3,660 research outputs found
Life Cycle of the Tapeworm Khawia sinensis Hsü, 1935, a Carp Parasite, in the Pond Dražský Skaličany near Blatná, Czechoslovakia
Near Infrared Spectroscopy of Young Brown Dwarfs in Upper Scorpius
Spectroscopic follow-up is a pre-requisite for studies of the formation and
early evolution of brown dwarfs. Here we present IRTF/SpeX near-infrared
spectroscopy of 30 candidate members of the young Upper Scorpius association,
selected from our previous survey work. All 24 high confidence members are
confirmed as young very low mass objects with spectral types from M5 to L1,
15-20 of them are likely brown dwarfs. This high yield confirms that brown
dwarfs in Upper Scorpius can be identified from photometry and proper motions
alone, with negligible contamination from field objects (<4%). Out of the 6
candidates with lower confidence, 5 might still be young very low mass members
of Upper Scorpius, according to our spectroscopy. We demonstrate that some very
low mass class II objects exhibit radically different near infrared (0.6 -
2.5micron) spectra from class III objects, with strong excess emission
increasing towards longer wavelengths and partially filled in features at
wavelengths shorter than 1.25micron. These characteristics can obscure the
contribution of the photosphere within such spectra. Therefore, we caution that
near infrared derived spectral types for objects with discs may be unreliable.
Furthermore, we show that the same characteristics can be seen to some extent
in all class II and even a significant fraction of class III objects (~40%),
indicating that some of them are still surrounded by traces of dust and gas.
Based on our spectra, we select a sample of objects with spectral types of M5
to L1, whose near-infrared emission represents the photosphere only. We
recommend the use of these objects as spectroscopic templates for young brown
dwarfs in the future.Comment: 12 pages, 9 figures, Accepted in MNRA
The SONYC survey: Towards a complete census of brown dwarfs in star forming regions
SONYC, short for "Substellar Objects in Nearby Young Clusters", is a survey
program to provide a census of the substellar population in nearby star forming
regions. We have conducted deep optical and near-infrared photometry in five
young regions (NGC1333, rho Ophiuchi, Chamaeleon-I, Upper Sco, and Lupus-3),
combined with proper motions, and followed by extensive spectroscopic campaigns
with Subaru and VLT, in which we have obtained more than 700 spectra of
candidate low-mass objects. We have identified and characterized more than 60
new substellar objects, among them a handful of objects with masses close to,
or below the Deuterium burning limit. Through SONYC and surveys by other
groups, the substellar IMF is now well characterized down to ~ 5 - 10 MJup, and
we find that the ratio of the number of stars with respect to brown dwarfs lies
between 2 and 6. A comprehensive survey of NGC 1333 reveals that, down to
~5MJup, free-floating objects with planetary masses are 20-50 times less
numerous than stars, i.e. their total contribution to the mass budget of the
clusters can be neglected.Comment: to appear in the proceedings of the conference 'Brown dwarfs come of
age', May 20-24 2013, Memorie della Societa Astronomica Italian
Observations of Mira stars with the IOTA/FLUOR interferometer and comparison with Mira star models
We present K'-band observations of five Mira stars with the IOTA
interferometer. The interferograms were obtained with the FLUOR fiber optics
beam combiner, which provides high-accuracy visibility measurements in spite of
time-variable atmospheric conditions. For the M-type Miras X Oph, R Aql, RU
Her, R Ser, and the C-type Mira V CrB we derived the uniform-disk diameters
11.7mas, 10.9mas, 8.4mas, 8.1mas, and 7.9mas (+/- 0.3mas), respectively.
Simultaneous photometric observations yielded the bolometric fluxes. The
derived angular Rosseland radii and the bolometric fluxes allowed the
determination of effective temperatures. For instance, the effective
temperature of R Aql was determined to be 2970 +/- 110 K. A linear Rosseland
radius for R Aql of (250 +100/-60) Rsun was derived from the angular Rosseland
radius of 5.5mas +/- 0.2mas and the HIPPARCOS parallax of 4.73mas +/- 1.19mas.
The observations were compared with theoretical Mira star models of Bessel et
al. (1996) and Hofmann et al. (1998). The effective temperatures of the M-type
Miras and the linear radius of R Aql indicate fundamental mode pulsation.Comment: 12 pages, 4 postscript figure
Cool White Dwarfs Revisited -- New Spectroscopy and Photometry
In this paper we present new and improved data on 38 cool white dwarfs
identified by Oppenheimer et al. 2001 (OHDHS) as candidate dark halo objects.
Using the high-res spectra obtained with LRIS, we measure radial velocities for
13 WDs that show an H alpha line. We show that the knowledge of RVs decreases
the UV-plane velocities by only 6%. The radial velocity sample has a W-velocity
dispersion of sig_W = 59 km/s--in between the values associated with the thick
disk and the stellar halo. We also see indications for the presence of two
populations by analyzing the velocities in the UV plane. In addition, we
present CCD photometry for half of the sample, and with it recalibrate the
photographic photometry of the remaining WDs. Using the new photometry in
standard bands, and by applying the appropriate color-magnitude relations for H
and He atmospheres, we obtain new distance estimates. New distances of the WDs
that were not originally selected as halo candidates yield 13 new candidates.
On average, new distances produce velocities in the UV plane that are larger by
10%, with already fast objects gaining more. Using the new data, while applying
the same UV-velocity cut (94 km/s) as in OHDHS, we find a density of cool WDs
of 1.7e-4 pc^-3, confirming the value of OHDHS. In addition, we derive the
density as a function of the UV-velocity cutoff. The density (corrected for
losses due to higher UV cuts) starts to flatten out at 150 km/s (0.4e-4 pc^-3),
and is minimized (thus minimizing a possible non-halo contamination) at 190
km/s (0.3e-4 pc^-3). These densities are in a rough agreement with the
estimates for the stellar halo WDs, corresponding to a factor of 1.9 and 1.4
higher values.Comment: Accepted to ApJ. New version contains some additional data. Results
unchange
Clinical outcome and long-term follow-up after liposuction procedures
Liposuction is one of the most common aesthetic procedure used in plastic surgery. Reports are available on the results, the probable complications, and the feedback of patients. However, systematic studies dealing with these aspects using reliable large-enough data are still needed. The data comprised 116 procedures during a 6-year period up to 2005. The data were processed and categories of results were formed. Furthermore, a follow-up examination and a survey on the feedback of patients were carried out. Significant differences were identified in indications, results, and complications. The follow-up examinations and the survey showed satisfying results. In the majority of cases, surgeons were satisfied with the operations. In conclusion, if conducted by qualified surgeons in appropriate surgical conditions and postoperative care possibilities, liposuction may be considered as a reliable surgical procedure. The success of this procedure depends, however, on suitable infrastructure and operative competenc
Injective split systems
A split system on a finite set , , is a set of
bipartitions or splits of which contains all splits of the form
, . To any such split system we can
associate the Buneman graph which is essentially a
median graph with leaf-set that displays the splits in . In
this paper, we consider properties of injective split systems, that is, split
systems with the property that for any 3-subsets
in , where denotes the median in
of the three elements in considered as leaves in
. In particular, we show that for any set there
always exists an injective split system on , and we also give a
characterization for when a split system is injective. We also consider how
complex the Buneman graph needs to become in order for
a split system on to be injective. We do this by introducing a
quantity for which we call the injective dimension for , as well as
two related quantities, called the injective 2-split and the rooted-injective
dimension. We derive some upper and lower bounds for all three of these
dimensions and also prove that some of these bounds are tight. An underlying
motivation for studying injective split systems is that they can be used to
obtain a natural generalization of symbolic tree maps. An important consequence
of our results is that any three-way symbolic map on can be represented
using Buneman graphs.Comment: 22 pages, 3 figure
In-plane magnetic anisotropy of Fe atoms on BiSe(111)
The robustness of the gapless topological surface state hosted by a 3D
topological insulator against perturbations of magnetic origin has been the
focus of recent investigations. We present a comprehensive study of the
magnetic properties of Fe impurities on a prototypical 3D topological insulator
BiSe using local low temperature scanning tunneling microscopy and
integral x-ray magnetic circular dichroism techniques. Single Fe adatoms on the
BiSe surface, in the coverage range are heavily relaxed
into the surface and exhibit a magnetic easy axis within the surface-plane,
contrary to what was assumed in recent investigations on the opening of a gap.
Using \textit{ab initio} approaches, we demonstrate that an in-plane easy axis
arises from the combination of the crystal field and dynamic hybridization
effects.Comment: 5 pages, 3 figures, typos correcte
B fields in OB stars (BOB): The discovery of a magnetic field in a multiple system in the Trifid Nebula, one of the youngest star forming regions
Recent magnetic field surveys in O- and B-type stars revealed that about 10%
of the core-hydrogen-burning massive stars host large-scale magnetic fields.
The physical origin of these fields is highly debated. To identify and model
the physical processes responsible for the generation of magnetic fields in
massive stars, it is important to establish whether magnetic massive stars are
found in very young star-forming regions or whether they are formed in close
interacting binary systems.
In the framework of our ESO Large Program, we carried out low-resolution
spectropolarimetric observations with FORS2 in 2013 April of the three most
massive central stars in the Trifid nebula, HD164492A, HD164492C, and
HD164492D. These observations indicated a strong longitudinal magnetic field of
about 500-600G in the poorly studied component HD164492C. To confirm this
detection, we used HARPS in spectropolarimetric mode on two consecutive nights
in 2013 June.
Our HARPS observations confirmed the longitudinal magnetic field in
HD164492C. Furthermore, the HARPS observations revealed that HD164492C cannot
be considered as a single star as it possesses one or two companions. The
spectral appearance indicates that the primary is most likely of spectral type
B1-B1.5V. Since in both observing nights most spectral lines appear blended, it
is currently unclear which components are magnetic. Long-term monitoring using
high-resolution spectropolarimetry is necessary to separate the contribution of
each component to the magnetic signal. Given the location of the system
HD164492C in one of the youngest star formation regions, this system can be
considered as a Rosetta Stone for our understanding of the origin of magnetic
fields in massive stars.Comment: Five pages, six figures, accepted for publication in A&
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