publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
|---|---|---|---|
2002-03-10 | Mass Composition of Cosmic Rays in the Range 2 x 10^17 - 3 x 10^18 Measured with Haverah Park Array | At the Haverah Park Array a number of air shower observables were measured
that are relevant to the determination of the mass composition of cosmic rays.
In this paper we discuss measurements of the risetime of signals in large area
water-Cherenkov detectors and of the lateral distribution function of the
water-Cherenk... | 0203150v1 |
2002-03-13 | Reprocessing of X-rays in AGN. I. Plane parallel geometry -- test of pressure equilibrium | We present a model of the vertical stratification and the spectra of an
irradiated medium under the assumption of constant pressure. Such a solution
has properties intermediate between constant density models and hydrostatic
equilibrium models, and it may represent a flattened configuration of gas
clumps accreting onto... | 0203202v1 |
2002-03-15 | Chandra Observations of the Gravitational Potential Structure in Abell 1060 | We present results from a Chandra observation of Abell 1060, the nearby
cluster of galaxies. The ACIS-I image shows that the central cusp-like
structure, previously seen from PSPC, is caused mainly by an emission from the
central elliptical galaxy NGC 3311. We confirmed that the central region is
remarkably isothermal ... | 0203244v1 |
2002-03-18 | X-Ray Spectroscopy of Gamma-Ray Bursts | Observational evidence of iron absorption and emission lines in X-ray spectra
of Gamma-Ray Bursts is quite compelling. I will briefly review the results,
summarize different models and describe the connection with massive progenitors
in star-forming regions implied by these results. This link is also supported
by measu... | 0203275v1 |
2002-03-20 | Lyman-break galaxies: are they young spheroids? | We have compared the results from a model for the chemical evolution of an
elliptical galaxy with initial luminous mass of 2x10^10 M_sun and effective
radius of 2 kpc with the recent abundance determinations for the Lyman-break
galaxy MS 1512-cB58 at a redshift z=2.7276. After correcting the iron abundance
determinatio... | 0203329v1 |
2002-03-22 | Iron abundance in HII regions | Optical CCD spectra are used to determine the Fe abundances at several
positions inside seven bright Galactic HII regions. The observed [FeIII] line
ratios are compared with the predictions of different sets of collision
strengths and transition probabilities for this ion to select the atomic data
providing the best fi... | 0203394v1 |
2002-03-26 | New Members of the Cluster Family in Nearby Lenticulars | Using spectra obtained with the Keck I telescope we have demonstrated
conclusively that the faint (23<V<24 mag.) and unusually extended objects we
discovered in HST images of the lenticular galaxies, NGC 1023 and NGC 3384, are
star clusters associated with their respective galaxies. In the case of NGC
1023 we were furt... | 0203454v2 |
2002-04-10 | The broad band X-ray spectrum of the black hole candidate GRS1758-258 | We present the results of a BeppoSAX observation of the black hole candidate
GRS1758-258 carried out in 1997, while the source was in its low/hard state.
The X-ray spectrum, simultaneously observed over the broad energy range from
0.1 to 200 keV, can be well described by a Comptonized emission model with
electron tempe... | 0204176v1 |
2002-05-02 | An unusual iron Lo-BAL quasar detected by ISOCAM | We report the discovery of an unusual low--ionization broad absorption line
quasar at z=1.776 which exhibits absorption lines from many excited states of
Feii. This member of the rare class of 'FeLoBAL' quasars was serendipitously
found in a mid-infrared (MIR) survey of distant clusters carried out with the
ISOCAM came... | 0205022v1 |
2002-05-17 | Rotation and activity in the solar-metallicity open cluster NGC2516 | We report new measures of radial velocities and rotation rates (v sin i) for
51 F and early-G stars in the open cluster NGC2516, and combine these with
previously published data. From high signal-to-noise spectra of two stars, we
show that NGC2516 has a relative iron abundance with respect to the Pleiades of
delta([Fe/... | 0205300v1 |
2002-06-10 | On the formation of inner vacuum gaps in radio pulsars | The problem of formation of the Ruderman-Sutherland type inner vacuum gap in
neutron stars with ${\bf\Omega}\cdot{\bf B}<0$ is considered. It is argued by
means of the condition $T_i/T_s>1$ (where $T_i$ is the critical temperature
above which $^{56}_{26}$Fe ions will not be bound at the surface and $T_s$ is
the actual ... | 0206141v1 |
2002-06-11 | Multiple X-ray reflection from ionized slabs | Multiple reflection of X-rays may be important when an accretion disc and its
hot corona have a complicated geometry, or if returning radiation due to
gravitational light bending is important, or in emission from a funnel such as
proposed in some gamma-ray burst models. We simulate the effects of multiple
reflection by... | 0206170v1 |
2002-07-01 | XMM-Newton observations of MR Vel/RX J0925.7-4758 | We report on XMM-Newton observations of the galactic supersoft X-ray source
RX J0925.7-4758. The RGS spectrum exhibits a wealth of spectral features from
iron and oxygen. XMM-Newton data confirm the finding of previous Chandra
HETGS/MEG observations that NLTE models of hot white dwarf atmospheres fail to
represent the ... | 0207004v1 |
2002-06-29 | Discovery of an ionized Fe-K edge in the z=3.91 Broad Absorption Line Quasar APM 08279+5255 with XMM-Newton | Recent XMM-Newton observations of the high-redshift, lensed, broad absorption
line (BAL) quasi-stellar object APM 08279+5255, one of the most luminous
objects in the universe, allowed the detection of a high column density
absorber ($N_H \approx 10^{23}$ cm$^{-2}$) in the form of a K-shell absorption
edge of significan... | 0207005v1 |
2002-07-12 | Reflection at large distance from the central engine in Seyfert 1s | We consider the possibility that most of the reflection component, observed
in the hard X-ray spectra of Seyfert galaxies, could be formed on an extended
medium, at large distance from the central source of primary radiation (e.g. on
a torus). Then, the reflector cannot respond to the rapid fluctuations of the
primary ... | 0207269v1 |
2002-07-15 | On the Structure of the Iron K-Edge | It is shown that the commonly held view of a sharp Fe K edge must be modified
if the decay pathways of the series of resonances converging to the K
thresholds are adequately taken into account. These resonances display damped
Lorentzian profiles of nearly constant widths that are smeared to impose
continuity across the... | 0207324v2 |
2002-07-18 | Mrk 1014: An AGN Dominated ULIRG at X-rays | In this paper we report on an XMM-Newton observation of the ultraluminous
infrared QSO Mrk 1014. The X-ray observation reveals a power-law dominated
(photon index of about 2.2) spectrum with a slight excess in the soft energy
range. AGN and starburst emission models fit the soft excess emission equally
well, however, t... | 0207378v1 |
2002-08-01 | Chemical Composition of the Carbon-rich, Extremely Metal-Poor Star CS 29498--043: A New Class of Extremely Metal-Poor Stars with Excesses of Magnesium and Silicon | We analyze a high-resolution, high signal-to-noise spectrum of the
carbon-rich, extremely metal-poor star CS29498-043, obtained with the Subaru
Telescope High Dispersion Spectrograph. We find its iron abundance is extremely
low ([Fe/H] = -3.7), placing it among the few stars known with [Fe/H] < -3.5,
while Mg and Si ar... | 0208019v1 |
2002-08-02 | Using Cepheids to determine the galactic abundance gradient. III.First results for the outer disc | As a continuation of our previous work, which concerned the radial abundance
distribution in the galactic disc over the distances 4-10 kpc this paper
presents the first results on the metallicicty in the outer disc (RG > 10 kpc).
Based on high-resolution spectra obtained for 19 distant Cepheids we sampled
galactocentri... | 0208056v1 |
2002-08-09 | Elemental Abundances and Ionization States within the Local Interstellar Cloud Derived from HST and FUSE Observations of the Capella Line of Sight | We use ultraviolet spectra of Capella from the Hubble Space Telescope (HST)
and Far Ultraviolet Spectroscopic Explorer (FUSE) satellites to study
interstellar absorption lines from the Local Interstellar Cloud (LIC).
Measurements of these lines are used to empirically determine the ionization
states of carbon, nitrogen... | 0208214v1 |
2002-08-25 | A new measurement of zinc metallicity in a DLA at z=3.35 | We present chemical abundance measurements in the z_abs=3.35045 Damped
Lyman-alpha (DLA) system observed in the UVES spectrum of the BAL quasar BR
1117-1329. We measure a neutral hydrogen column density N(HI)=6.9+/-1.7*10^{20}
atoms/cm2 and derive mean abundances relative to solar: [Si/H] = -1.26+/-0.13,
[Fe/H]=-1.51+/... | 0208450v1 |
2002-09-05 | X-ray spectroscopy of Eta Carinae with XMM-Newton | We present XMM-Newton observations of the luminous star Eta Carinae,
including a high resolution soft X-ray spectrum of the surrounding nebula
obtained with the Reflection Grating Spectrometer. The EPIC image of the field
around Eta Car shows many early-type stars and diffuse emission from hot,
shocked gas. The EPIC sp... | 0209087v2 |
2002-09-11 | Ultra-High Energy Heavy Nuclei Propagation in Extragalactic Magnetic Fields | We extend existing work on the propagation of ultra-high energy cosmic rays
in extragalactic magnetic fields to a possible component of heavy nuclei,
taking into account photodisintegration, pion production, and creation of e+e-
pairs. We focus on the influence of the magnetic field on the spectrum and
chemical composi... | 0209192v1 |
2002-09-12 | A Chandra observation of the H2O megamaser IC2560 | A short Chandra ACIS-S observation of the Seyfert 2 galaxy IC 2560, which
hosts a luminous nuclear water megamaser, shows: 1) the X-ray emission is
extended; 2) the X-ray spectrum shows emission features in the soft (E<2 keV)
X-ray band; this is the major component of the extended emission; and 3) a very
strong (EW~3.6... | 0209245v1 |
2002-10-08 | Spectral Features and Masses in the PeV Region | An analysis is made of the masses and spectral features for cosmic rays in
the PeV region, insofar as they have a bearing on the problem of the
interaction of cosmic ray particles. In our Single Source Model we identified
two 'peaks' seen in a summary of the world's data on primary spectra, and
claimed that they are pr... | 0210192v1 |
2002-10-18 | The Chemistry of Extragalactic Globular Clusters | We present preliminary results of VLT/FORS spectroscopy of globular clusters
in nearby early-type galaxies. Our project aims at studying the chemistry and
determine the ages of globular cluster (sub-)populations. First results
indicate that the different galaxies host from little to significant
intermediate-age populat... | 0210419v1 |
2002-10-21 | Globular Clusters in nearby Galaxy Cluster | The discovery of a large population of intra-cluster star clusters in the
central region of the Hydra I and Centaurus galaxy clusters is presented. Based
on deep VLT photometry (V,I), many star clusters have been identified not only
around the early-type galaxies, but also in the intra-cluster field, as far as
250 kpc ... | 0210466v1 |
2002-11-11 | Stationary models of relativistic magnetohydrodynamic jets | Highly relativistic jets are most probably driven by strong magnetic fields
and are launched from the accretion disk surrounding a central black hole. In
this paper we review some of our recent results considering the two-dimensional
magnetic field structure and the dynamics of collimating relativistic jets.
Applying t... | 0211233v1 |
2002-11-20 | Quiet Sun magnetic fields at high spatial resolution | We present spectro-polarimetric observations of Inter-Network magnetic fields
at the solar disk center. A Fabry-Perot spectrometer was used to scan the two
Fe I lines at 6301.5 A and 6302.5 A. High spatial resolution (0.5")
magnetograms were obtained after speckle reconstruction. The patches with
magnetic fields above ... | 0211454v1 |
2002-12-16 | Status of the KASCADE-Grande Experiment | The status and capabilities of the KASCADE-Grande extensive air shower
experiment are presented. The installation is located at Forschungszentrum
Karlsruhe and comprises a large collecting area (0.5 km^2) electromagnetic
array (Grande) operated jointly with the existing KASCADE detectors.
KASCADE-Grande will cover the ... | 0212347v1 |
2003-01-09 | An XMM-Newton observation of the Narrow Line Seyfert 1 Galaxy, Markarian 896 | XMM-Newton observations of the NLS1 Markarian 896 are presented. Over the
2-10 keV band, an iron emission line, close to 6.4 keV, is seen. The line is
just resolved and has an equivalent width of ~170 eV. The broad-band spectrum
is well modelled by a power law slope of gamma ~ 2.03, together with two
blackbody componen... | 0301152v1 |
2003-01-17 | On the Progenitor of Supernova 2001du in NGC 1365 | Hubble Space Telescope (HST) WFPC2 archival images obtained years prior to
the explosion of the Type II-plateau supernova (SN) 2001du in NGC 1365
previously have been analyzed to isolate the progenitor star. The SN site was
located using precise astrometry applied to the HST images, with significant
uncertainty, leavin... | 0301346v2 |
2003-01-17 | Supernovae, Gamma-Ray Bursts, and Stellar Rotation | One of the most dramatic possible consequences of stellar rotation is its
influence on stellar death, particularly of massive stars. If the angular
momentum of the iron core when it collapses is such as to produce a neutron
star with a period of 5 ms or less, rotation will have important consequences
for the supernova ... | 0301373v1 |
2003-01-27 | The nature of the absorbing torus in compact Radio Galaxies | We present BeppoSAX observations of the two radio galaxies PKS 1934-63 and S5
1946+708. Strong Iron Kalpha lines are detected in both objects indicating that
the two sources are absorbed by column densities higher than 10^24 cm^(-2).
Combining radio continuum, HI absorption and X-ray data we can constrain the
physica... | 0301522v1 |
2003-02-07 | Parallel Universes | I survey physics theories involving parallel universes, which form a natural
four-level hierarchy of multiverses allowing progressively greater diversity.
Level I: A generic prediction of inflation is an infinite ergodic universe,
which contains Hubble volumes realizing all initial conditions - including an
identical... | 0302131v1 |
2003-02-11 | A search for X-ray variability in the open cluster NGC 2516 | We present the results of a search for X-ray variability in the galactic open
cluster NGC 2516. This cluster has been observed on 8 occasions using
XMM-Newton making it an excellent target for such a study. We find 4 sources
which show significant variability, implying the detection of one significantly
variable source... | 0302200v1 |
2003-02-28 | X-ray spectral evolution of low-mass X-ray binary GX 349+2 | We present the results of a systematic investigation of spectral evolution in
the Z source GX 349+2, using data obtained during 1998 with
Proportional-Counter-Array (PCA) on-board the RXTE satellite. The source traced
a extended normal branch (NB) and flaring branch (FB) in the color-color
diagram (CD) and hardness-int... | 0302581v2 |
2003-03-18 | Iron Emission in z~6 QSOs | We have obtained low-resolution near infrared spectra of three QSOs at 5.7 <
z < 6.3 using the NICMOS instrument of the Hubble Space Telescope. The spectra
cover the rest-frame ultraviolet emission of the objects between lambda_rest ~
1600A - 2800A. The Fe II emission-line complex at 2500A is clearly detected in
two of... | 0303424v1 |
2003-03-19 | Absorption spectra of Fe L-lines in Seyfert 1 galaxies | Absorption L-lines of iron ions are observed, in absorption, in spectra of
Seyfert 1 galaxies by the new generation of X-ray satellites: Chandra (NASA)
and XMM-Newton (ESA). Lines associated to Fe23+ to Fe17+ are well resolved.
Whereas, those corresponding to Fe16+ to Fe6+ are unresolved. Forbidden
transitions of the F... | 0303435v1 |
2003-03-20 | A grid of synthetic ionizing spectra for very hot compact stars from NLTE model atmospheres | The precise analysis of properties of planetary nebulae is strongly dependent
on good models for the stellar ionizing spectrum. Observations in the UV -
X-ray wavelength range as well as NLTE model atmosphere calculations of spectra
of their exciting stars have shown that neither blackbody fluxes nor "standard"
NLTE at... | 0303464v1 |
2003-03-28 | The properties of the absorbing and line emitting material in IGR J16318-4848 | We have performed a detailed analysis of the XMM-Newton observation of IGR
J16318-4848, to study the properties of the matter responsible for the
obscuration and for the emission of Fe and Ni lines. Even if the line of sight
material has a column density of about 2x10^24 cm^-2, from the Fe Kalpha line
EW and Compton Sh... | 0303626v1 |
2003-04-02 | Binary Blue Metal-Poor Stars: Evidence for AGB Mass Transfer | We present new abundance analyses of six blue metal-poor (BMP) stars with
very low iron abundances ([Fe/H] < -2), based on new high resolution echelle
spectra. Three are spectroscopic binaries and three have constant radial
velocities. The chemical compositions of these two groups are very different,
as the binary BMP ... | 0304064v1 |
2003-04-03 | Induced Formation of Primordial Low-Mass Stars | We show that the explosion of the first supernovae can trigger low-mass star
formation via gravitational fragmentation of the supernova-driven gas shell. If
the shell mass does not exceed the host galaxy gas mass, all explosions with
energies E_SN > 10^{51} erg can lead to shell fragmentation. However, the
minimum ambi... | 0304074v2 |
2003-04-04 | Metastable strange matter and compact quark stars | Strange quark matter in beta equilibrium at high densities is studied in a
quark confinement model. Two equations of state are dynamically generated for
the {\it same} set of model parameters used to describe the nucleon: one
corresponds to a chiral restored phase with almost massless quarks and the
other to a chiral b... | 0304096v1 |
2003-04-14 | Low-Mass Relics of Early Star Formation | The earliest stars to form in the Universe were the first sources of light,
heat and metals after the Big Bang. The products of their evolution will have
had a profound impact on subsequent generations of stars. Recent studies of
primordial star formation have shown that, in the absence of metals (elements
heavier than... | 0304254v1 |
2003-04-15 | Detailed Analysis of Nearby Bulgelike Dwarf Stars III. Alpha and Heavy-element abundances | The present sample of nearby bulgelike dwarf stars has kinematics and
metallicities characteristic of a probable inner disk or bulge origin. Ages
derived by using isochrones give 10-11 Gyr for these stars and metallicities
are in the range -0.80< [Fe/H]< +0.40. We calculate stellar parameters from
spectroscopic data, a... | 0304282v2 |
2003-04-23 | How did the metals in a giant star originate? | The chemical composition of stars with extremely low metal contents (taking
``metals'' to mean all elements other than hydrogen and helium) provides us
with information on the masses of the stars that produced the first metals.
Such a direct connection is not possible, however, if the surface of the star
has been pollu... | 0304415v1 |
2003-05-12 | Stellar Abundances in Dwarf Irregular Galaxies | Dwarf irregular galaxies appear to have undergone very slow chemical
evolution since they have low nebular abundances, but have had ongoing star
formation over the past 15 Gyr. They are too distant for red giant abundance
analyses to examine the details of their chemical evolution, however the
isolated, bright blue sup... | 0305188v1 |
2003-05-19 | A BeppoSAX observation of MKN6 | We have used the BeppoSAX satellite to study the broad band (0.5-100 keV)
X-ray spectrum of the Seyfert 1.5 galaxy MKN6. The source is characterized by a
power law of Gamma=1.7 [+0.08, -0.07] and there is no strong evidence for
either a reflection bump or a high energy cut-off. We have detected a narrow
iron line at 6.... | 0305329v1 |
2003-05-20 | An Estimate Of The Primary Mass Of Cosmic Rays At $10^{18}$ eV As Inferred From Volcano Ranch Data | Accurate measurements of the lateral distribution of extensive air showers
produced by cosmic rays of energy greater than $10^{17}$ eV were made in the
1970s by Linsley. At the time, the state of knowledge about the best hadronic
interaction model to use to describe such data prevented conclusions about the
cosmic ray ... | 0305351v1 |
2003-05-23 | Metal Rich Stars in omega Centauri | I present some preliminary results from a high-resolution spectroscopic
observing campaign conducted with UVES at the ESO VLT, devoted to the study of
the newly discovered, metal-rich red giant branch (RGB-a) in omega Centauri. In
particular, I derive and discuss accurate abundances of iron-peak elements,
alpha-element... | 0305449v1 |
2003-05-26 | XMM-Newton study of the persistent X-ray source 1E1743.1-2843 located in the Galactic Center direction | We report the results of an XMM-Newton observation of the persistent X-ray
source 1E1743.1-2843, located in the Galactic Center (GC) direction. We
determine the position of the source at alpha_J2000=17h46m21.0s,
delta_J2000=-28deg43'44" (with an uncertainty of 1.5"), which is the most
accurate to date, and will enable ... | 0305489v1 |
2003-06-05 | Where was the Iron Synthesized in Cassiopeia A? | We investigate the properties of Fe-rich knots on the east limb of the
Cassiopeia A supernova remnant using observations with Chandra/ACIS and
analysis methods developed in a companion paper. We use the fitted ionization
age and electron temperature of the knots to constrain the ejecta density
profile and the Lagrangia... | 0306120v1 |
2003-06-09 | An AGN Sample with High X-ray-to-optical Flux Ratio from RASS II.Optical Emission Line Properties of Seyfert 1 Type AGN | This work studies the optical emission line properties of a sample of 155
low-redshift bright X-ray selected ROSAT Seyfert~1 type AGN for which adequate
signal-to-noise ratio spectroscopic observations are available. We measured
emission line properties by performing multi-component fits to the emission
line profiles, ... | 0306169v1 |
2003-06-12 | Long Term X-ray Variability in GX13+1: Energy Dependent Periodic Modulation | A search is made for periodic modulation in the X-ray flux from the low mass
X-ray binary GX13+1 using Rossi X-ray Timing Explorer All Sky Monitor data
collected over a period of almost seven years. From a filtered data set, which
excludes measurements with exceptionally large error bars and so maximizes
signal to nois... | 0306262v1 |
2003-06-13 | Delayed soft X-ray emission lines in the afterglow of GRB 030227 | Strong, delayed X-ray line emission is detected in the afterglow of GRB
030227, appearing near the end of the XMM-Newton observation, nearly twenty
hours after the burst. The observed flux in the lines, not simply the
equivalent width, sharply increases from an undetectable level (<1.7e-14
erg/cm^2/s, 3 sigma) to 4.1e-... | 0306284v2 |
2003-06-16 | Modeling of iron K lines: radiative and Auger decay data for Fe II-Fe IX | A detailed analysis of the radiative and Auger de-excitation channels of
K-shell vacancy states in Fe II-Fe IX has been carried out. Level energies,
wavelengths, A-values, Auger rates and fluorescence yields have been calculated
for the lowest fine-structure levels populated by photoionization of the ground
state of th... | 0306321v2 |
2003-06-27 | The Chemical Composition and Gas-to-Dust Mass Ratio of Nearby Interstellar Matter | Recent results on nearby interstellar gas and interstellar byproducts within
the solar system are used to select among the equilibrium radiative transfer
models of the nearest interstellar material of Slavin and Frisch (2002).
Assuming O/H~400 ppm, Models 2 and 8 are found to yield good fits to available
data on local ... | 0306590v2 |
2003-07-08 | The Chemistry of Galaxy Clusters | From X-ray observations of galaxy clusters one derives the mass of the
intracluster medium along with its chemical composition. Optical/infrared
observations are used to estimate the mass of the stellar components of
galaxies, along with their chemical composition and age. This review shows that
when combining all this... | 0307146v1 |
2003-07-09 | Nitrogen Abundances in High-z DLAs | Determination of chemical abundances for elements produced mainly by Type I
SNae and intermediate mass stars in high redshift DLAs probes the early
chemical build-up on time-scales comparable with their production. Nitrogen
shows a peculiar behaviour never detected before in any other class of objects.
For [N/H] < -3 t... | 0307173v1 |
2003-07-30 | On the origin of HE0107-5240, the most iron deficient star presently known | We show that the "puzzling" chemical composition observed in the extremely
metal poor star HE0107-5240 may be naturally explained by the concurrent
pollution of at least two supernovae. In the simplest possible model a
supernova of quite low mass (~15 Msun), underwent a "normal" explosion and
ejected ~0.06 Msun of 56Ni... | 0307527v1 |
2003-08-15 | Stellar pollution and [Fe/H] in the Hyades | The Hyades open cluster presents a unique laboratory for planet formation and
stellar pollution studies because all of the stars have essentially the same
age and were born from the same cloud of gas. Furthermore, with an age of
roughly 650 Myr most of the intermediate and low mass stars are on the main
sequence. Given... | 0308268v1 |
2003-08-20 | The chemical composition of a mild barium star HD202109 | We present the result of chemical abundances of a mild barium star HD202109
(zeta Cyg) determined from the analysis of spectrum obtained by using a 2-m
telescope at the Peak Terskol Observatory and a high-resolution spectrometer
with R=80,000, signal to noise ratio >100. We also present the atmospheric
parameters of th... | 0308337v2 |
2003-08-20 | Rosseland and Planck Mean Opacities for Protoplanetary Discs | In this paper, we present mean gas and dust opacities relevant to the
physical conditions typical of protoplanetary discs. As the principal absorber
for temperatures below ~1,500 K, we consider spherical and aggregate dust
particles of various sizes, chemical structure, and porosity, consisting of
ice, organics, troili... | 0308344v1 |
2003-08-21 | Sgr A East and its surroundings observed in X-rays | We report the results of an XMM-Newton observation of Sgr A East and its
surroundings. The X-ray spectrum of Sgr A East is well represented with a
two-temperature plasma model with temperatures of ~1 and ~4 keV. Only the iron
abundance shows clear spatial variation; it concentrates in the core of Sgr A
East. The derive... | 0308373v1 |
2003-08-27 | 3EG J2027+3429 another Blazar behind the Galactic Plane | We report on the association of an X-ray source (WGA J2025.1+3342),
serendipitously found with BeppoSAX in two separate observations, with the
unidentified EGRET source 3EG J2027+3429. The source is detected from 1 keV up
to about 100 keV, has a flat (0.6-1.5) spectrum and is highly variable both in
intensity and shape... | 0308473v1 |
2003-08-28 | On the filling factor of emitting material in the upper atmosphere of Epsilon Eri (K2 V) | The emission measure distribution in the upper transition region and corona
of Epsilon Eri is derived from observed emission line fluxes. Theoretical
emission measure distributions are calculated assuming that the radiation
losses are balanced by the net conductive flux. We discuss how the area factor
of the emitting r... | 0308502v1 |
2003-09-01 | Fe II lifetimes and transition probabilities | Fe II radiative lifetimes were measured applying the time-resolved nonlinear
laser-induced fluoresence technique. We investigated 21 levels of up to 47000
1/cm. The uncertainties are typically 2-3%. The lifetimes provide an improved
absolute scale to our branching fractions which were measured with a Fourier
transform ... | 0309023v3 |
2003-09-16 | XMM-Newton Observations of the Perseus Cluster II: Evidence for Gas Motions in the Core | The 5-9 keV spectrum of the inner ~100 kpc of the Perseus cluster measured by
XMM-Newton can be well described by an optically thin plasma emission model as
predicted by the APEC code, without any need for invoking a strong Ni
overabundance or the effects of resonant scattering. For the strongest 6.7 keV
line of He-lik... | 0309427v1 |
2003-09-18 | Inferring the coronal flaring patterns in AGN from reverberation maps | The relativistically broadened iron K-alpha line at 6.4 keV observed in the
Seyfert 1 galaxy MCG-6-30-15 has provided a probe of the strong-gravity
environment near a black hole, in particular suggesting that it is rapidly
spinning. An important variable in such analyses is the geometry of the
illuminating source. We p... | 0309518v2 |
2003-09-29 | A common trend in the chemical evolution of Local Group dwarf spheroidals and Damped Ly-alpha systems | We compare chemical abundances of Local Group dwarf spheroidals, obtained
from recent UVES/VLT observations, and of high redshift Damped Lyman alpha
systems (DLAs), corrected for dust effects. We focus, in particular, on the
abundance ratio between alpha-capture elements and iron, alpha/Fe, a well known
indicator of ch... | 0309765v1 |
2003-10-06 | A new population of X-ray transients in the Galactic Centre | A comparison of the XMM-Newton and Chandra Galactic Centre (GC) Surveys has
revealed two faint X-ray transients with contrasting properties. The X-ray
spectrum of XMM J174544-2913.0 shows a strong iron line with an equivalent
width of ~2 keV, whereas that of XMM J174457-2850.3 is characterised by a very
hard continuum ... | 0310140v1 |
2003-10-06 | Emission Line Properties of AGN from a post-COSTAR FOS HST Spectral Atlas | This paper joins a series compiling consistent emission line measurements of
large AGN spectral databases, useful for reliable statistical studies of
emission line properties. It is preceded by emission line measurements of 993
spectra from the Large Bright Quasar Survey (Forster et al. 2001) and 174
spectra of AGN obt... | 0310165v1 |
2003-10-08 | Determination of the calorimetric energy in extensive air showers | The contribution of different components of an air shower to the total energy
deposit in the atmosphere, for different angles and primary particles, was
studied using the CORSIKA air shower simulation code. The amount of missing
energy, parameterized in terms of the calorimetric energy, was calculated. The
results show... | 0310234v3 |
2003-10-21 | Coronal abundances from high-resolution X-ray data: The case of Algol | We discuss the determination of elemental abundances from high resolution
X-ray data. We emphasize the need for an accurate determination of the
underlying temperature structure and advocate the use of a line ratio method
which allows us to utilize, first, the strongest lines observed in the X-ray
spectra, and second, ... | 0310594v1 |
2003-10-21 | The Formation of the First Low-Mass Stars From Gas With Low Carbon and Oxygen Abundances | The first stars in the Universe are predicted to have been much more massive
than the Sun. Gravitational condensation accompanied by cooling of the
primordial gas due to molecular hydrogen, yields a minimum fragmentation scale
of a few hundred solar masses. Numerical simulations indicate that once a gas
clump acquires ... | 0310622v1 |
2003-10-22 | Accretion and Outflow in the AGN and Starburst of NGC 5135 | Observations of the Seyfert 2 and starburst galaxy NGC 5135 with the Chandra
X-ray Observatory demonstrate that both of these phenomena contribute
significantly to its X-ray emission. We spatially isolate the active galactic
nucleus (AGN) and demonstrate that it is entirely obscured by column density
N_H > 10^{24} cm^{... | 0310669v1 |
2003-10-27 | Oxygen trends in the Galactic thin and thick disks | We present oxygen abundances for 72 F and G dwarf stars in the solar
neighbourhood. Using the kinematics of the stars we divide them into two
sub-samples with space velocities that are typical for the thick and thin
disks, respectively. The metallicities of the stars range from [Fe/H] = -0.9 to
+0.4 and we use the deri... | 0310741v1 |
2003-10-29 | Luminosity and Redshift Dependence of Quasar Spectral Properties | Using a large sample of quasar spectra from the SDSS, we examine the
composite spectral trends of quasars as functions of both redshift and
luminosity, independently of one another. Aside from the well known Baldwin
effect (BE) -- the decrease of line equivalent width with luminosity -- the
average spectral properties ... | 0310840v1 |
2003-10-30 | Hints of star fomation at z>6: the chemical abundances of the DLA system in the QSO BRI 1202-0725 (z_abs = 4.383) | The Damped Ly-alpha (DLA) absorber at redshift z_abs=4.383 observed toward
QSO BRI 1202-0725 is studied by means of high resolution (FWHM ~ 7 km/s)
VLT-UVES spectra. We refine a previously determined Si abundance and derive
with confidence abundances for C, N and O which are poorly known in DLAs. The
[O/Fe] ratio is ~0... | 0310866v1 |
2003-11-26 | Evolution and nucleosynthesis of primordial low mass stars | We discuss in detail the evolutionary properties of low mass stars M< 1
M(Solar) having metallicity lower than Z=10^(-6) from the pre- main sequence up
to (almost) the end of the Asymptotic Giant Branch phase. We also discuss the
possibility that the large [C,N/Fe] observed on the surface of the most Iron
poor star pre... | 0311580v1 |
2003-12-05 | XMM-Newton observations of 3C 273 | A series of nine XMM-Newton observations of the radio-loud quasar 3C 273 are
presented, concentrating mainly on the soft excess. Although most of the
individual observations do not show evidence for iron emission, co-adding them
reveals a weak, broad line (EW ~ 56 eV). The soft excess component is found to
vary, confir... | 0312148v1 |
2003-12-17 | Doppler broadening of the iron line and R-Gamma correlation in black hole binaries | RXTE/PCA observations of several black hole X-ray binaries in the low
spectral state revealed a tight correlation between spectral parameters and
characteristic frequencies of variability of X-ray flux. In particular, the
amplitude of reflection increases and the slope of Comptonized radiation
steepens as the noise fre... | 0312445v1 |
2003-12-18 | Atomic and Molecular Data for Stellar Physics: Former Successes and Future Challenges | This review highlights current (and future) hot topics in astrophysics where
atomic or molecular input data are (or will be) essential, with special
emphasis on topics relating to nucleosynthesis and cosmochemistry.
We first discuss issues (like the abundances of oxygen and iron in the Sun,
and that of lithium in pos... | 0312486v1 |
2003-12-23 | Gamma-Ray Bursts observed by XMM-Newton | Analysis of observations with XMM-Newton have made a significant contribution
to the study of Gamma-ray Burst (GRB) X-ray afterglows. The effective area,
bandpass and resolution of the EPIC instrument permit the study of a wide
variety of spectral features. In particular, strong, time-dependent, soft X-ray
emission lin... | 0312602v1 |
2004-01-09 | The Evolution of the Accretion Disk around 4U 1820-30 During a Superburst | Accretion from a disk onto a collapsed, relativistic star -- a neutron star
or black hole -- is the mechanism widely believed to be responsible for the
emission from compact X-ray binaries. Because of the extreme spatial resolution
required, it is not yet possible to directly observe the evolution or dynamics
of the in... | 0401154v1 |
2004-01-14 | Abundances of neutron-capture elements in the Hot Extreme-Helium Stars V1920 Cygni and HD 124448 | Analysis of HST STIS ultraviolet spectra of two hot extreme helium stars
(EHes): V1920 Cyg and HD 124448 provide the first measurements of abundances of
neutron-capture elements for EHes. Although the two stars have similar
abundances for elements up through the iron-group, they differ strikingly in
their abundances of... | 0401263v1 |
2004-01-15 | INTEGRAL observations of the transient source IGR J19140+098 | IGR J19140+098 was discovered during the early INTEGRAL observations of
GRS1915+105 in March 2003. The following observations by INTEGRAL and RXTE show
significant variability on various time scales from 100s to 1ks, but no
pulsations. The ISGRI spectra show strong spectral variability in the 20-80keV
range. Combined J... | 0401308v1 |
2004-01-25 | Propagation of electromagnetic waves in space plasma | Coherent Raman Effect on Incoherent Light (CREIL), shifts the frequencies of
normally incoherent light without any blurring of the images or altering the
order of the spectra. CREIL operates in gases having quadrupolar resonances in
the megaherz range, and it is easily confused with Doppler effects. When CREIL
is taken... | 0401529v1 |
2004-02-05 | Timing and spectral studies of the transient X-ray pulsar EXO 053109-6609.2 with ASCA and Beppo-SAX | We report timing and spectral properties of the transient Be X-ray pulsar EXO
053109--6609.2 studied using observations made with the ASCA and BeppoSAX
observatories. Though there must have been at least one spin-down episode of
the pulsar since its discovery, the new pulse period measurements show a
monotonic spin-up ... | 0402127v1 |
2004-02-10 | Implications of the central metal abundance peak in cooling core clusters of galaxies | Recent XMM-Newton observations of clusters of galaxies have provided detailed
information on the distribution of heavy elements in the central regions of
clusters with cooling cores providing strong evidence that most of these metals
come from recent SN type Ia. In this paper we compile information on the
cumulative ma... | 0402216v1 |
2004-02-13 | Models for extremely metal-poor halo stars | Two alternative scenarios concerning the origin and evolution of extremely
metal-poor halo stars are investigated. The first one assumes that the stars
have been completely metal-free initially and produced observed carbon and
nitrogen overabundances during the peculiar core helium flash typical for
low-mass Population... | 0402334v1 |
2004-02-26 | A Far-UV Spectroscopic Analysis of the Central Star of the Planetary Nebula Longmore 1 | We have performed a non-LTE spectroscopic analysis using far-UV and UV data
of the central star of the planetary nebula K1-26 (Longmore 1), and found Teff
= 120+/-10 kK, logg = 6.7 +0.3/-0.7, and y = 0.10. The temperature is
significantly hotter than previous results based on optical line analyses,
highlighting the imp... | 0402653v1 |
2004-03-01 | An XMM-Newton study of the RGH 80 galaxy group | We present an X-ray study of the galaxy group RGH 80, observed by XMM-Newton.
The X-ray emission of the gas is detected out to ~ 462h^{-1}_{50} kpc,
corresponding to ~ 0.45 r_{200}. The group is relatively gas rich and luminous
with respect to its temperature of 1.01 +/- 0.01 keV. Using the deprojected
spectral analysi... | 0403026v1 |
2004-03-10 | Hydra Observations of Aluminum Abundances in the Red Giants of the Globular Clusters M80 and NGC 6752 | Aluminum and other metal abundances were determined in 21 red giants in the
globular clusters NGC 6752 and M80 as part of a larger study to determine
whether the aluminum distribution on the red giant branch is related to the
second parameter effect that causes clusters of similar metallicity to display
different horiz... | 0403263v1 |
2004-03-17 | Chemical Abundances in the Secondary Star in the Black Hole Binary A0620-00 | Using a high resolution spectrum of the secondary star in the black hole
binary A0620-00, we have derived the stellar parameters and veiling caused by
the accretion disk in a consistent way. We have used a chi^2 minimization
procedure to explore a grid of 800 000 LTE synthetic spectra computed for a
plausible range of ... | 0403402v1 |
2004-04-02 | The first broad-band persistent X-ray spectrum of the dipping low mass X-ray binary EXO 0748-676 | We report on the results of a BeppoSAX observation of the dipping LMXRB EXO
0748-676 performed in 2000 November. This is the first simultaneous observation
of this source over the 0.1-100 keV energy range. The persistent spectrum is
complex and shows a soft excess, which requires the inclusion of an ionized
absorber (w... | 0404038v1 |
2004-04-02 | The complex X-ray spectrum of NGC 4507 | XMM-Newton and Chandra/HETG spectra of the Compton-thin (NH 4x10^{23}
cm^{-2}) Seyfert 2 galaxy, NGC 4507, are analyzed and discussed. The main
results are: a) the soft X-ray emission is rich in emission lines; an (at
least) two--zone photoionization region is required to explain the large range
of ionization states. b... | 0404050v1 |
2004-04-16 | Revealing the nature of the highly obscured galactic source IGR J16318-4848 | The X-ray source IGR J16318-4848 was the first source discovered by INTEGRAL
on 2003, January 29. We carried out optical and near-infrared (NIR)
observations at the European Southern Observatory (ESO La Silla) in the course
of a Target of Opportunity (ToO) programme. We discovered the optical
counterpart and confirmed ... | 0404332v1 |
2004-04-19 | Central Stars of Planetary Nebulae in the Large Magellanic Cloud: A Far-UV Spectroscopic Analysis | We observed seven central stars of planetary nebulae (CSPN) in the Large
Magellanic Cloud (LMC) with the Far Ultraviolet Spectroscopic Explorer (FUSE),
and performed a model-based analysis of these spectra in conjunction with
Hubble Space Telescope (HST) spectra in the UV and optical range to determine
the stellar and ... | 0404367v1 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.