122 research outputs found
AKARI Mission Program: Excavating Mass Loss History in Extended Dust Shells of Evolved Stars (MLHES) I. Far-IR Photometry
We performed a far-IR imaging survey of the circumstellar dust shells of 144
evolved stars as a mission programme of the AKARI infrared astronomical
satellite using the Far-Infrared Surveyor (FIS) instrument. With this survey,
we deliver far-IR surface brightness distributions of roughly 10' x 40' or 10'
x 20' areas of the sky around the target evolved stars in the four FIS bands at
65, 90, 140, and 160 microns. Our objectives are to characterize the far-IR
surface brightness distributions of the cold dust component in the
circumstellar dust shells, from which we derive the amount of cold dust grains
as low as 20 K and empirically establish the history of the early mass loss
history. In this first installment of the series, we introduce the project and
its aims, describe the observations, data reduction, and surface brightness
correction process, and present the entire data set along with the results of
integrated photometry measurements (i.e., the central source and circumstellar
dust shell altogether). We find that (1) far-IR emission is detected from all
but one object at the spatial resolution about 30" - 50" in the corresponding
bands, (2) roughly 60 - 70 % of the target sources show some extension, (3)
previously unresolved nearby objects in the far-IR are now resolved around 28
target sources, (4) the results of photometry measurements are reasonable with
respect to the entries in the AKARI/FIS Bright Source Catalogue, despite the
fact that the targets are assumed to be point-sources when catalogue flux
densities were computed, and (5) an IR two-color diagram would place the target
sources in a roughly linear distribution that may correlate with the age of the
circumstellar dust shell and can potentially be used to identify which targets
are more extended than others.Comment: To be published in PASJ AKARI Special Issue: 25 pages, 5 figures, 5
tables (and 28 supplementary figures available only in PASJ on-line
Detection of planet candidates around K giants, HD 40956, HD 111591, and HD 113996
Aims. The purpose of this paper is to detect and investigate the nature of
long-term radial velocity (RV) variations of K-type giants and to confirm
planetary companions around the stars.
Methods. We have conducted two planet search programs by precise RV
measurement using the 1.8 m telescope at Bohyunsan Optical Astronomy
Observatory (BOAO) and the 1.88 m telescope at Okayama Astrophysical
Observatory (OAO). The BOAO program searches for planets around 55 early K
giants. The OAO program is looking for 190 G-K type giants.
Results. In this paper, we report the detection of long-period RV variations
of three K giant stars, HD 40956, HD 111591, and HD 113996. We investigated the
cause of the observed RV variations and conclude the substellar companions are
most likely the cause of the RV variations. The orbital analyses yield P =
578.6 3.3 d, sin = 2.7 0.6 , = 1.4
0.1 AU for HD 40956; P = 1056.4 14.3 d, sin = 4.4 0.4
, = 2.5 0.1 AU for HD 111591; P = 610.2 3.8 d,
sin = 6.3 1.0 , = 1.6 0.1 AU for HD 113996.Comment: 10 pages, 12 figures. Accepted for publication in Astronomy &
Astrophysic
SiO Maser Survey of the Inner Bar of the Galactic Bulge
We surveyed 291 MSX/2MASS infrared objects in the 7 x 2 deg area of the
galactic center in the 43 GHz SiO J=1--0 v=1 and 2 maser lines, obtaining
accurate radial velocities of 163 detected objects. The surveyed area is the
region where the IRAS catalog is incomplete due to contamination by high source
density. The objects in the present MSX/2MASS sample were chosen to have
similar infrared characteristics to those of the previous SiO-maser-survey
samples based on the color selected IRAS sources. The sampling based on the
2MASS catalog causes a bias to the foreside objects of the bulge due to heavy
obscuration by interstellar dust; the detections are considerably leaned on the
V_{lsr}<0 side. The l--v diagram reveals two conspicuous features, which were
not present or tenuous in the previous studies: one feature indicating a linear
velocity increase with longitude with |l|<1.5 deg, which is likely associated
with the inner bar, and the other feature having considerably eccentric
velocities more than those of the normal x_1-orbit family feature. The
extinction-corrected K magnitudes (if used as a distance modulus) tend to show
a sequential deposition of these objects along the line of sight toward the
Galactic center depending on their radial velocities. The tendency that
appeared in the distance measures is consistent with the bulge-bar dynamical
model utilizing the periodic orbit families in the bar potential.Comment: Full high resolution figures available as NRO report No.638 at
http://www.nro.nao.ac.jp/library/report/list.html. PASJ 58, No. 3 (June 25
issue in press
- …