STROBE-X: X-ray Timing and Spectroscopy on Dynamical Timescales from Microseconds to Years

Ray, Paul S.; Arzoumanian, Zaven; Ballantyne, D. R.; Bozzo, E.; Brandt, S.; Brenneman, Laura; Chakrabarty, Deepto; Christophersen, M.; DeRosa, Alessandra; Feroci, M.; Gendreau, Keith C.; Hartmann, D. H.; Hernanz, M.; Jenke, P.; Kara, Erin; Maccarone, Tom; McDonald, Michael; Nowak, Michael A.; Phlips, Bernard F.; Remillard, Ron; Stevens, Abigail; Tomsick, John A.; Watts, Anna L.; Wilson-Hodge, C.; Wood, K. S.; Zane, S.; Ajello, M.; Alston, Will; Altamirano, D.; Antoniou, Vallia; Arur, Kavitha; Ashton, Dominic; Auchettl, Katie; Ayres, T. R.; Bachetti, Matteo; Baloković, Mislav; Baring, Matthew G.; Baykal, A.; Begelman, M.; Bhat, N. R.; Bogdanov, Slavko; Briggs, M. S.; Bulbul, Esra; Bult, Petrus; Burns, E.; Cackett, E.; Campana, R.; Caspi, Amir; Cavecchi, Y.; Chenevez, J.; Cherry, J. Michael; Corbet, R. H. D.; Corcoran, M. F.; Corsi, A.; Degenaar, N.; Drake, J. J.; Eikenberry, S. S.; Enoto, T.; Fragile, Chris; Fuerst, F.; Gandhi, P.; Garcı́a, Javier; Goldstein, A.; Gonzalez, Anthony H.; Grefenstette, Brian W.; Grinberg, V.; Grossan, B.; Guillot, Sebastien; Güver, T.; Haggard, Daryl; Heinke, C. O.; Heinz, Sebastian; Hemphill, Paul; Homan, J.; Hui, C. M.; Huppenkothen, Daniela; Ingram, Adam; Irwin, Jimmy A.; Jaisawal, Gaurava; Jaodand, Amruta; Kalemci, Emrah; Kaplan, David L.; Keek, L.; Kennea, J. A.; Kerr, M.; Klis, M. van der; Kocevski, D.; Koss, Mike; Kowalski, Adam F.; Dong, Lei; Lamb, Fred S.; Laycock, S.; Lazio, Joseph; Lazzati, Davide; Longcope, D. W.; Loewenstein, Michael; Maitra, Dipankair; Majid, Walid A.; Maksym, W. Peter; Malacaria, C.; Margutti, R.; Martindale, A.; McHardy, I. M.; Meyer, M.; Middleton, Matt; Miller, J. M.; Miller, M. Coleman; Motta, S.; Neilsen, Joey; Nelson, Tommy; Noble, Scott C.; O’Brien, P. T.; Osborne, J. P.; Osten, Rachel A.; Özel, Feryal; Palliyaguru, Nipuni; Pasham, Dheeraj; Patruno, A.; Pelassa, Vero; Πετροπούλου, Μαρία; Pilia, M.; Pohl, M.; Pooley, David; Prescod-Weinstein, Chanda; Psaltis, Dimitrios; Raaijmakers, G.; Reynolds, C. S.; Riley, Thomas E.; Salvesen, Greg; Santangelo, A.; Scaringi, Simone; Schanne, S.; Schnittman, Jeremy D.; Smith, David J.; Smith, Krista Lynne; Snios, Bradford; Steiner, Andrew W.; Steiner, J. E.; Stella, L.; Strohmayer, Tod E.; Sun, Min; Tauris, T. M.; Taylor, Corbin; Tohuvavohu, A.; Vacchi, A.; Vasilopoulos, Georgios; Veledina, Alexandra; Walsh, Jonelle L.; Weinberg, Nevin N.; Wilkins, D. R.; Willingale, R.; Wilms, J.; Winter, L. M.; Wolff, Michael; Zand, J. in ’t; Zezas, A.; Zhang, Bing; Zoghbi, A.

doi:10.48550/arxiv.1903.03035

Cited by 38 publications

(46 citation statements)

References 274 publications

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“…Given that the handful of persistent PULXs that are known lie at distances of a few Mpc, their detailed study is hampered by limitations of current X-ray observatories. While this might change with the launch of future proposed missions (e.g., STROBE-X and eXTP, Ray et al 2019;Zhang et al 2019), at the moment the best laboratories to study super-Eddington accretion are major outbursts of BeXRBs in our local galaxy group. Perhaps the brightest X-ray outburst of a BeXRB was the 2017 outburst of the Galactic pulsar Swift J0243.6+6124 making it the first Galactic PULX (luminosity of ∼2×10 39 erg s −1 ; Wilson-Hodge et al 2018).…”

Section: Introductionmentioning

confidence: 99%

The 2019 super-Eddington outburst of RX J0209.6−7427: detection of pulsations and constraints on the magnetic field strength

Vasilopoulos

Ray

Gendreau

et al. 2020

Monthly Notices of the Royal Astronomical Society

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In November 2019, MAXI detected an X-ray outburst from the known Be X-ray binary system RX J0209.6−7427 located in the outer wing of the Small Magellanic Cloud. We followed the outburst of the system with NICER which led to the discovery of X-ray pulsations with a period of 9.3 s. We analyzed simultaneous X-ray data obtained with NuSTAR and NICER allowing us to characterize the spectrum and provide an accurate estimate of its bolometric luminosity. During the outburst the maximum broadband X-ray luminosity of the system reached 1-2×10 39 erg s −1 , thus exceeding by about one order of magnitude the Eddington limit for a typical 1.4 M ⊙ mass neutron star (NS). Monitoring observations with Fermi/GBM and NICER allowed us to study the spin evolution of the NS and compare it with standard accretion torque models. We found that the NS magnetic field should be of the order of 3×10 12 G. We conclude that RX J0209.6−7427 exhibited one of the brightest outbursts observed from a Be X-ray binary pulsar in the Magellanic Clouds, reaching similar luminosity level to the 2016 outburst of SMC X-3. Despite the super-Eddington luminosity of RX J0209.6−7427, the NS appears to have only a moderate magnetic field strength.

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Section: Introductionmentioning

confidence: 99%

The 2019 super-Eddington outburst of RX J0209.6−7427: detection of pulsations and constraints on the magnetic field strength

Vasilopoulos

Ray

Gendreau

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…The detection of pulsations, if they are indeed of thermal origin, seems to confirm that for the majority of MSPs the main source of their X-ray emission comes from their heated polar caps. The findings of this Letter also make these MSPs promising targets for follow-up X-ray observations with NICER and/or with future proposed telescopes such as STROBE-X (Ray et al 2019a) or eXTP (Watts et al 2019), to enable constraints on the NS massradius relation and the dense matter EOS via the pulse profile modeling technique. The binary MSPs with independent mass measurements from radio timing, PSR J0751+1807 and PSR J1012+5307, are of particular interest in this sense since they can offer more stringent constraints on the NS radius.…”

Section: Discussionmentioning

confidence: 82%

“…An additional science goal of the mission is to study the X-ray flux modulations of pulsars and discover new sources of Xray pulsations (Ray et al 2018). This includes searching for X-ray pulsations from NSs that would be suitable for pulse profile modeling with NICER or with future missions (e.g., STROBE-X, Ray et al 2019a;eXTP, Watts et al 2019; or the Athena X-ray Observatory, Nandra et al 2013). Prior to the launch of NICER, only four thermally-dominated MSPs were known to exhibit highly significant X-ray pulsations: PSR J0437−4715 (Becker & Trümper 1999;Zavlin et al 2002;Bogdanov 2013), PSR J0030+0451 (Becker & Aschenbach 2002;Bogdanov et al 2008), PSR J2124−3358 (Becker & Trümper 1999;Zavlin 2006;Bogdanov et al 2008) and PSR J1024−0719 (Zavlin 2006).…”

Section: Introductionmentioning

confidence: 99%

NICER X-Ray Observations of Seven Nearby Rotation-powered Millisecond Pulsars

Guillot

Kerr

Ray

et al. 2019

ApJL

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NICER observed several rotation-powered millisecond pulsars to search for or confirm the presence of X-ray pulsations. When broad and sine-like, these pulsations may indicate thermal emission from hot polar caps at the magnetic poles on the neutron star surface. We report confident detections (≥ 4.7σ after background filtering) of X-ray pulsations for five of the seven pulsars in our target sample: PSR J0614−3329, PSR J0636+5129, PSR J0751+1807, PSR J1012+5307, and PSR J2241−5236, while PSR J1552+5437 and PSR J1744−1134 remain undetected. Of those, only PSR J0751+1807 and PSR J1012+5307 had pulsations previously detected at the 1.7σ and almost 3σ confidence levels, respectively, in XMM-Newton data. All detected sources exhibit broad sine-like pulses, which are indicative of surface thermal radiation. As such, these MSPs are promising targets for future Xray observations aimed at constraining the neutron star mass-radius relation and the dense matter equation of state using detailed pulse profile modeling. Furthermore, we find that three of the detected millisecond pulsars exhibit a significant phase offset between their X-ray and radio pulses.

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“…It is hoped that future work will treat the oscillations of the optically thick levitating atmospheres, especially in the context of radius expansion X-ray bursts. Regardless of this, future instruments with high time resolution and good sensitivity to higher energy photons, such as STROBE-X (Ray et al 2019) and eXTP (Zhang et al 2016), may detect optically thin atmospheres, and their oscillations, outside Eddington luminosity neutron stars.…”

Section: Further Discussionmentioning

confidence: 99%

“…Planned, sensitive X-ray instruments e.g. STROBE-X (Ray et al 2019) and eXTP (Zhang et al 2016), should be able to measure the frequencies to exquisite precision, given by the ratio of the oscillation period to the time-scale for frequency change (as the luminosity varies), which should be less than one part in a hundred. To be conservative, in the remainder of this section we assume a frequency error of 3%.…”

Section: Error Budgetmentioning

confidence: 99%

Atmospheric oscillations provide simultaneous measurement of neutron star mass and radius

Bollimpalli

Wielgus

Abarca

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Neutron stars with near-Eddington observable luminosities were shown to harbour levitating atmospheres, suspended above their surfaces. We report a new method to simultaneously measure the mass and radius of a neutron star based on oscillations of such atmospheres. In this paper, we present an analytic derivation of a family of relativistic, oscillatory, spherically symmetric eigenmodes of the optically and geometrically thin levitating atmospheres, including the damping effects induced by the radiation drag. We discover characteristic maxima in the frequencies of the damped oscillations and show that from a measurement of the frequency maximum and of the luminosity one can determine the mass and radius of the neutron star. In addition to the stellar parameters, observation of the variation of the oscillation frequencies with flux would allow us to estimate the stellar luminosity and therefore the distance to the source with an accuracy of a few per cent. We also show that the ratio of any two undamped eigenfrequencies depends only on the adiabatic index of the atmosphere, while for the damped eigenfrequencies, this ratio varies with the luminosity. The damping coefficient is independent of the mode number of the oscillations. Signatures of the dynamics of such atmospheres will be reflected in the source's X-ray light curves.

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STROBE-X: X-ray Timing and Spectroscopy on Dynamical Timescales from Microseconds to Years

Cited by 38 publications

References 274 publications

The 2019 super-Eddington outburst of RX J0209.6−7427: detection of pulsations and constraints on the magnetic field strength

The 2019 super-Eddington outburst of RX J0209.6−7427: detection of pulsations and constraints on the magnetic field strength

NICER X-Ray Observations of Seven Nearby Rotation-powered Millisecond Pulsars

Atmospheric oscillations provide simultaneous measurement of neutron star mass and radius

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