2,187 research outputs found
Atiyah-Singer Index Theorem in an SO(3) Yang-Mills-Higgs system and derivation of a charge quantization condition
The Atiyah-Singer index theorem is generalized to a two-dimensional SO(3)
Yang-Mills-Higgs (YMH) system. The generalized theorem is proven by using the
heat kernel method and a nonlinear realization of SU(2) gauge symmetry. This
theorem is applied to the problem of deriving a charge quantization condition
in the four-dimensional SO(3) YMH system with non-Abelian monopoles. The
resulting quantization condition, eg=n (n: integer), for an electric charge e
and a magnetic charge g is consistent with that found by Arafune, Freund and
Goebel. It is shown that the integer n is half of the index of a Dirac
operator.Comment: 18pages, no figures, minor corrections, published versio
Identification of Very Red Counterparts of SiO Maser and OH/IR Objects in the GLIMPSE Survey
Using the 3.6/4.5/5.8/8.0 micron images with 1.2 arcsec pixel resolution from
the Spitzer/GLIMPSE survey, we investigated 23 masing and 18 very red objects
that were not identified in the 2MASS survey. Counterparts for all selected
objects were found in the GLIMPSE images. Color indices in these IR bands
suggest the presence of a high-extinction layer of more than a few tenths of a
solar mass in front of the central star. Furthermore, radio observations in the
SiO and H2O maser lines found characteristic maser-line spectra of the embedded
objects, e.g., the SiO J=1-0 line intensity in the v=2 state stronger than that
of the v=1 state, or very widespread H2O maser emission spectra. This indicates
that these objects are actually enshrouded by very thick circumstellar matter,
some of which cannot be ascribed to the AGB wind of the central star.
Individually interesting objects are discussed, including two newly found water
fountains and an SiO source with nebulosity.Comment: High resolution figures available at
ftp://ftp.nro.nao.ac.jp/nroreport/no653.pdf.gz. ApJ No. 655 no.1 issue in
pres
Kinematics of Red Variables in the Solar Neighborhood I. Basic Data Obtained by an SiO Maser Survey
In order to study the streaming motions of miras in the Solar neighborhood,
we newly surveyed 379 red variables in the SiO maser lines at 42.821 and 43.122
GHz with the Nobeyama 45m radio telescope. Accurate radial velocities were
obtained for 229 (220 new) detected stars. The sample is selected from optical
variables found by new automated surveys: the Northern Sky Variability Survey
and the All Sky Automated Survey. The new sample consists of the "bluer"
objects compared with those observed in the previous SiO surveys. The distances
to the objects are estimated using the period-luminosity relation, and they are
mostly less than 3 kpc from the Sun. The longitude-velocity diagram reveals
three prominent groups of stars deviant from the circular Galactic rotation
with a flat rotation curve. In addition to the Hercules group of stars which
was studied before, we found two new deviant groups: one toward the Perseus arm
and the other toward the Sagittarius arm. These two groups both exhibit
anomalous motions toward the Galactic center, which seem to be consistent with
the noncircular motions of these spiral arms found in the recent VLBI
proper-motion measurements for maser gas clumps.Comment: PASJ 64 no.1 (2012 Feb. 25 issue) in press. A full version including
Fig. 8a-m, and Fig. 9 are available at
http://www.nro.nao.ac.jp/~lib_pub/report/data/no680.pd
Study of the Bipolar Nebula IRAS 19312+1950. I. Mapping Observations
IRAS 19312+1950 is an SiO maser source that exhibits a prominent bipolar
nebulosity. Mapping observations of this object were made in the CO J=1--0,
13CO J=1--0, C18O J=1--0, CS J=2--1, and HCN J=1--0 lines and in the 150 GHz
continuum band. Near-infrared imaging observations were also made in the J, H,
and K-bands. The line profiles of the 12CO and HCN spectra consist of a weak
broad component with a line width of about 50 km/s and a strong narrow
component of the width of about 3 km/s. The profiles of the 13CO, C18O, and CS
lines have only the narrow component. Both of the components have an intensity
peak at the IRAS position. The narrow component was clearly resolved with a
15'' telescope beam. The spectral energy distribution of this object exhibits a
doubly peaked profile between 1 and 25 micron. The 150 GHz continuum flux
density was found to be 0.07 Jy, which is consistent with the flux density
predicted by the expanding envelope model with a mass loss rate of ~10^{-4}
M_sun/y at a distance of 2.5 kpc. We argue that the broad component originates
from the expanding envelope of this object, and that the hot dust cloud, which
is the source of the narrow component, is also physically associated with this
object. Though the present observations do not preclude the possibility of a
young stellar object, we argue that it is less plausible. We conclude that IRAS
19312+1950 is an AGB/post-AGB star that is evolved from a massive progenitor.Comment: 13 pages, 6 figures (jpg), high resolution figures available as no598
in http://www.nro.nao.ac.jp/library/report/list.html. PASJ, 56 No. 1 in pres
JVN observations of H2O masers around the evolved star IRAS 22480+6002
We report on the H2O maser distributions around IRAS 22480+6002 (=IRC+60370)
observed with the Japanese VLBI Network (JVN) at three epochs spanning 2
months. This object was identified as a K-type supergiant in 1970s, which was
unusual as a stellar maser source. The spectrum of H2O masers consists of 5
peaks separated roughly equally by a few km/s each. The H2O masers were
spatially resolved into more than 15 features, which spread about 50 mas along
the east--west direction. However, no correlation was found between the proper
motion vectors and their spatial distributions; the velocity field of the
envelope seems random. A statistical parallax method applied to the observed
proper-motion data set gives a distance of 1.0+-0.4 kpc for this object, that
is considerably smaller than previously thought. The distance indicates that
this is an evolved star with L~5800 Lsun. This star shows radio, infrared, and
optical characteristics quite similar to those of the population II post-AGB
stars such as RV Tau variables.Comment: 7 pages, 5 figures, PASJ 60, No. 1 (2008 Feb. 25 issue) in press.
High res. figures available at ftp://ftp.nro.nao.ac.jp/nroreport/no657.pdf.g
BIMA Array Observations of the Highly Unusual SiO Maser Source with a Bipolar Nebulosity, IRAS 19312+1950
We report the results of mapping observations of the bipolar nebula with SiO
maser emission, IRAS 19312+1950, in the CO (J=1-0 and J=2-1), 13CO (J=1-0 and
J=2-1), C18O (J=1-0), CS (J=2-1), SO (J_K=3_2-2_1) and HCO+ (J=3-2) lines with
the Berkeley-Illinois-Maryland Association array. Evolutional status of this
source has been evoking a controversy since its discovery, though SiO maser
sources are usually identified as late-type stars with active mass loss. In
line profiles, two kinematical components are found as reported in previous
single-dish observations: a broad pedestal component and a narrow component.
Spatio-kinetic properties of a broad component region traced by 12CO lines are
roughly explained by a simple spherical outflow model with a typical expanding
velocity of an AGB star, though some properties of the broad component region
still conflict with properties of a typical AGB spherical outflow. A narrow
component region apparently exhibits a bipolar flow. The angular size of the
narrow component region is spatially larger than that of a broad component
region. Intensity distribution of the CS emission avoids the central region of
the source, and that of an SO broad component emission exhibits a small feature
peaked exactly at the mapping center. According to the present results, if a
broad component really originates in a spherical outflow, an oxygen-rich
evolved stellar object seems to be a natural interpretation for the central
star of IRAS 19312+1950.Comment: 27 pages, 11 figures; accepted for publication in Ap
Correlation between Infrared Colors and Intensity Ratios of SiO Maser Lines
We present the results of SiO millimeter-line observations of a sample of
known SiO maser sources covering a wide dust-temperature range. A cold part of
the sample was selected from the SiO maser sources found in our recent SiO
maser survey of cold dusty objects. The aim of the present research is to
investigate the causes of the correlation between infrared colors and SiO maser
intensity ratios among different transition lines. In particular, the
correlation between infrared colors and SiO maser intensity ratio among the
J=1-0 v=1, 2, and 3 lines are mainly concerned in this paper. We observed in
total 75 SiO maser sources with the Nobeyama 45m telescope quasi-simultaneously
in the SiO J=1-0 v=0, 1, 2, 3, 4 and J=2-1 v=1, 2 lines. We also observed the
sample in the 29SiO J=1-0 v=0 and J=2-1 v=0, and 30SiO J=1-0 v=0 lines, and the
H2O 6(1,6)-5(2,3) line. As reported in previous papers, we confirmed that the
intensity ratios of the SiO J=1-0 v=2 to v=1 lines clearly correlate with
infrared colors. In addition, we found possible correlation between infrared
colors and the intensity ratios of the SiO J=1-0 v=3 to v=1&2 lines. Two
overlap lines of H2O (i.e., 11(6,6) nu_2=1 -> 12(7,5) nu_2=0 and 5(0,5) nu_2=2
-> 6(3,4) nu_2=1) might explain these correlation if these overlap lines become
stronger with increase of infrared colors, although the phenomena also might be
explained by more fundamental ways if we take into account the variation of
opacity from object to object.Comment: 49 pages, 7 figures, 3 tables, accepted for publication in ApJ. Full
resolution version available at
http://www.asiaa.sinica.edu.tw/~junichi/paper
SiO and H2O Maser Observations of Red Supergiants in Star Clusters Embedded in the Galactic Disk
We present the result of radio observations of red supergiants in the star
cluster, Stephenson's #2, and candidates for red supergiants in the star
clusters, Mercer et al. (2005)'s #4, #8, and #13, in the SiO and HO maser
lines.The Stephenson's #2 cluster and nearby aggregation at the South-West
contain more than 15 red supergiants. We detected one at the center of
Stephenson's #2 and three in the south-west aggregation in the SiO maser line,
and three of these 4 were also detected in the H2O maser line. The average
radial velocity of the 4 detected objects is 96 km s^{-1}, giving a kinematic
distance of 5.5 kpc, which locates this cluster near the base of the
Scutum-Crux spiral arm. We also detected 6 SiO emitting objects associated with
the other star clusters. In addition, mapping observations in the CO J=1--0
line toward these clusters revealed that an appreciable amount of molecular gas
still remains around Stephenson's #2 cluster in contrast to the prototypical
red-supergiant cluster, Bica et al.'s #122. It indicates that a time scale of
gas expulsion differs considerably in individual clusters.Comment: high res. figures available at
http://www.nro.nao.ac.jp/~lib_pub/report/data/no674.pdf. PASJ 62, No.2 (2010,
April 25 issue) in pres
A Measurement of Proper Motions of SiO Maser Sources in the Galactic Center with the VLBA
We report on the high-precision astrometric observations of maser sources
around the Galactic Center in the SiO J=1--0 v=1 and 2 lines with the VLBA
during 2001 -- 2004. With phase-referencing interferometry referred to the
radio continuum source Sgr A*, accurate positions of masers were obtained for
three detected objects: IRS 10 EE (7 epochs), IRS 15NE (2 epochs), and SiO 6
(only 1 epoch). Because circumstellar masers of these objects were resolved
into several components, proper motions for the maser sources were derived with
several different methods. Combining our VLBA results with those of the
previous VLA observations, we obtained the IRS 10EE proper motion of 76+-3 km
s^{-1} (at 8 kpc) to the south relative to Sgr A*. Almost null proper motion of
this star in the east--west direction results in a net transverse motion of the
infrared reference frame of about 30+-9 km s^{-1} to the west relative to Sgr
A*. The proper-motion data also suggests that IRS 10EE is an astrometric binary
with an unseen massive companion.Comment: High-res. figures are available at
ftp://ftp.nro.nao.ac.jp/nroreport/no656.pdf.gz . PASJ 60, No. 1 (2008) in
pres
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