Gomez's Hamburger (IRAS 18059-3211): a pre main-sequence A-type star

Bujarrabal, V.; Young, Kenneth H.; Fong, D.

doi:10.1051/0004-6361:20079273

Cited by 17 publications

(43 citation statements)

References 25 publications

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“…The code itself is similar to that described by Bujarrabal et al (2008), Paper I (see further details there, including discussions about the basic assumptions). The method used to find the bestfit solution and the uncertainties in the derived parameter values are presented in Sect.…”

Section: Co Emission Modelmentioning

confidence: 99%

“…However, high-resolution CO maps (Bujarrabal et al 2008, hereafter, Paper I) were used to demonstrate that the nebula is almost exactly in Keplerian rotation, around the symmetry axis clearly identifiable in its image.…”

Section: Introductionmentioning

confidence: 99%

“…Bujarrabal et al (2008) estimated the central (presumably stellar) mass and concluded that, for any possible distance, its high value in combination with the relatively low total luminosity of the source is incompatible with the idea that GoHam is an evolved object. These authors concluded that Gomez's Hamburger is very probably a pre-main-sequence object at a much smaller distance than previously believed, of 500 pc, although this value remains uncertain.…”

Section: Introductionmentioning

confidence: 99%

“…4 the nature of the central star(s), taking into account our new results. Bujarrabal et al (2008) presented only 12 CO J = 2−1 maps obtained with the SMA, together with a preliminary modeling of the data. The development of these models was limited significantly by the small amount of available data.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, the high optical depth expected in this line prevented any accurate determination of the gas density distribution. A significant revision of some parameters tentatively discussed by Bujarrabal et al (2008) was therefore necessary. In this paper, we also present maps of 13 CO J = 2−1, 12 CO J = 3−2, and C 17 O J = 3−2.…”

Section: Introductionmentioning

confidence: 99%

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The physical conditions in Gomez's Hamburger (IRAS 18059-3211), a pre-MS rotating disk

Bujarrabal¹,

Young²,

Castro-Carrizo³

2009

A&A

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Aims. We aim to study the structure, dynamics, and physical conditions of Gomez's Hamburger (IRAS 18059-3211; GoHam), and in particular confirm that GoHam mainly consists of a flaring disk in Keplerian rotation around a young, probably pre-MS star. Methods. We present high resolution SMA maps of 12 CO J = 2−1, 13 CO J = 2−1, 12 CO J = 3−2, and C 17 O J = 3−2, as well as data on 12 CO J = 6−5 and the continuum flux at these wavelengths. Spatial resolutions as high as 1 are attained. Except for the C 17 O data, the dynamical ranges are larger than 10. The maps are compared with a numerical model, which simulates the emission of a rotating disk with the expected general properties of such objects, and a very satisfactory fitting of our maps is obtained. The meaning and reliability of our results are thoroughly discussed. Results. Our observations allow measurement of the main properties of GoHam on scales of between ∼1 (∼5 × 10 15 cm, for the assumed distance, 300 pc) and the total extent of the nebula, 14 . We are able to measure the global structure of the gas-rich disk, which is found to be flaring, and its dynamics, which is clearly dominated by Keplerian rotation, with a small degree of turbulence. The combination of different lines, in particular of different opacities, allows us to estimate reasonably the distributions of gas temperature and density. We clearly find a significant and sharp increase in temperature at large distances from the equator, accompanied by a decrease in density of the same order. Finally, we identify a condensation in the southern part of the disk that has no counterparts in the northern nebula. This condensation is quite extended (about 5 × 10 15 cm), contains a significant amount of mass (roughly, ∼6 × 10 −3 M ), and seems to be associated with a detectable distortion of the global rotation kinematics. We discuss several possible interpretations of that feature.

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Section: Co Emission Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The physical conditions in Gomez's Hamburger (IRAS 18059-3211), a pre-MS rotating disk

Bujarrabal¹,

Young²,

Castro-Carrizo³

2009

A&A

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Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles

Beck

Decin

Koter

et al. 2010

A&A

234

281

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Context. The evolution of intermediate and low-mass stars on the asymptotic giant branch is dominated by their strong dust-driven winds. More massive stars evolve into red supergiants with a similar envelope structure and strong wind. These stellar winds are a prime source for the chemical enrichment of the interstellar medium. Aims. We aim to (1) set up simple and general analytical expressions to estimate mass-loss rates of evolved stars, and (2) from those calculate estimates for the mass-loss rates of the asymptotic giant branch, red supergiant, and yellow hypergiant stars in our galactic sample. Methods. The rotationally excited lines of carbon monoxide (CO) are a classic and very robust diagnostic in the study of circumstellar envelopes. When sampling different layers of the circumstellar envelope, observations of these molecular lines lead to detailed profiles of kinetic temperature, expansion velocity, and density. A state-of-the-art, nonlocal thermal equilibrium, and co-moving frame radiative transfer code that predicts CO line intensities in the circumstellar envelopes of late-type stars is used in deriving relations between stellar and molecular-line parameters, on the one hand, and mass-loss rate, on the other. These expressions are applied to our extensive CO data set to estimate the mass-loss rates of 47 sample stars. Results. We present analytical expressions for estimating the mass-loss rates of evolved stellar objects for 8 rotational transitions of the CO molecule and thencompare our results to those of previous studies. Our expressions account for line saturation and resolving of the envelope, thereby allowing accurate determination of very high mass-loss rates. We argue that, for estimates based on a single rotational line, the CO(2-1) transition provides the most reliable mass-loss rate. The mass-loss rates calculated for the asympotic giant branch stars range from 4 × 10 −8 M yr −1 up to 8 × 10 −5 M yr −1 . For red supergiants they reach values between 2 × 10 −7 M yr −1 and 3 × 10 −4 M yr −1 . The estimates for the set of CO transitions allow time variability to be identified in the mass-loss rate. Possible mass-loss-rate variability is traced for 7 of the sample stars. We find a clear relation between the pulsation periods of the asympotic giant branch stars and their derived mass-loss rates, with a levelling off at ∼3 × 10 −5 M yr −1 for periods exceeding 850 days. Conclusions.

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Detection of Keplerian dynamics in a disk around the post-AGB star AC Herculis

Bujarrabal

Castro-Carrizo

Winckel

2015

A&A

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Aims. So far, only one rotating disk has been clearly identified and studied in AGB or post-AGB objects (in the Red Rectangle), by means of observations with high spectral and spatial resolution. However, disks are thought to play a key role in the late stellar evolution and are suspected to surround many evolved stars. We aim to extend our knowledge on these structures. Methods. We present interferometric observations of 12 CO J = 2−1 emission from the nebula surrounding the post-AGB star AC Her, a source belonging to a class of objects that share properties with the Red Rectangle and show hints of Keplerian disks. Results. We clearly detect the Keplerian dynamics of a second disk orbiting an evolved star. Its main properties (size, temperature, central mass) are derived from direct interpretation of the data and model fitting. With this we confirm that there are disks orbiting the stars of this relatively wide class of post-AGB objects.

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Gomez's Hamburger (IRAS 18059-3211): a pre main-sequence A-type star

Cited by 17 publications

References 25 publications

The physical conditions in Gomez's Hamburger (IRAS 18059-3211), a pre-MS rotating disk

The physical conditions in Gomez's Hamburger (IRAS 18059-3211), a pre-MS rotating disk

Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles

Detection of Keplerian dynamics in a disk around the post-AGB star AC Herculis

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