RX J0524+42: A New Asynchronous Magnetic CV

AbstractExtensive optical photometry of the canditate magnetic CV RX J0524+42 has uncovered three persistent periods at 157, 146 and 136 minutes, which are the manifestation of the orbital motion of the system, the white dwarf spin and a possible side-band period of the latter. Depending on the interpretation of the 146 or the 136 minute period as the spin period, the system is an asynchronous by 7% or 14% (1 – PSpin/Porb), and therefore intermediate between the near-synchronous polars (< 2%) and the two DQ Her stars with long spin periods (EX Hya and V1025 Cen). Sampling the data over the beat period of 1.4 or 0.7 days reveals a prominent double-humped modulation on the spin period for certain fractions of the beat cycle. The phasing of this modulation strongly suggests that either pole switching onto two diametrically opposed accretion sites, or pole migration is operating in this system. With a period right within the period gap, RX J0524+42 is a key object for MCV evolution: it might be the first transition object between the DQ and AM Her subclasses where the white dwarf is currently in the process of synchronisation.

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X-ray and optical observations of BY Cam

International Astronomical Union Colloquium ◽

10.1017/s0252921100038665 ◽

1996 ◽

Vol 158 ◽

pp. 213-214 ◽

Cited By ~ 1

Author(s):

Gavin Ramsay ◽

Paul A. Mason

Keyword(s):

Power Spectrum ◽

Orbital Period ◽

White Dwarf ◽

Optical Observations ◽

Optical Data ◽

Spin Orbit ◽

Side Band ◽

X Ray ◽

Beat Period ◽

Spin Period

We present preliminary results of an analysis of X-ray and optical data of the asynchronous AM Her star BY Cam [1]. We use X-ray data from EXOSAT (0.1… 50 keV), Ginga (1.5… 50 keV) and ROSAT (0.1…2.0 keV) and optical data obtained during a 45-day campaign in 1994.There are 4 known periods: the orbital period (201.30 m), the spin period of the white dwarf (199.3303 m), a spin-orbit beat period (14.15 d) and a side-band period (197.4 m). The detection of this side-band period lends credence to the theory of [2], who suggest that for a stream accreting, diskless, magnetic CV a frequency, f = 2ωspin − Ωorb (=197.399 m), will appear as a strong spike in the power spectrum for certain systems. Wu & Mason (this volume) discuss a competing model where Pspin = 197.4 m.

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TESS observations of the asynchronous polar CD Ind: mapping the changing accretion geometry

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz992 ◽

2019 ◽

Vol 486 (2) ◽

pp. 2549-2556 ◽

Cited By ~ 2

Author(s):

Pasi Hakala ◽

Gavin Ramsay ◽

Stephen B Potter ◽

Andrew Beardmore ◽

David A H Buckley ◽

...

Keyword(s):

Light Curve ◽

White Dwarf ◽

Pulse Shape ◽

Optical Observations ◽

Mapping Technique ◽

Beat Period ◽

Spin Period ◽

Cyclotron Emission

ABSTRACT We present the results of near continuous TESS optical observations of the asynchronous polar CD Ind (RX J2115−5840). The 27.9 d long light curve, with 2 min resolution, reveals remarkable changes in the magnetic accretion geometry of the system over the 7.3 d beat period. We have modelled the changes in the optical spin period pulse shape using a cyclotron emission mapping technique. The resulting cyclotron emission maps of the magnetic white dwarf reveal how the accretion geometry changes from single- to two-pole accretion and back over the beat cycle. Finally, we present the results from particle-based numerical magnetic accretion simulations, which agree with our interpretation of the changing accretion scenario.

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A magnetic white dwarf with five H α components

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2394 ◽

2019 ◽

Vol 489 (3) ◽

pp. 3648-3654 ◽

Cited By ~ 1

Author(s):

Mukremin Kilic ◽

B Rolland ◽

P Bergeron ◽

Z Vanderbosch ◽

P Benni ◽

...

Keyword(s):

Magnetic Field ◽

White Dwarf ◽

White Dwarfs ◽

Surface Composition ◽

Degenerate System ◽

Inhomogeneous Surface ◽

Optical Photometry ◽

Photometric Variability ◽

Rotational Modulation ◽

Complex Magnetic Field

ABSTRACT G183−35 is an unusual white dwarf that shows an H α line split into five components, instead of the usual three components seen in strongly magnetic white dwarfs. Potential explanations for the unusual set of lines include a double degenerate system containing two magnetic white dwarfs and/or rotational modulation of a complex magnetic field structure. Here, we present time-resolved spectroscopy of G183−35 obtained at the Gemini Observatory. These data reveal two sets of absorption lines that appear and disappear over a period of about 4 h. We also detect low-level (0.2 per cent) variability in optical photometry at the same period. We demonstrate that the spectroscopic and photometric variability can be explained by the presence of spots on the surface of the white dwarf and a change in the average field strength from about 4.6 to 6.2 MG. The observed variability is clearly due to G183−35’s relatively short spin period. However, rotational modulation of a complex magnetic field by itself cannot explain the changes seen in the central H α component. An additional source of variability in the line profiles, most likely due to a chemically inhomogeneous surface composition, is also needed. We propose further observations of similar objects to test this scenario.

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An improved spin-down rate for the proposed white dwarf pulsar AR scorpii

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1901 ◽

2020 ◽

Vol 496 (4) ◽

pp. 4849-4856

Author(s):

Y Gaibor ◽

P M Garnavich ◽

C Littlefield ◽

S B Potter ◽

D A H Buckley

Keyword(s):

White Dwarf ◽

Heterogeneous Data ◽

Colour Index ◽

Data Sets ◽

Emission Model ◽

Arrival Times ◽

Spin Period ◽

Orbital Phase ◽

Period Derivative ◽

Primary Pulse

ABSTRACT We analyse rapid-cadence, multiwavelength photometry of AR Scorpii from three observatories, covering five observing seasons. We measure the arrival times of the system’s beat pulses and use them to compute an updated ephemeris. The white dwarf spin-down rate is estimated with an uncertainty of only 4 per cent. These results confirm, beyond any doubt, that the white dwarf’s spin period is increasing at the rate consistent with by that of Stiller et al. (2018). We study the evolution of the beat pulse’s colour index across the orbit. The colour of the primary pulse maxima varies significantly across the orbit, with the peaks being bluer after superior conjunction than in the first half of the orbit. Specifically, at orbital phase 0.5, the colour index of the primary pulse shows a very sharp discontinuity towards bluer indices. This supports the Potter & Buckley (2018b) synchrotron emission model where the two emitting poles differ significantly in colour. However, no corresponding jump in the colour of the secondary pulses is seen. Furthermore, our analysis reveals that the arrival times of the pulses can differ by as much as 6 s in simultaneous u and r photometry, depending on the binary orbital phase. If left uncorrected, this wavelength-dependent timing offset could lead to erroneous measurements of the spin-period derivative, particularly with heterogeneous data sets.

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The Spin-Resolved He ɪɪ Profile of RX J0558+53

International Astronomical Union Colloquium ◽

10.1017/s0252921100043591 ◽

1997 ◽

Vol 163 ◽

pp. 715-716

Author(s):

E.T. Harlaftis ◽

K. Horne

Keyword(s):

Emission Line ◽

White Dwarf ◽

Gas Flow ◽

Complex Structure ◽

Double Pulse ◽

Spin Period

AbstractWe observed the new intermediate polar RX J0558+53 withthe 4.2m WHT in March 1995. We detect 2–3%% pulsations of the He ɪɪ emission line on the 545s spin period. The spin-resolved Hell spectrogram shows a complex structure with two roughly anti-phased components moving from red to blue (double pulse). This is most likely produced by non-axisymmetric gas flow in the rotating magnetosphere of the white dwarf.

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Bi-Modality in the short-term photometric Properties of the Intermediate Polar V1062 Tau

International Astronomical Union Colloquium ◽

10.1017/s0252921100002153 ◽

2004 ◽

Vol 190 ◽

pp. 243-249

Author(s):

Y. Lipkin ◽

E. M. Leibowitz ◽

M. Orio

Keyword(s):

White Dwarf ◽

Strongly Correlated ◽

Time Resolved ◽

Spin Period ◽

Long Period ◽

System A ◽

Secular Variations ◽

Short Time ◽

Orbital Cycle

AbstractWe conducted coordinated time-resolved observations of the long-period Intermediate Polar V1062 Tauri at the WIYN Observatory in Kitt Peak, Arizona and at Wise Observatory, Israel, and follow-up observations at the second site. We confirm the presence of two previously reported periodicities of the system: a long period (P≈10 h) which was interpreted as the orbital period of the underlying binary system, and a shorter one (P≈ 1 h), which was interpreted as the spin of the white dwarf. Our data also revealed a third photometric periodicity, corresponding to the orbital sideband of the spin period (OSB). The amplitude of the OSB was found to be strongly correlated with the varying brightness of the system at the orbital cycle.Our observations suggest bi-modality in the photometric characteristics of the star. In one mode, the light of V1062 Tau varies with the spin period of the white dwarf, whereas the OSB is undetected. In the other mode, the OSB is the main modulation at short time-scales, and the spin period is absent from the light curve. Switching between the two modes occurred three times during the 10 weeks that spanned our observations. Also, we detected an outburst of 1.1 mag, which lasted between ~1 and ~5 days. In addition to the outburst, secular variations in the brightness of the star (0.3 mag on time scale of a few of tens of days) suggest that the system was in a brief low state during 2002 January.

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SPIN-CYCLE ECLIPSE MAPPING OF THE 71 s OSCILLATIONS IN DQ HERCULIS: REPROCESSING SITES AND THE TRUE WHITE DWARF SPIN PERIOD

The Astrophysical Journal ◽

10.1088/0004-637x/693/1/l16 ◽

2009 ◽

Vol 693 (1) ◽

pp. L16-L18 ◽

Cited By ~ 8

Author(s):

R. K. Saito ◽

R. Baptista

Keyword(s):

White Dwarf ◽

Spin Period

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The Spin-Up Rate of the White Dwarf in GK Per

International Astronomical Union Colloquium ◽

10.1017/s0252921100001937 ◽

2004 ◽

Vol 190 ◽

pp. 120-123

Author(s):

Christopher W. Mauche

Keyword(s):

White Dwarf ◽

Light Curves ◽

Optical Measurements ◽

Pulse Period ◽

X Ray ◽

Spin Period

AbstractWe use hard X-ray light curves measured by the Chandra HETG and RXTE PCA during the late rise and plateau phases of the 2002 March–April outburst of the intermediate polar GK Per to determine that its X-ray pulse period P = 351.332 ± 0.002 s. Combined with previous X-ray and optical measurements of the spin period of the white dwarf, we find that its spin-up rate Ṗ = 0.00027 ± 0.00005 s yr−1.

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Spectroscopic and Photometric Observations of the Magnetic Cataclysmic Variable TX Col

International Astronomical Union Colloquium ◽

10.1017/s0252921100001998 ◽

2004 ◽

Vol 190 ◽

pp. 156-162

Author(s):

Nceba Mhlahlo ◽

Stephen B. Potter ◽

David Buckley

Keyword(s):

Orbital Period ◽

Power Spectra ◽

Radial Velocities ◽

Cataclysmic Variable ◽

Beat Period ◽

Spin Period ◽

Photometric Observations ◽

Optical Wavelengths ◽

First Time

AbstractSimultaneous photometry and spectroscopy of the Intermediate Polar TX Col were obtained in order to investigate its accretion mode and dynamics. The spectroscopic and photometric power spectra of TX Col are observed to change on relatively short timescales. Spectroscopy reveals a dominant periodicity at the orbital period (5.69 hr) and a spin period of 1909 s in radial velocities, while line equivalent widths show a strong periodicity at the beat period (2106 s). It is the first time that the orbital period has been detected in optical wavelengths.

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