Zaven Arzoumanian
YOU?
Author Swipe
View article: The double neutron star PSR J1946+2052
The double neutron star PSR J1946+2052 Open
Aims. Double neutron star (DNS) systems are superb laboratories for testing theories of gravity and constraining the equation of state of ultra-dense matter. PSR J1946+2052 is a particularly intriguing DNS system due to its orbital period …
View article: CHIME-o-Grav: Wideband Timing of Four Millisecond Pulsars from the NANOGrav 15-yr dataset
CHIME-o-Grav: Wideband Timing of Four Millisecond Pulsars from the NANOGrav 15-yr dataset Open
Wideband timing of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) datasets, where a single time-of-arrival (TOA) and a single dispersion measure (DM) are measured using the entire bandwidth of each observation,…
View article: Searching for Exotrojans in Pulsar Binary Systems
Searching for Exotrojans in Pulsar Binary Systems Open
Trojan asteroids are found in the equilateral triangle Lagrange points of the Sun-Jupiter system in great number, though they also exist less prolifically in other Sun-planet systems. Despite up to planetary mass Trojans being predicted in…
View article: The double neutron star PSR J1946+2052 I. Masses and tests of general relativity
The double neutron star PSR J1946+2052 I. Masses and tests of general relativity Open
We conducted high-precision timing of PSR J1946+2052 to determine the masses of the two neutron stars in the system, test general relativity (GR) and assessed the system's potential for future measurement of the moment of inertia of the pu…
View article: The NANOGrav 15-Year Data Set: Improved Timing Precision With VLBI Astrometric Priors
The NANOGrav 15-Year Data Set: Improved Timing Precision With VLBI Astrometric Priors Open
Accurate pulsar astrometric estimates play an essential role in almost all high-precision pulsar timing experiments. Traditional pulsar timing techniques refine these estimates by including them as free parameters when fitting a model to o…
View article: Quasiperiodic Variation during a Fast X-Ray Outburst of a High-mass X-Ray Binary MAXI J0709-159/LY CMa Observed by NICER
Quasiperiodic Variation during a Fast X-Ray Outburst of a High-mass X-Ray Binary MAXI J0709-159/LY CMa Observed by NICER Open
We report on a quasiperiodic variation at ∼1 Hz during a fast X-ray outburst of a high-mass X-ray binary MAXI J0709−159/LY CMa observed by the Neutron star Interior Composition ExploreR (NICER). The new X-ray transient MAXI J0709−159 was d…
View article: Timing and Spectral Evolution of the Magnetar 1E 1841-045 in Outburst
Timing and Spectral Evolution of the Magnetar 1E 1841-045 in Outburst Open
We present timing and spectral analyses of Neutron star Interior Composition Explorer (NICER), Nuclear Spectroscopic Telescope Array (NuSTAR), and IXPE observations of the magnetar 1E 1841−045 covering 82 days following its 2024 August bur…
View article: SRG/eROSITA No. 5: Discovery of Quasiperiodic Eruptions Every ∼3.7 days from a Galaxy at <i>z</i> > 0.1
SRG/eROSITA No. 5: Discovery of Quasiperiodic Eruptions Every ∼3.7 days from a Galaxy at <i>z</i> > 0.1 Open
Quasiperiodic eruptions (QPEs) are repeating soft-X-ray bursts from the nuclei of galaxies, tantalizingly proposed to be extreme-mass-ratio inspirals. Here, we report the discovery of a new galaxy showing X-ray QPEs, the fifth found throug…
View article: Quasi-periodic variation during a fast X-ray outburst of a high-mass X-ray binary MAXI J0709-159 / LY CMa observed by NICER
Quasi-periodic variation during a fast X-ray outburst of a high-mass X-ray binary MAXI J0709-159 / LY CMa observed by NICER Open
We report on a quasi-periodic variation at $\sim1$ Hz during a fast X-ray outburst of a high-mass X-ray binary MAXI J0709$-$159 / LY CMa observed by the Neutron-star interior composition explorer (NICER). The new X-ray transient MAXI J0709…
View article: The NANOGrav 15 yr Data Set: Search for Gravitational-wave Memory
The NANOGrav 15 yr Data Set: Search for Gravitational-wave Memory Open
We present the results of a search for nonlinear gravitational-wave (GW) memory in the NANOGrav 15 yr data set. We find no significant evidence for memory signals in the data set, with a maximum Bayes factor of 3.1 in favor of a model incl…
View article: The NANOGrav 12.5 yr Data Set: Probing Interstellar Turbulence and Precision Pulsar Timing with PSR J1903+0327
The NANOGrav 12.5 yr Data Set: Probing Interstellar Turbulence and Precision Pulsar Timing with PSR J1903+0327 Open
Free electrons in the interstellar medium refract and diffract radio waves along multiple paths, resulting in angular and temporal broadening of radio pulses that limits pulsar timing precision. We determine multifrequency, multiepoch scat…
View article: The NANOGrav 12.5 yr Data Set: Probing Interstellar Turbulence and Precision Pulsar Timing with PSR J1903+0327
The NANOGrav 12.5 yr Data Set: Probing Interstellar Turbulence and Precision Pulsar Timing with PSR J1903+0327 Open
Free electrons in the interstellar medium refract and diffract radio waves along multiple paths, resulting in angular and temporal broadening of radio pulses that limits pulsar timing precision. We determine multifrequency, multiepoch scat…
View article: The NANOGrav 15-Year Data Set: A Case Study for Simplified Dispersion Measure Modeling for PSR J1455-3330 and the Impact on Gravitational Wave Sensitivity
The NANOGrav 15-Year Data Set: A Case Study for Simplified Dispersion Measure Modeling for PSR J1455-3330 and the Impact on Gravitational Wave Sensitivity Open
Evidence for a low-frequency gravitational-wave background using pulsar timing arrays has generated recent interest into its underlying contributing sources. However, multiple investigations have seen that the significance of the evidence …
View article: On the Origin of Spectral Features Observed during Thermonuclear X-Ray Bursts and in the Aftermath Emission of a Long Burst from 4U 1820–30
On the Origin of Spectral Features Observed during Thermonuclear X-Ray Bursts and in the Aftermath Emission of a Long Burst from 4U 1820–30 Open
We study 15 thermonuclear X-ray bursts from 4U 1820–30 observed with the Neutron Star Interior Composition Explorer (NICER). We find evidence of a narrow emission line at 1.0 keV and three absorption lines at 1.7, 3.0, and 3.75 keV, primar…
View article: Evolution of the Inner Accretion Flow and the White Dwarf Spin Pulse during the 2023 Outburst in GK Persei
Evolution of the Inner Accretion Flow and the White Dwarf Spin Pulse during the 2023 Outburst in GK Persei Open
We present our X-ray and optical observations performed by NICER, NuSTAR, and Tomo-e Gozen during the 2023 outburst in the intermediate polar GK Persei. The X-ray spectrum consisted of three components: blackbody (BB) emission of several t…
View article: X-Ray Polarization of the Magnetar 1E 1841−045
X-Ray Polarization of the Magnetar 1E 1841−045 Open
We report on IXPE and NuSTAR observations beginning 40 days after the 2024 outburst onset of magnetar 1E 1841−045, marking the first IXPE observation of a magnetar in an enhanced state. Our spectropolarimetric analysis indicates that both …
View article: The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations
The NANOGrav 15 yr Data Set: Harmonic Analysis of the Pulsar Angular Correlations Open
Pulsar timing array observations have found evidence for an isotropic gravitational-wave background with the Hellings–Downs angular correlations between pulsar pairs. This interpretation hinges on the measured shape of the angular correlat…
View article: Pulse Profile Variability of PSR J1022+1001 in NANOGrav Data
Pulse Profile Variability of PSR J1022+1001 in NANOGrav Data Open
Pulse profile stability is a central assumption of standard pulsar timing methods. Thus, it is important for pulsar timing array experiments such as the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) to account for…
View article: The Anomalous Acceleration of PSR J2043+1711: Long-period Orbital Companion or Stellar Flyby?
The Anomalous Acceleration of PSR J2043+1711: Long-period Orbital Companion or Stellar Flyby? Open
Based on the rate of change of its orbital period, PSR J2043+1711 has a substantial peculiar acceleration of 3.5 ± 0.8 mm s –1 yr –1 , which deviates from the acceleration predicted by equilibrium Milky Way (MW) models at a 4 σ level. The …
View article: The NANOGrav 15-year Data Set: Search for Gravitational Wave Memory
The NANOGrav 15-year Data Set: Search for Gravitational Wave Memory Open
We present the results of a search for nonlinear gravitational wave memory in the NANOGrav 15-year data set. We find no significant evidence for memory signals in the dataset, with a maximum Bayes factor of 3.1 in favor of a model includin…
View article: The NANOGrav 15 yr Data Set: Running of the Spectral Index
The NANOGrav 15 yr Data Set: Running of the Spectral Index Open
The NANOGrav 15 yr data provide compelling evidence for a stochastic gravitational-wave (GW) background at nanohertz frequencies. The simplest model-independent approach to characterizing the frequency spectrum of this signal consists of a…
View article: The NANOGrav 15 Yr Data Set: Removing Pulsars One by One from the Pulsar Timing Array
The NANOGrav 15 Yr Data Set: Removing Pulsars One by One from the Pulsar Timing Array Open
Evidence has emerged for a stochastic signal correlated among 67 pulsars within the 15 yr pulsar-timing data set compiled by the NANOGrav collaboration. Similar signals have been found in data from the European, Indian, Parkes, and Chinese…
View article: The NANOGrav 15 yr Data Set: Looking for Signs of Discreteness in the Gravitational-wave Background
The NANOGrav 15 yr Data Set: Looking for Signs of Discreteness in the Gravitational-wave Background Open
The cosmic merger history of supermassive black hole binaries (SMBHBs) is expected to produce a low-frequency gravitational wave background (GWB). Here we investigate how signs of the discrete nature of this GWB can manifest in pulsar timi…
View article: X-ray polarization of the magnetar 1E 1841-045
X-ray polarization of the magnetar 1E 1841-045 Open
We report on IXPE and NuSTAR observations beginning forty days after the 2024 outburst onset of magnetar 1E 1841-045, marking the first IXPE observation of a magnetar in an enhanced state. Our spectropolarimetric analysis indicates that bo…
View article: Pulse Profile Variability of PSR J1022+1001 in NANOGrav Data
Pulse Profile Variability of PSR J1022+1001 in NANOGrav Data Open
Pulse profile stability is a central assumption of standard pulsar timing methods. Thus, it is important for pulsar timing array experiments such as the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) to account for…
View article: Exploring Pulsar Timing Precision: A Comparative Study of Polarization Calibration Methods for NANOGrav Data from the Green Bank Telescope
Exploring Pulsar Timing Precision: A Comparative Study of Polarization Calibration Methods for NANOGrav Data from the Green Bank Telescope Open
Pulsar timing array experiments have recently uncovered evidence for a nanohertz gravitational wave background by precisely timing an ensemble of millisecond pulsars. The next significant milestones for these experiments include characteri…
View article: The NANOGrav 15 Yr Data Set: Removing Pulsars One by One from the Pulsar Timing Array
The NANOGrav 15 Yr Data Set: Removing Pulsars One by One from the Pulsar Timing Array Open
Evidence has emerged for a stochastic signal correlated among 67 pulsars within the 15-year pulsar-timing data set compiled by the NANOGrav collaboration. Similar signals have been found in data from the European, Indian, Parkes, and Chine…
View article: STROBE-X low-energy modular array (LEMA) instrument
STROBE-X low-energy modular array (LEMA) instrument Open
View article: A NICER View of PSR J1231−1411: A Complex Case
A NICER View of PSR J1231−1411: A Complex Case Open
Recent constraints on neutron star mass and radius have advanced our understanding of the equation of state (EOS) of cold dense matter. Some of them have been obtained by modeling the pulses of three millisecond X-ray pulsars observed by t…
View article: Exploring Waveform Variations among Neutron Star Ray-tracing Codes for Complex Emission Geometries
Exploring Waveform Variations among Neutron Star Ray-tracing Codes for Complex Emission Geometries Open
Pulse profile modeling (PPM), the technique used to infer mass, radius, and geometric parameters for rotation-powered millisecond pulsars using data from the Neutron Star Interior Composition Explorer (NICER), relies on relativistic ray-tr…