TY  - JOUR
A1  - Toalá, Jesús Alberto
A1  - Bowman, Dominic
A1  - Van Reeth, Timothy
A1  - Todt, Helge Tobias
A1  - Dsilva, Karan
A1  - Shenar, Tomer
A1  - Koenigsberger, Gloria Suzanne
A1  - Estrada-Dorado, Sandino
A1  - Oskinova, Lidia M.
A1  - Hamann, Wolf-Rainer
T1  - Multiple variability time-scales of the early nitrogen-rich Wolf-Rayet star WR 7
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present the analysis of the optical variability of the early, nitrogen-rich Wolf-Rayet (WR) star WR 7. The analysis of multisector Transiting Exoplanet Survey Satellite (TESS) light curves and high-resolution spectroscopic observations confirm multiperiodic variability that is modulated on time-scales of years. We detect a dominant period of 2.6433 +/- 0.0005 d in the TESS sectors 33 and 34 light curves in addition to the previously reported high-frequency features from sector 7. We discuss the plausible mechanisms that may be responsible for such variability in WR 7, including pulsations, binarity, co-rotating interaction regions (CIRs), and clumpy winds. Given the lack of strong evidence for the presence of a stellar or compact companion, we suggest that WR 7 may pulsate in quasi-coherent modes in addition to wind variability likely caused by CIRs on top of stochastic low-frequency variability. WR 7 is certainly a worthy target for future monitoring in both spectroscopy and photometry to sample both the short (less than or similar to 1 d) and long (greater than or similar to 1000 d) variability time-scales.
KW  - stars: atmospheres
KW  - stars: evolution
KW  - stars: individual: WR 7
KW  - stars: winds
KW  - outflows
KW  - stars: Wolft-Rayet
Y1  - 2022
U6  - https://doi.org/10.1093/mnras/stac1455
SN  - 0035-8711
SN  - 1365-2966
VL  - 514
IS  - 2
SP  - 2269
EP  - 2277
PB  - Oxford University Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Geist, Emily
A1  - Gallagher, John S.
A1  - Kotulla, Ralf
A1  - Oskinova, Lidia M.
A1  - Hamann, Wolf-Rainer
A1  - Ramachandran, Varsha
A1  - Sabbi, Elena
A1  - Smith, Linda J.
A1  - Kniazev, Alexey
A1  - Nota, Antonella
A1  - Rickard, Matthew J.
T1  - Ionization and star formation in the giant H ii region SMC-N66
JF  - Publications of the Astronomical Society of the Pacific
N2  - The NGC 346 young stellar system and associated N66 giant H ii region in the Small Magellanic Cloud are the nearest example of a massive star-forming event in a low metallicity (Z approximate to 0.2Z (circle dot)) galaxy. With an age of less than or similar to 3 Myr this system provides a unique opportunity to study relationships between massive stars and their associated H ii region. Using archival data, we derive a total H alpha luminosity of L(H alpha) = 4.1 x 10(38) erg s(-1) corresponding to an H-photoionization rate of 3 x 10(50) s(-1). A comparison with a predicted stellar ionization rate derived from the more than 50 known O-stars in NGC 346, including massive stars recently classified from Hubble Space Telescope far-ultraviolet (FUV) spectra, indicates an approximate ionization balance. Spectra obtained with SALT suggest the ionization structure of N66 could be consistent with some leakage of ionizing photons. Due to the low metallicity, the FUV luminosity from NGC 346 is not confined to the interstellar cloud associated with N66. Ionization extends through much of the spatial extent of the N66 cloud complex, and most of the cloud mass is not ionized. The stellar mass estimated from nebular L(H alpha) appears to be lower than masses derived from the census of resolved stars which may indicate a disconnect between the formation of high and low mass stars in this region. We briefly discuss implications of the properties of N66 for studies of star formation and stellar feedback in low metallicity environments.
Y1  - 2022
U6  - https://doi.org/10.1088/1538-3873/ac697b
SN  - 0004-6280
SN  - 1538-3873
VL  - 134
IS  - 1036
PB  - IOP Publishing
CY  - Bristol
ER  -