Rotation and mass loss are crucially interlinked properties of massive stars, strongly affecting their evolution and ultimate fate. Massive stars rotating near their breakup limit shed mass centrifugally, creating Be stars with circumstellar disks and possibly driving outbursts. Using the MESA stellar evolution code, we examine the effects of efficient angular momentum transport on the main sequence and post-main sequence rotational evolution of massive stars. In rapid rotators, angular momentum transported from the contracting core to the expanding envelope can spin up the surface layers past the breakup rate, particularly for stars near (or beyond) the end of the main sequence and in low-metallicity environments. We also demonstrate that centrifugal instabilities could arise in rapidly rotating massive stars, potentially triggering the S Doradus outbursts observed in luminous blue variable stars. Prior mass accretion from a binary companion increases both the likelihood and the intensity of centrifugal mass loss. We discuss implications for massive stellar evolution, Be stars, and luminous blue variables.
The classical nova V2491 Cyg was once suggested to be a recurrent nova. We have broadly reproduced the light curve of V2491 Cyg by a nova outburst model on a cold $1.36~M_\odot$ white dwarf (WD), which strongly suggests that V2491 Cyg is a classical nova outbursting on a cold very massive WD rather than a recurrent nova outbursting on a warmer WD like the recurrent nova RS Oph. In a long-term evolution of a cataclysmic binary, an accreting WD has been settled down to a thermal equilibrium state with the balance of gravitational energy release and neutrino loss. The central temperature of the W…
We report the discovery of a massive protostar M17~MIR embedded in a hot molecular core in M17. The multiwavelength data obtained during 1993--2019 show significant mid-IR (MIR) variations, which can be split into three stages: the decreasing phase during 1993.03--mid-2004, the quiescent phase from mid-2004 to mid-2010, and the rebrightening phase from mid-2010 until now. The variation of the 22\,GHz H$_2$O maser emission, together with the MIR variation, indicates an enhanced disk accretion rate onto M17~MIR during the decreasing and rebrightening phases. Radiative transfer modeling of the sp…
Mode Instability and a Massive, Isolated Outburst in the Pulsating White Dwarf GD 1212
Boston University（波士顿大学）；Queens College, City University of New York（纽约市立大学皇后学院）；University of Texas at Austin（德克萨斯大学奥斯汀分校）；Iowa State University（爱荷华州立大学）；McDonald Observatory（麦克唐纳天文台）；University of Warwick（华威大学）
In recent years, dramatic outbursts have been identified toward massive protostars via infrared and millimeter dust continuum and molecular maser emission. The longest lived outburst ($>6$ yr) persists in NGC6334I-MM1, a deeply-embedded object with no near-IR counterpart. Using FORCAST and HAWC+ on SOFIA, we have obtained the first mid-infrared images of this field since the outburst began. Despite being undetected in pre-outburst ground-based 18 $μ$m images, MM1 is now the brightest region at all three wavelengths (25, 37, and 53 $μ$m), exceeding the ultracompact HII region MM3 (NGC6334F). Co…
The extraordinary outburst in the massive protostellar system NGC6334I-MM1: Flaring of the water masers in a north-south bipolar outflow driven by MM1B
Massive stars are rare but of paramount importance for their immediate environment and their host galaxies. They lose mass from their birth through strong stellar winds up to their spectacular end of their lives as supernovae. The mass loss changes as they evolve and in some phases it becomes episodic or displays outburst activity. One such phase is the Yellow Hypergiants, in which they experience outbursts due to their pulsations and atmosphere instabilities. This is depicted in photometry as a decrease in their apparent magnitude. The object $ρ$ Cassiopeia (Cas) is a bright and well known va…
A millimeter methanol maser ring tracing the deceleration of the heat wave powered by the massive protostellar accretion outburst in G358.93-0.03 MM1
National Radio Astronomy Observatory（美国国家射电天文台）；University of Virginia（弗吉尼亚大学）；Xinjiang Astronomical Observatory, Chinese Academy of Sciences（中国科学院新疆天文台）；Hartebeesthoek Radio Astronomy Observatory（哈特比斯霍克射电天文台）；University of St. Andrews（圣安德鲁斯大学）；RIKEN Pioneering Research Institute（理化学研究所先锋研究本部）；Ventspils University of Applied Sciences（文茨皮尔斯应用科学大学）；Massachusetts Institute of Technology（麻省理工学院）
Helium superluminous SN 2021bnw : an explosion of a massive star with a pre-outburst
Sapienza Università di Roma（罗马第一大学）；Université Paris-Saclay（巴黎萨克雷大学）；Université Paris Cité（巴黎西岱大学）；CEA（法国原子能及替代能源委员会）；CNRS（法国国家科学研究中心）；AIM（天体物理研究所与分子研究中心）；Institut d’Astrophysique de Paris（巴黎天文台）；INAF, Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Sternberg Astronomical Institute, Moscow State University（莫斯科国立大学斯登伯格天文研究所）；Astro Space Center（太空天文中心）
Following an eruptive accretion event in NGC6334I-MM1, flares in the various maser species, including water masers, were triggered. We report the observed relative proper motion of the highly variable water masers associated with the massive star-forming region, NGC6334I. High velocity H$_2$O maser proper motions were detected in 5 maser clusters, CM2-W2 (bow-shock structure), MM1-W1, MM1-W3, UCHII-W1 and UCHII-W3. The overall average of the derived relative proper motion is 85 km s$^{-1}$. This mean proper motion is in agreement with the previous results from VLA multi-epoch observations. Our…
In recent years, many Type IIn supernovae have been found to share striking similarities with the peculiar SN 2009ip, whose true nature is still under debate. Here, we present 10 years of observations of SN 2011fh, an interacting transient with spectroscopic and photometric similarities to SN 2009ip. SN 2011fh had a M$_r \sim -16$ mag brightening event, followed by a brighter M$_r \sim -18$ mag luminous outburst in August 2011. The spectra of SN 2011fh are dominated by narrow to intermediate Balmer emission lines throughout its evolution, with P Cygni profiles indicating fast-moving material a…
Giant outbursts of clumpy material preceding Type II supernova 2024qiw
University of Turku（图尔库大学）；Aalto University（阿尔托大学）；Aalto University Metsähovi Radio Observatory（阿尔托大学梅特霍维无线电天文台）；Aalto University Department of Electronics and Nanoengineering（阿尔托大学电子与纳米工程系）；University of Sheffield（谢菲尔德大学）；National Astronomical Observatory of Japan, National Institutes of Natural Sciences（日本国立天文台，国立自然科学研究院）；Finnish Centre for Astronomy with ESO (FINCA)（芬兰ESO天文学中心（FINCA））；Kyoto University（京都大学）；European University Cyprus（塞浦路斯欧洲大学）；University of Warwick（华威大学）
A probable inside-out dwarf nova outburst from the period bouncer candidate ASASSN-25dc
South African Astronomical Observatory（南非天文台）；University of Cape Town（开普敦大学）；Okayama Observatory, Kyoto University（京都大学冈山天文台）；Kyoto University（京都大学）；Kanazawa University（金泽大学）；The University of Tokyo（东京大学）；University of the Free State（自由州大学）
We address the shocks from acoustic pulses and wave trains in general one-dimensional flows, with an emphasis on the application to super-Eddington outbursts in massive stars. Using approximate adiabatic invariants, we generalize the classical equal-area technique in its integral and differential forms. We predict shock evolution for the case of an initially sinusoidal but finite wave train, with separate solutions for internal shocks and head or tail shocks, and demonstrate detailed agreement with numerical simulations. Our internal shock solution motivates improved expressions for the shock …
