The distance and size of the red hypergiant NML Cygni from VLBA and VLA astrometry

Zhang, B.; Reid, M. J.; Menten, K. M.; Zheng, Xingwu; Brunthaler, A.

doi:10.1051/0004-6361/201219587

Cited by 32 publications

(27 citation statements)

References 45 publications

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“…The strong emission from the background superbubble has much substructure at all wavelengths and therefore blends with the circumstellar shell emission making it near impossible to discern the difference between the two. This emission is a result of the large dust content of the Cyg X superbubble (Zhang et al 2012). De Beck et al (2010) derived a constant gas MLR of 8.7 × 10 −5 M yr −1 for this RSG and an outer circumstellar shell radius of 0.07 pc based on this constant MLR.…”

Section: Nml Cygmentioning

confidence: 84%

Extended Dust Emission from Nearby Evolved Stars★

Dharmawardena

Kemper

Scicluna

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present JCMT SCUBA-2 450µm and 850µm observations of 14 Asymptotic Giant Branch (AGB) stars (9 O-rich, 4 C-rich and 1 S-type) and one Red Supergiant (RSG) in the Solar Neighbourhood. We combine these observations with Herschel /PACS observations at 70µm and 160µm and obtain azimuthally-averaged surface-brightness profiles and their PSF subtracted residuals. The extent of the SCUBA-2 850 µm emission ranges from 0.01 to 0.16 pc with an average of ∼ 40% of the total flux being emitted from the extended component. By fitting a modified black-body to the four-point SED at each point along the radial profile we derive the temperature (T ), spectral index of dust emissivity (β) and dust column density (Σ) as a function of radius. For all the sources, the density profile deviates significantly from what is expected for a constant mass-loss rate, showing that all the sources have undergone variations in mass-loss during this evolutionary phase. In combination with results from CO line emission, we determined the dust-to-gas mass ratio for all the sources in our sample. We find that, when sources are grouped according to their chemistry, the resulting average dust-to-gas ratios are consistent with the respective canonical values. However we see a range of values with significant scatter which indicate the importance of including spatial information when deriving these numbers.

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Section: Nml Cygmentioning

confidence: 84%

Extended Dust Emission from Nearby Evolved Stars★

Dharmawardena

Kemper

Scicluna

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…The data of distance d, terminal velocity of CO envelope V e , and mean mass-loss rateṀ of the selected sources were compiled from Woods et al (2003), , Justtanont et al (2012), and Schöier et al (2013). We note that Schöier et al (2013) adopted smaller distances for χ Cyg (110 pc) and RX Boo (120 pc), and the distance to VY CMa was averaged from two measurements (Choi et al 2008;Zhang et al 2012 Tsuji et al (1994), TX Cam from Cho & Ukita (1998), and CIT 6 from Zhang et al (2009). Spectral types were taken from the SIMBAD database, , and the references therein.…”

Section: Discussionmentioning

confidence: 99%

Silicon isotopic abundance toward evolved stars and its application for presolar grains

Peng¹,

Humphreys²,

Testi³

et al. 2013

A&A

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Aims. Galactic chemical evolution (GCE) is important for understanding the composition of the present-day interstellar medium (ISM) and of our solar system. In this paper, we aim to track the GCE by using the 29 Si/ 30 Si ratios in evolved stars and tentatively relate this to presolar grain composition. Methods. We used the APEX telescope to detect thermal SiO isotopologue emission toward four oxygen-rich M-type stars. Together with the data retrieved from the Herschel science archive and from the literature, we were able to obtain the 29 Si ratios inferred from the thermal SiO emission tend to be lower toward low-mass oxygen-rich stars (e.g., down to about unity for W Hya), and close to an interstellar or solar value of 1.5 for the higher-mass carbon star IRC+10216 and two red supergiants. There is a tentative correlation between the 29 Si/ 30 Si ratios and the mass-loss rates of evolved stars, where we take the mass-loss rate as a proxy for the initial stellar mass or current stellar age. This is consistent with the different abundance ratios found in presolar grains. Before the formation of the Sun, the presolar grains indicate that the bulk of presolar grains already had 29 Si/ 30 Si ratios of about 1.5, which is also the ratio we found for the objects younger than the Sun, such as VY CMa and IRC+10216. However, we found that older objects (up to possibly 10 Gyr old) in our sample trace a previous, lower 29 Si/ 30 Si value of about 1. Material with this isotopic ratio is present in two subclasses of presolar grains, providing independent evidence of the lower ratio. Therefore, the 29 Si/ 30 Si ratio derived from the SiO emission of evolved stars is a useful diagnostic tool for the study of the GCE and presolar grains.

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“…The first data release of Gaia does not include a parallax for VX Sgr, and as red hypergiants are large, variable, and often surrounded by copious dust, these issues may limit the accuracy of future optical astrometry. Of the "fabulous-four" red hypergiants in the Milky Way, strong maser emission VLBI parallaxes have been determined for VY CMa (Choi et al 2008;Zhang et al 2012a), NML Cyg (Zhang et al 2012b), and S Per  (Asaki et al 2010), leaving only VX Sgr without a reliable distance.…”

Section: Introductionmentioning

confidence: 99%

The Parallax of the Red Hypergiant VX Sgr with Accurate Tropospheric Delay Calibration

Zhang

Reid

et al. 2018

ApJ

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We report astrometric results of VLBI phase-referencing observations of 22 GHz H 2 O masers emission toward the red hypergiant VX Sgr, one of most massive and luminous red hypergiant stars in our Galaxy, using the Very Long Baseline Array. A background source, J1820−2528, projected 4°.4 from the target VX Sgr, was used as the phase reference. For the low decl. of these sources, such a large separation normally would seriously degrade the relative astrometry. We use a two-step method of tropospheric delay calibration, which combines the VLBI geodetic-block (or Global Positioning System) calibration with an image-optimization calibration, to obtain a trigonometric parallax of 0.64±0.04 mas, corresponding to a distance of -+ 1.56 0.10 0.11 kpc. The measured proper motion of VX Sgr is 0.36±0.76 and −2.92±0.78 mas yr −1 in the eastward and northward directions. The parallax and proper motion confirms that VX Sgr belong to the Sgr OB1 association. Rescaling bolometric luminosities in the literature to our parallax distance, we find that the luminosity of VX Sgris (1.95±0.62)×105 L e , where the uncertainty is dominated by differing photometry measurements.

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The distance and size of the red hypergiant NML Cygni from VLBA and VLA astrometry

Cited by 32 publications

References 45 publications

Extended Dust Emission from Nearby Evolved Stars★

Extended Dust Emission from Nearby Evolved Stars★

Silicon isotopic abundance toward evolved stars and its application for presolar grains

The Parallax of the Red Hypergiant VX Sgr with Accurate Tropospheric Delay Calibration

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