scholarly journals Uniqueness and evolutionary status of MWC 349A

2010 ◽  
Vol 6 (S272) ◽  
pp. 632-633
Author(s):  
Vladimir Strelnitski ◽  
Kamber Schwarz ◽  
John Bieging ◽  
Josh T. Fuchs ◽  
Gary Walker
Keyword(s):  
Observational Data ◽  
High Gain ◽  
Radio Continuum ◽  
Circumstellar Disk ◽  
Evolutionary Status ◽  
Hydrogen Recombination ◽  
Protoplanetary Nebula ◽  
Ordinary Member ◽  
Stellar Source

AbstractMWC349A, which had remained an ordinary member of the MWC catalog for a few decades, is now known as: (1) the brightest stellar source of radio continuum; (2) the only known high-gain natural maser in hydrogen recombination lines; and (3) the only strictly proven natural high-gain laser (in IR hydrogen recombination lines). These phenomena seem to occur in the circumstellar disk seen almost edge-on. They help us understand the structure and kinematics of the disk. The evolutionary status of MWC 349A is still debated: a young HAeBe star with a pre-planetary disk or an old B[e] star or even a protoplanetary nebula? We discuss new observational data obtained at the Maria Mitchell Observatory and elsewhere which may cast light on this issue.

scholarly journals Introduction to the session

1979 ◽  
Vol 84 ◽  
pp. 323-323
Keyword(s):  
High Resolution ◽  
Observational Data ◽  
Far Infrared ◽  
List Type ◽  
Type Number ◽  
Ionized Gas ◽  
The Past ◽  
Hydrogen Recombination ◽  
Great Development

There has been a great development in the past few years of observational data of various kinds: (a)HI observations of high resolution and sensitivity (Cohen and Davies, Burton et al., Kerr et al.)(b)Observations of molecules, in particular high-resolution observations of CO (Burton, Gordon, Bania, Liszt, Solomon et al.)(c)Infrared and far-infrared(d)Ionized gas: hydrogen recombination lines, and in particular Nell (with 4″ beam) (Mezger et al., Townes, Wollman et al.)

scholarly journals Intragroup Gas in Differently Evolved Compact Groups of Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 221-221
Author(s):  
L. Verdes-Montenegro ◽  
J. Rasmussen ◽  
T. Ponman ◽  
M. S. Yun ◽  
S. Borthakur
Keyword(s):  
Star Formation ◽  
Detection Rate ◽  
Virgo Cluster ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Compact Groups ◽  
Evolutionary Status ◽  
X Ray ◽  
Groups Of Galaxies ◽  
Star Formation Activity

AbstractCompact groups are highly isolated, dense galaxy systems, and therefore tidal interactions are expected to be continuous and dynamically important. For this reason they represent unique laboratories for studying interactions in extreme environments and tidally induced star formation as well as morphological and dynamical evolution of galaxies in general. This study is part of a broader investigation of the evolutionary status of HCGs. In order to explain the HI deficiency found in compact groups of galaxies we have proposed a broad evolutionary scenario in which the amount of HI decreases with the secular evolutionary state of a group. The fate of this gas is however not clear. In order to investigate the physical mechanisms responsible for these changes in the gas content of galaxies we have started a study to look for an intragroup medium (IGM). We have considered this IGM to be neutral (see e.g. reports of HI clouds within Virgo cluster (Oosterloo & Van Gorkom 2005), or hot gas (a higher X-ray detection rate of HI deficient groups is found relative to groups with a normal HI content, Verdes-Montenegro et al. 2001). Enhanced star formation activity might also be contributing to exhausting the gas supply. We have observed 25 HCGs with diverse HI content and distribution with the Green Bank radiotelescope, and performed VLA-HI as well as X-ray (XMM or Chandra) observations of the most HI deficient groups HCG 7, 15, 30, 37, 40, 44 and 97. We have also analysed FIR data from Verdes-Montenegro et al. (1998).Our results are: (a) HI deficient groups show a larger amount of diffuse neutral and X-ray gas when compared to non-deficient ones, consistent with our evolutionary picture; (b) Most groups are still deficient after including diffuse gas. (c) A hot IGM is not detected in most of these systems, but the detection rate is higher for the high velocity dispersion groups, and in these cases ram pressure stripping could potentially cause the observed HI-deficiency. (d) In several of these groups we detect intragroup radio continuum emission, which is surprising since similar features were seen previously only in massive clusters (known as “relic” sources). (e) Star formation activity traced by FIR luminosity is not enhanced, contrary to the general expectation of tidally interacting systems.Hence neither the presence of a hot or cold IGM nor star formation activity seem to be able to uniquely explain the HI deficiency found in compact groups of galaxies. We plan to explore the possibility that earlier starbursts could have contributed to the present HI deficiency.

Natural Masers and Lasers and Bioastronomy

1997 ◽  
Vol 161 ◽  
pp. 381-390
Author(s):  
Vladimir Strelnitski ◽  
Tsevi Mazeh
Keyword(s):  
Massive Star ◽  
Extrasolar Planets ◽  
Planetary System ◽  
Circumstellar Disks ◽  
Circumstellar Disk ◽  
General Properties ◽  
Hydrogen Recombination ◽  
Molecular Lines

AbstractWe discuss three possible applications of natural masers and lasers interesting to bioastronomy: 1) the study of protoplanetary circumstellar disks, 2) the study of extrasolar planets, 3) interstellar communications. Masers and lasers in hydrogen recombination lines are observed from the circumstellar disk of a massive star MWC349 A and serve as probes of the disk’s kinematics and structure. They give, in particular, some indications for avoidin the central (R≈ 40 AU) part of the disk, which may be caused by a forming planetary system. We demonstrate that masers (but not lasers) in molecular lines from the atmospheres of the recently discovered extrasolar planets on close orbits around their suns (51 Peg, τ Boo) can be detectable with theexisting ground-basedradioastronomical facilities. The importance of such a detection solicits a deeper analysis of general properties of the planetary masing and lasing and an analysis of the candidate lines to be searched. We argue against the use ofnaturallasers for SETI.

scholarly journals The Galactic Distribution of O-Rich AGB Stars

1993 ◽  
Vol 155 ◽  
pp. 328-328
Author(s):  
B.W. Jiang ◽  
J.Y. Hu
Keyword(s):  
Observational Data ◽  
Spiral Structure ◽  
Hii Regions ◽  
High Accuracy ◽  
Radio Continuum ◽  
Agb Stars ◽  
Hii Region ◽  
Balmer Lines ◽  
Galactic Distribution

In 1976 Georgelin et al.(1976) combined optical and radio observational data of HII regions to study the structure of our Galaxy. The distance of each HII region can be obtained from its radio continuum flux caused by free-free emission and the flux of the Balmer lines with high accuracy. The results clearly show three arms and are used to draw the spiral structure of our Galaxy. It is commonly accepted now.

scholarly journals ALMA observations of PSR B1259−63/LS 2883 in an inactive period: Variable circumstellar disk?

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Yutaka Fujita ◽  
Hiroshi Nagai ◽  
Takuya Akahori ◽  
Akiko Kawachi ◽  
Atsuo T Okazaki
Keyword(s):  
Binary System ◽  
Massive Star ◽  
Gamma Ray ◽  
Thermal Emission ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Circumstellar Disk ◽  
Inactive Period ◽  
Period Variable ◽  
Pulsar Winds

Abstract We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of the gamma-ray binary system containing the pulsar PSR B1259−63 orbiting around a massive star LS 2883 in an inactive period between the 2017 and 2021 periastron passages. We detected radio continuum emission from the binary system at 97 GHz (Band 3) and 343 GHz (Band 7). Compared with our previous ALMA observations performed soon after the 2017 periastron passage, the fluxes have decreased by a factor of six at 97 GHz and of two at 343 GHz. The flux at 343 GHz is large relative to that at 97 GHz and appears to be thermal emission from the circumstellar disk around LS 2883. The decrease of the 343 GHz flux may indicate that the disk has expanded and become partially optically thin since the disk is no longer affected by pulsar winds. The flux at 97 GHz is consistent with that expected from the pulsed emission from the pulsar, which indicates that the unpulsed emission that had been produced through pulsar-disk or pulsar-stellar wind interaction has disappeared. The image of the system is consistent with a point source and shows no sign of ejecta.

scholarly journals Some Aspects of the Evolutionary Status Of W Ursae Majoris Binaries Deduced from Observational Data

1982 ◽  
Vol 69 ◽  
pp. 301-304
Author(s):  
Walter Van Hamme
Keyword(s):  
Observational Data ◽  
Spectral Type ◽  
Main Sequence ◽  
Type A ◽  
Type Systems ◽  
Primary Component ◽  
Main Sequence Star ◽  
Evolutionary Status ◽  
Evolutionary Stage ◽  
Evolutionary State

AbstractWe have developed a test for the evolutionary state of W Ursae Majoris binaries by comparing the observed spectral type of 31 of these systems (14 of type W and 17 of type A) with the expected one when their primary component is an unevolved main sequence star. It appears that both the W- and A-type systems have a primary with a mass and radius too large to be compatible with the observed spectral type,so there is no indication that each type should mark a different evolutionary stage.

scholarly journals Evolutionary Aspects of Wolf-Rayet Stars

1973 ◽  
Vol 49 ◽  
pp. 141-162 ◽  
Author(s):  
B. Paczyński
Keyword(s):  
Mass Loss ◽  
Observational Data ◽  
Driving Force ◽  
Historical Development ◽  
Joint Institute ◽  
Laboratory Astrophysics ◽  
Evolutionary Status ◽  
Interior Structure ◽  
Evolutionary Aspects

Problems related to Wolf-Rayet stars were recently reviewed by Underhill (1968) and were discussed at length during the symposium held at the Joint Institute for Laboratory Astrophysics in Boulder (Gebbie and Thomas, 1968). Therefore, I shall not review here the historical development of ideas, and I shall not give detailed references in those cases when all the information is available in the sources mentioned above. I shall discuss first those observational data that are most important for the understanding of the evolutionary status of these stars. Later I shall discuss the problem of the interior structure and the origin of WR stars. And finally theories of the driving force for the observed mass loss will be presented.

A Circumstellar Disk in IRAS 23151+5912?

2017 ◽  
Vol 13 (S336) ◽  
pp. 315-316
Author(s):  
Miguel A. Trinidad ◽  
Tatiana Rodríguez-Esnard ◽  
Josep M. Masqué
Keyword(s):  
Radio Continuum ◽  
High Mass ◽  
Circumstellar Disk ◽  
Mass Star ◽  
Hii Region ◽  
Star Forming ◽  
Continuum Source ◽  
Water Masers ◽  
Water Maser ◽  
The Continuum

AbstractWe present radio continuum and water maser observations toward the high-mass star-forming region IRAS 23151+5912 from the VLA and VLBA archive, respectively. We detected a continuum source, which seems to be a hypercompact HII region. In addition, a water maser group about 4″ south from the continuum source was detected. We present preliminary results of the analysis of three observations epochs of the water masers, which are tracing an arc-like structure. However, its kinematics is quite complex, since while one section of the structure seems to be moving away from one center, another section seems to be approaching.

Sign in / Sign up

Export Citation Format

Share Document