scholarly journals High-resolution observations of IRAS 08544−4431

2018 ◽  
Vol 614 ◽  
pp. A58 ◽  
Author(s):  
V. Bujarrabal ◽  
A. Castro-Carrizo ◽  
H. Van Winckel ◽  
J. Alcolea ◽  
C. Sánchez Contreras ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Binary System ◽  
Binary Stars ◽  
Asymptotic Giant Branch ◽  
Rotating Disks ◽  
Low Velocity ◽  
Central Mass ◽  
Stellar Orbits ◽  
Disk Rotation ◽  
Late Evolution

Context. Aims. In order to study the effects of rotating disks in the post-asymptotic giant branch (post-AGB) evolution, we observe a class of binary post-AGB stars that seem to be systematically surrounded by equatorial disks and slow outflows. Although the rotating dynamics had only been well identified in three cases, the study of such structures is thought to be fundamental to the understanding of the formation of disks in various phases of the late evolution of binary stars and the ejection of planetary nebulae from evolved stars. Methods. We present ALMA maps of 12CO and 13CO J = 3−2 lines in the source IRAS 08544−4431, which belongs to the above mentioned class of objects. We analyzed the data by means of nebula models, which account for the expectedly composite source and can reproduce the data. From our modeling, we estimated the main nebula parameters, including the structure and dynamics and the density and temperature distributions. We discuss the uncertainties of the derived values and, in particular, their dependence on the distance. Results. Our observations reveal the presence of an equatorial disk in rotation; a low-velocity outflow is also found, probably formed of gas expelled from the disk. The main characteristics of our observations and modeling of IRAS 08544−4431 are similar to those of better studied objects, confirming our interpretation. The disk rotation indicates a total central mass of about 1.8 M⊙, for a distance of 1100 pc. The disk is found to be relatively extended and has a typical diameter of ~4 × 1016 cm. The total nebular mass is ~2 × 10−2 M⊙, of which ~90% corresponds to the disk. Assuming that the outflow is due to mass loss from the disk, we derive a disk lifetime of ~10 000 yr. The disk angular momentum is found to be comparable to that of the binary system at present. Assuming that the disk angular momentum was transferred from the binary system, as expected, the high values of the disk angular momentum in this and other similar disks suggest that the size of the stellar orbits has significantly decreased as a consequence of disk formation.

scholarly journals Birth sites of young stellar associations and recent star formation in a flocculent corrugated disc

2020 ◽  
Vol 499 (4) ◽  
pp. 5623-5640
Author(s):  
Alice C Quillen ◽  
Alex R Pettitt ◽  
Sukanya Chakrabarti ◽  
Yifan Zhang ◽  
Jonathan Gagné ◽  
...  
Keyword(s):  
Space Distribution ◽  
Solar Neighbourhood ◽  
Low Velocity ◽  
Stellar Association ◽  
Stellar Orbits ◽  
Pattern Speeds ◽  
Moving Groups ◽  
Orbit Integration ◽  
Stellar Associations ◽  
Spiral Arm

ABSTRACT With backwards orbit integration, we estimate birth locations of young stellar associations and moving groups identified in the solar neighbourhood that are younger than 70 Myr. The birth locations of most of these stellar associations are at a smaller galactocentric radius than the Sun, implying that their stars moved radially outwards after birth. Exceptions to this rule are the Argus and Octans associations, which formed outside the Sun’s galactocentric radius. Variations in birth heights of the stellar associations suggest that they were born in a filamentary and corrugated disc of molecular clouds, similar to that inferred from the current filamentary molecular cloud distribution and dust extinction maps. Multiple spiral arm features with different but near corotation pattern speeds and at different heights could account for the stellar association birth sites. We find that the young stellar associations are located in between peaks in the radial/tangential (UV) stellar velocity distribution for stars in the solar neighbourhood. This would be expected if they were born in a spiral arm, which perturbs stellar orbits that cross it. In contrast, stellar associations seem to be located near peaks in the vertical phase-space distribution, suggesting that the gas in which stellar associations are born moves vertically together with the low-velocity dispersion disc stars.

scholarly journals Gaseous Disks in the Nuclei of Elliptical Galaxies

1997 ◽  
Vol 163 ◽  
pp. 620-625 ◽  
Author(s):  
H. Ford ◽  
Z. Tsvetanov ◽  
L. Ferrarese ◽  
G. Kriss ◽  
W. Jaffe ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Elliptical Galaxies ◽  
Central Mass ◽  
Massive Black Holes ◽  
Radio Jets

AbstractHST images have led to the discovery that small (r ~ 1″ r ~ 100 – 200 pc), well-defined, gaseous disks are common in the nuclei of elliptical galaxies. Measurements of rotational velocities in the disks provide a means to measure the central mass and search for massive black holes in the parent galaxies. The minor axes of these disks are closely aligned with the directions of the large–scale radio jets, suggesting that it is angular momentum of the disk rather than that of the black hole that determines the direction of the radio jets. Because the disks are directly observable, we can study the disks themselves, and investigate important questions which cannot be directly addressed with observations of the smaller and unresolved central accretion disks. In this paper we summarize what has been learned to date in this rapidly unfolding new field.

scholarly journals Physical Parameters and Chemical Composition of Components of the Am-Type Binary System RR Lyncis

1993 ◽  
Vol 138 ◽  
pp. 192-196
Author(s):  
L.S. Lyubimkov ◽  
T.M. Rachkovskaya
Keyword(s):  
Chemical Composition ◽  
Binary System ◽  
Binary Stars ◽  
Spectroscopic Binaries ◽  
Theoretical Modelling ◽  
Physical Parameters ◽  
Accurate Data ◽  
Element Abundances ◽  
Widespread Phenomenon ◽  
Chemical Anomalies

Duplicity is a very widespread phenomenon among Am-stars. For instance, Abt (1961) investigating 25 such stars found out that 22 of them are spectroscopic binaries. However this important phenomenon is ignored usually in chemical composition investigations of Am-stars. Consequently some “mean” element abundances are determined, which can noticeably differ from real abundances in atmospheres of components. Moreover false chemical anomalies can appear, as shown by the theoretical modelling of spectra of binary stars (Lyubimkov, 1989, 1992). Meanwhile accurate data on chemical composition of Am-stars must be considered as observational test for any hypothesis suggested for explanation of these objects.

scholarly journals Angular Momentum Changes Due to Direct Impact Accretion in a Binary System

2010 ◽  
Author(s):  
Jeremy F. Sepinsky ◽  
Bart Willems ◽  
Vassiliki Kalogera ◽  
Frederic A. Rasio ◽  
Vicky Kologera ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Binary System ◽  
Direct Impact

scholarly journals Instabilities of Uniformly Rotating Disks

1996 ◽  
Vol 169 ◽  
pp. 349-350 ◽  
Author(s):  
P. Vauterin ◽  
H. Dejonghe
Keyword(s):  
Distribution Function ◽  
Differential Rotation ◽  
Mass Concentration ◽  
Expansion Method ◽  
Rotating Disks ◽  
Central Mass ◽  
Reasonable Approximation ◽  
Central Regions ◽  
Series Expansion Method

We explore a series expansion method to calculate the instabilities and the structure of the perturbations for a variety of uniformly rotating finite stellar disks. This survey focuses on the role of the distribution function in stability analyses. Although the potential does not show differential rotation, it will in many cases be a reasonable approximation for the disk in the central regions of galaxies without massive central mass concentration.

Non-axisymmetric Unstable Modes in a Thin Differentially Rotating Gaseous Disk

1991 ◽  
Vol 02 (01) ◽  
pp. 367-370
Author(s):  
M.H.M. HEEMSKERK ◽  
G.J. SAVONIJE
Keyword(s):  
Angular Momentum ◽  
Conservation Laws ◽  
Numerical Solutions ◽  
Gravitational Attraction ◽  
Rotating Disc ◽  
Central Mass ◽  
Reflecting Boundaries ◽  
Self Gravity ◽  
Axisymmetric Perturbations ◽  
Gaseous Disc

We consider the linear stability of a thin differentially rotating gaseous disc with reflecting boundaries against non-axisymmetric perturbations. We assume the unperturbed disc to be in centrifugal equilibrium with the gravitational attraction of a central mass M, and consider discs whose mass can be neglected relative to M. We discuss the relevant conservation laws for the energy and angular momentum of linear non-axisymmetric modes in a thin rotating disc without self-gravity and illustrate the basic mode amplification mechanisms with help of some of our numerical solutions [1].

scholarly journals The J vs. M Relation for Binary Stars

1989 ◽  
Vol 8 ◽  
pp. 137-138
Author(s):  
J. E. Tohline
Keyword(s):  
Angular Momentum ◽  
Binary Stars ◽  
Binary Systems ◽  
Environmental Temperature ◽  
Physical Systems ◽  
Young Binary Systems

AbstractFor a given mass M and environmental temperature T, there is a well-defined angular momentum Jmax above which physical systems cannot exist as self-gravitating entities. The quantity Jmax α M2 T−½. Observations of J and M in young binary systems should put useful constraints on the temperature of the medium from which they formed.

scholarly journals AGB winds in interacting binary stars

2020 ◽  
Vol 493 (2) ◽  
pp. 2606-2617 ◽  
Author(s):  
Luis C Bermúdez-Bustamante ◽  
G García-Segura ◽  
W Steffen ◽  
L Sabin
Keyword(s):  
Radiation Pressure ◽  
Stellar Wind ◽  
Binary Stars ◽  
Massive Star ◽  
Density Ratio ◽  
Asymptotic Giant Branch ◽  
Surface Layers ◽  
Outflow Velocity ◽  
Analytical Formulae ◽  
Set Up

ABSTRACT We perform numerical simulations to investigate the stellar wind from interacting binary stars. Our aim is to find analytical formulae describing the outflow structure. In each binary system the more massive star is in the asymptotic giant branch (AGB) and its wind is driven by a combination of pulsations in the stellar surface layers and radiation pressure on dust, while the less massive star is in the main sequence. Time averages of density and outflow velocity of the stellar wind are calculated and plotted as profiles against distance from the centre of mass and colatitude angle. We find that mass is lost mainly through the outer Lagrangian point L2. The resultant outflow develops into a spiral at low distances from the binary. The outflowing spiral is quickly smoothed out by shocks and becomes an excretion disc at larger distances. This leads to the formation of an outflow structure with an equatorial density excess, which is greater in binaries with smaller orbital separation. The pole-to-equator density ratio reaches a maximum value of ∼105 at Roche lobe overflow state. We also find that the gas stream leaving L2 does not form a circumbinary ring for stellar mass ratios above 0.78, when radiation pressure on dust is taken into account. Analytical formulae are obtained by curve fitting the two-dimensional, azimuthally averaged density and outflow velocity profiles. The formulae can be used in future studies to set-up the initial outflow structure in hydrodynamic simulations of common-envelope evolution and formation of planetary nebulae.

scholarly journals The morpho-kinematics of the circumstellar envelope around the AGB star EP Aqr

2019 ◽  
Vol 484 (2) ◽  
pp. 1865-1888 ◽  
Author(s):  
D T Hoai ◽  
P T Nhung ◽  
P Tuan-Anh ◽  
P Darriulat ◽  
P N Diep ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Loss Rate ◽  
Equatorial Region ◽  
Data Cube ◽  
Asymptotic Giant Branch ◽  
Expansion Velocity ◽  
Circumstellar Envelope ◽  
Low Velocity ◽  
Loss Mechanism ◽  
Asymptotic Giant Branch Star

ABSTRACT ALMA observations of CO(1–0) and CO(2–1) emissions of the circumstellar envelope of EP Aqr, an oxygen-rich asymptotic giant branch star, are reported. A thorough analysis of their properties is presented using an original method based on the separation of the data cube into a low-velocity component associated with an equatorial outflow and a faster component associated with a bipolar outflow. A number of important and new results are obtained concerning the distribution in space of the effective emissivity, the temperature, the density, and the flux of matter. A mass-loss rate of (1.6 ± 0.4)×10−7 solar masses per year is measured. The main parameters defining the morphology and kinematics of the envelope are evaluated and uncertainties inherent to de-projection are critically discussed. Detailed properties of the equatorial region of the envelope are presented including a measurement of the line width and a precise description of the observed inhomogeneity of both morphology and kinematics. In particular, in addition to the presence of a previously observed spiral enhancement of the morphology at very small Doppler velocities, a similarly significant but uncorrelated circular enhancement of the expansion velocity is revealed, both close to the limit of sensitivity. The results of the analysis place significant constraints on the parameters of models proposing descriptions of the mass-loss mechanism, but cannot choose among them with confidence.

Sign in / Sign up

Export Citation Format

Share Document