Article
Astronomy & Astrophysics
Richa Kundu, Camila Navarrete, Jose G. Fernandez-Trincado, Dante Minniti, Harinder P. Singh, Luca Sbordone, Andres E. Piatti, Celine Reyle
Summary: This study aims to search for extratidal stars in Galactic globular clusters NGC 6397, NGC 2808, and NGC 6266 using photometry and proper motion measurements from the Gaia DR2 database. The study found extratidal candidate stars outside the tidal radii of all three clusters, with different spatial distributions and potential causes for the presence of these stars.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
G. Valle, M. Dell'Omodarme, E. Tognelli
Summary: This study explores the analysis methods for multiple stellar populations in globular clusters, using NGC 2808 as a case study. By employing established statistical clustering methods and addressing the issue of measurement errors, the results obtained differ from those reported in previous literature. The findings suggest that the existence of multiple populations is reliable in high-resolution spectroscopy data, but questionable in low-resolution spectroscopy data. Additionally, it is revealed that the commonly used histogram analysis is prone to generating false-positive findings. Therefore, the use of statistically grounded methods is crucial for conducting more robust and reproducible research.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Alessandro Paduano, Arash Bahramian, James C. A. Miller-Jones, Adela Kawka, Jay Strader, Laura Chomiuk, Craig O. Heinke, Thomas J. Maccarone, Christopher T. Britt, Richard M. Plotkin, Aarran W. Shaw, Laura Shishkovsky, Evangelia Tremou, Vlad Tudor, Gregory R. Sivakoff
Summary: Transitional millisecond pulsars are pulsars that switch between rotation-powered millisecond pulsar state and accretion-powered X-ray binary state, considered as an evolutionary stage between neutron star low-mass X-ray binaries and millisecond pulsars. NGC 6652B, a low-mass X-ray binary in the globular cluster NGC 6652, is observed to display prolonged X-ray flaring behavior and variable optical spectra.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
M. Carlos, A. F. Marino, A. P. Milone, E. Dondoglio, S. Jang, M. V. Legnardi, A. Mohandasan, G. Cordoni, E. P. Lagioia, A. M. Amarsi, H. Jerjen
Summary: Pseudo two-colour diagrams or Chromosome maps (ChM) show the presence of five different stellar populations in NGC 2808. To overcome the limitations of existing ChMs, which are derived from Hubble Space Telescope photometry and cover a small field of view, we built a ChM using U, B, I photometry from ground-based facilities over a wider field of view. By analyzing the spectra of 70 red giant branch and seven asymptotic giant branch stars, we were able to determine the abundances of various elements in these stars and provide the most complete characterization of the stellar populations in NGC 2808 to date. Our findings support the existence of multiple stellar populations in globular clusters and challenge current stellar evolution models.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Wasundara Ranhari Athukoralalage, Kristen C. Dage, Stephen E. Zepf, Arash Bahramian, Edward M. Cackett, Arunav Kundu, Thomas J. Maccarone
Summary: NGC 4472 is home to five ultraluminous X-ray sources hosted by globular clusters, which are considered good black hole candidates. This study focuses on the X-ray and optical follow-up of one of these sources, CXOUJ1229410+075744 (GCU1). The results show no evidence of significant evidence for super-Eddington outflows and no detected X-ray emission above a certain level, but suggest similarities in behavior to other known black hole binaries.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Kyle Kremer, Brenna Mockler, Anthony L. Piro, James C. Lombardi
Summary: Tidal disruptions of stars by stellar-mass black holes are expected to occur frequently in dense star clusters. In this study, we explore the formation and long-term evolution of thick, super-Eddington accretion disks formed during these encounters. We find that bright transients can be produced when radiation from the central engine is reprocessed by the optically-thick disk wind. By combining hydrodynamic simulations with our disk + wind model, we predict that all-sky surveys will detect thousands of these events per year in dense star clusters.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Martijn J. C. Wilhelm, Simon Portegies Zwart
Summary: Recent studies have revealed that 'Peter Pan discs' phenomenon can only occur around M dwarf stars, not around stars of higher mass. The lifetime of primordial discs depends on the host star's mass, with stars less than 0.6 solar masses being able to retain the discs for about 50 Myr.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Alessandro Paduano, Arash Bahramian, James C. A. Miller-Jones, Adela Kawka, Fabian Goettgens, Jay Strader, Laura Chomiuk, Sebastian Kamann, Stefan Dreizler, Craig O. Heinke, Tim-Oliver Husser, Thomas J. Maccarone, Evangelia Tremou, Yue Zhao
Summary: The Galactic globular cluster NGC 3201 has been observed to host stellar-mass black holes, and the radio and X-ray emissions from these black holes are found to be very weak, indicating a low accretion rate. Additionally, analysis of multiple wavelengths reveals new sources and provides insight into the sub-subgiant population.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
C. Lardo, M. Salaris, S. Cassisi, N. Bastian, A. Mucciarelli, I. Cabrera-Ziri, E. Dalessandro
Summary: Photometric investigations have discovered internal metallicity variations in Galactic globular clusters, contradicting previous beliefs of homogeneous initial chemical composition. However, spectroscopic evidence has not fully supported this finding. In this study, a high-resolution re-analysis of stars in the NGC 2808 cluster revealed a range of iron abundances, indicating intrinsic abundance spreads among first-population stars. The variations in Si, Ca, Ti, and Ni abundances are correlated with iron variations, and the total abundance spreads for all elements are consistent, suggesting the contribution of massive stars as supernovae to gas self-enrichment during star formation.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
T. Ghosh, V Rana
Summary: High-quality XMM-NEWTON observations of an ultraluminous X-ray source in galaxy NGC 4190 revealed that the spectral properties suggest the source is in a broadened disc state with unusual state evolution, possibly a slim disc state. Long-term spectral and flux variability were also observed, along with a clear anticorrelation between flux and power-law photon index. The results further support the presence of a stellar mass black hole in the ULX.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
M. McKenzie, D. Yong, A. F. Marino, S. Monty, E. Wang, A. Karakas, A. P. Milone, M. Legnardi, I. U. Roederer, S. Martell, D. Horta
Summary: High-quality VLT/UVES spectra of six red giant branch stars in M22 reveal variations in abundance of elements such as Fe, Na, and Si. The study suggests that M22 hosts two stellar populations with abundance differences, possibly indications of a nuclear star cluster, merged clusters, or an original building block of the Milky Way.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Eugenio Carretta
Summary: NGC 4833 is a metal-poor Galactic globular cluster with extreme chemical composition, including a broad Na-O anti-correlation and significant excesses of Ca and Sc. The study confirms that self-enrichment from first generation polluters occurred at high temperatures, producing species such as K and possibly Ca. The abundance of potassium in GCs appears to be related to other elements, indicating a complex chemical pattern in multiple stellar populations.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
N. Chang, F. G. Xie, X. Liu, L. C. Ho, A-J Dong, Z. H. Han, X. Wang
Summary: The study re-analyzed a sample of Seyfert galaxies and found similarities in the X-ray origin of radio-quiet and radio-loud Seyferts, with all sources exhibiting a similar correlation slope. When considering luminosities in radio and X-rays, radio morphology and Seyfert classification played a role in the correlations observed.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Gavin A. L. Coleman, Thomas J. Haworth
Summary: This study explores the evolution and dispersal of protoplanetary discs under the influence of internal and external photoevaporation and varying degrees of viscous transport. It identifies five distinct dispersal pathways and shows that the relative impact of internal and external winds, as well as the clearing pathway, vary with different stellar/disc/radiation properties. The study highlights the importance of considering both internal and external winds in understanding protoplanetary disc evolution.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Katarzyna Nowak, Martin G. H. Krause, Daniel Schaerer
Summary: A strong nuclear kilomaser, W1, associated with a forming super star cluster, has been discovered. This kilomaser could arise from the accretion disc around supermassive stars, which are proposed as polluters that caused chemical peculiarities in globular clusters. The study investigates the survival of an accretion disc in a dynamic environment and compares the simulated maser spectrum with the observed W1 kilomaser. The results suggest that kilomasers could pinpoint supermassive stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
S. A. Farrell, M. Servillat, K. Wiersema, D. Barret, O. Godet, I. Heywood, T. J. Maccarone, S. R. Oates, B. Plazolles, N. A. Webb
ASTRONOMISCHE NACHRICHTEN
(2011)
Article
Astronomy & Astrophysics
M. Servillat, A. Dieball, N. A. Webb, C. Knigge, R. Cornelisse, D. Barret, K. S. Long, M. M. Shara, D. R. Zurek
ASTRONOMY & ASTROPHYSICS
(2008)
Article
Astronomy & Astrophysics
Mathieu Servillat, Sean A. Farrell, Dacheng Lin, Olivier Godet, Didier Barret, Natalie A. Webb
ASTROPHYSICAL JOURNAL
(2011)
Article
Astronomy & Astrophysics
M. Servillat, N. A. Webb, F. Lewis, C. Knigge, M. van den Berg, A. Dieball, J. Grindlay
ASTROPHYSICAL JOURNAL
(2011)
Article
Astronomy & Astrophysics
M. Servillat, J. Grindlay, M. van den Berg, J. Hong, P. Zhao, B. Allen
ASTROPHYSICAL JOURNAL
(2012)
Article
Astronomy & Astrophysics
Sebastien Guillot, Mathieu Servillat, Natalie A. Webb, Robert E. Rutledge
ASTROPHYSICAL JOURNAL
(2013)
Article
Astronomy & Astrophysics
K. Wiersema, S. A. Farrell, N. A. Webb, M. Servillat, T. J. Maccarone, D. Barret, O. Godet
ASTROPHYSICAL JOURNAL LETTERS
(2010)
Article
Astronomy & Astrophysics
S. A. Farrell, M. Servillat, J. Pforr, T. J. Maccarone, C. Knigge, O. Godet, C. Maraston, N. A. Webb, D. Barret, A. J. Gosling, R. Belmont, K. Wiersema
ASTROPHYSICAL JOURNAL LETTERS
(2012)
Article
Astronomy & Astrophysics
M. Servillat, C. O. Heinke, W. C. G. Ho, J. E. Grindlay, J. Hong, M. van den Berg, S. Bogdanov
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2012)
Article
Astronomy & Astrophysics
M. Servillat, A. Coleiro, S. Chaty, F. Rahoui, J. A. Zurita Heras
ASTROPHYSICAL JOURNAL
(2014)
Article
Astronomy & Astrophysics
M. Servillat, N. A. Webb, D. Barret
ASTRONOMY & ASTROPHYSICS
(2008)
