Stars, Interstellar Medium and the Galaxy Commons^™

X-Ray Microcalorimeter Observations Of High-Mass X-Ray Binaries With The Resolve Instrument Onboard Xrism, Pragati Pradhan, Masahiro Tsujimoto

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The X-ray Imaging and Spectrometer Mission (XRISM) was put into orbit successfully in September 2023. Resolve, one of the scientific instruments onboard XRISM, hosts an X-ray spectrometer based on X-ray microcalorimetery technology. It excels in high spectral resolution, a large throughput, a large bandpass, low background, and good timing accuracy. These properties are suited to bring new insights especially in high-mass X-ray binaries (HMXB). We describe these unique features of Resolve and present initial highlights of two HMXB sources.

The Giant Outburst Of Exo 2030+375, P. Thalhammer, R. Ballhausen, E. Sokolova-Lapa, J. Stierhof, A. Zainab, R. Staubert, K. Pottschmidt, J.B. Coley, R.E. Rothschild, G.K. Jaisawal, B. West, P.A. Becker, Pragati Pradhan, P. Kretschmar, J. Wilms

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The Be X-ray binary EXO 2030+375 went through its third recorded giant outburst from June 2021 to early 2022. We present the results of both spectral and timing analysis based on NICER monitoring, covering the 2−10 keV flux range from 20 to 310 mCrab. Dense monitoring with observations carried out about every second day and a total exposure time of ∼160 ks allowed us to closely track the source evolution over the outburst. Changes in the spectral shape and pulse profiles showed a stable luminosity dependence during the rise and decline. The same type of dependence has been seen in …

The Unaltered Pulsar: Gro J1750-27, A Supercritical X-Ray Neutron Star That Does Not Blink An Eye, C. M. Malacaria, L. Moritz Ducci, M. Falanga, D. A. Altamirano, E. Bozzo, S. J. Guillot, G.K. Jaisawal, P. Kretschmar, M. Ng, Pragati Pradhan, R. Rothschild, A. Sanna, P. Thalhammer, J. Wilms

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When accreting X-ray pulsars (XRPs) undergo bright X-ray outbursts, their luminosity-dependent spectral and timing features can be analyzed in detail. The XRP GRO J1750-27 recently underwent one such episode, during which it was observed with NuSTAR and monitored with NICER. Such a data set is rarely available, as it samples the outburst over more than 1 month at a luminosity that is always exceeding ∼5 × 1037 erg s−1 . This value is larger than the typical critical luminosity value, where a radiative shock is formed above the surface of the neutron star. Our data analysis of the joint spectra …

Multi-Wavelength Study Of 1erass J085039.9−421151 With Erosita, Nustar, And X-Shooter, A. Zainab, A. Avakyan, V. Doroshenko, P. Thalhammer, E. Sokolova-Lapa, R. Ballhausen, N. Zalot, J. Stierhof, S. Hämmerich, C. M. Diez, P. Weber, T. Dauser, K. Berger, P. Kretschmar, K. Pottschmidt, Pragati Pradhan, N. Islam, C. Maitra, J.B. Coley, P. Blay, R.H.D. Corbet, R.E. Rothschild, K. Wood, A. Santangelo, U. Heber, J. Wilms

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The eROSITA instrument on board Spectrum-Roentgen-Gamma (SRG) has completed four scans of the X-ray sky, leading to the detection of almost one million X-ray sources in eRASS1 alone, including multiple new X-ray binary candidates. We report on analysis of the X-ray binary 1eRASS J085039.9−421151, using a ∼55 ks long NuSTAR observation, following its detection in each eROSITA scan. An analysis of the eROSITA and NuSTAR X-ray spectra in combination with X-shooter data of the optical counterpart provide evidence of an X-ray binary with a red supergiant (RSG) companion, confirming previous results. However, we did determine a cooler spectral type for …

Stable Coronal X-Ray Emission Over 20 Yr Of Xz Tau, Steven M. Silverberg, Hans Moritz Günther, Pragati Pradhan, David A. Principe, P.C. Schneider, Scott J. Wolk

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XZ Tau AB is a frequently observed binary young stellar object in the Taurus Molecular Cloud; XZ Tau B has been classified as an EXOr object. We present new Chandra/HETG-ACIS-S observations of XZ Tau AB, complemented with variability monitoring of the system with XMM-Newton, to constrain the variability of this system and identify high-resolution line diagnostics to better understand the underlying mechanisms that produce the X-rays. We observe two flares with XMM-Newton but find that outside of these flares the coronal X-ray spectrum of XZ Tau AB is consistent over 20 yr of observations. We compare the ensemble of XZ …

A Search For Subdwarf B Binaries Using Pulsation Timing From Tess, Tomomi Otani, Andrzej S. Baran, Lindsay C. Spence, Ted A. Von Hippel, Ellesse A. Lynum-Lozano, Julia M. Clark

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Hot subdwarf B (sdB) stars are post-main-sequence stars of high temperature and gravity. Approximately 30% of sdBs exhibit stable pressure and/or gravity-mode pulsations, which can be used via the timing method to test for companion stars and determine their orbital solutions. We used short cadence data from the Transiting Exoplanet Survey Satellite (TESS) to search for previously undiscovered companions to sdBs. In this paper, we focus on searching for companions with orbital periods shorter than 13.5 days which are detectable within one sector of TESS data (about 27 days). The timing method requires that we derive pulsation frequencies in subsets …

Rapid Mid-Infrared Spectral Timing With Jwst: Grs 1915+105 During An Mir-Bright And X-Ray-Obscured State, P. Gandhi, E.S. Borowski, J. Byrom, R.I. Hynes, T.J. Maccarone, A.W. Shaw, O.K. Adegoke, D. Altamirano, M.C. Baglio, Y. Bhargava, C.T. Britt, D.A.H. Buckley, D.J.K. Buisson, P. Casella, N. Castro Segura, P.A. Charles, J.M. Corral-Santana, V.S. Dhillon, R. Fender, A. Gurpide, C.O. Heinke, A.B. Igl, C. Knigge, S. Markoff, G. Mastroserio, M.L. Mccollough, M. Middleton, J.M. Miller, J.C.A. Miller-Jones, S.E. Motta, J.A. Paice, D.D. Pawar, R.M. Plotkin, P. Pradhan, M.E. Ressler, D.M. Russell, T.D. Russell, P. Santos-Sanz, T. Shahbaz, T. Shahbaz, G.R. Sivakoff, D. Steeghs, A.J. Tetarenko, J.A. Tomsick, F.M. Vincentelli, M. George, M. Gurwell, R. Rao

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No abstract provided.

A Time-Dependent Spectral Analysis Of Γ Cassiopeiae, Sean J. Gunderson, David P. Huenemoerder, José M. Torrejón, Dustin K. Swarm, Joy S. Nichols, Pragati Pradhan, Richard Ignace, Hans Moritz Guenther, A.M.T. Pollock, Norbert S. Schulz

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We investigated the temporal and spectral features of γ Cassiopeiae’s X-ray emission within the context of the white dwarf (WD) accretion hypothesis. We find that the variabilities present in the X-ray data show two different signals, one primarily due to absorption and the other due to flickering like in nonmagnetic cataclysmic variables. We then use this two-component insight to investigate previously unreported simultaneous XMM and NuSTAR data. The results of model fitting find WD properties consistent with optical studies alongside a significant secondary, thermal source. We propose a secondary shock between the Be decretion disk and WD accretion disk as …

Pulse-Profile Modeling And Spin–Orbit Alignment In A Suzaku Sample Of Accreting X-Ray Binary Pulsars, Silas G.T. Laycock, Rigel C. Cappallo, Pragati Pradhan, Dimitris M. Christodoulou, Biswajit Paul

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We report pulse-profile modeling of a sample of 23 X-ray binary pulsars observed with the Suzaku X-ray satellite. These pulsars have spin periods ranging from 0.7 to 9400 s, and their X-ray emission is powered by the accretion from their stellar companions. We fitted each individual pulse profile with the Polestar geometric model, which accounts for X-ray emission from two hot spots modeled as a simple combination of fan+pencil beam components, including an approximation for gravitational light bending. In 14 of 21 cases, our measurements of the inclinations of the pulsar spin axes broadly agree with the corresponding inclinations of …

Detection Of The Orbital Modulation Of Fe Kα Fluorescence Emission In Centaurus X-3 Using The High-Resolution Spectrometer Resolve On Board Xrism, Yuto Mochizuki, Masahiro Tsujimoto, Richard L. Kelley, Bert Vander Meulen, Teruaki Enoto, Yutaro Nagai, Chris Done, Pragati Pradhan, Natalie Hell, Katja Pottschmidt, Ken Ebisawa, Ehud Behar

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The Fe Kα fluorescence line emission in X-ray spectra is a powerful diagnostic tool for various astrophysical objects to reveal the distribution of cold matter around photoionizing sources. The advent of the X-ray microcalorimeter on board the XRISM satellite will bring new constraints on the emission line. We present one of the first such results for the high-mass X-ray binary Centaurus X-3, which is composed of an O-type star and a neutron star (NS). We conducted a 155 ks observation covering an entire binary orbit. A weak Fe Kα line was detected in all orbital phases at an equivalent width …

Sharp Periodic Flares And Long-Term Variability In The High-Mass X-Ray Binary Xte J1829−098 From Rxte Pca, Swift Bat, And Maxi Observations, Robin H.D. Corbet, Ralf Ballhausen, Peter A. Becker, Joel B. Coley, Felix Fuerst, Keith C. Gendreau, Sebastien Guillot, Nazma Islam, Gaurava Kumar Jaisawal, Peter Jenke, Peter Kretschmar, Alexander Lange, Christian Malacaria, Mason Ng, Katja Pottschmidt, Pragati Pradhan, Paul S. Ray, Richard E. Rothschild, Philipp Thalhammer, Lee J. Townsend, Joern Wilms, Colleen A. Wilson-Hodge, Michael T. Wolff

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XTE J1829−098 is a transient X-ray pulsar with a period of ∼7.8 s. It is a candidate Be star system, although the evidence for this is not yet definitive. We investigated the twenty-year-long X-ray light curve using the Rossi X-ray Timing Explorer Proportional Counter Array (PCA), Neil Gehrels Swift Observatory Burst Alert Telescope, and the Monitor of All-sky X-ray Image. We find that all three light curves are clearly modulated on the ∼244 days orbital period previously reported from PCA monitoring observations, with outbursts confined to a narrow phase range. The light curves also show that XTE J1829−098 was in …

Prospects For Time-Domain And Multi-Messenger Science With Axis, Riccardo Arcodia, Franz E. Bauer, S. Bradley Cenko, Kristen C. Dage, Daryl Haggard, Wynn C.G. Ho, Erin Kara, Michael Koss, Tingting Liu, Labani Mallick, Michela Negro, Pragati Pradhan, J. Quirola-Vásquez, Mark T. Reynolds, Claudio Ricci, Richard E. Rothschild, Navin Sridhar, Eleonora Troja, Yuhan Yao

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The Advanced X-ray Imaging Satellite (AXIS) promises revolutionary science in the X-ray and multi-messenger time domain. AXIS will leverage excellent spatial resolution (< 1.5 arcsec), sensitivity (80× that of Swift), and a large collecting area (5–10× that of Chandra) across a 24-arcmin diameter field of view at soft X-ray energies (0.3–10.0 keV) to discover and characterize a wide range of X-ray transients from supernova-shock breakouts to tidal disruption events to highly variable supermassive black holes. The observatory’s ability to localize and monitor faint X-ray sources opens up new opportunities to hunt for counterparts to distant binary neutron star mergers, fast radio bursts, and exotic phenomena like fast X-ray transients. AXIS will offer a response time of < 2 h to community alerts, enabling studies of gravitational wave sources, high-energy neutrino emitters, X-ray binaries, magnetars, and other targets of opportunity. This white paper highlights some of the discovery science that will be driven by AXIS in this burgeoning field of time domain and multi-messenger astrophysics. This White Paper is part of a series commissioned for the AXIS Probe Concept Mission; additional AXIS White Papers can be found at the AXIS website.

An In-Depth Analysis Of The Variable Cyclotron Lines In Gx 301−2, Nicolas Zalot, Ekaterina Sokolova-Lapa, Jakob Stierhof, Ralf Ballhausen, Aafia Zainab, Katja Pottschmidt, Felix Fürst, Philipp Thalhammer, Nazma Islam, Camille M. Diez, Peter Kretschmar, Katrin Berger, Richard Rothschild, Christian Malacaria, Pragati Pradhan, Jörn Wilms

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Context. The high-mass X-ray binary system GX 301−2 is a persistent source with a well-known variable cyclotron line centered at 35 keV. Recently, a second cyclotron line at 50 keV has been reported with a presumably different behavior than the 35 keV line. Aims. We investigate the presence of the newly discovered cyclotron line in the phase-averaged and phase-resolved spectra at higher luminosities than before. We further aim to determine the pulse-phase variability of both lines.

Methods. We analyze a NuSTAR observation of GX 301−2 covering the pre-periastron flare, where the source luminosity reached its peak of ∼4×1037 …

Chandra Hetg X-Ray Spectra And Variability Of Π Aqr, A Γ Cas-Type Be Star, David P. Huenemoerder, Pragati Pradhan, Claude R. Canizares, Sean Gunderson, Richard Ignace, Joy S. Nichols, A.M.T. Pollock, Norbert S. Schulz, Dustin K. Swarm, José M. Torrejón

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High-resolution X-ray spectra of π Aqr, a γ Cas-type star, obtained with the Chandra/HETG spectrometer, revealed emission lines of H-like ions of Mg, Si, S, and Fe; a strong, hard continuum; and a lack of He-like ions, indicating the presence of very hot thermal plasma. The X-ray light curve showed significant fluctuations, with coherent variability at a period of about 3400 s in one observation. The hardness ratio was relatively constant except for one observation in which the spectrum was much harder and more absorbed. We interpret the X-ray emission as arising from accretion onto the secondary, which is likely …

Energy Dependence Of Quasi-Periodic Oscillations In Accreting X-Ray Pulsars, Hemanth Manikantan, Biswajit Paul, Rahul Sharma, Pragati Pradhan, Vikram Rana

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We present the results from an investigation of the energy dependence of quasi-periodic oscillations (QPOs) exhibited by accreting X-ray pulsars using data from archival XMM-Newton, NuSTAR, RXTE, and NICER observations. In a search for the presence of QPOs in 99 XMM-Newton and NuSTAR observations, we detected QPOs in eleven observations of five sources, viz., 4U 1626–67 (48 mHz), IGR J19294+1816 (30 mHz), V 0332+53 (2, 18, and 40 mHz), Cen X–3 (30 mHz), and XTE J1858+034 (180 mHz). A positive correlation of the QPO rms amplitude with energy is exhibited by 4U 1626–67, IGR J19294+1816, Cen X–3 and XTE J1858+034, …

Density And Magnetic Field Asymmetric Kelvin‐Helmholtz Instability, Xuanye Ma, Peter Delamere, Katariina Nykyri, Antonius Otto, Stefan Eriksson, Lihui Chai, Brandon Burkholder, Andrew Dimmock, Yu-Lun Liou, Shiva Kavosi

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The Kelvin‐Helmholtz (KH) instability can transport mass, momentum, magnetic flux, and energy between the magnetosheath and magnetosphere, which plays an important role in the solar‐wind‐ magnetosphere coupling process for different planets. Meanwhile, strong density and magnetic field asymmetry are often present between the magnetosheath (MSH) and magnetosphere (MSP), which could affect the transport processes driven by the KH instability. Our magnetohydrodynamics simulation shows that the KH growth rate is insensitive to the density ratio between the MSP and the MSH in the compressible regime, which is different than the prediction from linear incompressible theory. When the interplanetary magnetic field (IMF) …

Observed Epochal Variations In X-Ray Lines From The O Supergiant Ζ Puppis Do Not Require Substantial Changes In The Wind Mass Flux, Sean J. Gunderson, Kenneth G. Gayley, David P. Huenemoerder, Pragati Pradhan, Nathan A. Miller

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We fit the high-resolution Chandra X-ray spectra of the O supergiant ζ Puppis using the variable boundary condition (VBC) line model to test the stability of its mass-loss rate between two epochs of observation: 2000 March and 2018 July – 2019 August. At issue is whether the observed variations are induced by global changes in the cool (unshocked) wind itself or are isolated to the local pockets of hot gas (i.e. changes in the frequency and location of the shocks). Evidence in the literature favoured the possibility of a 40 per cent increase in the mass flux of the entire …

The High Energy X-Ray Probe (Hex-P): A New Window Into Neutron Star Accretion, R.M. Ludlam, C. Malacaria, E. Sokolova-Lapa, F. Fuerst, P. Pradhan, A.W. Shaw, K. Pottschmidt, S. Pike, G. Vasilopoulos, J. Wilms, J.A. Garcia, K. Madsen, D. Stern, C. Maitra, M. Del Santo, D.J. Walton, M.C. Brumback, J. Van Den Eijnden

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Accreting neutron stars (NSs) represent a unique laboratory for probing the physics of accretion in the presence of strong magnetic fields (B ≳ 10⁸ G). Additionally, the matter inside the NS itself exists in an ultra-dense, cold state that cannot be reproduced in Earth-based laboratories. Hence, observational studies of these objects are a way to probe the most extreme physical regimes. Here we present an overview of the field and discuss the most important outstanding problems related to NS accretion. We show how these open questions regarding accreting NSs in both low-mass and high-mass X-ray binary systems can …

The Life Cycle Of Stars And Their Planets From The High Energy Perspective, Lia Corrales, Keivan G. Stassun, Tim Cunningham, Girish M. Duvvuri, Jeremy J. Drake, Catherine Espaillat, Adina D. Feinstein, Elena Gallo, Hans Moritz Günther, George W. King, Marina Kounkel, Carey M. Lisse, Rodolfo Montez Jr., David A. Principe, Jesús A. Toalá, Scott J. Wolk, Raven Cilley, Tansu Daylan, Margarita Karovska, Pragati Pradhan, Peter J. Wheatley, Jun Yang

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One of the key research themes identified by the Astro2020 decadal survey is Worlds and Suns in Context. The Advanced X-ray Imaging Satellite (AXIS) is a proposed NASA APEX mission that will become the prime high-energy instrument for studying star-planet connections from birth to death. This work explores the major advances in this broad domain of research that will be enabled by the AXIS mission, through X-ray observations of stars in clusters spanning a broad range of ages, flaring M-dwarf stars known to host exoplanets, and young stars exhibiting accretion interactions with their protoplanetary disks. In addition, we explore the …

The Rs Oph Outburst Of 2021 Monitored In X-Rays With Nicer, Marina Orio, Keith Gendreau, Morgan Giese, Gerardo Jaun M. Luna, Jozef Magdolen, Tod E. Strohmayer, Andy E. Zhang, Diego Altamirano, Andrej Dobrotka, Teruaki Enoto, Elizabeth C. Ferrara, Richard Ignace, Sebastian Heinz, Craig Markwardt, Joy S. Nichols, Michael L. Parker, Dheeraj R. Pasham, Songpeng Pei, Pragati Pradhan, Ron Remillard, James F. Steiner, Francesco Tombesi

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The 2021 outburst of the symbiotic recurrent nova RS Oph was monitored with the Neutron Star Interior Composition Explorer Mission (NICER) in the 0.2–12 keV range from day one after the optical maximum, until day 88, producing an unprecedented, detailed view of the outburst development. The X-ray flux preceding the supersoft X-ray phase peaked almost 5 days after optical maximum and originated only in shocked ejecta for 21–25 days. The emission was thermal; in the first 5 days, only a non-collisional-ionization equilibrium model fits the spectrum, and a transition to equilibrium occurred between days 6 and 12. The ratio of …

Survey Of X-Rays From Massive Stars Observed At High Spectral Resolution With Chandra, Pragati Pradhan, David P. Huenemoerder, Richard Ignace, Joy S. Nichols, A.M.T. Pollock

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Identifying trends between observational data and the range of physical parameters of massive stars is a critical step to the still-elusive full understanding of the source, structure, and evolution of X-ray emission from the stellar winds, requiring a substantial sample size and systematic analysis methods. As of 2022, the Chandra data archive contains 37 high-resolution spectra of O, B, and WR stars, observed with the Chandra/HETGS, and of sufficient quality to fit the continua and emission-line profiles. Using a systematic approach to the data analysis, we explore morphological trends in the line profiles (i.e., O, Ne, Mg, and Si) and …

Quiet, But Not Silent: Uncovering Quiescent State Properties Of Two Transient High-Mass X-Ray Binaries, Gayathri Raman, Pragati Pradhan, Jamie Kennea

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We present the first set of broad-band spectral and timing studies of two transient X-ray pulsars, MXB 0656 −072 and MAXI J1409 −619 using NuSTAR observations conducted during quiescence. Despite being captured at one of their lowest luminosity states, both these targets show signs of ongoing low-level accretion. Results from the time-averaged spectral analysis indicate for the first time, the presence of a strong soft power-law component along with thermal emission from the neutron star hotspots. For both targets, the quiescent thermal X-ray emission is consistent with the deep crustal heating model. In MXB 0656 −072, we do not detect …

Bayesian Inference For The White Dwarf Initial-Final Mass Relation, Nathan Stein, Ted Von Hippel, David Van Dyk, Steven Degennaro, Elizabeth Jeffery, Bill Jefferys

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Stars lose mass as they age, and understanding mass loss is important for understanding stellar evolution. The initial-final mass relation (IFMR) is the relationship between a white dwarf’s initial mass on the main sequence and its final mass. We have developed a new method for fitting the IFMR based on a Bayesian analysis of photometric observations, combining deterministic models of stellar evolution in an internally coherent way. No mass data are used. Our method yields precise inferences (with uncertainties) for a parameterized linear IFMR. Our method can also return posterior distributions of white dwarf initial and final masses.

Clumpy Wind Studies And The Nondetection Of A Cyclotron Line In Oao 1657–415, Pragati Pradhan, Carlo Ferrigno, Biswajit Paul, Enrico Bozzo, Ileyk El Mellah, David P. Huenemoerder, James F. Steiner, Victoria Grinberg, Felix Furst, Chandreyee Maitra, Patrizia Romano, Peter Kretschmar, Jamie Kennea, Deepto Chakrabarty

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Winds of massive stars are suspected to be inhomogeneous (or clumpy), which biases the measures of their mass-loss rates. In high-mass X-ray binaries (HMXBs), the compact object can be used as an orbiting X-ray point source to probe the wind and constrain its clumpiness. We perform a spectrotiming analysis of the HMXB OAO 1657–415 with nonsimultaneous NuSTAR and NICER observations. We compute the hardness ratio from the energy-resolved light curves, and, using an adaptive rebinning technique, we thus select appropriate time segments to search for rapid spectral variations on timescales of a few hundred to thousands of seconds. The column …

Two Substellar Survivor Candidates; One Found And One Missing, T. Von Hippel, N. Walters, J. Farihi, T.R. Marsh, E. Breedt, P.W. Cauley, J.J. Hermes

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This study presents observations of two possible substellar survivors of post-main sequence engulfment, currently orbiting white dwarf stars. Infrared and optical spectroscopy of GD 1400 reveal a 9.98 h orbital period, where the benchmark brown dwarf has ��2 = 68 ± 8 MJup, ��eff ≈ 2100 K, and a cooling age under 1 Gyr. A substellar mass in the lower range of allowed values is favoured by the gravitational redshift of the primary. Synthetic brown dwarf spectra are able to reproduce the observed CO bands, but lines below the bandhead are notably overpredicted. The known infrared excess towards PG 0010+281 …

Revisit Of Open Clusters Upk 39, Upk 41 And Phoc 39 : A New Binary Open Cluster Found, Xianhao Ye, Terry D. Oswalt, Jingkun Zhao, Yong Yang, Gang Zhao

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We investigate the three open clusters near Aquila Rift cloud, named as UPK 39 (c1 hereafter), UPK 41 (c2 hereafter) in Sim et al. (2019) and PHOC 39 (c3 hereafter) in Hunt & Reffert (2021), respectively. Using photometric passpands, reddening, and extinction from Gaia DR3, we construct the color-absolute-magnitude diagram (CAMD). Using isochrone fits their ages are estimated as 6.3 ± 0.9, 8.1 ± 1.4 and 21.8 ± 2.2 Myr, respectively. Their proper motions and radial velocities, estimated using data from Gaia and LAMOST are very similar. From their orbits, relative distances among them at different times, kinematics, ages, and …

A Monte Carlo Method For Evaluating Empirical Gyrochronology Models And Its Application To Wide Binary Benchmarks, Tomomi Otani, Ted Von Hippel, Derek Buzasi, Terry Oswalt, Alexander Stone-Martinez, Patrice Majewski

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No abstract provided.

Improving White Dwarfs As Chronometers With Gaia Parallaxes And Spectroscopic Metallicities, Adam Moss, Ted Von Hippel, Elliot Robinson, Kareem El-Badry, David C. Stenning, David Van Dyk, Morgan Fouesneau, Coryn A.L. Bailer-Jones, Elizabeth Jeffery, Jimmy Sargent, Isabelle Kloc, Natalie Moticska

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White dwarfs (WDs) offer unrealized potential in solving two problems in astrophysics: stellar age accuracy and precision. WD cooling ages can be inferred from surface temperatures and radii, which can be constrained with precision by high-quality photometry and parallaxes. Accurate and precise Gaia parallaxes along with photometric surveys provide information to derive cooling and total ages for vast numbers of WDs. Here we analyze 1372 WDs found in wide binaries with main-sequence (MS) companions and report on the cooling and total age precision attainable in these WD+MS systems. The total age of a WD can be further constrained if its …

Discovery Of Quasi-Periodic Oscillations In The Persistent X-Ray Emission Of Accreting Binary X-Ray Pulsar Lmc X-4, Ketan Rikame, Biswajit Paul, Pragati Pradhan, K.T. Paul

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We report the discovery of quasi-periodic oscillations (QPOs) in the high-mass X-ray binary (HMXB) pulsar LMC X-4 in its non-flaring (persistent) state using observations with XMM–Newton. In addition to the 74 mHz coherent pulsations, the persistent emission light curve shows a QPO feature in the frequency range of 20–30 mHz. Quasi-periodic flares have been previously observed from LMC X-4 in observations made with Rossi X-ray Timing Explorer (RXTE). However, this is the first time QPOs have been observed in the persistent emission observations of LMC X-4. QPOs in X-ray binaries are generally thought to be related to the rotation of …

Accreting On The Edge: A Luminosity-Dependent Cyclotron Line In The Be/X-Ray Binary 2s 1553-542 Accompanied By Accretion Regimes Transition, C. Malacaria, Y. Bhargava, Joel B. Coley, L. Ducci, Pragati Pradhan, R. Ballhausen, F. Fuerst, N. Islam, G. K. Jaisawal, P. Jenke, P. Kretschmar, I. Kreykenbohm, K. Pottschmidt, E. Sokolova-Lapa, R. Staubert, J. Wilms, C.A. Wilson-Hodge, Michael T. Wolff

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Accreting X-ray pulsars undergo luminous X-ray outbursts during which the luminosity-dependent spectral and timing features of the neutron star’s emission can be analyzed in detail, thus shedding light on the accretion regime at work. We took advantage of a monitoring campaign that was performed with NuSTAR, Swift/XRT, AstroSat and NICER to follow the Be/X-ray Binary 2S 1553-542 along one of its rare outbursts, and thus trace its spectral and timing evolution. We report the discovery of a luminosity-dependent cyclotron line energy for the first time in this source. The pulse profiles and pulsed fraction also show variability along the outburst, …