Article
Astronomy & Astrophysics
Z. Prudil, M. Hanke, B. Lemasle, J. Crestani, V. F. Braga, M. Fabrizio, A. J. Koch-Hansen, G. Bono, E. K. Grebel, N. Matsunaga, M. Marengo, R. da Silva, M. Dall'Ora, C. E. Martinez-Vazquez, G. Altavilla, H. Lala, B. Chaboyer, I. Ferraro, G. Fiorentino, C. Gilligan, M. Nonino, F. Thevenin
Summary: This study examines the Orphan stellar stream using RR Lyrae variable stars, identifying 20 likely associated stars. Through chemical analysis and orbital kinematics, a potential link between the ultra-faint dwarf galaxy Grus II and the Orphan stream is suggested, although the definitive connection remains uncertain due to large uncertainties in dynamical properties.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Gustavo E. Medina, Camilla J. Hansen, Ricardo R. Munoz, Eva K. Grebel, A. Katherina Vivas, Jeffrey L. Carlin, Clara E. Martinez-Vazquez
Summary: We conducted spectroscopic analysis of 20 halo ab-type RR Lyrae stars using medium-resolution spectra, obtaining systemic velocities of targets with uncertainties of 5-10 km s(-1) and calculating orbital parameters for a subsample. Our findings suggest that at least half of the sample stars might have an accreted origin, based on their orbital orientations in an isolated Milky Way or a perturbed model by the Large Magellanic Cloud. We also derived atmospheric parameters and chemical abundance ratios for seven stars beyond 20 kpc, with some displaying underabundance of alpha-elements, indicating association with accretion events.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Christina K. Gilligan, Brian Chaboyer, Massimo Marengo, Joseph P. Mullen, Giuseppe Bono, Vittorio F. Braga, Juliana Crestani, Massimo Dall'Ora, Giuliana Fiorentino, Matteo Monelli, Jill R. Neeley, Michele Fabrizio, Clara E. Martinez-Vazquez, Frederic Thevenin, Christopher Sneden
Summary: Accurate metallicities of RR Lyrae stars were analyzed in this study using high-resolution spectra from the Southern African Large Telescope. The study presented new period-luminosity-metallicity relationships in WISE W1 and W2 magnitudes, as well as the Wesenheit magnitudes W(W1, V - W1) and W(W2, V- W2) by combining new spectroscopic abundances with literature determinations for 93 stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Giuliano Iorio, Vasily Belokurov
Summary: We present the results of a multicomponent kinematic model of a large sample of RR Lyrae detected by Gaia, detecting two distinct components near the center of the Galaxy. The characteristics of the components indicate the possible existence of debris clouds from ancient massive mergers. Metallicity/HASP maps suggest the likelihood of in situ birth of halo RR Lyrae in the inner part of the Galaxy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Gaochao Liu, Yang Huang, Sarah Ann Bird, Huawei Zhang, Fei Wang, Haijun Tian
Summary: Based on a large spectroscopic sample of RR Lyrae stars, this study provides a detailed analysis of the chemical and kinematic properties of the Galactic halo, revealing distinct features between the inner and outer halo components. The inner halo is dominated by a metal-rich population with extreme radial anisotropy, possibly originating from a ancient merged satellite. The outer halo shows a broad metallicity distribution with weak peaks and a uniform anisotropy value.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
T. D. Muhie, A. K. Dambis, L. N. Berdnikov, A. Y. Kniazev, E. K. Grebel
Summary: This study presents results from photometric and statistical-parallax analysis of 850 field RR Lyrae (RRL) variables, determining the velocity distribution and calibrating the luminosity-metallicity and period-luminosity-metallicity relations. The findings show excellent agreement with literature and provide accurate velocity parameters and calibrated relations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Ata Sarajedini
Summary: In this study, we analyze archival images of the Wolf-Lundmark-Melotte (WLM) galaxy taken with the Hubble Space Telescope, and identify and characterize RR Lyrae and Cepheid variables. We find that the WLM globular cluster has a lower metallicity than previously thought.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Z. Prudil, A. J. Koch-Hansen, B. Lemasle, E. K. Grebel, T. Marchetti, C. J. Hansen, J. Crestani, V. F. Braga, G. Bono, B. Chaboyer, M. Fabrizio, M. Dall'Ora, C. E. Martinez-Vazquez
Summary: This study presents a chemo-dynamical analysis of the Orphan stellar stream, focusing on the properties of RR Lyrae pulsating variable stars and their connection to other celestial bodies. The results indicate a correlation between the Orphan stream and the positions, kinematics, and metallicities of the RR Lyrae stars. Additionally, nonvariable stars associated with the Orphan stream were also identified.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Kohei Hattori, Monica Valluri, Eugene Vasiliev
Summary: Using astrometric data from Gaia DR2 for halo RR Lyrae stars, the 3D density profile of the Galactic dark matter (DM) halo within 30kpc from the Galactic centre was estimated. It was found that 99% of the posterior distribution of density flattening parameter q is located at q > 0.963, disfavoring a flattened DM halo and potentially contradicting cosmological simulations. Further studies are needed to explore the discrepancy between observations and simulations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Chengdong Li, James Binney
Summary: A seven-parameter distribution function is fitted to RR-Lyrae stars using only astrometric data. The DF predicts the observational data along with the gravitational potential of a self-consistent model Galaxy. Tests show that missing line-of-sight velocities have little effect on the constraints of the DF. The recovered model confirms that the RR-Lyrae population is flattened and has a strongly radially biased velocity distribution.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Jiwon Jesse Han, Charlie Conroy, Benjamin D. Johnson, Joshua S. Speagle, Ana Bonaca, Vedant Chandra, Rohan P. Naidu, Yuan-Sen Ting, Turner Woody, Dennis Zaritsky
Summary: Modern Galactic surveys have identified an ancient merger, known as Gaia-Sausage-Enceladus (GSE), that dominates the stellar halo of our galaxy. Through the use of chemical abundances and kinematics, researchers have inferred the density profile of the accreted component of the stellar halo and discovered a triaxial ellipsoid tilted 25 degrees above the Galactic plane. This finding provides new insights into the initial conditions and evolution of the GSE merger, as well as implications for the dynamical mass modeling of the galaxy and dark matter detection experiments.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
V. F. Braga, G. Fiorentino, G. Bono, P. B. Stetson, C. E. Martinez-Vazquez, S. Kwak, M. Tantalo, M. Dall'Ora, M. Di Criscienzo, M. Fabrizio, M. Marengo, S. Marinoni, P. M. Marrese, M. Monelli
Summary: We investigated the properties of mixed-mode RR Lyrae variables in the Fornax dwarf spheroidal galaxy and compared them with variables in the Magellanic Clouds and nearby dwarf spheroidals. We found that the ratio of mixed-mode RR Lyrae decreases with metallicity, and Fornax fills a period gap in the Petersen diagram similarly to Small Magellanic Cloud variables. Additionally, a new pulsation diagnostics method reveals that Large Magellanic Cloud variables can be separated into two groups with different evolutionary properties. Our findings suggest that Fornax and Sculptor dwarf spheroidals have undergone different chemical enrichment histories.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Ata Sarajedini, Sevinc Gokmen
Summary: This study compares two relations for calculating the metal abundance of ab-type RR Lyrae variables and determines that knowing only the period of these variables is sufficient to determine the mean metallicity of a globular cluster. Both tested equations accurately reproduce the spectroscopic metal abundance of each cluster, with an accuracy of ±0.28 dex.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Review
Astronomy & Astrophysics
Andrea M. Kunder
Summary: RR Lyrae stars, some of the oldest stars in the Universe, serve as excellent tracers of the oldest structures in the inner Galaxy. Recent studies have shown that the kinematics of RR Lyrae stars in the inner Galaxy are complex, and there is no discernible difference in metallicity between different subsamples. Properly accounting for old, metal-poor stars is essential when discussing the formation of the inner Galaxy and the Galactic bar/bulge.
Article
Astronomy & Astrophysics
Kuan-Wei Huang, Sergey E. Koposov
Summary: We present an RR Lyrae (RRL) catalogue based on the combination of ZTF DR3 and Gaia EDR3, which includes period and light-curve parameter measurements and has high completeness and purity. This catalogue covers the Northern sky with declination >= -28 degrees and is more complete around the Galactic halo compared to other catalogues.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Christina Willecke Lindberg, Daniela Huppenkothen, R. Lynne Jones, Bryce T. Bolin, Mario Juric, V. Zach Golkhou, Eric C. Bellm, Andrew J. Drake, Matthew J. Graham, Russ R. Laher, Ashish A. Mahabal, Frank J. Masci, Reed Riddle, Kyung Min Shin
Summary: In the era of wide-field surveys, sparse photometric measurements constitute an increasing percentage of asteroid observations. To overcome sampling limitations, a flexible model based on Gaussian processes for Bayesian parameter inference of asteroid time-series data is introduced. This model reliably infers rotation periods from sparsely sampled light curves and provides well-constrained posterior probability densities for the model parameters.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Eric J. Mendelsohn, Heidi Jo Newberg, Siddhartha Shelton, Lawrence M. Widrow, Jeffery M. Thompson, Carl J. Grillmair
Summary: In this study, the mass and radial profile of the Orphan-Chenab Stream's dwarf-galaxy progenitor were analyzed using observational data and N-body simulations. The internal structure and mass distribution of the progenitor were inferred, and specific values were obtained.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Thomas Kupfer, Evan B. Bauer, Jan van Roestel, Eric C. Bellm, Lars Bildsten, Jim Fuller, Thomas A. Prince, Ulrich Heber, Stephan Geier, Matthew J. Green, Shrinivas R. Kulkarni, Steven Bloemen, Russ R. Laher, Ben Rusholme, David Schneider
Summary: We present the discovery of a new double-detonation progenitor system composed of a hot subdwarf B binary and a white dwarf companion. By analyzing the spectroscopic observations and light curve fits, the physical parameters of the system were estimated and the future evolution was predicted. These findings are important for understanding the formation mechanisms of double-detonation progenitor systems and thermonuclear supernovae.
ASTROPHYSICAL JOURNAL LETTERS
(2022)
Article
Astronomy & Astrophysics
Claudia M. Raiteri, Maria Carnerero, Barbara Balmaverde, Eric C. Bellm, William Clarkson, Filippo D'Ammando, Maurizio Paolillo, Gordon T. Richards, Massimo Villata, Peter Yoachim, Ilsang Yoon
Summary: Blazars are fundamental sources for studying extragalactic jets and their central engines, with variable emission on unpredictable timescales. Understanding the mechanisms behind their flux and spectral changes requires long-term observations and multiband light curves. The Vera C. Rubin Legacy Survey of Space and Time will provide a valuable tool for studying blazar variability statistically, especially in relation to outbursts and high-energy emissions.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2022)
Article
Astronomy & Astrophysics
Carl J. Grillmair
Summary: Using data from Gaia Early Data Release 3, researchers have discovered a trailing stellar debris stream associated with the old globular cluster NGC 7089. The extended stream is as dynamically cold as the coldest known streams. There is also evidence for an extended leading tail, although its detection is less certain due to its greater distance and similar proper motions to foreground stars.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Sergio B. Fajardo-Acosta, Andreas Faisst, Carl J. Grillmair, Ranga-Ram Chary, Roberta Paladini, Ben Rusholme, Nathaniel Stickley
Summary: We analyzed the stellar proper motions in the COSMOS field and found that late-type main sequence stars predominantly move towards the Galactic center. We also identified candidate high-velocity stars from the Gaia and faint star samples.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Gokul P. Srinivasaragavan, Brendan O'Connor, S. Bradley Cenko, Alexander J. Dittmann, Sheng Yang, Jesper Sollerman, G. C. Anupama, Sudhanshu Barway, Varun Bhalerao, Harsh Kumar, Vishwajeet Swain, Erica Hammerstein, Isiah Holt, Shreya Anand, Igor Andreoni, Michael W. Coughlin, Simone Dichiara, Avishay Gal-Yam, M. Coleman Miller, Jaime Soon, Roberto Soria, Joseph Durbak, James H. Gillanders, Sibasish Laha, Anna M. Moore, Fabio Ragosta, Eleonora Troja
Summary: We observed the optical counterpart of the long gamma-ray burst GRB 221009A, which is both nearby and highly energetic, providing a unique opportunity to explore the connection between massive star core collapse and relativistic jet formation. Our analysis suggests the presence of an associated supernova, SN 2022xiw, which is fainter than SN 1998bw. We find properties consistent with previous GRB-associated SNe but note that the SN parameters are weakly constrained.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Multidisciplinary Sciences
Erik C. Kool, Joel Johansson, Jesper Sollerman, Javier Moldon, Takashi J. Moriya, Seppo Mattila, Steve Schulze, Laura Chomiuk, Miguel Perez-Torres, Chelsea Harris, Peter Lundqvist, Matthew Graham, Sheng Yang, Daniel A. Perley, Nora Linn Strotjohann, Christoffer Fremling, Avishay Gal-Yam, Jeremy Lezmy, Kate Maguire, Conor Omand, Mathew Smith, Igor Andreoni, Eric C. Bellm, Joshua S. Bloom, Kishalay De, Steven L. Groom, Mansi M. Kasliwal, Frank J. Masci, Michael S. Medford, Sungmin Park, Josiah Purdum, Thomas M. Reynolds, Reed Riddle, Estelle Robert, Stuart D. Ryder, Yashvi Sharma, Daniel Stern
Summary: Through the study of SN 2020eyj, we discovered a type Ia supernova with helium-rich circumstellar material. Based on our modeling, we conclude that this circumstellar material likely originates from a single-degenerate binary system, which is a frequently proposed formation channel.
Article
Astronomy & Astrophysics
Eric C. Bellm, Yuankun Wang, Jan van Roestel, Rebecca A. Phillipson, Michael W. Coughlin, John A. Tomsick, Steven L. Groom, Brian Healy, Josiah Purdum, Ben Rusholme, Jesper Sollerman, Peter Bealo, Stefano Lora, Eddy Muyllaert, Ivo Peretto, Erik J. Schwendeman
Summary: Using the Zwicky Transient Facility, we discovered the first outburst of the black hole X-ray transient XTE J1859+226 since its discovery in 1999. The outburst lasted for less than 20 days and had a peak luminosity 2 orders of magnitude lower than its full outburst in 1999. From optical spectroscopy, we estimated an outer disk radius of 10^11 cm. These observations highlight the potential of optical and infrared surveys in discovering low-luminosity activity from X-ray transients.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
A. Bodaghee, J. -L. Chiu, J. A. Tomsick, V. Bhalerao, E. Bottacini, M. Clavel, C. Cox, F. Furst, M. J. Middleton, F. Rahoui, J. Rodriguez, P. Romano, J. Wilms
Summary: We conducted a NuSTAR observation of IGR J16320-4751 (= AX J1631.9-4752), a high-mass X-ray binary with a slowly rotating neutron star. The spin period was found to be 1308.8 +/- 0.4 s, with a period derivative of 2 x 10(-8) s s(-1) compared to the measurement in 2004. The pulsed fraction decreased with energy, indicating a change in the accretion geometry. Spectral analysis revealed positive residuals at 6.4 keV from an iron K alpha line and negative residuals at 14 keV from a candidate cyclotron line.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Anastasios Tzanidakis, James R. A. Davenport, Eric C. Bellm, Yuankun Wang
Summary: We report the serendipitous discovery of a binary star, Gaia17bpp/2MASS J19372316+1759029, which experienced a deep single large-amplitude dimming event lasting over 6.5 years. Spectral energy distribution analysis reveals that the primary star is a cool giant M0III star with a constrained mass. Analysis of the light curves suggests moderate asymmetries from optical to IR, indicating the presence of a large, optically thick disk transiting the primary giant star.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Yuhan Yao, Vikram Ravi, Suvi Gezari, Sjoert van Velzen, Wenbin Lu, Steve Schulze, Jean J. Somalwar, S. R. Kulkarni, Erica Hammerstein, Matt Nicholl, Matthew J. Graham, Daniel A. Perley, S. Bradley Cenko, Robert Stein, Angelo Ricarte, Urmila Chadayammuri, Eliot Quataert, Eric C. Bellm, Joshua S. Bloom, Richard Dekany, Andrew J. Drake, Steven L. Groom, Ashish A. Mahabal, Thomas A. Prince, Reed Riddle, Ben Rusholme, Yashvi Sharma, Jesper Sollerman, Lin Yan
Summary: We conducted a systematic analysis of tidal disruption events (TDEs) using a large sample, providing insights into the black hole mass range and event rates.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
Michael W. Coughlin, Joshua S. Bloom, Guy Nir, Sarah Antier, Theophile Jegou du Laz, Stefan van der Walt, Arien Crellin-Quick, Thomas Culino, Dmitry A. Duev, Daniel A. Goldstein, Brian F. Healy, Viraj Karambelkar, Jada Lilleboe, Kyung Min Shin, Leo P. Singer, Tomas Ahumada, Shreya Anand, Eric C. Bellm, Richard Dekany, Matthew J. Graham, Mansi M. Kasliwal, Ivona Kostadinova, R. Weizmann Kiendrebeogo, Shrinivas R. Kulkarni, Sydney Jenkins, Natalie LeBaron, Ashish A. Mahabal, James D. Neill, B. Parazin, Julien Peloton, Daniel A. Perley, Reed Riddle, Ben Rusholme, Jakob van Santen, Jesper Sollerman, Robert Stein, D. Turpin, Avery Wold, Carla Amat, Adrien Bonnefon, Adrien Bonnefoy, Manon Flament, Frank Kerkow, Sulekha Kishore, Shloke Jani, Stephen K. Mahanty, Celine Liu, Laura Llinares, Jolyane Makarison, Alix Ollieric, Ines Perez, Lydie Pont, Vyom Sharma
Summary: SkyPortal is an open-source software package designed to efficiently discover, manage, characterize, and visualize interesting transients in the field of astronomy. It provides rich user experiences, extensive documentation, and an application programming interface system for scientific inquiry. With its strong extensibility and multimessenger features, SkyPortal is capable of addressing the challenges and opportunities presented by the next chapter in the multimessenger era.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2023)
Article
Astronomy & Astrophysics
B. O'Connor, E. Gogus, J. Hare, K. Mukai, D. Huppenkothen, J. Brink, D. A. H. Buckley, A. Levan, M. G. Baring, R. Stewart, C. Kouveliotou, P. Woudt, E. Bellm, S. B. Cenko, P. A. Evans, J. Granot, C. Hailey, F. Harrison, D. Hartmann, A. J. van der Horst, L. Kaper, J. A. Kennea, S. B. Potter, P. O. Slane, D. Stern, R. A. M. J. Wijers, G. Younes
Summary: In this paper, we present the results of a multiwavelength campaign aimed at classifying Swift J170800-402551.8. By utilizing various observatories and archival data, we identified the periodicity and X-ray spectrum of the source, as well as studied its multiwavelength counterpart. Based on our findings, we classify Swift J170800-402551.8 as a candidate intermediate polar cataclysmic variable with a spin period of 784 seconds.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Akshat Singhal, Sourav Palit, Suman Bala, Gaurav Waratkar, Harsh Kumar, Varun Bhalerao
Summary: The advanced gravitational wave detector network is routinely detecting signals from merging compact binaries, with at least one component being a neutron star. The confirmed link between electromagnetic and gravitational wave radiation has only been established for one source, GW170817. Joint analysis of broadband multi-wavelength data and gravitational wave signals has provided valuable information spanning various fields.
JOURNAL OF ASTROPHYSICS AND ASTRONOMY
(2022)