Related papers: The Mass-Loss History of the Red Hypergiant VY CMa
Approximately 30% of luminous red giants exhibit a Long Secondary Period (LSP) of variation in their light curves, in addition to a shorter primary period of oscillation. The cause of the LSP has so far defied explanation: leading…
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 that in some circumstances it may have an important effect on…
The yellow hypergiant Rho Cassiopeiae (F-G Ia0) has recently become very active with a tremendous outburst event in the fall of 2000. During the event the pulsating supergiant dimmed by more than a visual magnitude, while its effective…
High-mass protostars are deeply embedded in dust inside their natal cores and are not easily detectable. However, maser emission at centimeter wavelengths, owing to its high brightness, enables us to study gas kinematics in protostars'…
Little Red Dots (LRDs) have emerged as one of the central puzzles of the JWST era. Their spectra increasingly require dense gas close to the source, yet the physical origin of that cocoon-like structure remains unclear. We examine whether…
We analyze the differences in infrared circumstellar dust emission between oxygen rich Mira and non-Mira stars, and find that they are statistically significant. In particular, we find that these stars segregate in the K-[12] vs. [12]-[25]…
We present spectroscopy of the ejecta of SN 1987A in 2017 and 2018 from the Hubble Space Telescope and the Very Large Telescope, covering the wavelength range between $1150$ and $10000$ {\AA}. At 31 years, this is the first epoch with…
We study the brightness variations of galactic red supergiant stars using long-term visual light curves collected by the American Association of Variable Star Observers (AAVSO) over the last century. The full sample contains 48 red…
Recent high-cadence transient surveys and rapid follow-up observations indicate that some massive stars may dynamically lose their own mass within decades before supernovae (SNe). Such a mass-loss forms `confined' circumstellar medium…
Massive clusters in our Galaxy are an ideal testbed to investigate the properties and evolution of high mass stars. They provide statistically significant samples of massive stars of uniform ages. To accurately determine the intrinsic…
We present late-time near-infrared (NIR) and optical observations of the type IIn SN 1998S. The NIR photometry spans 333-1242 days after explosion, while the NIR and optical spectra cover 333-1191 days and 305-1093 days respectively. The…
We present a R=10,000 M-band spectrum of LLN19 (IRAS 08470-4321), a heavily embedded intermediate-mass young stellar object located in the Vela Molecular Cloud, obtained with VLT-ISAAC. The data were fitted by a 2-slab cold-hot model and a…
[Abridged] Ensemble studies of red-giant stars with exquisite asteroseismic, spectroscopic, and astrometric constraints offer a novel opportunity to recast and address long-standing questions concerning the evolution of stars and of the…
The recent detection of optical emission lines from the circumgalactic medium (CGM) in combined, large samples of low-redshift, normal galaxy spectra hints at the potential to map the cool ($\sim$ 10$^4$ K) CGM in individual, representative…
Asteroseismology has started to provide constraints on stellar properties that will be essential to accurately reconstruct the history of the Milky Way. Here we look at the information content in data sets representing current and future…
We present the first results from a program of near-infrared spectroscopy aimed at studying the familiar rest-frame optical emission lines from the H II regions of Lyman break galaxies at z = 3. By targeting redshifts which bring the lines…
Based on the Ogorodnikov-Milne model, we analyze the proper motions of 95 633 red giant clump (RGC) stars from the Tycho-2 Catalogue. The following Oort constants have been found: A = 15.9+-0.2 km/s/kpc and B = -12.0+-0.2 km/s/kpc. Using…
A comprehensive picture of high-mass star formation has remained elusive, in part because examples of high-mass YSOs tend to be relatively distant, deeply embedded, and confused with other emission sources. These factors have impeded…
The windows of low extinction in the Milky Way (MW) plane are rare but important because they enable us to place structural constraints on the opposite side of the Galaxy, which has hitherto been done rarely. We use the near-infrared…
Betelgeuse, one of the most studied red supergiant stars, dimmed in the optical by ~1.2 mag between late 2019 and early 2020, reaching an historical minimum called "the Great Dimming." Thanks to enormous observational effort to date, two…