On the basis of far-infrared images obtained by the Herschel Space Observatory, we report the discovery of a large and massive dust shell around the yellow hypergiant Hen3-1379 . The nebula appears as a detached ring of 1 pc diameter which contains 0.17 Msun of dust. We estimate the total gas mass to be 7 Msun, ejected some 16000 years ago. The ring nebula is very similar to nebulae found around luminous blue variables (LBVs) except it is not photoionized. We argued that Hen3-1379 is in a pre-LBV stage, providing direct evidence that massive LBV ring nebulae can be ejected during the red supergiant phase.
We summarize the results of long-term spectral monitoring of yellow hypergiants (YHGs) of northern hemisphere with a R$\ge$60000 resolution. The spectra of these F-G stars of extremely high luminosity, compactly located at the top of the Hertzsprung-Russell diagram revealed a variety of spectral features: various types of H$α$ profile, the presence (or absence) of forbidden and permitted emissions, as well as circumstellar components. Variability of spectral details of various nature is studied. Absolute luminosity, circumstellar envelope expansion rate and amplitude of pulsations are determin…
Yellow hypergiants are evolved massive stars that were suggested to be in post-red supergiant stage. Post-red supergiants that evolve back to the blue, hot side of the Hertzsprung-Russell diagram can intersect a temperature domain in which their atmospheres become unstable against pulsations (the Yellow Void or Yellow Wall), and the stars can experience outbursts with short, but violent mass eruptions. The yellow hypergiant Rho Cas is famous for its historical and recent outbursts, during which the star develops a cool, optically thick wind with a very brief but high mass-loss rate, causing a …
Based on the data of spectral monitoring of the yellow hypergiant V509 Cas performed in 1996-2018 at the 6-m telescope with the spectral resolution of R$\ge$60 000, we studied in detail its kinematic state at various levels of extended atmosphere. No signs of presence of a companion were found. An agreement of radial velocities measured on the permitted and forbidden emissions of metal ions, as well as their strict temporal stability led us to the choice of the systemic velocity of the star Vsys=$-63$ km/s. The position of forbidden [NII] emissions forming in the circumstellar medium is strict…
How massive stars end their lives remains an open question in the field of star evolution. While the majority of stars above 9 M_sun will become red supergiants (RSGs), the terminal state of these massive stars can be heavily influenced by their mass-loss histories. Periods of enhanced circumstellar wind activity can drive stars off the RSG branch of the HR Diagram. This phase, known as post-RSG evolution, may well be tied to high mass-loss events or eruptions as seen in the Luminous Blue Variables and other massive stars. This article highlights some of the recent observational and modeling s…
Context. The fate of a massive star during the latest stages of its evolution is highly dependent on its mass-loss rate/geometry and therefore knowing the geometry of the circumstellar material close to the star and its surroundings is crucial. Aims. We aim to study the nature (i.e. geometry, rates) of mass-loss episodes. In this context, yellow hypergiants are great targets. Methods. We analyse a large set of optical/near-infrared data, in spectroscopic and photometric (X-shooter/VLT), spectropolarimetric (ISIS/WHT), and interferometric GRAVITY-AMBER/VLTI) modes, toward the yellow hypergiant …
The Hot, Continuum-compact State of the Yellow Hypergiant V509 Cassiopeiae: CHARA Diameters, CO-band Angular-extension Constraints, and Companion Limits
The CHARA Array of Georgia State University（佐治亚州立大学CHARA阵列）；University of Tartu（塔尔图大学）；University of Michigan（密歇根大学）；University of Exeter（埃克塞特大学）
We aim to explore the variable photometric and stellar properties of four yellow hypergiants (YHGs), HR8752, HR 5171A, $ρ$ Cas, and HD 179821, and their pulsations of hundreds of days, and long-term variations (LTVs) of years. We tackled multi-colour and visual photometric data sets, looked for photometric indications betraying eruptions or enhanced mass-loss episodes, calculated stellar properties mainly using a published temperature calibration, and investigated the nature of LTVs and their influence on quasi-periods and stellar properties. The $BV$ photometry revealed a high-opacity layer i…
The fate of a massive star during the latest stages of its evolution is highly dependent on its mass-loss history and geometry, with the yellow hypergiants being key objects to study those phases of evolution. We present near-IR interferometric observations of the famous yellow hypergiant IRC +10420 and blue spectra taken between 1994-2019. Our 2.2 $μ$m GRAVITY/VLTI observations attain a spatial resolution of $\sim$5 stellar radii and probe the hot emission in the K-band tracing the gas via Na i double emission and the Br$γ$ emission. The observed configurations spatially resolve the 2.2 $μ$m …
Probing the mass loss history of the yellow hypergiant IRC+10420
我们已经使用亚毫米阵列来成像IRC+10420周围的分子包膜。我们的观测揭示了恒星周围有一个巨大而密集的膨胀包层。分子包层显示出西南方向的$^{12}$ CO J=2--1发射明显不对称。在$^{13}$ CO J=2- 1和SO J $_{\rm K}$ =6 $_5$ -5 $_4$的发射中发现包封的伸长甚至更明显。在这些线中可以看到跨速度通道的小的位置速度梯度，这表明在IRC+10420的包络中存在弱的双极流出。在高分辨率的$^{12}$ CO J=2- 1映象中，我们发现包层有两个组成部分：（1）位于半径约1”-2”之间的内壳层（壳层I）;（2）位于半径3”-6”之间的外壳层（壳层II）。这些壳代表IRC+10420中之前的两次质量损失事件。我们试图以自洽的方式推导出信封内的物理条件，通过模拟尘埃的性质，和加热和冷却的分子气体。我们估计的质量损失率$\sim$ 9 10 $^{-4}$ M $_\odot$ yr $^{-1}$为壳I和7 10 $^{-4}$ M $_\odot$ yr $^{-1}$为壳II。与其他富氧包层相比，IRC+10420中的气体温度异常高。气体温度的升高主要是由于中心恒星的大光度导致的较高的加热速率。我们还推导出同位素比$^{12}$ C/ $^{13}$ C = 6。
This contribution focuses on a rare example of the class of post-Red Supergiants, IRAS 17163-3907, the central star of the Fried Egg nebula. In particular, we discuss some of our recently published results in detail. The inner parts of the circumstellar environment of this evolved massive star are probed at milli-arcsec resolution using VLTI's GRAVITY instrument operating in the K-band (2 $μ$m), while larger, arcsecond, scales are probed by VISIR diffraction limited images around 10 $μ$m, supplemented by a complete Spectral Energy Distribution. The spectro-interferometric data cover important …
The dramatic transition of the extreme Red Supergiant WOH G64 to a Yellow Hypergiant
National Observatory of Athens（雅典国家天文台）；Department of Physics, National and Kapodistrian University of Athens（雅典国立卡波迪斯特里安大学物理系）；Institute of Astrophysics, FORTH（希腊研究所天体物理研究所）
We report new 5.5 GHz radio observations of the massive star cluster Westerlund 1, taken by the Australia Telescope Compact Array, detecting nine of the ten yellow hypergiants (YHGs) and red supergiants (RSGs) within the cluster. Eight of nine sources are spatially resolved. The nebulae associated with the YHGs Wd1-4a, -12a and -265 demonstrate a cometary morphology - the first time this phenomenon has been observed for such stars. This structure is also echoed in the ejecta of the RSGs Wd1-20 and -26; in each case the cometary tails are directed away from the cluster core. The nebular emissio…
We present the results of multicolor (UBVJHKLM) photometry (2009-2017) and low-resolution spectroscopy (2016-2017) of the semi-regular variable V1427 Aql=HD 179821, a yellow supergiant with gas-dust envelope. The star displays low-amplitude (ΔV<0.2 mag) semi-periodic brightness variation superimposed on a long-term trend. The light curve shape and timescale change from cycle to cycle. There are temperature variations characteristic for pulsations, and brightness oscillations with no significant change of color are also observed. The UBV data for the 2009-2011 interval are well reproduced by a …
Spatial and spectral constraints on resolved mass-loss of the massive Post-RSG star IRAS 17163-3907 and its Fried Egg Nebula
Joint ALMA Observatory（ALMA联合天文台）；ESO（欧洲南方天文台）；Gemini Observatory/NSF’s NOIRLab（吉米尼天文台/美国国家光学红外天文实验室）；IAASARS, National Observatory of Athens（雅典国家天文台天体物理学、天文学与空间应用研究所）；Department of Astrophysical Sciences, Princeton University（普林斯顿大学天体物理科学系）；Royal Observatory of Belgium（比利时皇家天文台）；School of Physics & Astronomy, University of Leeds（利兹大学物理与天文学院）；Department of Space, Earth, and Environment, Chalmers University of Technology, Onsala Space Observatory（查尔姆斯理工大学地球空间环境学院翁萨拉太空天文台）；Armagh Observatory and Planetarium（阿马赫天文台和天文馆）；Xinjiang Astronomical Observatory, Chinese Academy of Sciences（中国科学院新疆天文台）；Jodrell Bank Centre for Astrophysics（乔德雷尔银行天体物理学中心）
