701 research outputs found
Spectroscopy of the bright optical counterparts of X-ray sources in the direction of M 31. II
A recent survey of the Local Group spiral galaxy M 31 with XMM-Newton yielded
a large number of X-ray sources. This is the second in a series of papers with
the aim of identifying the optical counterparts of these X-ray sources. We have
obtained optical spectra for 21 bright optical counterparts of 20 X-ray sources
in the direction of M 31, using the 1.3-m Skinakas telescope in Crete, Greece.
For 17 of the 20 X-ray sources, we have identified the optical counterpart as a
normal late type star (of type F or later) in the foreground (i.e. in the Milky
Way). For two more sources there were two possible optical counterparts in each
case, while two more objects have X-ray properties that are not compatible with
the spectral characteristics of late type non-flaring stars.Comment: Accepted for publication by Astronomy & Astrophysics (7 pages, 8
figures, and 2 tables
Le vétérinaire sanitaire : Evolution de la législation et de la réglementation relatives aux conditions de nomination et aux garanties en matière disciplinaire
Mornet Paul. Le vétérinaire sanitaire. Evolution de la législation et de la réglementation relatives aux conditions de nomination et aux garanties en matière disciplinaire. In: Bulletin de l'Académie Vétérinaire de France tome 128 n°9-10, 1975. pp. 415-419
La lutte contre les maladies des animaux. Evolution de la législation et de la réglementation au cours des cent dernières années
Mornet Paul. La lutte contre les maladies des animaux. Évolution de la législation, et de la réglementation au cours des cent dernières années. In: Bulletin de l'Académie Vétérinaire de France tome 126 n°1, 1973. pp. 37-46
The investigation of absolute proper motions of the XPM Catalogue
The XPM-1.0 is the regular version of the XPM catalogue. In comparison with
XPM the astrometric catalogue of about 280 millions stars covering entire sky
from -90 to +90 degrees in declination and in the magnitude range 10^m<B<22^m
is something improved. The general procedure steps were followed as for XPM,
but some of them are now performed on a more sophisticated level. The XPM-1.0
catalogue contains star positions, proper motions, 2MASS and USNO photometry of
about 280 millions of the sources. We present some investigations of the
absolute proper motions of XPM-1.0 catalogue and also the important information
for the users of the catalogue. Unlike previous version, the XPM-1.0 contains
the proper motions over the whole sky without gaps. In the fields, which cover
the zone of avoidance or which contain less than of 25 galaxies a quasi
absolute calibration was performed. The proper motion errors are varying from 3
to 10 mas/yr, depending on a specific field. The zero-point of the absolute
proper motion frame (the absolute calibration) was specified with more than 1
million galaxies from 2MASS and USNO-A2.0. The mean formal error of absolute
calibration is less than 1 mas/yr.Comment: 11 pages, 9 figures, accepte
Calibrating Type Ia Supernovae using the Planetary Nebula Luminosity Function I. Initial Results
We report the results of an [O III] lambda 5007 survey for planetary nebulae
(PN) in five galaxies that were hosts of well-observed Type Ia supernovae: NGC
524, NGC 1316, NGC 1380, NGC 1448 and NGC 4526. The goals of this survey are to
better quantify the zero-point of the maximum magnitude versus decline rate
relation for supernovae Type Ia and to validate the insensitivity of Type Ia
luminosity to parent stellar population using the host galaxy Hubble type as a
surrogate. We detected a total of 45 planetary nebulae candidates in NGC 1316,
44 candidates in NGC 1380, and 94 candidates in NGC 4526. From these data, and
the empirical planetary nebula luminosity function (PNLF), we derive distances
of 17.9 +0.8/-0.9 Mpc, 16.1 +0.8/-1.1 Mpc, and 13.6 +1.3/-1.2 Mpc respectively.
Our derived distance to NGC 4526 has a lower precision due to the likely
presence of Virgo intracluster planetary nebulae in the foreground of this
galaxy. In NGC 524 and NGC 1448 we detected no planetary nebulae candidates
down to the limiting magnitudes of our observations. We present a formalism for
setting realistic distance limits in these two cases, and derive robust lower
limits of 20.9 Mpc and 15.8 Mpc, respectively.
After combining these results with other distances from the PNLF, Cepheid,
and Surface Brightness Fluctuations distance indicators, we calibrate the
optical and near-infrared relations for supernovae Type Ia and we find that the
Hubble constants derived from each of the three methods are broadly consistent,
implying that the properties of supernovae Type Ia do not vary drastically as a
function of stellar population. We determine a preliminary Hubble constant of
H_0 = 77 +/- 3 (random) +/- 5 (systematic) km/s/Mpc for the PNLF, though more
nearby galaxies with high-quality observations are clearly needed.Comment: 25 pages, 12 figures. Accepted for publication by the Astrophysical
Journal. Figures degraded to comply with limit. Full paper is available at:
http://www.as.ysu.edu/~jjfeldme/pnlf_Ia.pd
Searching for the pulsar in G18.95-1.1: Discovery of an X-ray point source and associated synchrotron nebula with Chandra
Using the Chandra X-ray Observatory, we have pinpointed the location of a
faint X-ray point source (CXOUJ182913.1-125113) and an associated diffuse
nebula in the composite supernova remnant G18.95-1.1. These objects appear to
be the long-sought pulsar and its wind nebula. The X-ray spectrum of the point
source is best described by an absorbed powerlaw model with Gamma=1.6 and an
N_H of ~1x10^(22) cm^(-2). This model predicts a relatively low unabsorbed
X-ray luminosity of about L_X (0.5-8.0keV) = 4.1x10^(31)D_2^2 erg s^(-1), where
D_2 is the distance in units of 2kpc. The best-fitted model of the diffuse
nebula is a combination of thermal (kT = 0.48keV) and non-thermal (1.4 < Gamma
< 1.9) emission. The unabsorbed X-ray luminosity of L_X = 5.4x10^(33)D_2^2 erg
s^(-1) in the 0.5-8keV energy band seems to be largely dominated by the thermal
component from the SNR, providing 87% of L_X in this band. No radio or X-ray
pulsations have been reported for CXOUJ182913.1-125113. If we assume an age of
~5300yr for G18.95-1.1 and use the X-ray luminosity for the pulsar and the wind
nebula together with the relationship between spin-down luminosity (via
magnetic dipole radiation) and period, we estimate the pulsar's period to be P
= 0.4s. Compared to other rotation-powered pulsars, a magnetic field of
2.2x10^(13)G is implied by its location in the P-Pdot diagram, a value which is
close to that of the quantum critical field.Comment: 8 pages, 3 Figures, accepted for publication in Ap
CORMASS: A Compact and Efficient NIR Spectrograph for Studying Low-Mass Objects
CorMASS (Cornell Massachusetts Slit Spectrograph) is a compact,
low-resolution (R=300), double-pass prism cross-dispersed near-infrared (NIR)
spectrograph in operation on the Palomar Observatory 60-inch telescope. Its
2-dimensional spectral format provides simultaneous coverage from lambda ~ 0.75
microns to lambda ~ 2.5 microns (z'JHK bands). A remotely operated cold flip
mirror permits its NICMOS3 detector to function as a K_s slit viewer to assist
object placement into the 2 arcsec x 15 arcsec slit. CorMASS was primarily
designed for the rapid spectral classification of low-mass stellar and
sub-stellar objects identified by the Two-Micron All Sky Survey (2MASS).
CorMASS' efficiency and resolution also make it a versatile instrument for the
spectral observation and classification of many other types of bright objects
(K<14) including quasars, novae, and emission line objects.Comment: To be published in Feb 2001 PASP, 19 pages, 12 Figures, High
Resolution file can be retrieved from
ftp://iras2.tn.cornell.edu/pub/wilson/papers/cormass.ps.g
The Magellan/IMACS Catalog of Optical Supernova Remnant Candidates in M83
We present a new optical imaging survey of supernova remnants in M83, using
data obtained with the Magellan I 6.5m telescope and IMACS instrument under
conditions of excellent seeing. Using the criterion of strong [S II] emission
relative to Halpha, we confirm all but three of the 71 SNR candidates listed in
our previous survey, and expand the SNR candidate list to 225 objects, more
than tripling the earlier sample. Comparing the optical survey with a new deep
X-ray survey of M83 with Chandra, we find 61 of these SNR candidates to have
X-ray counterparts. We also identify an additional list of 46 [O III] -selected
nebulae for follow-up as potential ejecta-dominated remnants, seven of which
have associated X-ray emission that makes them strong candidates. Some of the
other [O III]-bright objects could also be normal ISM-dominated supernova
remnants with shocks fast enough to doubly ionize oxygen, but with Halpha and
[S II] emission faint enough to have been missed. A few of these objects may
also be H II regions with abnormally high [O III] emission compared with the
majority of M83 H II regions, compact nebulae excited by young Wolf-Rayet
stars, or even background AGN. The supernova remnant Halpha luminosity function
in M83 is shifted a factor of ~ 4.5x higher than for M33 supernova remnants,
indicative of a higher mean ISM density in M83. We describe the search
technique used to identify the supernova remnant candidates and provide basic
information and finder charts for the objects.Comment: 40 pages, 15 figures, accepted for ApJ
Chandra Observations of Galaxy Cluster Abell 2218
We present results from two observations (combined exposure of ~17 ks) of
galaxy cluster A2218 using the Advanced CCD Imaging Spectrometer on board the
Chandra X-ray Observatory that were taken on October 19, 1999. Using a
Raymond-Smith single temperature plasma model corrected for galactic absorption
we find a mean cluster temperature of kT = 6.9+/-0.5 keV, metallicity of
0.20+/-0.13 (errors are 90 % CL) and rest-frame luminosity in the 2-10 keV
energy band of 6.2x10^{44} erg/s in a LambdaCDM cosmology with H_0=65 km/s/Mpc.
The brightness distribution within 4'.2 of the cluster center is well fit by a
simple spherical beta model with core radius 66".4 and beta = 0.705 . High
resolution Chandra data of the inner 2' of the cluster show the x-ray
brightness centroid displaced ~22" from the dominant cD galaxy and the presence
of azimuthally asymmetric temperature variations along the direction of the
cluster mass elongation. X-ray and weak lensing mass estimates are in good
agreement for the outer parts (r > 200h^{-1}) of the cluster; however, in the
core the observed temperature distribution cannot reconcile the x-ray and
strong lensing mass estimates in any model in which the intracluster gas is in
thermal hydrostatic equilibrium. Our x-ray data are consistent with a scenario
in which recent merger activity in A2218 has produced both significant
non-thermal pressure in the core and substructure along the line of sight; each
of these phenomena probably contributes to the difference between lensing and
x-ray core mass estimates.Comment: 33 pages, 6 figures, uses AASTeX 5.02, ApJ submitte
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