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ALMA high resolution observations of Betelgeuse: Persistent structure spanning the inner atmosphere
W. R. F. Dent, A. M. S. Richards, G. M. Harper +2
The extended atmosphere of red supergiants (RSGs) forms an important link in the process of mass loss and the subsequent enrichment of the interstellar medium. Large-scale convecti…
New Spatially Resolved Observations of Betelgeuse from the VLA and ALMA: Evidence for Atmospheric Perturbations from a Close Companion
L. D. Matthews, A. K. Dupree, A. M. S. Richards +1
We present new spatially resolved observations of the red supergiant Betelgeuse ( Orionis) at seven frequencies: 22 GHz (1.36cm); 44 GHz (6.8mm); 107 GHz (2.8mm); 136 G…
Mass Loss in Evolved Stars
Lynn D. Matthews
Intense mass loss through cool, low-velocity winds is a defining characteristic of low-to-intermediate mass stars during the asymptotic giant branch (AGB) evolutionary stage. Such…
First Detection of Radio Emission Associated with a Classical Cepheid
L. D. Matthews, N. R. Evans, M. P. Rupen
We report the detection of 15 GHz radio continuum emission associated with the classical Cepheid variable star delta Cephei based on observations with the Karl G. Jansky Very Large…
The Great Dimming of Betelgeuse: a Surface Mass Ejection (SME) and its Consequences
Andrea K. Dupree, Klaus G. Strassmeier, Thomas Calderwood +7
The bright supergiant, Betelgeuse (Alpha Orionis, HD 39801), underwent a historic optical dimming during 2020 January 27 February 13. Many imaging and spectroscopic observation…
Spatially Resolved Observations of Betelgeuse at 7mm and 1.3cm Just Prior to the Great Dimming
L. D. Matthews, A. K. Dupree
We present spatially resolved observations of Betelgeuse (Alpha Orionis) obtained with the Karl G. Jansky Very Large Array (VLA) at wavelengths of ~7mm (44~GHz) and ~1.3cm (22~GHz)…
X-rays in Cepheids: Identifying Low-Mass Companions of Intermediate-Mass Stars
Nancy Remage Evans, Scott Engle, Ignazio Pillitteri +12
X-ray observations have been made of a sample of 20 classical Cepheids, including two new observations (Polaris and {\it l} Car) reported here. The occurrence of X-ray flux around…
X-rays in Cepheids: XMM-Newton Observations of Aql
Nancy Remage Evans, Ignazio Pillitteri, Pierre Kervella +13
X-ray bursts have recently been discovered in the Cepheids Cep and Dor modulated by the pulsation cycle. We have obtained an observation of the Cepheid Aql with the XMM…
Spatially Resolved Ultraviolet Spectroscopy of the Great Dimming of Betelgeuse
Andrea K. Dupree, Klaus G. Strassmeier, Lynn D. Matthews +9
The bright supergiant, Betelgeuse (Alpha Orionis, HD 39801) experienced a visual dimming during 2019 December and the first quarter of 2020 reaching an historic minimum 2020 Februa…
X-ray Observations of the Peculiar Cepheid V473 Lyr Identify A Low-Mass Companion
Nancy Remage Evans, Ignazio Pillitteri, Laszlo Molnar +17
V473 Lyr is a classical Cepheid which is unique in having substantial amplitude variations with a period of approximately 3.3 years, thought to be similar to the Blazhko variations…
Exploring Regularized Maximum Likelihood Reconstruction for Stellar Imaging with the ngVLA
Kazunori Akiyama, Lynn D. Matthews
The proposed next-generation Very Large Array (ngVLA) will enable the imaging of astronomical sources in unprecedented detail by providing an order of magnitude improvement in sens…
Prevalence of SED turndown among classical Be stars: Are all Be stars close binaries?
Robert Klement, A. C. Carciofi, T. Rivinius +16
Rapid rotation is a fundamental characteristic of classical Be stars and a crucial property allowing for the formation of their circumstellar disks. Past evolution in a mass and an…
Astro2020: Molecular Masers as Probes of the Dynamic Atmospheres of Dying Stars
Lynn D. Matthews, Mark J Claussen, Graham M. Harper
More than half of the dust and heavy element enrichment in galaxies originates from the winds and outflows of evolved, low-to-intermediate mass stars on the asymptotic giant branch…
Astro2020: Unlocking the Secrets of Late-Stage Stellar Evolution and Mass Loss through Radio Wavelength Imaging
Lynn D. Matthews, Mark J Claussen, Graham M. Harper +2
During the late phases of evolution, low-to-intermediate mass stars like our Sun undergo periods of extensive mass loss, returning up to 80% of their initial mass to the interstell…
Precision Analysis of Evolved Stars
Stephen Ridgway, Rachel Akeson, Ellyn Baines +20
Evolved stars dominate galactic spectra, enrich the galactic medium, expand to change their planetary systems, eject winds of a complex nature, produce spectacular nebulae and illu…
Meter- to Millimeter Emission from Cool Stellar Systems: Latest Results, Synergies Across the Spectrum, and Outlook for the Next Decade
Jan Forbrich, Peter K. G. Williams, Emily Drabek-Maunder +12
Radio observations of cool stellar systems provide unique information on their magnetic fields, high-energy processes, and chemistry. Buoyed by powerful new instruments (e.g. ALMA,…
Science with an ngVLA: Evolved Stars
Lynn D. Matthews, Mark J Claussen
This chapter reviews some of the expected contributions of the ngVLA to the understanding of the late evolutionary stages of low-to-intermediate mass stars, including asymptotic gi…
Radio Stars: from kHz to THz
Lynn D. Matthews
Advances in technology and instrumentation have now opened up virtually the entire radio spectrum to the study of stars. An international workshop "Radio Stars: from kHz to THz" wa…
HI emission from the red giant Y CVn with the VLA and FAST
D. T. Hoai, P. T. Nhung, L. D. Matthews +2
Imaging studies with the VLA have revealed HI emission associated with the extended circumstellar shells of red giants. We analyse the spectral map obtained on Y CVn, a J-type carb…
Modeling the HI 21-cm line profile from circumstellar shells around red giants
Do Thi Hoai, Pham Thi Nhung, Eric Gérard +3
We present HI line profiles for various models of circumstellar shells around red giants. In the calculations we take into account the effect of the background at 21 cm, and show t…
Radio Stars and Their Lives in the Galaxy
Lynn D. Matthews
This paper summarizes the three-day international workshop "Radio Stars and Their Lives in the Galaxy", held at the Massachusetts Institute of Technology Haystack Observatory on 20…
First Spectroscopic Imaging Observations of the Sun at Low Radio Frequencies with the Murchison Widefield Array Prototype
Divya Oberoi, Lynn D. Matthews, Iver H. Cairns +67
We present the first spectroscopic images of solar radio transients from the prototype for the Murchison Widefield Array (MWA), observed on 2010 March 27. Our observations span the…
A Multi-Epoch Study of the Radio Continuum Emission of Orion Source I: Constraints on the Disk Evolution of a Massive YSO and the Dynamical History of Orion BN/KL
C. Goddi, E. M. L. Humphreys, L. J. Greenhill +2
We present new 7mm continuum observations of Orion BN/KL with the VLA. We resolve the emission from the protostar radio Source I and BN at several epochs. Source I is highly elonga…
HI and CO in the circumstellar environment of the S-type star RS Cnc
Yannick Libert, Jan Martin Winters, Thibaut Le Bertre +2
This paper presents interferometric and single-dish CO observations along with HI data obtained for the oxygen-rich semi-regular variable RS Cnc, in order to probe its circumstella…