Peter Jenke

University of Alabama in Huntsville

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Co-Authors

C. Wilson‐Hodge

Marshall Space Flight Center

112

V. Connaughton

Universities Space Research Association

M. S. Briggs

University of Alabama in Huntsville

Mark H. Finger

Universities Space Research Association

A. Camero-Arranz

Universidad de La Laguna

A. Goldstein

Universities Space Research Association

R. D. Preece

University of Alabama in Huntsville

W. S. Pačiesas

Universities Space Research Association

M. L. Cherry

Louisiana State University

R. M. Kippen

Los Alamos National Laboratory

Cooperative Institutions

Centre National de la Recherche Scientifique

973

California Institute of Technology

786

National Institute for Astrophysics

555

Goddard Space Flight Center

555

Max Planck Society

426

Université Paris Cité

365

Cardiff University

361

Institut National de Physique Nucléaire et de Physique des Particules

330

Australian National University

324

LIGO Scientific Collaboration

324

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Studying geometry of the ultraluminous X-ray pulsar Swift J0243.6+6124 using X-ray and optical polarimetry

Astronomy and Astrophysics (2024)

Juri Poutanen Sergey S. Tsygankov Victor Doroshenko Sofia V. Forsblom Peter Jenke

Discovery of pulsations from a number of ultra-luminous X-ray (ULX) sources proved that accretion onto neutron stars can produce luminosities exceeding the Eddington limit by several orders of magnitude. The conditions necessary to achieve such high luminosities as well as the exact geometry of the accretion flow in the neutron star vicinity are, however, a matter of debate. The pulse phase-resolved polarization measurements that became possible with the launch of the Imaging X-ray Polarimetry Explorer (IXPE) can be used to determine the pulsar geometry and its orientation relative to the orbital plane. They provide an avenue to test different theoretical models of ULX pulsars. In this paper we present the results of three IXPE observations of the first Galactic ULX pulsar Swift J0243.6+6124 during its 2023 outburst. We find strong variations in the polarization characteristics with the pulsar phase. The average polarization degree increases from about 5% to 15% as the flux dropped by a factor of three in the course of the outburst. The polarization angle (PA) as a function of the pulsar phase shows two peaks in the first two observations, but changes to a characteristic sawtooth pattern in the remaining data set. This is not consistent with a simple rotating vector model. Assuming the existence of an additional constant polarized component, we were able to fit the three observations with a common rotating vector model and obtain constraints on the pulsar geometry. In particular, we find the pulsar angular momentum inclination with respect to the line of sight of i p = 15°–40°, the magnetic obliquity of θ p = 60°–80°, and the pulsar spin position angle of χ p ≈ −50°, which significantly differs from the constant component PA of about 10°. Combining these X-ray measurements with the optical PA, we find evidence for at least a 30° misalignment between the pulsar angular momentum and the binary orbital axis.

Swift

10.1051/0004-6361/202450696

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Hard X-ray Variations in the Crab Nebula

C. Wilson‐Hodge M. L. Cherry G. L. Case W. H. Baumgartner E. Beklen

In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008 to August 2010, approximately 7% (70 mcrab) decline was discovered in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline was independently confirmed with four other instruments: the RXTE/PCA, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA from 1999-2010 was consistent with the pulsar spin-down, indicating that the observed changes were nebular. From 2001 to 2010, the Crab nebula flux measured with RXTE/ PCA was particularly variable, changing by up to approximately 3.5% per year in the 15-50 keV band. These variations were confirmed with INTEGRAL/SPI starting in 2003, Swift/BAT starting in 2005, and Fermi GBM starting in 2008. Before 2001 and since 2010, the Crab nebula flux has appeared more stable, varying by less than 2% per year. I will present updated light curves in multiple energy bands for the Crab Nebula, including recent data from Fermi GBM, Swift/BAT, INTEGRAL and MAXI, and a 16-year long light curve from RXTE/PCA.

Crab Nebula

Occultation

Crab Pulsar

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The Variable Crab Nebula: Evidence for a Connection Between GeV Flares and Hard X-ray Variations

C. Wilson‐Hodge A. K. Harding E. Hays M. L. Cherry G. L. Case

In 2010, hard X-ray variations (Wilson-Hodge et al. 2011) and GeV flares (Tavani et al 2011, Abdo et al. 2011) from the Crab Nebula were discovered. Connections between these two phenomena were unclear, in part because the timescales were quite different, with yearly variations in hard X-rays and hourly to daily variations in the GeV flares. The hard X-ray flux from the Crab Nebula has again declined since 2014, much like it did in 2008-2010. During both hard X-ray decline periods, the Fermi LAT detected no GeV flares, suggesting that injection of particles from the GeV flares produces the much slower and weaker hard X-ray variations. The timescale for the particles emitting the GeV flares to lose enough energy to emit synchrotron photons in hard X-rays is consistent with the yearly variations observed in hard X-rays and with the expectation that the timescale for variations slowly increases with decreasing energy. This hypothesis also predicts even slower and weaker variations below 10 keV, consistent with the non-detection of counterparts to the GeV flares by Chandra (Weisskopf et al 2013). We will present a comparison of the observed hard X-ray variations and a simple model of the decay of particles from the GeV flares to test our hypothesis.

Crab Nebula

Flare

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SEARCH FOR GRAVITATIONAL WAVES ASSOCIATED WITH GAMMA-RAY BURSTS DURING LIGO SCIENCE RUN 6 AND VIRGO SCIENCE RUNS 2 AND 3

The Astrophysical Journal (2012)

J. Abadie B. P. Abbott R. Abbott T. D. Abbott M. R. Abernathy

We present the results of a search for gravitational waves associated with 154 gamma-ray bursts (GRBs) that were detected by satellite-based gamma-ray experiments in 2009–2010, during the sixth LIGO science run and the second and third Virgo science runs. We perform two distinct searches: a modeled search for coalescences of either two neutron stars or a neutron star and black hole, and a search for generic, unmodeled gravitational-wave bursts. We find no evidence for gravitational-wave counterparts, either with any individual GRB in this sample or with the population as a whole. For all GRBs we place lower bounds on the distance to the progenitor, under the optimistic assumption of a gravitational-wave emission energy of 10−2 M☉ c2 at 150 Hz, with a median limit of 17 Mpc. For short–hard GRBs we place exclusion distances on binary neutron star and neutron-star–black-hole progenitors, using astrophysically motivated priors on the source parameters, with median values of 16 Mpc and 28 Mpc, respectively. These distance limits, while significantly larger than for a search that is not aided by GRB satellite observations, are not large enough to expect a coincidence with a GRB. However, projecting these exclusions to the sensitivities of Advanced LIGO and Virgo, which should begin operation in 2015, we find that the detection of gravitational waves associated with GRBs will become quite possible.

Black hole (networking)

10.1088/0004-637x/760/1/12

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Citations (124)

FERMI GBM OBSERVATIONS OF V404 CYG DURING ITS 2015 OUTBURST

The Astrophysical Journal (2016)

Peter Jenke C. Wilson‐Hodge J. Homan P. Vereš M. S. Briggs

V404 Cygni was discovered in 1989 by the $Ginga$ X-ray satellite during its only previously observed X-ray outburst and soon after confirmed as a black hole binary. On June 15, 2015, the Gamma Ray Burst Monitor (GBM) triggered on a new outburst of V404 Cygni. We present 13 days of GBM observations of this outburst including Earth occultation flux measurements, spectral and temporal analysis. The Earth occultation fluxes reached 30 Crab with detected emission to 100 keV and determined, via hardness ratios, that the source was in a hard state. At high luminosity, spectral analysis between 8 and 300 keV showed that the electron temperature decreased with increasing luminosity. This is expected if the protons and electrons are in thermal equilibrium during an outburst with the electrons cooled by the Compton scattering of softer seed photons from the disk. However, the implied seed photon temperatures are unusually high, suggesting a contribution from another source, such as the jet. No evidence of state transitions is seen during this time period. The temporal analysis reveals power spectra that can be modeled with two or three strong, broad Lorentzians, similar to the power spectra of black hole binaries in their hard state.

Occultation

Black hole (networking)

Spectral Analysis

10.3847/0004-637x/826/1/37

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Citations (28)

Renewed activity of the Be/X-ray binary KS 1947+300

The astronomer's telegram (2015)

Mark H. Finger Peter Jenke C. Wilson‐Hodge

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