Resolving Vega and the Inclination Controversy With Chara/Mirc

Monnier, John D.; Chen, Xiao; Zhao, M.; Ekström, Sylvia; Maestro, Vicente; Aufdenberg, J. P.; Baron, Fabien; Georgy, Cyril; Kraus, Stefan; McAlister, Harold A.; Pedretti, E.; Ridgway, Stephen T.; Sturmann, J.; Sturmann, L.; Brummelaar, T. ten; Thureau, N.; Turner, N.; Tuthill, P. G.

doi:10.1088/2041-8205/761/1/l3

Cited by 114 publications

(122 citation statements)

References 41 publications

Supporting

Mentioning

116

Contrasting

Order By: Relevance

“…13 we extend this comparison by adding α Lyr (Vega; Monnier et al 2012) and Achernar (α Eri; present work). These two new stars provide a crucial test for the ELR model since they have, respectively, the lowest and highest flattening in the sample.…”

Section: Gravity Darkeningmentioning

confidence: 83%

The environment of the fast rotating star Achernar

Souza¹,

Kervella²,

Faes³

et al. 2014

A&A

View full text Add to dashboard Cite

Context. Rotation significantly impacts on the structure and life of stars. In phases of high rotation velocity (close to critical), the photospheric structure can be highly modified, and present in particular geometrical deformation (rotation flattening) and latitudinaldependent flux (gravity darkening). The fastest known rotators among the nondegenerate stars close to the main sequence, Be stars, are key targets for studying the effects of fast rotation on stellar photospheres. Aims. We seek to determine the purely photospheric parameters of Achernar based on observations recorded during an emission-free phase (normal B phase). Methods. Several recent works proved that optical/IR long-baseline interferometry is the only technique able to sufficiently spatially resolve and measure photospheric parameters of fast rotating stars. We thus analyzed ESO-VLTI (PIONIER and AMBER) interferometric observations of Achernar to measure its photospheric parameters by fitting our physical model CHARRON using a Markov chain Monte Carlo method. This analysis was also complemented by spectroscopic, polarimetric, and photometric observations to investigate the status of the circumstellar environment of Achernar during the VLTI observations and to cross-check our model-fitting results. Results. Based on VLTI observations that partially resolve Achernar, we simultaneously measured five photospheric parameters of a Be star for the first time: equatorial radius (equatorial angular diameter), equatorial rotation velocity, polar inclination, position angle of the rotation axis projected on the sky, and the gravity darkening β coefficient (effective temperature distribution). The close circumstellar environment of Achernar was also investigated based on contemporaneous polarimetry, spectroscopy, and interferometry, including image reconstruction. This analysis did not reveal any important circumstellar contribution, so that Achernar was essentially in a normal B phase at least from mid-2009 to end-2012, and the model parameters derived in this work provide a fair description of its photosphere. Finally, because Achernar is the flattest interferometrically resolved fast rotator to-date, the measured β and flattening, combined with values from previous works, provide a crucial test for a recently proposed gravity darkening model. This model offers a promising explanation to the fact that the measured β parameter decreases with flattening and shows significantly lower values than the classical prediction of von Zeipel.

show abstract

Section: Gravity Darkeningmentioning

confidence: 83%

The environment of the fast rotating star Achernar

Souza¹,

Kervella²,

Faes³

et al. 2014

A&A

View full text Add to dashboard Cite

show abstract

“…Mass Age (2003) 7.95±0.09 Nordgren et al (2001) 7.97±0.11 Nordgren et al (2001) 8.035±0.08 Mozurkewich et al (1991) 9.26±0.15 Shao et al (1988) 7.90±0.31 di Benedetto & Rabbia (1987) (2016) 3.722±0.071 Mozurkewich et al (2003) 3.34±0.07 Nordgren et al (2001) 3.68±0.05 Nordgren et al (2001) 148856 3.472±0.008 3.462±0.035 Mozurkewich et al (2003) 3.53±0.08 Nordgren et al (2001) 3.51±0.05 Nordgren et al (2001) 150997 2.493±0.018 2.624±0.034 Mozurkewich et al (2003) 2.50±0.08 Nordgren et al (2001) 2.64±0.04 Nordgren et al (2001) 2.42±0.07 Nordgren et al (1999) 156283 5.519±0.011 5.275±0.067 Mozurkewich et al (2003) 5.26±0.06 Nordgren et al (2001) 5.27±0.07 Nordgren et al (2001) 5.20±0.03 Nordgren et al (1999) (2016) 2.12±0.02 Ligi et al (2012) 2.041±0.043 Baines et al (2010) 172167 3.280±0.016 2.930±0.007 Monnier et al (2012) 3.08±0.03 * Mourard et al (2009) 3.202±0.005 * Absil et al (2006) 3.329±0.006 Aufdenberg et al (2006) 3.225±0.032 Mozurkewich et al (2003) 3.28±0.01 Ciardi et al (2001) Mozurkewich et al (2003) 3.11±0.04 Nordgren et al (2001) 3.20±0.05 Nordgren et al (2001) 3.08±0.03 Nordgren et al (1999) Note- * No LD diameter was provided, therefore we list the UD diameter here. Figure 4 shows a graphical representation of this table.…”

Section: Targetmentioning

confidence: 98%

Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer

et al. 2017

View full text Add to dashboard Cite

We present the fundamental properties of 87 stars based on angular diameter measurements from the Navy Precision Optical Interferometer, 36 of which have not been measured previously using interferometry. Our sample consists of 5 dwarfs, 3 subgiants, 69 giants, 3 bright giants, and 7 supergiants, and span a wide range of spectral classes from B to M. We combined our angular diameters with photometric and distance information from the literature to determine each star's physical radius, effective temperature, bolometric flux, luminosity, mass, and age.

show abstract

“…Hou et al (2012) were the first group to implement this algorithm in astrophysics. The implementation presented here is an independent effort that has already proved effective in several projects (Sanders & Fabian 2013;Reis et al 2013;Weisz et al 2013;Cieza et al 2013;Akeret et al 2012;Huppenkothen et al 2012;Monnier et al 2012;Morton 2012;Crossfield et al 2012;Roškar et al 2012;Bovy et al 2012aBovy et al , 2012bBovy et al , 2012cBrown et al 2012;Brammer et al 2012;Bussmann et al 2012;Lang & Hogg 2012;Olofsson et al 2012;Dorman et al 2012). In what follows, we summarize the algorithm from GW10 and the implementation decisions made in emcee.…”

Section: Introductionmentioning

confidence: 99%

`emcee`: The MCMC Hammer

Foreman-Mackey¹,

Hogg²,

Lang³

et al. 2013

Publications of the Astronomical Society of the Pacific

10,383

5,624

View full text Add to dashboard Cite

ABSTRACT. We introduce a stable, well tested Python implementation of the affine-invariant ensemble sampler for Markov chain Monte Carlo (MCMC) proposed by Goodman & Weare (2010). The code is open source and has already been used in several published projects in the astrophysics literature. The algorithm behind emcee has several advantages over traditional MCMC sampling methods and it has excellent performance as measured by the autocorrelation time (or function calls per independent sample). One major advantage of the algorithm is that it requires hand-tuning of only 1 or 2 parameters compared to ∼N 2 for a traditional algorithm in an N-dimensional parameter space. In this document, we describe the algorithm and the details of our implementation. Exploiting the parallelism of the ensemble method, emcee permits any user to take advantage of multiple CPU cores without extra effort. The code is available online at http://dan.iel.fm/emcee under the GNU General Public License v2.Note: If you want to get started immediately with the emcee package, start at Appendix A or visit the online documentation at http://dan.iel.fm/emcee. If you are sampling with emcee and having low-acceptance-rate or other issues, there is some advice in § 4.

show abstract

Resolving Vega and the Inclination Controversy With Chara/Mirc

Cited by 114 publications

References 41 publications

The environment of the fast rotating star Achernar

The environment of the fast rotating star Achernar

Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer

`emcee`: The MCMC Hammer

Contact Info

Product

Resources

About

Resolving Vega and the Inclination Controversy With Chara/Mirc

Cited by 114 publications

References 41 publications

The environment of the fast rotating star Achernar

The environment of the fast rotating star Achernar

Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer

emcee: The MCMC Hammer

Contact Info

Product

Resources

About

`emcee`: The MCMC Hammer