A5049219332- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- High-pressure geophysics and materials
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Mechanics and Biomechanics Studies
- Astronomy and Astrophysical Research
- Advanced Sensor Technologies Research
- Stellar, planetary, and galactic studies
- Scientific Measurement and Uncertainty Evaluation
- Adaptive optics and wavefront sensing
- Galaxies: Formation, Evolution, Phenomena
- Solar and Space Plasma Dynamics
University of Amsterdam
2013-2018
Massachusetts Institute of Technology
2008-2015
Kavli Institute for Particle Astrophysics and Cosmology
2008-2012
Vassar College
2010-2011
We report on an analysis of Rossi X-Ray Timing Explorer data the transient neutron star low-mass X-ray binary (NS-LMXB) XTE J1701–462, obtained during its 2006–2007 outburst. The properties source changed between those various types NS-LMXB subclasses. At high luminosities, switched two Z behavior and at low luminosities we observed a transition from to atoll behavior. These transitions subclasses primarily manifest themselves as changes in shapes tracks color–color (CD) hardness-intensity...
We present Chandra, XMM-Newton, and Swift observations of the quiescent neutron star in transient low-mass X-ray binary MAXI J0556–332. Observations source made during outburst (with Rossi Timing Explorer) reveal tracks its color–color hardness–intensity diagrams that closely resemble those neutron-star Z sources, suggesting J0556–332 had near- or super-Eddington luminosities for a large part ∼16 month outburst. A comparison these with other sources suggests distance 46 ± 15 kpc. Fits to...
Recent work on jets and disk winds in low-mass X-ray binaries (LMXBs) suggests that they are to a large extent mutually exclusive, with observed spectrally hard states soft states. In this paper we use existing literature the luminous neutron star (NS) LMXB GX 13+1, combination archival Rossi Timing Explorer data, show source is likely able produce simultaneously. We find occur same location source's track its color-color diagram. A further study of other LMXBs reveals behavior more common,...
We present Rossi X-Ray Timing Explorer and Swift observations made during the final three weeks of 2006-2007 outburst super-Eddington neutron star (NS) transient XTE J1701-462, as well Chandra XMM-Newton covering first ~800 days subsequent quiescent phase. The source transitioned quickly from active accretion to quiescence, with luminosity dropping by over 3 orders magnitude in ~13 days. spectra obtained quiescence exhibit both a thermal component, presumed originate emission NS surface,...
We present the results of continued monitoring quiescent neutron star low-mass X-ray binary XTE J1701−462 with Chandra and Swift. A new observation from 2010 October extends our tracking surface temperature ≃800 days to ≃1160 since end an exceptionally luminous 19 month outburst. This indicates that crust may still be slowly cooling toward thermal equilibrium core; another further into quiescence is needed verify this. The shape overall curve consistent a broken power law, although...
We present the first multi-wavelength follow-up observations of two candidate gravitational-wave (GW) transient events recorded by LIGO and Virgo in their 2009-2010 science run. The were selected with low latency network GW detectors sky locations observed Swift observatory. Image detection was used to analyze collected electromagnetic data, which found be consistent background. Off-line analysis data alone has also established that show no evidence an astrophysical origin; one them is...
The accreting millisecond X-ray pulsar SAX J1808.4--3658 shows peculiar low luminosity states known as "reflares" after the end of main outburst. During this phase source varies by up to three orders magnitude in less than 1-2 days. lowest observed reaches a value ~1e32 erg/s, only factor few brighter its typical quiescent level. We investigate 2008 and 2005 reflaring state J1808.4-3658 determine whether there is any evidence for change accretion flow with respect perform multiwavelength...
A recent joint XMM-Newton/Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the accreting neutron star Cen X-4 ($L_{\rm X}\sim10^{33}{\rm~erg~s}^{-1}$) revealed a hard power-law component ($\Gamma\sim1$-$1.5$) with relatively low cut-off energy (~10 keV), suggesting bremsstrahlung emission. The physical requirements for combined other observed properties suggest emission comes from boundary layer rather than accretion flow. flow itself is thus undetected (with an upper limit...
A number of studies have revealed variability from neutron star low-mass X-ray binaries during quiescence. Such is not well characterised, or understood, but may be a common property that has been missed due to lack multiple observations. One such source where observed Aql X-1. Here, we analyse 14 Chandra and XMM-Newton observations X-1 in quiescence, covering period approximately 2 years. There clear between the epochs, with most striking feature being flare-like increase flux by factor 5....
When neutron stars reside in transient X-ray binaries, their crustal layers become heated during accretion outbursts and subsequently cool quiescence. Observing modelling this thermal response has yielded valuable insight into the physics of star crusts. However, one unresolved problem is evidence several for an extra energy source, located at shallow depth crust, that not accounted by standard heating models. Its origin remains puzzling, it currently unclear whether additional occurs all...
We present new Chandra X-ray observations of the transient black hole binary MAXI J1659-152 in quiescence. These were made more than one year after end source's 2010-2011 outburst. detect source at a 0.5-10 keV flux 2.8(8)e-15 erg/cm^2/s, which corresponds to luminosity ~1.2e31 (d/ 6 kpc)^2 erg/s. This level, while being lowest has been detected, is within factors ~2 levels seen initial decay outburst and soon major reflare source. The quiescent J1659-152, shortest-orbital-period (~2.4 hr),...
The transient neutron star low-mass X-ray binary and 11 Hz pulsar IGR J17480–2446 in the globular cluster Terzan 5 exhibited an week accretion outburst 2010. Chandra observations performed within five months after end of revealed evidence that crust became substantially heated during episode was subsequently cooling quiescence. This provides rare opportunity to probe structure composition crust. Here, we report on new extend monitoring ≃2.2 yr into We find thermal flux temperature have...
The transient neutron star (NS) low-mass X-ray binary MAXI J0556$-$332 provides a rare opportunity to study NS crust heating and subsequent cooling for multiple outbursts of the same source. We examine {\it MAXI}, Swift}, Chandra}, XMM-Newton} data obtained during after three accretion different durations brightness. report on new outburst III. source has been tracked up $\sim$1800 d end I. Outburst I heated strongly, but no significant reheating was observed II. Cooling from $\sim$333 eV...
We analyze data from five Chandra observations of the spiral galaxy NGC 6946 and three irregular/spiral interacting pair 4485/4490, with an emphasis on investigating long-term variability exhibited by source populations. detect 90 point sources coincident down to luminosities a few times 10^36 erg/s, 38 4485/90 luminosity ~1x10^37 erg/s. Twenty-five (15) in (NGC 4485/90) exhibit (i.e., weeks years) luminosity; 11 (4) are transient candidates. The single ultraluminous X-ray (ULX) all but one...
The quasi-persistent neutron star low-mass X-ray binary MXB 1659−29 went into quiescence in 2001, and we have followed its quiescent evolution since. Observations over the first 4 yr showed a rapid drop flux temperature of atmosphere, interpreted as cooling crust which had been heated during 2.5 outburst. However, observations taken approximately 1400 2400 days were consistent with each other, suggesting reached thermal equilibrium core. Here present new Chandra observation 11 since last...
The X-ray transient XTE J1701–462 was the first source observed to evolve through all known subclasses of low-magnetic-field neutron star low-mass binaries (NS-LMXBs), as a result large changes in its mass accretion rate. To investigate what extent similar evolution is seen other NS-LMXBs we have performed detailed study color–color and hardness–intensity diagrams (CDs HIDs) Cyg X-2, Cir X-1, GX 13+1—three luminous binaries, containing weakly magnetized stars, exhibit strong secular their...
Using the High Resolution Camera on board Chandra X-ray Observatory, we have measured an accurate position for bright persistent neutron star binary and atoll source GX 3+1. At a location that is consistent with this new position, discovered near-infrared (NIR) counterpart to 3+1 in images taken PANIC FourStar cameras Magellan Baade Telescope. The identification of Ks = 15.8 ± 0.1 mag as based presence Br γ emission line NIR spectrum Folded-port InfraRed Echelette spectrograph absolute...
We report on a detailed analysis of the so-called ~1 Hz quasi-periodic oscillation (QPO) in eclipsing and dipping neutron-star low-mass X-ray binary EXO 0748-676. This type QPO has previously been shown to have geometric origin. Our study focuses evolution as source moves through color-color diagram, which it traces out an atoll-source-like track. The frequency increases from ~0.4 hard state ~25 approaches soft state. Combining power spectra based reveals additional features that strongly...
We present NuSTAR observations of the luminous neutron star low-mass X-ray binary (NS LMXB) and Z source GX 5-1. During our three made with separations roughly two days, traced out an almost complete track. extract spectra from various branches fit them a continuum model that has been successfully applied to other sources. Surprisingly, unlike most (luminous) NS-LMXBs observed NuSTAR, we do not find evidence for reflection features in any discuss several possible explanations absence...
When neutron stars reside in transient X-ray binaries, their crustal layers become heated during accretion outbursts and subsequently cool quiescence. Observing modeling this thermal response has yielded valuable insight into the physics of star crusts. However, one unresolved problem is evidence several for an extra energy source, located at shallow depth crust, that not accounted by standard heating models. Its origin remains puzzling, it currently unclear whether additional occurs all...