Global observations of the intermediate polar 1RXS J165443. 5-191620 (original) (raw)
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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.
A 150 MG Magnetic White Dwarf in the Cataclysmic Variable RX J1554.2+2721
The Astrophysical Journal, 2004
We report the detection of Zeeman-split Lyα absorption π and σ + lines in the far-ultraviolet Hubble Space Telescope/Space Telescope Imaging Spectrograph spectrum of the magnetic cataclysmic variable RX J1554.2+2721. Fitting the STIS data with magnetic white dwarf model spectra, we derive a field strength of B ≃ 144 MG and an effective temperature of 17 000 K T eff 23 000 K. This measurement makes RX J1554.2+2721 only the third cataclysmic variable containing a white dwarf with a field exceeding 100 MG. Similar to the other high-field polar AR UMa, RX J1554.2+2721 is often found in a state of feeble mass transfer, which suggests that a considerable number of high-field polars may still remain undiscovered.
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.
Astronomy & Astrophysics, 2014
The system RX J0806.3+1527 (HM Cnc) is a pulsating X-ray source with 100 percent modulation on a period of 321.5 s (5.4 min). This period reflects the orbital motion of a close binary consisting of two interacting white dwarfs. Here we present a series of simultaneous X-ray (0.2-10 keV) and near-ultraviolet (2600 Å and 1928 Å) observations that were carried out with the Swift satellite. In the near-ultraviolet, the counterpart of RX J0806.3+1527 was detected at flux densities consistent with a blackbody with temperature (27 ± 8) × 10 3 K. We found that the emission at 2600 Å is modulated at the 321.5-s period with the peak ahead of the X-ray one by 0.28 ± 0.02 cycles and is coincident within ±0.05 cycles with the optical. This phase-shift measurement confirms that the X-ray hot spot (located on the primary white dwarf) is at about 80 • -100 • from the direction that connects the two white dwarfs. Albeit at lower significance, the 321.5-s signature is also present in the 1928-Å data; at this wavelength, however, the pulse peak is better aligned with that observed at X-rays. We use the constraints on the source luminosity and the geometry of the emitting regions to discuss the merits and limits of the main models for RX J0806.3+1527.
Astronomy and Astrophysics
Time-resolved observations of a 6' x 6' field, containing the position error boxes of the X-ray source 1WGA J1958.2+3232, were performed in June 1999 with the 91 cm Catania telescope, equipped with a Photon Counting Intensified CCD. The star recently proposed as the optical counterpart of the 1WGA J1958.2+3232, exhibited a strong optical modulation with a period compatible with that seen in X-ray (~12 min). The optical modulation was detected again in September and October 1999. These results confirm the identification of the optical counterpart and support the classification of 1WGA J1958.2+3232 as a cataclysmic variable, possibly an Intermediate Polar. Modulation at period twice as large was also found in one observation run, suggesting that the true spin period of the White Dwarf could be 24 min rather than 12 min, thus 1WGA J1958.2+3232 appears to be, among the IPs, the slowest rotator which exhibit double peaked spin profile.
Discovery of the X-Ray Counterpart to the Rotating Radio Transient J1819-1458
Astrophysical Journal, 2006
We present the discovery of the first X-ray counterpart to a Rotating RAdio Transient (RRAT) source. RRAT J1819--1458 is a relatively highly magnetized (B sim5times1013\sim 5\times10^{13}sim5times1013 G) member of a new class of unusual pulsar-like objects discovered by their bursting activity at radio wavelengths. The position of RRAT J1819--1458 was serendipitously observed by the {\sl Chandra} ACIS-I camera in 2005 May. At that position we have discovered a pointlike source, CXOU J181934.1--145804, with a soft spectrum well fit by an absorbed blackbody with NH=7+7−4times1021N_H = 7^{+7}_{-4} \times 10^{21}NH=7+7−4times1021 cm$^{-2}$ and temperature kT=0.12pm0.04kT=0.12 \pm 0.04kT=0.12pm0.04 keV, having an unabsorbed flux of sim2times10−12\sim2 \times 10^{-12}sim2times10−12 ergs cm$^{-2}$ s$^{-1}$ between 0.5 and 8 keV. No optical or infrared (IR) counterparts are visible within 1′′1''1′′ of our X-ray position. The positional coincidence, spectral properties, and lack of an optical/IR counterpart make it highly likely that CXOU J181934.1--145804 is a neutron star and is the same object as RRAT J1819--1458. The source showed no variability on any timescale from the pulse period of 4.26~s up to the five-day window covered by the observations, although our limits (especially for pulsations) are not particularly constraining. The X-ray properties of CXOU J181934.1--145804, while not yet measured to high precision, are similar to those of comparably-aged radio pulsars and are consistent with thermal emission from a cooling neutron star.
Optical outbursts of the cataclysmic variable 1RXS J140429.5+172352
2014
We present the nine-year light curve of the cataclysmic variable 1RXS J140429.5+172352 from 2005 April to 2014 July. We identified four dwarf nova-like outbursts, which typically lasted 3 to 5 days, with an amplitude of 3.1 to 5.3 magnitudes. Time resolved photometry during two outbursts revealed small hump-like structures with peak-to-peak amplitude up to 0.5 mag. They occurred on timescales of 20 min to an hour, but did not exhibit a stable period. We suggest that the system might be an Intermediate Polar.
We report on the first near-simultaneous X-ray and optical observations of RX J0806.3+1527. The source is believed to be a 321 s orbital period ultracompact binary system hosting an X-ray-emitting white dwarf. Data were obtained with Chandra and the ESO Very Large Telescope (VLT) in 2001 November. We found an optical/X-ray phase shift in the periodic modulation of about 0.5, strongly favoring the existence of two distinct emission regions in the two bands (for the pulsed fluxes). The Chandra data allow us to study, for the first time, the spectral continuum of RX J0806.3+1527 in soft X-rays. This was well fitted by a blackbody spectrum with kT~65 eV and hydrogen column density of N_H ~ 5×10^20 cm^-2. The average (unabsorbed) source 0.1-2.5 keV luminosity during the modulation-on phase is L_X ~ 5×10^32 ergs s^-1 (assuming a distance of 500 pc). Such a value is lower than the luminosity expected if stable mass transfer between two white dwarfs were driven by gravitational radiation. Evidence for absorption-like features are present in the phase-averaged spectrum at about 0.53, 0.64, and 1.26 keV, which may be attributed to heavy elements (C and N). We compare and discuss these findings with other binary systems hosting an accreting white dwarf.
The 1–50 keV spectral and timing analysis of IGR J18027-2016: an eclipsing, high mass X-ray binary
Astronomy and Astrophysics, 2005
We report the association of the INTEGRAL source IGR J18027-2016 with the BeppoSAX source SAX J1802.7-2017. IGR J18027-2016 is seen to be a weak, persistent source by the IBIS/ISGRI instrument on board INTEGRAL with an average source count rate of 0.55 counts s −1 (∼6.1 mCrab) in the 20-40 keV band. Timing analysis performed on the ISGRI data identifies an orbital period of 4.5696 ± 0.0009 days and gives an ephemeris of mid-eclipse as, T mid = 52931.37 ± 0.04 MJD. Re-analysis of archival BeppoSAX data has provided a mass function for the donor star, f (m) = 16 ± 1M ⊙ and a projected semimajor axis of a x sin i = 68 ± 1 lt-s. We conclude that the donor is an OB-supergiant with a mass of 18.8-29.3 M ⊙ and a radius of 15.0-23.4 R ⊙ . Spectra obtained by XMM-Newton and ISGRI indicate a high hydrogen column density of N H = 6.8 × 10 22 cm −2 , which suggests intrinsic absorption. The source appears to be a high mass X-ray binary with the neutron star emitting X-rays through wind-fed accretion while in an eclipsing orbit around an OB-supergiant.