48 research outputs found
B- and A-Type Stars in the Taurus-Auriga Star Forming Region
We describe the results of a search for early-type stars associated with the
Taurus-Auriga molecular cloud complex, a diffuse nearby star-forming region
noted as lacking young stars of intermediate and high mass. We investigate
several sets of possible O, B and early A spectral class members. The first is
a group of stars for which mid-infrared images show bright nebulae, all of
which can be associated with stars of spectral type B. The second group
consists of early-type stars compiled from (i) literature listings in SIMBAD;
(ii) B stars with infrared excesses selected from the Spitzer Space Telescope
survey of the Taurus cloud; (iii) magnitude- and color-selected point sources
from the 2MASS; and (iv) spectroscopically identified early-type stars from the
SDSS coverage of the Taurus region. We evaluated stars for membership in the
Taurus-Auriga star formation region based on criteria involving: spectroscopic
and parallactic distances, proper motions and radial velocities, and infrared
excesses or line emission indicative of stellar youth. For selected objects, we
also model the scattered and emitted radiation from reflection nebulosity and
compare the results with the observed spectral energy distributions to further
test the plausibility of physical association of the B stars with the Taurus
cloud. This investigation newly identifies as probable Taurus members three
B-type stars: HR 1445 (HD 28929), tau Tau (HD 29763), 72 Tau (HD 28149), and
two A-type stars: HD 31305 and HD 26212, thus doubling the number of stars A5
or earlier associated with the Taurus clouds. Several additional early-type
sources including HD 29659 and HD 283815 meet some, but not all, of the
membership criteria and therefore are plausible, though not secure, members.Comment: 31 pages, 18 figures, 6 tables. Accepted for publication in The
Astrophysical Journa
Addressing Distress Management Challenges: Recommendations From the Consensus Panel of the American Psychosocial Oncology Society and the Association of Oncology Social Work
Distress management (DM) (screening and response) is an essential component of cancer care across the treatment trajectory. Effective DM has many benefits, including improving patientsâ quality of life; reducing distress, anxiety, and depression; contributing to medical cost offsets; and reducing emergency department visits and hospitalizations. Unfortunately, many distressed patients do not receive needed services. There are several multilevel barriers that represent key challenges to DM and affect its implementation. The Consolidated Framework for Implementation Research was used as an organizational structure to outline the barriers and facilitators to implementation of DM, including: 1) individual characteristics (individual patient characteristics with a focus on groups who may face unique barriers to distress screening and linkage to services), 2) intervention (unique aspects of DM intervention, including specific challenges in screening and psychosocial intervention, with recommendations for resolving these challenges), 3) processes for implementation of DM (modality and timing of screening, the challenge of triage for urgent needs, and incorporation of patient-reported outcomes and quality measures), 4) organizationâinner setting (the context of the clinic, hospital, or health care system); and 5) organizationâouter setting (including reimbursement strategies and health-care policy). Specific recommendations for evidence-based strategies and interventions for each of the domains of the Consolidated Framework for Implementation Research are also included to address barriers and challenges. CA Cancer J Clin 2021;71:407-436. Š 2021 The Authors. CA: A Cancer Journal for Clinicians published by Wiley Periodicals LLC on behalf of American Cancer Society. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial- NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made
Formation and Evolution of Planetary Systems: Cold Outer Disks Associated with Sun-like stars
We present the discovery of debris systems around three solar mass stars
based upon observations performed with the Spitzer Space Telescope as part of a
Legacy Science Program, ``the Formation and Evolution of Planetary Systems''
(FEPS). We also confirm the presence of debris around two other stars. All the
stars exhibit infrared emission in excess of the expected photospheres in the
70 micron band, but are consistent with photospheric emission at <= 33 micron.
This restricts the maximum temperature of debris in equilibrium with the
stellar radiation to T < 70 K. We find that these sources are relatively old in
the FEPS sample, in the age range 0.7 - 3 Gyr. Based on models of the spectral
energy distributions, we suggest that these debris systems represent materials
generated by collisions of planetesimal belts. We speculate on the nature of
these systems through comparisons to our own Kuiper Belt, and on the likely
planet(s) responsible for stirring the system and ultimately releasing dust
through collisions. We further report observations of a nearby star HD 13974 (d
=11 pc) that is indistinguishable from a bare photosphere at both 24 micron and
70 micron. The observations place strong upper limits on the presence of any
cold dust in this nearby system (L_IR/L_* < 10^{-5.2}).Comment: 31 pages, 9 figures, accepted for publication in Ap
Unusually Wide Binaries: Are They Wide or Unusual?
We describe an astrometric and spectroscopic campaign to confirm the youth
and association of a complete sample of candidate wide companions in Taurus and
Upper Sco. Our survey found fifteen new binary systems (3 in Taurus and 12 in
Upper Sco) with separations of 3-30" (500-5000 AU) among all of the known
members with masses of 2.5-0.012 Msun. The total sample of 49 wide systems in
these two regions conforms to only some expectations from field multiplicity
surveys. Higher-mass stars have a higher frequency of wide binary companions,
and there is a marked paucity of wide binary systems near the substellar
regime. However, the separation distribution appears to be log-flat, rather
than declining as in the field, and the mass ratio distribution is more biased
toward similar-mass companions than the IMF or the field G dwarf distribution.
The maximum separation also shows no evidence of a limit at <5000 AU until the
abrupt cessation of any wide binary formation at system masses of ~0.3 Msun. We
attribute this result to the post-natal dynamical sculpting that occurs for
most field systems; our binary systems will escape to the field intact, but
most field stars are formed in denser clusters and do not. In summary, only
wide binary systems with total masses <0.3 Msun appear to be "unusually wide".Comment: Accepted to ApJ; 23 pages, 9 figures, 9 tables in emulateapj. Table 6
is online-only and is attached as tab6.te
Formation and Evolution of Planetary Systems: Placing Our Solar System in Context with Spitzer
We summarize the progress to date of our Legacy Science Program entitled "The
Formation and Evolution of Planetary Systems" (FEPS) based on observations
obtained with the Spitzer Space Telescope during its first year of operation.
In addition to results obtained from our ground-based preparatory program and
our early validation program, we describe new results from a survey for
near-infrared excess emission from the youngest stars in our sample as well as
a search for cold debris disks around sun-like stars. We discuss the
implications of our findings with respect to current understanding of the
formation and evolution of our own solar system.Comment: 8 postscript pages including 3 figures. To appear in "Spitzer New
Views of the Cosmos" ASP Conference Series, eds. L. Armus et al. FEPS website
at http://feps.as.arizona.ed
Formation and Evolution of Planetary Systems (FEPS): Properties of Debris Dust around Solar-type Stars
We present Spitzer photometric (IRAC and MIPS) and spectroscopic (IRS low
resolution) observations for 314 stars in the Formation and Evolution of
Planetary Systems (FEPS) Legacy program. These data are used to investigate the
properties and evolution of circumstellar dust around solar-type stars spanning
ages from approximately 3 Myr to 3 Gyr. We identify 46 sources that exhibit
excess infrared emission above the stellar photosphere at 24um, and 21 sources
with excesses at 70um. Five sources with an infrared excess have
characteristics of optically thick primordial disks, while the remaining
sources have properties akin to debris systems. The fraction of systems
exhibiting a 24um excess greater than 10.2% above the photosphere is 15% for
ages < 300 Myr and declines to 2.7% for older ages. The upper envelope to the
70um fractional luminosity appears to decline over a similar age range. The
characteristic temperature of the debris inferred from the IRS spectra range
between 60 and 180 K, with evidence for the presence of cooler dust to account
for the strength of the 70um excess emission. No strong correlation is found
between dust temperature and stellar age. Comparison of the observational data
with disk models containing a power-law distribution of silicate grains suggest
that the typical inner disk radius is > 10 AU. Although the interpretation is
not unique, the lack of excess emission shortwards of 16um and the relatively
flat distribution of the 24um excess for ages <300~Myr is consistent with
steady-state collisional models.Comment: 85 pages, 18 figures, 4 tables; accepted for publication in ApJ
Feedback from the heart: emotional learning and memory is controlled by cardiac cycle, interoceptive accuracy and personality
Feedback processing is critical to trial-and-error learning. Here, we examined whether interoceptive signals concerning the state of cardiovascular arousal influence the processing of reinforcing feedback during the learning of âemotionalâ face-name pairs, with subsequent effects on retrieval. Participants (N = 29) engaged in a learning task of face-name pairs (fearful, neutral, happy faces). Correct and incorrect learning decisions were reinforced by auditory feedback, which was delivered either at cardiac systole (on the heartbeat, when baroreceptors signal the contraction of the heart to the brain), or at diastole (between heartbeats during baroreceptor quiescence). We discovered a cardiac influence on feedback processing that enhanced the learning of fearful faces in people with heightened interoceptive ability. Individuals with enhanced accuracy on a heartbeat counting task learned fearful face-name pairs better when feedback was given at systole than at diastole. This effect was not present for neutral and happy faces. At retrieval, we also observed related effects of personality: First, individuals scoring higher for extraversion showed poorer retrieval accuracy. These individuals additionally manifested lower resting heart rate and lower state anxiety, suggesting that attenuated levels of cardiovascular arousal in extraverts underlies poorer performance. Second, higher extraversion scores predicted higher emotional intensity ratings of fearful faces reinforced at systole. Third, individuals scoring higher for neuroticism showed higher retrieval confidence for fearful faces reinforced at diastole. Our results show that cardiac signals shape feedback processing to influence learning of fearful faces, an effect underpinned by personality differences linked to psychophysiological arousal
Optical TiO and VO band emission in two embedded protostars: IRAS 04369+2539 and IRAS 05451+0037
Archival optical spectra from the Sloan Digital Sky Survey of two optically
faint flat spectrum protostars, IRAS 04369+2539 and IRAS 05451+0037, show
strong emission-line features including -- notably -- clear and broad emission
across several molecular bands of TiO and VO. The molecular emission is
indicative of dense, warm circumstellar gas and has been seen previously in
only one object: the flat spectrum protostar IRAS 20496+4354 during a strong
optical outburst (PTF 10nvg; Covey et al. 2011). The presence of broad
molecular emission features in two additional objects having similar
mid-infrared properties (but not known to be undergoing outbursts) could
provide new insight into phases of rapid accretion / outflow at early stages of
the protoplanetary disk. At present, the relevant geometry and the formation or
heating mechanisms responsible for the observed TiO / VO cooling emission
remain unexplained.Comment: accepted to A
Multiple Star Formation to the Bottom of the IMF
The frequency and properties of multiple star systems offer powerful tests of
star formation models. Multiplicity surveys over the past decade have shown
that binary properties vary strongly with mass, but the functional forms and
the interplay between frequency and semimajor axis remain largely
unconstrained. We present the results of a large-scale survey of multiplicity
at the bottom of the IMF in several nearby young associations, encompassing 78
very low mass members observed with Keck laser guide star adaptive optics. Our
survey confirms the overall trend observed in the field for lower-mass binary
systems to be less frequent and more compact, including a null detection for
any substellar binary systems with separations wider than ~7 AU. Combined with
a Bayesian re-analysis of existing surveys, our results demonstrate that the
binary frequency and binary separations decline smoothly between masses of 0.5
Msun and 0.02 Msun, though we can not distinguish the functional form of this
decline due to a degeneracy between the total binary frequency and the mean
binary separation. We also show that the mass ratio distribution becomes
progressively more concentrated at q~1 for declining masses, though a small
number of systems appear to have unusually wide separations and low mass ratios
for their mass. Finally, we compare our results to synthetic binary populations
generated by smoothed particle hydrodynamic simulations, noting the
similarities and discussing possible explanations for the differences.Comment: Accepted to ApJ; 18 pages of text+figures, 20 pages of tables in
emulateapj forma