Article
Astronomy & Astrophysics
Alexis L. Quintana, Nicholas J. Wright
Summary: This study reexamines the existence and membership of the Cygnus OB associations, identifying six new associations with two resembling the historical Cyg OB2 and OB3. The properties of the new associations and their expansion trends are consistent with typical values for OB associations. Large-scale kinematic expansion patterns across the Cygnus region are attributed to feedback from previous generations of stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Mate Szilagyi, Maria Kun, Peter abraham, Gabor Marton
Summary: Using Gaia DR3 data, this study investigates the structure and kinematics of the Cepheus OB2 association and characterizes its star formation history, with particular focus on the Cepheus Bubble. Thirteen stellar groups belonging to Cep OB2 are identified using a clustering algorithm, with four older groups located inside the bubble and younger groups found on the periphery. The tangential velocities suggest different formation mechanisms, with some groups born in an expanding system of star-forming clouds and others formed due to collision with the expanding bubble.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
M. Vlasblom, G. De Marchi
Summary: We studied the young stellar populations in the NGC 299 cluster in the Small Magellanic Cloud using observations obtained with the Hubble Space Telescope in three different bands. We identified pre-main-sequence (PMS) objects still undergoing active accretion and determined their physical stellar parameters. Our findings suggest the existence of two populations of PMS stars with different ages and support the idea that the metallicity and density of the forming environment can affect the star formation process. The spatial distribution of massive stars and PMS objects in the cluster suggests a possible dispersal of the latter due to two-body relaxation.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
F. Comeron, N. Schneider, A. A. Djupvik
Summary: The study focuses on the young stellar populations associated with two isolated globules, DR 18 and ECX 6-21, irradiated by O-type stars. It reveals embedded populations in both globules, with differences in evolution between the two main star-forming sites in ECX 6-21.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
R. Carini, K. Biazzo, G. De Marchi, N. Panagia, G. Beccari, E. Brocato
Summary: In this study, the accretion properties of low-mass pre-main sequence stars in the LH 91 association within the Large Magellanic Clouds are investigated using optical multiband photometry obtained with the Hubble Space Telescope. The age distribution suggests a period of active star formation ranging from a few million years up to approximately 60 million years, with a gap between 5 million years and 10 million years. The masses of the pre-main sequence candidates range from 0.2 solar masses to 1.0 solar mass, with an average of approximately 0.80 solar mass. The results also show variations in accretion luminosity and mass accretion rate with the age of the stars. Comparison with LH 95 reveals that LH 91 appears to be in a more evolved stage. Additionally, the pre-main sequence candidates are found to be uniformly distributed without any evidence of clumps around more massive stars.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
E. Flaccomio, J. F. Albacete-Colombo, J. J. Drake, M. G. Guarcello, V. Kashyap, N. J. Wright, K. Briggs, B. Ercolano, M. McCollough, S. Sciortino
Summary: We analyze the X-ray spectra of about 8000 sources detected in the Cygnus OB2 Chandra Legacy Survey to study the coronal plasma and X-ray luminosities of young low-mass stars in the region. We use different strategies for sources with more or less than 20 detected photons, fitting the spectra with absorbed isothermal models or using a conversion factor from detected photon flux to intrinsic flux. Our results show consistent ratios between optical and X-ray extinction with standard Galactic values, and the abundance patterns are similar to those found in the Orion Nebula Cluster.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2023)
Article
Astronomy & Astrophysics
Kieran A. Stuart, Scott G. Gregory
Summary: The complexity of the large-scale magnetic field of PMS stars increases as they age, resulting in a decrease in coronal X-ray emission. This is consistent with observations showing a decrease in X-ray luminosity with age.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Joseph J. Armstrong, Nicholas J. Wright, R. D. Jeffries, R. J. Jackson, Tristan Cantat-Gaudin
Summary: The kinematics of stars in OB associations, particularly in the Vela OB2 region, have been studied in this paper. Multiple separate kinematic groups are identified, with strong evidence for anisotropic expansion in the Vela OB2 association. The presence of NGC 2547, an interloper, suggests that Vela OB2 has formed with considerable spatial and kinematic substructure.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
M. E. Shultz, E. Alecian, V Petit, S. Bagnulo, T. Bohm, C. P. Folsom, G. A. Wade
Summary: W 601 is a previously unreported spectroscopic binary, composed of two B2 stars with a mass ratio of 1.8. The star is not a classical Herbig Be star, but is likely on the pre-main sequence.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Styliani Tsilia, Guido De Marchi, Nino Panagia
Summary: In this study, we investigate the properties of low-mass stars in the NGC376 cluster of the Small Magellanic Cloud using photometric observations from the Hubble Space Telescope. We identify 244 candidate pre-main-sequence stars showing H alpha excess emission and calculate their physical parameters including masses, ages, and mass accretion rates. Comparing with the NGC346 cluster, we find that the mass accretion rate is lower in NGC376, suggesting the influence of other environmental factors on this process.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Marusa Zerjal, Michael J. Ireland, Timothy D. Crundall, Mark R. Krumholz, Adam D. Rains
Summary: Using new kinematic decomposition method (chronostar) with six-dimensional kinematic data, we analyze the Scorpius-Centaurus OB2 association (Sco-Cen) and identify eight kinematically distinct components with independently fit kinematic age. One component includes PDS 70, a well-studied system currently forming planets, with a kinematic age of 15 +/- 3 Myr.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Yash Bhargava, Nandini Hazra, A. R. Rao, Ranjeev Misra, Dipankar Bhattacharya, Jayashree Roy, Md Shah Alam
Summary: This study analyses the aperiodic flaring features observed in Cyg X-1, measuring the truncation of the inner accretion disc and studying the movement of the inner edge. The research discusses possible mechanisms causing these phenomena.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
E. Lai, B. De Marco, A. A. Zdziarski, T. M. Belloni, S. Mondal, P. Uttley, V Grinberg, J. Wilms, A. Rozanska
Summary: The clumpy stellar wind from the companion star in high-mass X-ray binaries has a significant impact on the short-time-scale X-ray spectral-timing properties of Cygnus X-1. The study reveals enhanced variability power on long time scales and suppressed variability on short time scales. The coherence between different light curves is reduced, as well as the amplitude of the hard X-ray lags. The increase in low-frequency variability power is attributed to variations in wind column density, while the behavior at high frequencies is suggested to be due to scattering in an optically thicker medium.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
O. Vilhu, K. I. I. Koljonen, D. C. Hannikainen
Summary: In wind-fed X-ray binaries, the X-ray irradiation from the compact secondary star can suppress the radiatively driven wind of the primary star, leading to an increased accretion rate. This feedback process between the released accretion power and the X-ray luminosity of the compact star is investigated in the high-mass X-ray binary Cygnus X-3, suggesting that the erratic behavior of the observed X-ray light curve and spectral state transitions could be explained by this scenario.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
R. B. Orellana, M. S. De Biasi, L. G. Paiz
Summary: The study reveals the existence of different substructures in the Cygnus OB2 region, with analysis of high-quality data enabling identification of members, mean proper motions, and distances for each overdensity.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Gregor Rauw, Yael Naze, Fran Campos
ASTRONOMY & ASTROPHYSICS
(2019)
Article
Astronomy & Astrophysics
Yael Naze, Gregor Rauw, Myron Smith
ASTRONOMY & ASTROPHYSICS
(2019)
Article
Astronomy & Astrophysics
S. Rosu, G. Rauw, K. E. Conroy, E. Gosset, J. Manfroid, P. Royer
ASTRONOMY & ASTROPHYSICS
(2020)
Article
Astronomy & Astrophysics
Yael Naze, Christian Motch, Gregor Rauw, Shami Kumar, Jan Robrade, Raimundo Lopes de Oliveira, Myron A. Smith, Jose M. Torrejon
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
Yael Naze, Andrzej Pigulski, Gregor Rauw, Myron A. Smith
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
E. Mossoux, J. M. Pittard, G. Rauw, Y. Naze
ASTRONOMY & ASTROPHYSICS
(2020)
Article
Astronomy & Astrophysics
S. Rosu, A. Noels, M-A. Dupret, G. Rauw, M. Farnir, S. Ekstrom
ASTRONOMY & ASTROPHYSICS
(2020)
Article
Astronomy & Astrophysics
Yael Naze, Gregor Rauw, Andrzej Pigulski
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
Yael Naze, Gregor Rauw, Eric Gosset
Summary: This study analyzed high-cadence space photometry data of a sample of evolved massive stars taken by the Transiting Exoplanet Survey Satellite (TESS), including 26 Wolf-Rayet stars and eight luminous blue variables. Red noise was detected in all cases, and coherent variability was found in 20% of the WR sample, with most detections happening at moderately high frequency. This work doubles the number of WRs known to exhibit high-frequency signals.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
G. Rauw, Y. Naze, C. Motch, M. A. Smith, J. Guarro Flo, R. Lopes de Oliveira
Summary: The study of gamma Cas reveals no direct link between the outer regions of the Be disc and the hard X-ray emission, but suggests a correlation between the X-ray emission level and the inner part of the Be disc. Results disfavour an accretion or colliding wind scenario, but show a strong correlation between long-term X-ray flux variations and optical variations in the V-band photometry.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Gregor Rauw, Yael Naze, Asif ud-Doula, Coralie Neiner
Summary: We analyzed optical and X-ray spectroscopy of the Of?p star HD 108, finding recovery of optical emission lines from their minimum emission state. The variations of H alpha emission provide constraints on the rotation axis and magnetic axis. Balmer emission lines show stochastic variability, and TESS photometry reveals transient modulations and red noise variations. X-ray observations indicate increased flux and spectral hardening compared to previous observations. Magnetohydrodynamic simulations and synthetic X-ray spectra agree well with the observations. Radial velocities suggest the presence of an unseen companion.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
S. Rosu, E. A. Quintero, G. Rauw, P. Eenens
Summary: HD 165052 is a binary system that consists of two massive stars with a short period and eccentric orbit. The study of this system provides insight into the internal structure of stars through the analysis of apsidal motion. By using medium- and high-resolution spectroscopic observations, the fundamental properties of the binary system and the evolutionary state of its components are constrained. The analysis includes the reconstruction of artifact-free spectra of individual stars and the determination of stellar properties through spectral analysis.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Yael Naze, Nikolay Britavskiy, Gregor Rauw, Jonathan Labadie-Bartz, Sergio Simon-Diaz
Summary: The origin of rapid rotation in massive stars is still debated. This paper presents the discovery and analysis of multiplicity in three fast-rotating massive stars and suggests a new explanation that their companions are non-degenerate low-mass pre-main sequence stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Yael Naze, Gregor Rauw, Rachel Johnson, Eric Gosset, Jennifer L. Hoffman
Summary: Observations of WR21 and WR31 have revealed phase-locked variations related to colliding winds. The variations are maximum in the soft band and show absorption effects. In the hard band, the variations are limited. Eclipses are not observed in these systems due to lower orbital inclinations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Gregor Rauw, Yael Naze
Summary: The study of Oef stars reveals the diversity of their behavior, with most targets showing substantial red noise components in their photometric data, and Pup displaying a possible long-lived periodicity. While stars in the sample exhibit a dominant signal at low frequencies, it appears relatively short-lived, akin to rotational modulations by transient photospheric spots. Furthermore, no evidence of persistent non-radial p-mode pulsations is found, suggesting that only temporary excitation of g-mode pulsations could offer an alternative explanation for the dominant signals observed.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)