22 research outputs found
Investigating the low-flux states in six Intermediate Polars
No full textAva E. Covington, Aarran W. Shaw, Koji Mukai, Colin Littlefield, Craig O. Heinke, Richard M. Plotkin, Doug Barrett, James Boardman, David Boyd, Stephen M. Brincat, Rolf Carstens, Donald F. Collins, Lewis M. Cook, Walter R. Cooney, David Cejudo Fernández, Sjoerd Dufoer, Shawn Dvorak, Charles Galdies, William Goff, Franz-Josef Hambsch, Steve Johnston, Jim Jones, Kenneth Menzies, Libert A. G. Monard, Etienne Morelle, Peter Nelson, Yenal Öğmen, John W. Rock, Richard Sabo, Jim Seargeant, Geoffrey Stone, Joseph Ulowetz, Tonny VanmunsterWe present optical photometry of six intermediate polars that exhibit transitions to a low-flux state. For four of these systems, DW Cnc, V515 And, V1223 Sgr and RX J2133.7+5107, we are able to perform timing analysis in and out of the low states. We find that, for DW Cnc and V515 And, the dominant periodicities in the light curves change as the flux decreases, indicating a change in the sources' accretion properties as they transition to the low state. For V1223 Sgr we find that the variability is almost completely quenched at the lowest flux, but do not find evidence for a changing accretion geometry. For RX J2133.7+5107, the temporal properties do not change in the low state, but we do see a period of enhanced accretion that is coincident with increased variability on the beat frequency, which we do not associate with a change in the accretion mechanisms in the system.The authors thank the anonymous referee for com ments that helped improve the manuscript. AEC ac knowledges partial support from the Nevada Under graduate Research Award. AWS thanks Jean-Marie
Hameury for fruitful discussions on the outbursts in
V1223 Sgr. We acknowledge with thanks the vari able star observations from the AAVSO International
Database contributed by observers worldwide and used
in this research. AWS thanks Elizabeth Waagen of
the AAVSO for facilitating the inclusion of AAVSO ob servers as co-authorshttps://arxiv.org/abs/2202.0836
Spectral and timing analysis of NuSTAR and Swift/XRT observations of the X-ray transient MAXI J0637-430
No full textWe present results for the first observed outburst from the transient X-ray binary source MAXI J0637–430. This study is based on eight observations from the Nuclear Spectroscopic Telescope Array (NuSTAR) and six observations from the Neil Gehrels Swift Observatory X-Ray Telescope (Swift/XRT) collected from 2019 November 19 to 2020 April 26 as the 3–79 keV source flux declined from 8.2 × 10−10 to 1.4 × 10−12 erg cm−2 s−1. We see the source transition from a soft state with a strong disk-blackbody component to a hard state dominated by a power-law or thermal Comptonization component. NuSTAR provides the first reported coverage of MAXI J0637–430 above 10 keV, and these broadband spectra show that a two-component model does not provide an adequate description of the soft-state spectrum. As such, we test whether blackbody emission from the plunging region could explain the excess emission. As an alternative, we test a reflection model that includes a physical Comptonization continuum. Finally, we also test a spectral component based on reflection of a blackbody illumination spectrum, which can be interpreted as a simple approximation to the reflection produced by returning disk radiation due to the bending of light by the strong gravity of the black hole. We discuss the physical implications of each scenario and demonstrate the value of constraining the source distance
The radius of the quiescent neutron star in the globular cluster M13
No full textX-ray spectra of quiescent low-mass X-ray binaries containing neutron stars can be fit with atmosphere models to constrain the mass and the radius. Mass-radius constraints can be used to place limits on the equation of state of dense matter. We perform fits to the X-ray spectrum of a quiescent neutron star in the globular cluster M13, utilizing data from ROSAT, Chandra and XMM-Newton, and constrain the mass-radius relation. Assuming an atmosphere composed of hydrogen and a 1.4Msun neutron star, we find the radius to be RNS = 12.2+1.5-1.1 km, a significant improvement in precision over previous measurements. Incorporating an uncertainty on the distance to M13 relaxes the radius constraints slightly and we find RNS = 12.3+1.9-1.7 km (for a 1.4Msun neutron star with a hydrogen atmosphere), which is still an improvement in precision over previous measurements, some of which do not consider distance uncertainty. We also discuss how the composition of the atmosphere affects the derived radius, finding that a helium atmosphere implies a significantly larger radius
An elevation of 0.1 light-seconds for the optical jet base in an accreting Galactic black hole system
No full textRelativistic plasma jets are observed in many accreting black holes. According to theory, coiled magnetic fields close to the black hole accelerate and collimate the plasma, leading to a jet being launched. Isolating emission from this acceleration and collimation zone is key to measuring its size and understanding jet formation physics. But this is challenging because emission from the jet base cannot be easily disentangled from other accreting components. Here, we show that rapid optical flux variations from a Galactic black-hole binary are delayed with respect to X-rays radiated from close to the black hole by ~0.1 seconds, and that this delayed signal appears together with a brightening radio jet. The origin of these sub-second optical variations has hitherto been controversial. Not only does our work strongly support a jet origin for the optical variations, it also sets a characteristic elevation of <~10^3 Schwarzschild radii for the main inner optical emission zone above the black hole, constraining both internal shock and magnetohydrodynamic models. Similarities with blazars suggest that jet structure and launching physics could potentially be unified under mass-invariant models. Two of the best-studied jetted black-hole binaries show very similar optical lags, so this size scale may be a defining feature of such systems
Classifying IGR J18007-4146 as an intermediate polar using XMM and NuSTAR
No full textInternational audienceMany new and unidentified Galactic sources have recently been revealed by ongoing hard X-ray surveys. A significant fraction of these have been shown to be the type of accreting white dwarfs known as cataclysmic variables (CVs). Follow-up observations are often required to categorize and classify these sources, and may also identify potentially unique or interesting cases. One such case is IGR J18007-4146, which is likely a CV based on follow-up Chandra observations and constraints from optical/IR catalogues. Utilizing simultaneous XMM-Newton and NuSTAR observations, as well as the available optical/IR data, we confirm the nature of IGR J18007-4146 as an intermediate polar type CV. Timing analysis of the XMM data reveals a periodic signal at 424.4 ± 0.7 s that we interpret as the spin period of the white dwarf. Modelling the 0.3-78 keV spectrum, we use a thermal bremsstrahlung continuum but require intrinsic absorption as well as a soft component and strong Fe lines between 6 and 7 keV. We model the soft component using a single-temperature blackbody with eV. From the X-ray spectrum, we are able to measure the mass of the white dwarf to be , which means IGR J18007-4146 is more massive than the average for magnetic CVs
Classifying IGR J18007-4146 as an intermediate polar using XMM and NuSTAR
No full textMany new and unidentified Galactic sources have recently been revealed by ongoing hard X-ray surveys. A significant fraction of these have been shown to be the type of accreting white dwarfs known as cataclysmic variables (CVs). Follow-up observations are often required to categorize and classify these sources, and may also identify potentially unique or interesting cases. One such case is IGR J18007-4146, which is likely a CV based on follow-up Chandra observations and constraints from optical/IR catalogs. Utilizing simultaneous XMM-Newton and NuSTAR observations, as well as the available optical/IR data, we confirm the nature of IGR J18007-4146 as an intermediate polar type CV. Timing analysis of the XMM data reveals a periodic signal at 424.4 +/- 0.7 s that we interpret as the spin period of the white dwarf. Modeling the 0.3-78 keV spectrum, we use a thermal bremsstrahlung continuum but require intrinsic absorption as well as a soft component and strong Fe lines between 6 and 7 keV. We model the soft component using a single-temperature blackbody with kT = 73 +8/-6 eV. From the X-ray spectrum, we are able to measure the mass of the white dwarf to be 1.06 +0.19/-0.10 Msun, which means IGR J18007-4146 is more massive than the average for magnetic CVs.B.M.C. acknowledges partial support from the National Aeronau tics and Space Administration (NASA) through Chandra Award
Numbers GO7-18030X and GO8-19030X issued by the Chandra
X-ray Observatory Center, which is operated by the Smithsonian
Astrophysical Observatory under NASA contract NAS8-03060.
J.A.T. acknowledges partial support from NASA under NuSTAR
Guest Observer grant 80NSSC21K0064. M.C. acknowledges
financial support from the Centre National d’Etudes Spatiales
(CNES). J.H. acknowledges support from an appointment to the
NASA Postdoctoral Program at the Goddard Space Flight Center,
administered by the Universities Space Research Association
under contract with NASA. R.K. acknowledges support from
the Russian Science Foundation (grant 19-12-00369). This work
made use of data from the NuSTAR mission, a project led by the
California Institute of Technology, managed by the Jet Propulsion
Laboratory, and funded by the National Aeronautics and Space
Administration. This research has made use of the NuSTAR Data
Analysis Software (NuSTARDAS) jointly developed by the ASI
Science Data Center (ASDC, Italy) and the California Institute of
Technology (USA).https://arxiv.org/abs/2201.1117
Classifying IGR J15038-6021 as a magnetic CV with a massive white dwarf
No full textCataclysmic variables (CVs) are binary systems consisting of a white dwarf
(WD) accreting matter from a companion star. Observations of CVs provide an
opportunity to learn about accretion disks, the physics of compact objects,
classical novae, and the evolution of the binary and the WD that may ultimately
end in a type Ia supernova (SN). As type Ia SNe involve a WD reaching the
Chandrasekhar limit or merging WDs, WD mass measurements are particularly
important for elucidating the path from CV to type Ia SN. For intermediate
polar (IP) type CVs, the WD mass is related to the bremsstrahlung temperature
of material in the accretion column, which typically peaks at X-ray energies.
Thus, the IPs with the strongest hard X-ray emission, such as those discovered
by the INTEGRAL satellite, are expected to have the highest masses. Here, we
report on XMM-Newton, NuSTAR, and optical observations of IGR J15038-6021. We
find an X-ray periodicity of 1678+/-2s, which we interpret as the WD spin
period. From fitting the 0.3-79 keV spectrum with a model that uses the
relationship between the WD mass and the post-shock temperature, we measure a
WD mass of 1.36+0.04-0.11 Msun. This follows an earlier study of IGR
J14091-6108, which also has a WD with a mass approaching the Chandrasekhar
limit. We demonstrate that these are both outliers among IPs in having massive
WDs and discuss the results in the context of WD mass studies as well as the
implications for WD mass evolution.Comment: Accepted for publication in MNRA
Using Chandra Localizations and Gaia Distances and Proper Motions to Classify Hard X-Ray Sources Discovered by INTEGRAL
No full textInternational audienceHere, we report on X-ray observations of ten 17–60 keV sources discovered by the International Gamma-Ray Astrophysics Laboratory satellite. The primary new information is sub-arcsecond positions obtained by the Chandra X-ray Observatory. In six cases (IGR J17040-4305, IGR J18017-3542, IGR J18112-2641, IGR J18434-0508, IGR J19504+3318, and IGR J20084+3221), a unique Chandra counterpart is identified with a high degree of certainty, and for five of these sources (all but J19504), Gaia distances or proper motions indicate that they are Galactic sources. For four of these, the most likely classifications are that the sources are magnetic cataclysmic variables (CVs). J20084 could be either a magnetic CV or a high-mass X-ray binary. We classify the sixth source (J19504) as a likely active galactic nucleus (AGN). In addition, we find likely Chandra counterparts to IGR J18010-3045 and IGR J19577+3339, and the latter is a bright radio source and probable AGN. The other two sources, IGR J12529-6351 and IGR J18013-3222, do not have likely Chandra counterparts, indicating that they are transient, highly variable, or highly absorbed
Hitting a New Low: The Unique 28 h Cessation of Accretion in the TESS Light Curve of YY Dra (DO Dra)
No full textWe present the Transiting Exoplanet Surveying Satellite (TESS) light curve of
the intermediate polar YY Draconis (YY Dra, also known as DO Dra). The power
spectrum indicates that while there is stream-fed accretion for most of the
observational period, there is a day-long, flat-bottomed low state at the
beginning of 2020 during which the only periodic signal is ellipsoidal
variation and there is no appreciable flickering. We interpret this low state
to be a complete cessation of accretion, a phenomenon that has been observed
only once before in an intermediate polar. Simultaneous ground-based
observations of this faint state establish that when accretion is negligible,
YY Dra fades to , which we infer to be the magnitude of the
combined photospheric contributions of the white dwarf and its red dwarf
companion. Using survey photometry, we identify additional low states in
2018-2019 during which YY Dra repeatedly fades to -- but never below -- this
threshold. This implies relatively frequent cessations in accretion.
Spectroscopic observations during future episodes of negligible accretion can
be used to directly measure the field strength of the white dwarf by Zeeman
splitting. Separately, we search newly available catalogs of variable stars in
an attempt to resolve the long-standing dispute over the proper identifier of
this system.Comment: 12 pages, 4 figures, submitted to the Astronomical Journal and
reviewed favorabl
Classifying IGR J15038−6021 as a magnetic CV with a massive white dwarf
No full textCataclysmic variables (CVs) are binary systems consisting of a white dwarf (WD) accreting matter from a companion star. Observations of CVs provide an opportunity to learn about accretion discs, the physics of compact objects, classical novae, and the evolution of the binary and the WD that may ultimately end in a Type Ia supernova (SN). As Type Ia SNe involve a WD reaching the Chandrasekhar limit or merging WDs, WD mass measurements are particularly important for elucidating the path from CV to Type Ia SN. For intermediate polar (IP) type CVs, the WD mass is related to the bremsstrahlung temperature of material in the accretion column, which typically peaks at X-ray energies. Thus, the IPs with the strongest hard X-ray emission, such as those discovered by the INTEGRAL satellite, are expected to have the highest masses. Here, we report on XMM–Newton, Nuclear Spectroscopic Telescope Array (NuSTAR), and optical observations of IGR J15038−6021. We find an X-ray periodicity of 1678 ± 2 s, which we interpret as the WD spin period. From fitting the 0.3–79 keV spectrum with a model that uses the relationship between the WD mass and the post-shock temperature, we measure a WD mass of 1.36⁺⁰.⁰⁴₋₀.₁₁
M⊙. This follows an earlier study of IGR J14091−6108, which also has a WD with a mass approaching the Chandrasekhar limit. We demonstrate that these are both outliers among IPs in having massive WDs and discuss the results in the context of WD mass studies as well as the implications for WD mass evolution.JAT acknowledges partial support from National Aeronautics and
Space Administration (NASA) under NuSTAR Guest Observer grant
no. 80NSSC21K0064. BMC acknowledges partial support under
NASA contract no. NNG08FD60C. JH acknowledges support from
an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by the ORAU through a
contract with NASA. MC acknowledges financial support from
the Centre National d’Etudes Spatiales (CNES). RK acknowledges
support from the Russian Science Foundation (grant no. 19-12-
00396). This work made use of data from the NuSTAR mission,
a project led by the California Institute of Technology, managed
by the Jet Propulsion Laboratory, and funded by the NASA. This
research has made use of the NuSTAR Data Analysis Software
(NUSTARDAS) jointly developed by the ASI Science Data Center
(ASDC, Italy) and the California Institute of Technology (USA).
This research made use of PHOTUTILS, an ASTROPY package for
detection and photometry of astronomical sources (Bradley et al.
2022). This research made use of ASTROPY,
7 a community developed core PYTHON package for Astronomy (Astropy Collaboration
2013, 2018).https://academic.oup.com/mnras/article/523/3/4520/719338
