102 research outputs found
IRAS03063+5735: A Bowshock Nebula Powered by an Early B Star
Mid-infrared images from the Spitzer Space Telescope Galactic Legacy Infrared
MidPlane Survey Extraordinaire program reveal that the infrared source IRAS
03063+5735 is a bowshock nebula produced by an early B star, 2MASS
03101044+5747035. We present new optical spectra of this star, classify it as a
B1.5 V, and determine a probable association with a molecular cloud complex at
V_LSR=-38 -- -42 km/s in the outer Galaxy near l=140.59 degr, b=-0.250 degr. On
the basis of spectroscopic parallax, we estimate a distance of 4.0 +/-1 kpc to
both the bowshock nebula and the molecular complex. One plausible scenario is
that this a high-velocity runaway star impinging upon a molecular cloud. We
identify the HII region and stellar cluster associated with IRAS 03064+5638 at
a projected distance of 64 pc as one plausible birth site. The
spectrophotometric distance and linkage to a molecular feature provides another
piece of data helping to secure the ill-determined rotation curve in the outer
Galaxy. As a by-product of spectral typing this star, we present empirical
spectral diagnostic diagrams suitable for approximate spectral classification
of O and B stars using He lines in the little-used yellow-red portion of the
optical spectrum.Comment: Accepted for publication in the Astronomical Journa
OB Stars & Stellar Bowshocks in Cygnus-X: A Novel Laboratory Estimating Stellar Mass Loss Rates
We use mid-IR images from the Spitzer Cygnus~X Legacy Survey to search for
stellar bowshocks, a signature of early type "runaway" stars with high space
velocities. We identify ten arc-shaped nebulae containing centrally located
stars as candidate bowshocks. New spectroscopic observations of five stars show
that all are late O to early B dwarfs. Our morphologically selected sample of
bowshock candidates encompasses diverse physical phenomena. Three of the stars
appear to be pre-main-sequence objects on the basis of rising SEDs in the
mid-IR, and their nebulae may be photon-dominated regions (PDRs). Four objects
have ambiguous classification. These may be partial dust shells or bubbles. We
conclude that three of the objects are probable bowshocks, based on their
morphological similarity to analytic prescriptions. Their nebular morphologies
reveal no systematic pattern of orientations that might indicate either a
population of stars ejected from or large-scale hydrodynamic outflows from Cyg
OB2. The fraction of runaways among OB stars near Cyg OB2 identified either by
radial velocity or bowshock techniques is ~0.5%, much smaller than the 8%
estimated among field OB stars. We also obtained a heliocentric radial velocity
for the previously known bowshock star, BD+43\degr3654, of -66.2+/-9.4 km/s,
solidifying its runaway status and implying a space velocity of 77+/-10 km/s.
We use the principles of momentum-driven bowshocks to arrive at a novel method
for estimating stellar mass loss rates. Derived mass loss rates range between
10^-7 and few x10^-6 solar masses/yr for the three O5V -- ~B2V stars identified
as generating bowshocks. These values are at the upper range of, but broadly
consistent with, estimates from other methods. (Abridged)Comment: 49 pages, 19 figures; Accepted for publication in ApJ;
full-resolution color figure version available at
http://physics.uwyo.edu/~chip/Papers/CygXBowshocks; comments invite
Five More Massive Binaries in the Cygnus OB2 Association
We present the orbital solutions for four OB spectroscopic binaries, MT145,
GSC 03161-00815, 2MASS J20294666+4105083, and Schulte 73, and the partial
orbital solution to the B spectroscopic binary, MT372, as part of an ongoing
study to determine the distribution of orbital parameters for massive binaries
in the Cygnus OB2 Association. MT145 is a new, single-lined, moderately
eccentric (e=0.291+/-0.009) spectroscopic binary with period of 25.140+/-0.008
days. GSC 03161-00815 is a slightly eccentric (e=0.10+/-0.01), eclipsing,
interacting and double-lined spectroscopic binary with a period of
4.674+/-0.004 days. 2MASS J20294666+4105083 is a moderately eccentric
(e=0.273+/-0.002) double-lined spectroscopic binary with a period of
2.884+/-0.001 days. Schulte 73 is a slightly eccentric (e=0.169+/-0.009),
double-lined spectroscopic binary with a period of 17.28+/-0.03 days and the
first "twin" in our survey with a mass ratio of q=0.99+/-0.02. MT372 is a
single-lined, eclipsing system with a period of 2.228 days and low eccentricity
(e~0). Of the now 18 known OB binaries in Cyg OB2, 14 have periods and mass
ratios. Emerging evidence also shows that the distribution of log(P) is flat
and consistent with Oepik's Law.Comment: Accepted to Astronomical Journa
Ecdysis-related pleiotropic neuropeptides expression during Anopheles albimanus development
Objective. To analyze the transcription pattern of neuropeptides in the ontogeny of a malaria vector, the mosquito Anopheles albimanus. Materials and methods. The transcription pattern of Crustacean CardioActive peptide (CCAP), corazonin, Ecdysis Triggering Hormone (ETH), allatostatin-A, orcokinin, Insulin Like Peptide 2 (ILP2), Insulin Like Peptide 5 (ILP5) and bursicon was evaluated using qPCR on larvae (1st – 4th instar), pupae and adult mosquitoes. Results. Unlike in other insects, transcripts of CCAP (70.8%), ETH (60.2%) and corazonin (76.5%) were expressed in 4th instar larvae, probably because these three neuropeptides are associated with the beginning of ecdysis. The neuropeptide ILP2 showed higher transcription levels in other stages and orcokinin decreased during the development of the mosquito. Conclusion. The CCAP, corazonin and ETH neuropeptidesare potential targets for the design of control strategies aimed at disrupting An. albiamnus larval development
Additional Massive Binaries in the Cygnus OB2 Association
We report the discovery and orbital solutions for two new OB binaries in the
Cygnus OB2 Association, MT311 (B2V+B3V) and MT605 (B0.5V+B2.5:V). We also
identify the system MT429 as a probable triple system consisting of a tight
eclipsing 2.97 day B3V+B6V pair and a B0V at a projected separation of 138 AU.
We further provide the first spectroscopic orbital solutions to the eclipsing,
double-lined, O-star binary MT696 (O9.5V+B1:V), the double-lined, early B
binary MT720 (B0-1V+B1-2V), and the double-lined, O-star binary MT771
(O7V+O9V). These systems exhibit orbital periods between 1.5 days and 12.3
days, with the majority having P<6 days. The two new binary discoveries and six
spectroscopic solutions bring the total number of known massive binaries in the
central region of the Cygnus OB2 Association to 20, with all but two having
full orbital solutions.Comment: 42 pages, 16 figures, accepted for publication in the Astrophysical
Journal, minor typos have been fixe
Autoimmune Response as a Mechanism for a Dobzhansky-Muller-Type Incompatibility Syndrome in Plants
Epistatic interactions between genes are a major factor in evolution. Hybrid necrosis is an example of a deleterious phenotype caused by epistatic interactions that is observed in many intra- and interspecific plant hybrids. A large number of hybrid necrosis cases share phenotypic similarities, suggesting a common underlying mechanism across a wide range of plant species. Here, we report that approximately 2% of intraspecific crosses in Arabidopsis thaliana yield F1 progeny that express necrosis when grown under conditions typical of their natural habitats. We show that several independent cases result from epistatic interactions that trigger autoimmune-like responses. In at least one case, an allele of an NB-LRR disease resistance gene homolog is both necessary and sufficient for the induction of hybrid necrosis, when combined with a specific allele at a second locus. The A. thaliana cases provide insights into the molecular causes of hybrid necrosis, and serve as a model for further investigation of intra- and interspecific incompatibilities caused by a simple epistatic interaction. Moreover, our finding that plant immune-system genes are involved in hybrid necrosis suggests that selective pressures related to host–pathogen conflict might cause the evolution of gene flow barriers in plants
Astro2020 Must Issue Actionable Recommendations Regarding Diversity, Inclusion, and Harassment
The 2010 Decadal survey failed to issue any recommendations on diversity and inclusion.Astro2020 cannot make the same mistake. Findings can be ignored by funding agencies;recommendations cannot. In the past decade, multiple groups have assembled detailed actionplans to fix a broken climate within our profession. Astro2020 should play a key role, bysynthesizing this work to produce actionable recommendations to support diversity andinclusion and stop harassment within our profession
- …