635 research outputs found
OBSERVATIONS ON NAVICULA THALLODES (BACILLARIOPHYCEAE), A BLADE-FORMING DIATOM FROM THE BERING SEA 1
A thallus-forming diatom, Navicula thallodes Proschkina-Lavrenko, previously known only from the original collection at Bering Island (U.S.S.R.), has been found at Amchitka Island in the Aleutians, Alaska. The most remarkable observation of the present report is that N. thallodes may form blades up to 50 cm long, which to our knowledge is the greatest length reported for a colonial diatom. SEM observations of this diatom are presented for the first time.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65176/1/j.1529-8817.1988.tb04487.x.pd
Probing the face-on disc-corona system of the bare AGN Mrk 110 from UV to hard X-rays: A moderate changing-state AGN?
Context. The X-ray broadband spectra of the bare active galactic nucleus (AGN) Mrk 110, obtained by simultaneous XMM-Newton and NuSTAR observations performed in November 2019 and April 2020, are characterised by the presence of a prominent and absorption-free smooth soft X-ray excess, moderately broad O VII and Fe Kα emission lines, and a lack of a strong Compton hump. The disc-corona system is almost viewed face-on as inferred from the O VII accretion disc lines. While relativistic reflection as the sole emission is ruled out, a simplified combination of soft and hard Comptonisation (using COMPTT) from a warm and a hot corona, plus mild relativistic disc reflection (occuring at a few 10 s Rg) reproduces the data very well.Aims. We aim to confirm the physical origin of the soft X-ray excess of Mrk 110 and to determine its disc-corona system properties from its energetics using two new sophisticated models: REXCOR and RELAGN, respectively.Methods. We applied these models to the 0.3–79 keV X-ray broadband spectra and to the spectral energy distribution (SED) from UV to hard X-rays, respectively.Results. At both epochs, the inferred high values of the warm-corona heating from the X-ray broadband spectral analysis using REXCOR confirm that the soft X-ray excess of Mrk 110 mainly originates from a warm corona rather than relativistic reflection. The intrinsic best-fit SED determined at both epochs using RELAGN show a high X-ray contribution relative to the UV and are very well reproduced by a warm and hot corona plus mild relativistic reflection. The outer radii of the hot and warm corona are located at a few 10 s and ∼100 Rg, respectively. Moreover, combining the inferred low Eddington ratio (approximatively a few percent) from this work, and previous multi-wavelength spectral and timing studies suggest that Mrk 110 could be classified as a moderate changing-state AGN.Conclusions. Our analysis confirms the existence of a warm corona as a significant contribution to the soft X-ray excess and UV emission in Mrk 110, adding to growing evidence that AGN accretion deviates from standard disc theory. This strengthens the importance of long-term multi-wavelength monitoring on both single targets and large AGN surveys to reveal the real nature of the disc-corona system in AGNs
Detection of a possible multiphase ultra-fast outflow in IRAS 13349+2438 with NuSTAR and XMM-Newton
We present joint NuSTAR and XMM-Newton observations of the bright, variable
quasar IRAS 13349+2438. This combined dataset shows two clear iron absorption
lines at 8 and 9 keV, which are most likely associated with two layers of
mildly relativistic blueshifted absorption, with velocities of 0.14c and 0.27c.
We also find strong evidence for a series of Ly absorption lines at
intermediate energies in a stacked XMM-Newton EPIC-pn spectrum, at the same
blueshift as the lower velocity iron feature. This is consistent with a
scenario where an outflowing wind is radially stratified, so faster, higher
ionization material is observed closer to the black hole, and cooler, slower
material is seen from streamlines at larger radii.Comment: 5 pages, 2 figures, accepted for publication in MNRAS letter
The Hot and Energetic Universe: Astrophysics of feedback in local AGN
Understanding the astrophysics of feedback in active galactic nuclei (AGN) is
key to understanding the growth and co-evolution of supermassive black holes
and galaxies. AGN-driven winds/outflows are potentially the most effective way
of transporting energy and momentum from the nuclear scales to the host galaxy,
quenching star formation by sweeping away the gas reservoir. Key questions in
this field are: 1) how do accretion disks around black holes launch
winds/outflows, and how much energy do these carry? 2) How are the energy and
metals accelerated in winds/outflows transferred and deposited into the
circumgalactic medium? X-ray observations are a unique way to address these
questions because they probe the phase of the outflows which carries most of
the kinetic energy. We show how a high throughput, high spectral resolution
instrument like the X-ray Integral Field Unit (X-IFU) on Athena+ will allow us
to address these questions by determining the physical parameters (ionization
state, density, temperature, abundances, velocities, geometry, etc.) of the
outflows on a dynamical time-scale, in a broad sample of nearby bright AGN. The
X-IFU will also allow direct spectral imaging of the impact of these winds on
the host galaxy for local AGN, forming a template for understanding AGN at
higher redshifts where wind shocks cannot be resolved.Comment: Supporting paper for the science theme "The Hot and Energetic
Universe" to be implemented by the Athena+ X-ray observatory
(http://www.the-athena-x-ray-observatory.eu). 10 pages, 6 figure
Ice XII in its second regime of metastability
We present neutron powder diffraction results which give unambiguous evidence
for the formation of the recently identified new crystalline ice phase[Lobban
et al.,Nature, 391, 268, (1998)], labeled ice XII, at completely different
conditions. Ice XII is produced here by compressing hexagonal ice I_h at T =
77, 100, 140 and 160 K up to 1.8 GPa. It can be maintained at ambient pressure
in the temperature range 1.5 < T < 135 K. High resolution diffraction is
carried out at T = 1.5 K and ambient pressure on ice XII and accurate
structural properties are obtained from Rietveld refinement. At T = 140 and 160
K additionally ice III/IX is formed. The increasing amount of ice III/IX with
increasing temperature gives an upper limit of T ~ 150 K for the successful
formation of ice XII with the presented procedure.Comment: 3 Pages of RevTeX, 3 tables, 3 figures (submitted to Physical Review
Letters
Patient perspective on the management of atrial fibrillation in five European countries
Bakhai A, Sandberg A, Mittendorf T, et al. Patient perspective on the management of atrial fibrillation in five European countries. In: BMC Cardiovascular Disorders. Vol 13. BMC; 2013
<i>Planothidium juandenovense</i> sp. nov. (Bacillariophyta) from Juan de Nova (Scattered Islands, Mozambique Channel) and other tropical environments: a new addition to the <i>Planothidium delicatulum</i> complex
Planothidium juandenovense sp. nov. (Bacillariophyta) is described from the marine tropical environments of Juan de Nova I. (Mozambique Channel), Rodrigues I. (Mascarene Archipelago) and from Guam (Northern Mariana Is., Pacific). This small and relatively rare taxon has short multiseriate striae on the sternum valve (SV), hooked raphe valve (RV) terminal raphe endings and no SV cavum or hoof–shaped area. This taxon has similarities with Planothidium delicatulum (Kütz.) Round et Bukht. and Planothidium septentrionale (Østrup) Round et Bukht. ex Rumrich et al., but also differences: e.g. a relatively narrow and rhombic SV sternum, void of areolae, with vestigial radiate structures and an uninterrupted marginal SV elevated crest or ‘crista marginalis’. P. juandenovense sp. nov. is compared to some other Achnanthales with short SV striae. Cocconeis quarnerensis var. lanceolata Jurilj and Planothidium quarnerense f. rhombica (Giffen) comb. nov. may be close to our new taxon
Observations of Outflowing UV Absorbers in NGC 4051 with the Cosmic Origins Spectrograph
We present new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph
observations of the Narrow-Line Seyfert 1 galaxy NGC 4051. These data were
obtained as part of a coordinated observing program including X-ray
observations with the Chandra/High Energy Transmission Grating (HETG)
Spectrometer and Suzaku. We detected nine kinematic components of UV
absorption, which were previously identified using the HST/Space Telescope
Imaging Spectrograph. None of the absorption components showed evidence for
changes in column density or profile within the \sim 10 yr between the STIS and
COS observations, which we interpret as evidence of 1) saturation, for the
stronger components, or 2) very low densities, i.e., n_H < 1 cm^-3, for the
weaker components. After applying a +200 km s^-1 offset to the HETG spectrum,
we found that the radial velocities of the UV absorbers lay within the O VII
profile. Based on photoionization models, we suggest that, while UV components
2, 5 and 7 produce significant O VII absorption, the bulk of the X-ray
absorption detected in the HETG analysis occurs in more highly ionized gas.
Moreover, the mass loss rate is dominated by high ionization gas which lacks a
significant UV footprint.Comment: 41 pages, 10 Figures; accepted for publication in the Astrophysical
Journa
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