Monitoring the spin up in RX J0806+15 (original) (raw)
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Spin up in RX J0806+15: the shortest period binary
Monthly Notices of the Royal Astronomical Society, 2003
RX J0806+15 has recently been identified as the binary system with the shortest known orbital period. We present a series of observations of RX J0806+15 including new optical observations taken one month apart. Using these observations and archival data we find that the period of this system is decreasing over time. Our measurements implyḟ = 6.11 × 10 −16 Hz/s, which is in agreement with a rate expected from the gravitational radiation for two white dwarfs orbiting at a given period. However, a smaller value ofḟ = 3.14 × 10 −16 Hz/s cannot be ruled out. Our result supports the idea that the 321.5 s period is the orbital period and that the system is the shortest period binary known so far and that it is one of the strongest sources of constant gravitational radiation in the sky. Furthermore, the decrease of the period strongly favours the unipolar inductor (or electric star) model rather than the accretion models.
Confirmation of 1RXS J165443.5–191620 as an intermediate polar and its orbital and spin periods
Astronomy & Astrophysics, 2011
Aims. We investigate the physical nature of the X-ray emitting source 1RXS J165443.5−191620 through optical photometry and time-resolved spectroscopy. Methods. Optical photometry is obtained from a variety of telescopes all over the world spanning ≈27 days. Additionally, time-resolved spectroscopy is obtained from the MDM observatory. Results. The optical photometry clearly displays modulations consistent with those observed in magnetic cataclysmic variables: a low-frequency signal interpreted as the orbital period, a high-frequency signal interpreted as the white dwarf spin period, and an orbital sideband modulation. Our findings and interpretations are further confirmed through optical, time-resolved, spectroscopy that displays Hα radial velocity shifts modulated on the binary orbital period. Conclusions. We confirm the true nature of 1RXS J165443.5−191620 as an intermediate polar with a spin period of 546 seconds and an orbital period of 3.7 hours. In particular, 1RXS J165443.5−191620 is part of a growing subset of intermediate polars, all displaying hard X-ray emission above 15keV, white dwarf spin periods below 30 minutes, and spin-to-orbital ratios below 0.1.
Superhumps and spin-period variations in the intermediate polar RX J2133.7+5107
Monthly Notices of the Royal Astronomical Society, 2017
We report the results of long-term time series photometry on RX J2133.7+5107, an intermediate polar distinguished by its long orbital period (7.14 h) and rapid rotation (571 s) of its white dwarf. The light curves show the presence of a conspicuous modulation with a 6.72-h period, 6.1 ± 0.1 per cent shorter than the orbital period, which we interpret as a (negative) superhump associated with the nodal precession of the accretion disc. This detection may prove a challenge to the idea that superhumps are limited to binaries of short orbital period. Our rotational timings over the 7 yr spanned by our observations show spin-up at a rate of 3.41(2) ms yr −1 or, equivalently, on a timescale |P /Ṗ | = 0.17 × 10 6 yr. The latter is sensibly shorter than the timescale of spin period variations reported for other intermediate polars, possibly due to a greater accretion rate.
Unveiling the nature of the 321s Orbital Period X-ray source RX J0806.3+1527
2003
A nearly simultaneous X-ray/optical (Chandra and VLT) observational campaign of RX J0806.3+1527 has been carried out during November 2001. These observations allowed us to phase the X-ray and optical light curves for the first time. We measured a phase-shift of about 0.5, in good agreement with the presence of two distinct emission regions and with the X-ray irradiation process predictions.
Global observations of the intermediate polar 1RXS J165443. 5-191620
2010
Aims. We investigate the physical nature of the X-ray emitting source 1RXS J165443.5−191620 through optical photometry and time-resolved spectroscopy. Methods. Optical photometry is obtained from a variety of telescopes all over the world spanning ≈27 days. Additionally, time-resolved spectroscopy is obtained from the MDM observatory. Results. The optical photometry clearly displays modulations consistent with those observed in magnetic cataclysmic variables: a low-frequency signal interpreted as the orbital period, a high-frequency signal interpreted as the white dwarf spin period, and an orbital sideband modulation. Our findings and interpretations are further confirmed through optical, time-resolved, spectroscopy that displays Hα radial velocity shifts modulated on the binary orbital period. Conclusions. We confirm the true nature of 1RXS J165443.5−191620 as an intermediate polar with a spin period of 546 seconds and an orbital period of 3.7 hours. In particular, 1RXS J165443.5−191620 is part of a growing subset of intermediate polars, all displaying hard X-ray emission above 15keV, white dwarf spin periods below 30 minutes, and spin-to-orbital ratios below 0.1.
RX J0806+15: the shortest period binary?
Monthly Notices of the Royal Astronomical Society, 2002
The X-ray source RX J0806+15 was discovered using ROSAT, and shows an X-ray light curve with a prominent modulation on a period of 321.5 sec. We present optical observations in which we report the detection of its optical counterpart. We find an optical period consistent with the X-ray period. We do not find convincing evidence for a second period in the data: this implies the 321.5 sec period is the orbital period. As such it would be the shortest period stellar binary system yet known. We discuss the nature of this system. We conclude that an isolated neutron star and an intermediate polar interpretation is unlikely and that a double degenerate interpretation is the most likely.
Timing analysis of the isolated neutron star RX J0720.4-3125
Monthly Notices of the Royal Astronomical Society, 2002
We present a combined analysis of XMM-Newton, Chandra and Rosat observations of the isolated neutron star RXJ0720.4-3125, spanning a total period of ∼ 7 years. We develop a maximum likelihood periodogramme for our analysis based on the ∆Cstatistic and the maximum likelihood method, which are appropriate for the treatment of sparse event lists. Our results have been checked a posteriori by folding a further BeppoSAX-dataset with the period predicted at the time of that observation: the phase is found to be consistent. The study of the spin history and the measure of the spin-down rate is of extreme importance in discriminating between the possible mechanisms suggested for the nature of the X-ray emission. The value ofṖ , here measured for the first time, is ≈ 10 −14 s/s. This value can not be explained in terms of torque from a fossil disk. When interpreted in terms of dipolar losses, it gives a magnetic field of B ≈ 10 13 G, making also implausible that the source is accreting from the underdense surroundings. On the other hand, we also find unlikely that the field decayed from a much larger value (B ≈ 10 15 G, as expected for a magnetar powered by dissipation of a superstrong field) since this scenario predicts a source age of ≈ 10 4 yrs, too young to match the observed X-ray luminosity. The observed properties are more compatible with a scenario in which the source is ≈ 10 6 yrs old, and its magnetic field has not changed substantially over the lifetime.
Optical/infrared spectroscopy and photometry of the short-period binary RX J1914+24
Monthly Notices of the Royal Astronomical Society, 2002
We present observations of the proposed double degenerate polar RX J1914+24. Our optical and infrared spectra show no emission lines. This, coupled with the lack of significant levels of polarisation provide difficulties for a double degenerate polar interpretation. Although we still regard the double degenerate polar model as feasible, we have explored alternative scenarios for RX J1914+24. These include a double degenerate algol system, a neutron star-white dwarf pair and an electrically powered system. The latter model is particularly attractive since it naturally accounts for the lack of both emission lines and detectable polarisation in RX J1914+24. The observed X-ray luminosity is consistent with the predicted power output. If true, then RX J1914+24 would be the first known stellar binary system radiating largely by electrical energy.
Astronomical Journal - ASTRON J, 2002
We have analyzed nearly eight years of MACHO optical photometry of the supersoft X-ray binary RX J0513.9-6951 and derived a revised orbital period and ephemeris. Previously published velocities are reinterpreted using the new ephemeris. We show that the spectroscopic characteristics of the system depend strongly on whether the system is in a high or low optical state. We also discuss the properties of the source's high and low optical states and its long-term light curve. Evidence for an 83.3 day periodicity in the photometry is presented. This paper utilizes public-domain data obtained by the MACHO Project, jointly funded by the US Department of Energy through the University of California, Lawrence Livermore National Laboratory, under contract W-7405-Eng-48, by the National Science Foundation through the Center for Particle Astrophysics of the University of California under coopertative agreement AST 88-09616, and by the Mount Stromlo and Siding Spring Observatory, part of the...