global warming may be opening up more Arctic waters in the summer, ice still infests key shipping lanes in the northern hemisphere during the winter months. To safely navigate these areas, mariners rely on daily ice coverage charts produced by national governmental agencies. Ice charts are primarily issued in paper format or as a fax. However, there is increased interest to ice coverage information on vessel navigation systems such as an Electronic Chart and Display Information Systems (ECDIS). However, to do so, the ice information must be provided as a separate layer of information to the Electronic Navigational Chart (ENC)
Integrating digital document acquisition into a university library : A case study of social and organizational challenges
In this article we report on the effort of the university library of the Vienna University of Economics and Business Administration to integrate a digital library component for research documents authored at the university into the existing library infrastructure. Setting up a digital library has become a relatively easy task using the current data base technology and the components and tools freely available. However, to integrate such a digital library into existing library systems and to adapt existing document acquisition work-flows in the organization are non-trivial tasks. We use a research frame work to identify the key players in this change process and to analyze their incentive structures. Then we describe the light-weight integration approach employed by our university and show how it provides incentives to the key players and at the same time requires only minimal adaptation of the organization in terms of changing existing work-flows. Our experience suggests that this light-weight integration offers a cost efficient and low risk intermediate step towards switching to exclusive digital document acquisition
The VIMOS Public Extragalactic Survey (VIPERS): First Data Release of 57 204 spectroscopic measurements
We present the first Public Data Release (PDR-1) of the VIMOS Public
Extragalactic Survey (VIPERS). It comprises 57 204 spectroscopic measurements
together with all additional information necessary for optimal scientific
exploitation of the data, in particular the associated photometric measurements
and quantification of the photometric and survey completeness. VIPERS is an ESO
Large Programme designed to build a spectroscopic sample of ' 100 000 galaxies
with iAB < 22.5 and 0.5 < z < 1.5 with high sampling rate (~45%). The survey
spectroscopic targets are selected from the CFHTLS-Wide five-band catalogues in
the W1 and W4 fields. The final survey will cover a total area of nearly 24
deg2, for a total comoving volume between z = 0.5 and 1.2 of ~4x10^7
h^(-3)Mpc^3 and a median galaxy redshift of z~0.8. The release presented in
this paper includes data from virtually the entire W4 field and nearly half of
the W1 area, thus representing 64% of the final dataset. We provide a detailed
description of sample selection, observations and data reduction procedures; we
summarise the global properties of the spectroscopic catalogue and explain the
associated data products and their use, and provide all the details for
accessing the data through the survey database (http://vipers.inaf.it) where
all information can be queried interactively.Comment: Accepted for publication in A&A Added and/or replaced some figure,
added section on DataBase interface, expaned Introductio
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