217 research outputs found
V1647 ORIONIS: Keck/Nirspec 2 MICRON Echelle Observations
We present new Keck II NIRSPEC high-spectral resolution 2 um echelle
observations of the young eruptive variable star V1647 Orionis. This star went
into outburst in late 2003 and faded to its pre-outburst brightness after
approximately 26 months. V1647 Orionis is the illuminating star of McNeil's
Nebula and is located near M 78 in the Lynds 1630 dark cloud. Our spectra have
a resolving power of approximately 18,000 and allow us to study in detail the
weak absorption features present on the strong near-IR veiled continuum. An
analysis of the echelle orders containing Mg I (2.1066 um) and Al I (2.1099
um), Br-gamma (2.1661 um), the Na I doublet (2.206 and 2.209 um), and the CO
overtone bandhead (2.2935 um) gives us considerable information on the physical
and geometric characteristics of the regions producing these spectral features.
We find that, at high-spectral resolution, V1647 Orionis in quiescence
resembles a significant number of FU Orionis type eruptive variables and does
not appear similar to the quiescent EX Lupi variables observed. This
correspondence is discussed and implications for the evolutionary state of the
star are considered.Comment: 37 pages, 3 Tables, 17 Figure
Xe Irradiation of Graphene on Ir(111): From Trapping to Blistering
Using X-ray photoelectron spectroscopy, thermal desorption spectroscopy, and
scanning tunneling microscopy we show that upon keV Xe + irradiation of
graphene on Ir(111), Xe atoms are trapped under the graphene. Upon annealing,
aggregation of Xe leads to graphene bulges and blisters. The efficient trapping
is an unexpected and remarkable phenomenon, given the absence of chemical
binding of Xe to Ir and to graphene, the weak interaction of a perfect graphene
layer with Ir(111), as well as the substantial damage to graphene due to
irradiation. By combining molecular dynamics simulations and density functional
theory calculations with our experiments, we uncover the mechanism of trapping.
We describe ways to avoid blister formation during graphene growth, and also
demonstrate how ion implantation can be used to intentionally create blisters
without introducing damage to the graphene layer. Our approach may provide a
pathway to synthesize new materials at a substrate - 2D material interface or
to enable confined reactions at high pressures and temperatures
Spitzer, Near-Infrared, and Submillimeter Imaging of the Relatively Sparse Young Cluster, Lynds 988e
We present {\it Spitzer} images of the relatively sparse, low luminosity
young cluster L988e, as well as complementary near-infrared (NIR) and
submillimeter images of the region. The cluster is asymmetric, with the western
region of the cluster embedded within the molecular cloud, and the slightly
less dense eastern region to the east of, and on the edge of, the molecular
cloud. With these data, as well as with extant H data of stars
primarily found in the eastern region of the cluster, and a molecular CO
gas emission map of the entire region, we investigate the distribution of
forming young stars with respect to the cloud material, concentrating
particularly on the differences and similarities between the exposed and
embedded regions of the cluster. We also compare star formation in this region
to that in denser, more luminous and more massive clusters already investigated
in our comprehensive multi-wavelength study of young clusters within 1 kpc of
the Sun.Comment: 21 pages, 6 tables, 13 figures. Full resolution figures at:
http://astro.pas.rochester.edu/~tom/Preprints/L988e.pd
IRAM-PdBI Observations of Binary Protostars I: The Hierarchical System SVS13 in NGC1333
We present millimeter interferometric observations of the young stellar
object SVS13 in NCG1333 in the N2H+(1-0) line and at 1.4 and 3mm dust
continuum, using the IRAM Plateau de Bure interferometer. The results are
complemented by infrared data from the Spitzer Space Telescope. The millimeter
dust continuum images resolve four sources (A, B, C, and VLA3) in SVS13. With
the dust continuum images, we derive gas masses of 0.2-1.1 M_sun for the
sources. N2H+(1-0) line emission is detected and spatially associated with the
dust continuum sources B and VLA3. The observed mean line width is ~0.48 km/s
and the estimated virial mass is ~0.7 M_sun. By simultaneously fitting the
seven hyperfine line components of N2H+, we derive the velocity field and find
a symmetric velocity gradient of about 28 km/s/pc across sources B and VLA3,
which could be explained by core rotation. The velocity field suggests that
sources B and VLA3 are forming a physically bound protobinary system embedded
in a common N2H+ core. Spitzer images show mid-infrared emission from sources A
and C, which is spatially associated with the mm dust continuum emission. No
infrared emission is detected from source B, implying that the source is deeply
embedded. Based on the morphologies and velocity structure, we propose a
hierarchical fragmentation picture for SVS13 where the three sources (A, B, and
C) were formed by initial fragmentation of a filamentary prestellar core, while
the protobinary system (sources B and VLA3) was formed by rotational
fragmentation of a single collapsing sub-core.Comment: 26 pages, 9 figures, accepted by Ap
Identifying pre-bariatric subtypes based on temperament traits, emotion dysregulation, and disinhibited eating: A latent profile analysis
Objective: The efficacy of bariatric surgery has been proven; however, a subset of patients fails to achieve expected long-term weight loss postoperatively. As differences in surgery outcome may be influenced by heterogeneous psychological profiles in pre-bariatric patients, previous subtyping models differentiated patients based on temperament traits. The objective of the present study was to expand these models by additionally considering emotion dysregulation and disinhibited eating behaviors for subtyping, as these factors were associated with maladaptive eating behaviors and poor post-bariatric weight loss outcome. Methods: Within a prospective multicenter registry, N = 370 pre-bariatric patients were examined using interview and self-report questionnaires. A latent profile analysis was performed to identify subtypes based on temperament traits, emotion dysregulation, and disinhibited eating behaviors. Results: Five pre-bariatric subtypes were identified with specific profiles regarding self control, emotion dysregulation, and disinhibited eating behaviors. Subtypes were associated with different levels of eating disorder psychopathology, depression, and quality of life. The expanded model increased variance explanation compared to temperament-based models. Conclusion: By adding emotion dysregulation and disinhibited eating behaviors to previous subtyping models, specific pre-bariatric subtypes emerged with distinct psychological deficit patterns. Future investigations should test the predictive value of these subtypes for post bariatric weight loss and health-related outcomes
Extragalactic Foregrounds of the Cosmic Microwave Background: Prospects for the MAP Mission
(Abridged) While the major contribution to the Cosmic Microwave Background
(CMB) anisotropies are the sought-after primordial fluctuations produced at the
surface of last scattering, other effects produce secondary fluctuations at
lower redshifts. Here, we study the extragalactic foregrounds of the CMB in the
context of the upcoming MAP mission. We first survey the major extragalactic
foregrounds and show that discrete sources, the Sunyaev-Zel'dovich (SZ) effect,
and gravitational lensing are the most dominant ones for MAP. We then show that
MAP will detect (>5 sigma) about 46 discrete sources and 10 SZ clusters
directly with 94 GHz fluxes above 2 Jy. The mean SZ fluxes of fainter clusters
can be probed by cross-correlating MAP with cluster positions extracted from
existing catalogs. For instance, a MAP-XBACs cross-correlation will be
sensitive to clusters with S(94GHz)>200mJy, and will thus provide a test of
their virialization state and a measurement of their gas fraction. Finally, we
consider probing the hot gas on supercluster scales by cross-correlating the
CMB with galaxy catalogs. Assuming that galaxies trace the gas, we show that a
cross-correlation between MAP and the APM catalog should yield a marginal
detection, or at least a four-fold improvement on the COBE upper limits for the
rms Compton y-parameter.Comment: 27 LaTeX pages, including 5 ps figures and 2 tables. To appear in
ApJ. Minor revisions to match accepted version. Color figures and further
links available at http://www.astro.princeton.edu/~refreg
A portable sensor system for the detection of human volatile compounds against transnational crime
Human smuggling accounts for a significant part of transnational organized crime, creating a growing threat to national and international security and putting at risk the health and lives of the people being smuggled. Early detection and interception of human beings hidden in containers or trucks are therefore of considerable importance, especially at key transportation hubs, such as at international borders and harbors. The major challenge is to provide fast inspection procedures without needing to open sealed trucks and containers. The detection of trace key volatile organic compounds, which includes aldehydes and ketones, emitted by humans can be used to rapidly determine human presence, requiring only several ml of air to be taken from inside a container. In this paper, we describe a prototype portable device for the rapid detection of hidden or entrapped people, employing a combined ion mobility spectrometer and sensor array system for obtaining a volatile signature of human presence. The detection limits of this combined analytical device are sufficiently low for use in sensing ketones and aldehydes being emitted by humans in closed containers. For easy handling by security personnel, a classification algorithm is applied that provides a simple YES or NO decision. With a training dataset of more than 1000 measurements, the algorithm achieved an area under curve of 0.9 for untrained scenarios. The field measurements show that two people need to stay in a car for between 20 and 30 minutes in order for the emitted trace volatile organic compounds to reach concentrations high enough for reliable detection with our analytical device
Accretion in Evolved and Transitional Disks in Cep OB2: Looking for the Origin of the Inner Holes
We present accretion rates for a large number of solar-type stars in the Cep
OB2 region, based on U band observations. Our study comprises 95 members of the
~4 Myr-old cluster Tr 37 (including 20 "transition" objects; TO), as well as
the only CTTS in the ~12 Myr-old cluster NGC 7160. The stars show different
disk morphologies, with the majority of them having evolved and flattened
disks. The typical accretion rates are about one order of magnitude lower than
in regions aged 1-2 Myr, and we find no strong correlation between disk
morphology and accretion rates. Although half of the TO are not accreting, the
median accretion rates of normal CTTS and accreting "transition" disks are
similar (~3 10^{-9} and 2 10^{-9} Msun/yr, respectively). Comparison with other
regions suggests that the TO observed at different ages do not necessarily
represent the same type of objects, which is consistent with the fact that the
different processes that can lead to reduced IR excess/inner disk clearing
(e.g., binarity, dust coagulation/settling, photoevaporation, giant planet
formation) do not operate on the same timescales. Accreting TO in Tr 37 are
probably suffering strong dust coagulation/settling. Regarding the equally
large number of non-accreting TO in the region, other processes, like
photoevaporation, the presence of stellar/substellar companions, and/or giant
planet formation may account for their "transitional" SEDs and negligible
accretion rates.Comment: 37 pages, 5 figures, 6 tables Accepted by Ap
The mass ratio and formation mechanisms of Herbig Ae/Be star binary systems
We present B and R band spectroastrometry of a sample of 45 Herbig Ae/Be
stars in order to study their binary properties. All but one of the targets
known to be binary systems with a separation of ~0.1-2.0 arcsec are detected by
a distinctive spectroastrometric signature. Some objects in the sample exhibit
spectroastrometric features that do not appear attributable to a binary system.
We find that these may be due to light reflected from dusty halos or material
entrained in winds. We present 8 new binary detections and 4 detections of an
unknown component in previously discovered binary systems. The data confirm
previous reports that Herbig Ae/Be stars have a high binary fraction, 74+/-6
per cent in the sample presented here. We use a spectroastrometric
deconvolution technique to separate the spatially unresolved binary spectra
into the individual constituent spectra. The separated spectra allow us to
ascertain the spectral type of the individual binary components, which in turn
allows the mass ratio of these systems to be determined. In addition, we
appraise the method used and the effects of contaminant sources of flux. We
find that the distribution of system mass ratios is inconsistent with random
pairing from the Initial Mass Function, and that this appears robust despite a
detection bias. Instead, the mass ratio distribution is broadly consistent with
the scenario of binary formation via disk fragmentation.Comment: Accepted for publication in MNRAS, minor changes made in proof stag
V1647 Orionis: Reinvigorated Accretion and the Re-Appearance of McNeil's Nebula
In late 2003, the young eruptive variable star V1647 Orionis optically
brightened by over 5 magnitudes, stayed bright for around 26 months, and then
decline to its pre-outburst level. In August 2008 the star was reported to have
unexpectedly brightened yet again and we herein present the first detailed
observations of this new outburst. Photometrically, the star is now as bright
as it ever was following the 2003 eruption. Spectroscopically, a pronounced P
Cygni profile is again seen in Halpha with an absorption trough extending to
-700 km/s. In the near-infrared, the spectrum now possesses very weak CO
overtone bandhead absorption in contrast to the strong bandhead emission seen
soon after the 2003 event. Water vapor absorption is also much stronger than
previously seen. We discuss the current outburst below and relate it to the
earlier event.Comment: 6 pages, 3 figure
- âŠ