Browsing by Author "Coley, Joel B."
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Item Accreting on the edge: a luminosity-dependent cyclotron line in the Be/X-ray Binary 2S 1553-542 accompanied by accretion regimes transition(AAS, 2022-03-15) Malacaria, C.; Bhargava, Y.; Coley, Joel B.; Ducci, L.; Pradhan, P.; Ballhausen, R.; Fuerst, F.; Islam, N.; Jaisawal, G. K.; Jenke, P.; Kretschmar, P.; Kreykenbohm, I.; Pottschmidt, Katja; Sokolova-Lapa, E.; Staubert, R.; Wilms, J.; Wilson-Hodge, C.A.; Wolff, Michael T.Accreting X-ray pulsars (XRPs) 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 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 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, consistently with the interpretation that the source transitions from the sub-critical to the super-critical accretion regime, separated by a critical luminosity of Lᴄᵣᵢₜ≈ 4×10³⁷ erg/s.Item Apparent Superorbital Modulation in 4U 1538-52 at Four Times the Orbital Period(The Astronomer's Telegram, 2018-08-06) Corbet, Robin; Coley, Joel B.; Krimm, Hans A.; Pottschmidt, KatjaItem Continued X-ray Monitoring of LS V +44 17 with NICER, Swift/BAT, and MAXI(The Astronomer's Telegram, 2023-02-17) Coley, Joel B.; Gendreau, Keith; Pottschmidt, Katja; Pal, Sabyasachi; Salganik, Alexander; Mandal, Manoj; Kretschmar, Peter; Jaisawal, Gaurava K.; Malacaria, C.Item Early NICER Observations of the Historic Type II Outburst in 4U 0115+63(The Astronomer's Telegram, 2023-04-04) Coley, Joel B.; Gendreau, Keith; Arzoumanian, Zaven; Pradhan, Pragati; Pottschmidt, Katja; Corbet, Robin; Malacaria, C.; Wilms, Joern; Jenke, P.; Fuerst, Felix; Vasilopoulos, G.; Jaisawal, Gaurava K.; Wolff, Michael T.Item Investigating the superorbital modulations in 4U 1909+07, IGR J16418-4532 and IGR J16479-4514 with Swift XRT, BAT and NuSTAR observations(IOP Publishing, 2023-05-04) Islam, Nazma; Corbet, Robin; Coley, Joel B.; Pottschmidt, Katja; Fuerst, FelixA puzzling variety of superorbital modulations has been discovered in several supergiant high mass X-ray binaries (sgHMXBs). To investigate the mechanisms driving these superorbital modulations, we have analyzed long-term Neil Gehrels Swift Observatory (Swift) Burst Alert Telescope (BAT) observations of three sgHMXBs: 4U 1909 + 07, IGR J16418–4532, and IGR J16479–4514, and constructed their dynamic power spectra and superorbital intensity profiles. These Swift BAT observations are complemented by pointed Swift X-ray Telescope (XRT) and Nuclear Spectroscopic Telescope Array (NuSTAR) observations performed near the predicted maximum and minimum phase of a single superorbital cycle for each of these sources. The BAT dynamic power spectra show changes in the strength of the superorbital modulation on timescales of years, with either the peak at the fundamental frequency and/or the second harmonic present at different times for all three sources. The pointed Swift XRT and NuSTAR observations show no significant differences between the pulse profiles and spectral parameters at the superorbital maximum and minimum phase. This is likely due to the fact the superorbital modulation had weakened significantly during the times when the NuSTAR observations were carried out for all three sources. The results from the Swift XRT, BAT, and NuSTAR analysis indicate the possible presence of multiple corotating interaction regions (CIRs) in the stellar winds of the supergiant stars, although a structured stellar wind from the supergiant star due to tidal oscillations cannot be ruled out.Item Low-luminosity accretion in Cep X-4 during the transition to quiescence observed by NuSTAR(The Astronomer's Telegram, 2023-08-03) Sokolova-Lapa, E.; Zalot, N.; Stierhof, J.; Zainab, A.; Wilms, J.; Ballhausen, R.; Malacaria, C.; Kretschmar, P.; Escorial, A. Rouco; Pottschmidt, Katja; Fuerst, F.; Ferrigno, Carlo; Pradhan, P.; Coley, Joel B.; XMAG collaborationItem NICER monitoring of the outburst from the transient X-ray pulsar XTE J1829-098(The Astronomer's Telegram, 2022-08-17) Wolff, Michael T.; Ray, Paul S.; Ng, Mason; Pradhan, Pragati; Pottschmidt, Katja; Corbet, Robin; Gendreau, Keith C.; Jaisawal, Gaurava K.; Sanna, Andrea; Coley, Joel B.; Guillot, S.; Malacaria, C.; Wilms, J.Item NuSTAR looks at Swift J0243.6+6124 during the rise of the 2023 outburst(The Astronomer's Telegram, 2023-07-18) Pradhan, Pragati; Pike, Sean; Coley, Joel B.; Pottschmidt, Katja; Malacaria, C.; Ng, Mason; Jaisawal, Gaurava K.; Escorial, A. Rouco; Kretschmar, Peter; XMAG collaborationItem The Orbital Parameters of the Eclipsing High-mass X-Ray Binary Pulsar IGR J16493–4348 from Pulsar Timing(IOP Publishing, 2019-03-07) Pearlman, Aaron B.; Coley, Joel B.; Corbet, Robin; Pottschmidt, KatjaIGR J16493–4348 is an eclipsing supergiant high-mass X-ray binary (sgHMXB), where accretion onto the compact object occurs via the radially outflowing stellar wind of its early B-type companion. We present an analysis of the system's X-ray variability and periodic modulation using pointed observations (2.5–25 keV) and Galactic bulge scans (2–10 keV) from the Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA), along with Swift Burst Alert Telescope (BAT) 70-month snapshot (14–195 keV) and transient monitor (15–50 keV) observations. The orbital eclipse profiles from the PCA scan and BAT light curves are modeled using asymmetric and symmetric step and ramp functions. We obtain an improved orbital period measurement of 6.7828 ± 0.0004 days from an observed minus calculated (O–C) analysis of mid-eclipse times derived from the BAT transient monitor and PCA scan data. No evidence is found for the presence of a strong photoionization or accretion wake. We refine the superorbital period to 20.067 ± 0.009 days from the discrete Fourier transform (DFT) of the BAT transient monitor light curve. A pulse period of 1093.1036 ± 0.0004 s is measured from a pulsar timing analysis using pointed PCA observations spanning ∼1.4 binary orbits. We present pulse times of arrival (ToAs), circular and eccentric timing models, and calculations of the system's Keplerian binary orbital parameters. We derive an X-ray mass function of fₓ (M) =13.2⁺².⁴₋₂.₅ M⊙ and find a spectral type of B0.5 Ia for the supergiant companion through constraints on the mass and radius of the donor. Measurements of the eclipse half-angle and additional parameters describing the system geometry are provided.Item Rebrightening of 1 Crab from LS V+44 17 observed by Swift/BAT and NICER(The Astronomer's Telegram, 2023-01-20) Pal, Sabyasachi; Mandal, Manoj; Gendreau, Keith; Malacaria, Christian; Iwakiri, Wataru Buz; Arzoumanian, Zaven; Jaisawal, Gaurava K.; Sanna, Andrea; Wolff, Michael T.; Ferrara, Elizabeth C.; Salganik, Alexander; Coley, Joel B.; Pottschmidt, Katja; Steiner, James F.; Ng, Mason; Ray, Paul S.Item A Study of the 20 day Superorbital Modulation in the High-mass X-Ray Binary IGR J16493-4348(IOP Publishing, 2019-07-01) Coley, Joel B.; Corbet, Robin; Fürst, Felix; Huxtable, Gregory; Krimm, Hans A.; Pearlman, Aaron B.; Pottschmidt, KatjaWe report on Nuclear Spectroscopic Telescope Array (NuSTAR), Neil Gehrels Swift Observatory (Swift) X-ray Telescope (XRT), and Swift Burst Alert Telescope (BAT) observations of IGR J16493-4348, a wind-fed supergiant X-ray binary showing significant superorbital variability. From a discrete Fourier transform of the BAT light curve, we refine its superorbital period to be 20.058 ± 0.007 days. The BAT dynamic power spectrum and a fractional root mean square analysis both show strong variations in the amplitude of the superorbital modulation, but no observed changes in the period are found. The superorbital modulation is significantly weaker between MJD 55,700 and MJD 56,300. The joint NuSTAR and XRT observations, which were performed near the minimum and maximum of one cycle of the 20 day superorbital modulation, show that the flux increases by more than a factor of two between superorbital minimum and maximum. We find no significant changes in the 3–50 keV pulse profiles between superorbital minimum and maximum, which suggests a similar accretion regime. Modeling the pulse-phase-averaged spectra we find a possible Fe Kα emission line at 6.4 keV at superorbital maximum. This feature is not significant at superorbital minimum. While we do not observe any significant differences between the pulse-phase-averaged spectral continua apart from the overall flux change, we find that the hardness ratio near the broad main peak of the pulse profile increases from superorbital minimum to maximum. This suggests the spectral shape hardens with increasing luminosity. We discuss different mechanisms that might drive the observed superorbital modulation.Item Superorbital Modulation in the High-Mass X-ray Binary 4U 1538-52, and Possible Modulation in IGR J16393-4643(AAS) Corbet, Robin; Coley, Joel B.; Krimm, Hans A.; Pottschmidt, Katja; Roche, PaulHard X-ray observations with the Neil Gehrels Swift Observatory Burst Alert Telescope (BAT) reveal superorbital modulation in the wind-accreting supergiant high-mass X-ray binary (HMXB) 4U 1538-52 at a period of 14.9130 +/- 0.0026 days that is consistent with four times the 3.73 day orbital period. These periods agree with a previously suggested correlation between superorbital and orbital periods in similar HMXBs. During the ~14 years of observations the superorbital modulation changes amplitude, and since ~MJD 57,650 it was no longer detected in the power spectrum, although a peak near the second harmonic of this was present for some time. Measurements of the spin period of the neutron star in the system with the Fermi Gamma-ray Burst Monitor show a long-term spin-down trend which halted towards the end of the light curve, suggesting a connection between dP(spin)/dt and superorbital modulation, as proposed for 2S 0114+650. However, an earlier torque reversal from INTEGRAL observations was not associated with superorbital modulation changes. B and V band photometry from the Las Cumbres Observatory reveals orbital ellipsoidal photometric variability, but no superorbital optical modulation. However the photometry was obtained when the 14.9130 day period was no longer detected in the BAT power spectrum. We revisit possible superorbital modulation in BAT observations of IGR J16393-4643 but cannot conclusively determine whether this is present, although is not persistent. We consider superorbital modulation mechanisms, and suggest that the Corotating Interaction Region model, with small deviations from orbital synchronization, appears promising.Item Support for a 244 day Period in XTE J1829-098 from Swift BAT, MAXI and RXTE PCA Observations(The Astronomer's Telegram, 2022-09-12) Corbet, Robin; Coley, Joel B.; Gendreau, Keith C.; Guillot, S.; Islam, Nazma; Jaisawal, Gaurava K.; Malacaria, C.; Ng, Mason; Pottschmidt, Katja; Pradhan, Pragati; Ray, Paul S.; Sanna, Andrea; Wilms, J.; Wolff, Michael T.Item The X-Ray Pulsar XTE J1858+034 Observed with NuSTAR and Fermi/GBM: Spectral and Timing Characterization plus a Cyclotron Line(AAS, 2021-03-15) Malacaria, C.; Kretschmar, P.; Madsen, Kristin; Wilson-Hodge, C. A.; Coley, Joel B.; Jenke, P.; Lutovinov, Alexander A.; Pottschmidt, Katja; Tsygankov, Sergey S.; Wilms, J.Accreting X-ray pulsars (XRPs) undergo luminous X-ray outbursts during which the spectral and timing behavior of the neutron star can be studied in detail. We analyze a NuSTAR observation of the XRP XTE J1858+034 during its outburst in 2019. The spectrum is fit with a phenomenological, a semiempirical, and a physical spectral model. A candidate cyclotron line is found at 48 keV, implying a magnetic field of 5.4 × 1012 G at the site of emission. This is also supported by the physical best-fit model. We propose an orbital period of about 81 days based on the visual inspection of the X-ray outburst recurrence time. Based on Fermi/GBM data, the standard disk accretion-torque theory allowed us to infer a distance of 10.9 ± 1.0 kpc. Pulse profiles are single-peaked and show a pulsed fraction that is strongly energy-dependent at least up to 40 keV.