Herculis System Research Articles

Detection of the hot white dwarf in the magnetic nova V1500 Cygni with the Hubble Space Telescope

A comprehensive investigation of the AM Herculis-like nova system V1500 Cyg is presented, featuring time-resolved spectrophotometry with the Faint Object Spectrograph (FOS) of the Hubble Space Telescope (HST), coeval optical circular spectropolarimetry and spectrophotometry, and new broadband polarimetry. A revised ephemeris for the rotating white dwarf refines our knowledge of the timescale for synchronization with the orbital period -- and for becoming a bona fide AM Herculis system -- to 170 +/- 8 yrs. Three features of the orbital-phase-dependent spectral energy distribution are keys for understanding the relative contributions of several radiation sources in this system: (1) the brightness and shape of the ultraviolet continuum, which rises abruptly at short wavelengths and shows no significant phase dependence for lambda less than 2200 A, (2) the greater than or equal to 1 mag variations in the optical continuum and emission-line fluxes, and (3) a spectral slope in the optical which is reddest when brightest. These data lead us to conclude that the hot, postnova white dwarf is the dominant source of ultraviolet flux and of the unusually large bolometric luminosity of the system, compared with typical active AM Herculis binaries. The flat mid-ultraviolet spectrum requires a radiation component in addition to the white dwarf photosphere. We consider three possible origins: (1) cyclotron emission, (2) relatively broad, optically thick accretion columns with lumps of dense gas, and/or (3) orbiting debris in a disklike geometry. Observational tests are suggested to distinguish among these alternatives.

Polarimetry and photometry of the new AM Herculis system RE J1844-741

Polarimetry and photometry of the new AM Herculis system RE J1844-741

The Long-Period AM Herculis--like Cataclysmic Variable RXJ 051541+0104.6

We report the discovery of a new catacysmic variable system, RXJ051541+0104.6. The optical spectrum has a blue continuum with superposed H~I and He~I and II emission lines. The soft X-ray spectrum is well fit with a 50~eV black body. The X-ray and optical data are suggestive of an AM~Herculis system. The X-ray light curve shows extreme variability on timescales of seconds, and suggests an orbital period of order 8~hours, nearly twice that of the longest catalogued AM~Her period. When bright, the X-ray light curve breaks up into a series of discrete bursts, which may be due to accretion of dense blobs of material of about 10$^{17}$~gm mass.

Transition in the X-ray light curve of the AM Herculius system V834 Centauri (E1405-451): 1985-1986 EXOSAT observations

view Abstract Citations (7) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Transition in the X-Ray Light Curve of the AM Herculis System V834 Centauri (E1405-451): 1985--1986 EXOSAT Observations Sambruna, Rita M. ; Parmer, Arvind N. ; Chiappetti, Lucio ; Maraschi, Laura ; Treves, Aldo Abstract We analyze the EXOSAT observations of the AM Herculis system V834 Centauri (E1405-451), taken in 1985 March and 1986 August. Archival UV data, simultaneous with the 1986 observations, are also considered. The soft X-ray light curve has a double humped structure, with total eclipse at phi approximately 0.0. It differs significantly from that observed with EXOSAT in 1984. The soft X-ray emission can be described as a black-body of temperature around 10-30 eV, with column density consistent with the interstellar values (5 x 1019- 1.0 x 1020/sq cm). The hard X-ray emission is nearly sinusoidally modulated with a dip at phi approximately 0.0. This component is consistent with thermal bremsstrahlung emission, with rather high column densities (approximately 1022/sq cm. There is indication for absorption variable with orbital phase. At both epochs, evidence for an iron emission feature at approximately 7 keV and with high equivalent widths (approximately 0.8-2 keV) is found. The results are discussed in terms of a scenario of the source suggested by the optical and polarization light curves. Publication: The Astrophysical Journal Pub Date: April 1994 DOI: 10.1086/173944 Bibcode: 1994ApJ...424..947S Keywords: Binary Stars; Iron; Light Curve; Spectrum Analysis; Ultraviolet Astronomy; Ultraviolet Spectra; X Ray Astronomy; X Ray Imagery; Black Body Radiation; Bremsstrahlung; Density (Mass/Volume); Exosat Satellite; Heao 1; Heao 2; Iue; Optical Polarization; Astrophysics; STARS: BINARIES: CLOSE; STARS: INDIVIDUAL CONSTELLATION NAME: V834 CENTAURI; X-RAYS: STARS full text sources ADS | data products SIMBAD (4) MAST (1)

Detection of cyclotron emission features in the infrared spectrum of ST LMi

We present near-infrared spectroscopic observations of the AM Herculis system ST LMi over the wavelength range 1.0-2.5 μm. During the bright phase of the binary cycle, broad and resolvable cyclotron emission harmonics are visible near 1.42, 1.65 and 2.0 μm. We have interpreted the features in terms of an arc-shaped cyclotron emission region consisting of a high-density, high-temperature spot with an extended leading edge of cooler and lower density material. The accretion arc is located close to the weaker pole of magnetic field strength ≃ 12 MG

X-ray to infrared observations of the AM Herculis system E1405 - 451 (V834 Centauri)

view Abstract Citations (9) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-Ray to Infrared Observations of the AM Herculis System E1405-451 (V834 Centauri) Sambruna, R. M. ; Chiappetti, L. ; Treves, A. ; Bonnet-Bidaud, J. M. ; Bouchet, P. ; Maraschi, L. ; Motch, C. ; Mouchet, M. Abstract The Exosat satellite observed E1405 - 451 in the X-ray band in March 1984 during a high state; and simultaneous UV, optical, and IR coverage was obtained with IUE and from ESO telescopes. The low-energy X-ray curve exhibits a minimum at phase zero which is similar to the optical one, with some indication of temperature modulation with orbital phase. On the contrary, the medium-energy X-ray curve exhibits a broad minimum at phase zero, and the column density varies with phase, which may account for the entire modulation of the intensity. Publication: The Astrophysical Journal Pub Date: June 1991 DOI: 10.1086/170159 Bibcode: 1991ApJ...374..744S Keywords: Centaurus Constellation; Infrared Astronomy; Spaceborne Astronomy; X Ray Astronomy; X Ray Binaries; Exosat Satellite; Iue; Ultraviolet Spectra; Astrophysics; STARS: BINARIES; STARS: INDIVIDUAL CONSTELLATION NAME: V834 CENTAURI; ULTRAVIOLET: SPECTRA; X-RAYS: BINARIES full text sources ADS | data products SIMBAD (1) MAST (1) INES (1)

The origin of the 10 megagauss Zeeman features in the AM Herculis system EF Eridani

view Abstract Citations (15) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Origin of the 10 Megagauss Zeeman Features in the AM Herculis System EF Eridani Oestreicher, R. ; Seifert, W. ; Wunner, G. ; Ruder, H. Abstract This paper examines in detail the circularly polarized absorption feature present in the spectrum of EF Eri around 6300 A, reported by Schmidt et al. (1986) and interpreted in terms of magnetically strongly shifted sigma(-) absorption of H-alpha by circumstellar matter close to the surface of the white dwarf. The discovery of the corresponding circularly polarized sigma(+) component is reported, which strongly argues in favor of the above interpretation and confirms a magnetic field value around 10 MG. From an analysis of polarization spectra at different phases, values are obtained for the radial velocities of the absorbing cold circumstellar material and at detailed information on the geometry of the system. In particular, a double change of sign in the circular polarization in both the continuum and the 6300 A feature during one period suggests the presence of two accreting spots with opposite field polarity on the same hemisphere. Publication: The Astrophysical Journal Pub Date: February 1990 DOI: 10.1086/168385 Bibcode: 1990ApJ...350..324O Keywords: Circular Polarization; Magnetic Stars; Stellar Mass Accretion; Stellar Spectra; White Dwarf Stars; Zeeman Effect; H Alpha Line; Radial Velocity; Stellar Envelopes; Stellar Magnetic Fields; Astrophysics; POLARIZATION; STARS: ACCRETION; STARS: INDIVIDUAL CONSTELLATION NAME: EF ERIDANI; STARS: MAGNETIC; STARS: WHITE DWARFS; ZEEMAN EFFECT full text sources ADS | data products SIMBAD (3)

EXO 033319-2554.2: an Eclipsing AM Herculis System Showing Cyclotron Emission Features

view Abstract Citations (68) References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS EXO 033319-2554.2: an Eclipsing AM Herculis System Showing Cyclotron Emission Features Ferrario, Lilia ; Wickramasinghe, D. T. ; Bailey, Jeremy ; Tuohy, I. R. ; Hough, J. H. Abstract We report spectroscopic and circular polarization observations of the soft X-ray binary EXO 033319 - 2554.2 which confirm it as a member of the AM Herculis class with properties similar to VV Puppis. Circular polarization reaching 10% in the blue and less than or equal to 2% in the I band is seen during the bright phase which lasts for 70 minutes of the 126.5 minute orbital cycle. The optical light curve exhibits a narrow eclipse due to the companion star, lasting about 8 minutes and occurring toward the end of the bright phase. The radial velocity curves show a sharp discontinuity due to an eclipse of the line-forming region by the accretion funnel and the white dwarf. Broad resolvable and variable cyclotron harmonics are seen during the bright phase. At the center of the bright phase, the emission peaks are located near 4200 Å, 5200 Å, and 6550 Å, corresponding to a magnetic field B 5.6 × 107 gauss and a temperature T = 20 keV. Detailed theoretical models suggest the presence of a second emission region of field strength B ∼ 2.8 × 107 gauss which can be seen toward the end of the bright phase. We deduce a mass ratio of ∼0.1 and estimate an orbital inclination of ∼88° and a colatitude of ∼14° for the main emission region, assuming that it is a point source and that the duration of the bright phase is Δφ ∼ 0.55. Publication: The Astrophysical Journal Pub Date: February 1989 DOI: 10.1086/167153 Bibcode: 1989ApJ...337..832F Keywords: STARS: ECLIPSING BINARIES; POLARIZATION; STARS: INDIVIDUAL ALPHANUMERIC: EXO 033319-2554.2; STARS: MAGNETIC; STARS: WHITE DWARFS; X-RAYS: BINARIES full text sources ADS | data products SIMBAD (2)

The discovery of the 2 hour modulated X-ray source EXO 033319-2554.2, an AM Herculis system

view Abstract Citations (43) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Discovery of the 2 Hour Modulated X-Ray Source EXO 033319-2554.2, an AM Herculis System Osborne, J. P. ; Giommi, P. ; Angelini, L. ; Tagliaferri, G. ; Stella, L. Abstract The authors report the discovery of EXO 033319-2554.2, a soft X-ray source with 100% modulation of its soft X-ray flux, found during a systematic analysis of all of the EXOSAT soft X-ray data. The soft X-ray light curve, which has an on-off behavior, shows a period of 127.7±3.0 minutes. The bright part of the cycle lasts 0.55 in phase and is cut by an eclipse-like feature lasting 8 minutes. The optical counterpart has a magnitude of mv≈ 18.5. The characteristics of EXO 033319-2554.2 imply that it is an AM Her system. The companion star is probably responsible for the eclipse. Using the lengths of the bright phase and of the eclipse, the authors derive limits to the system geometry. Publication: The Astrophysical Journal Pub Date: May 1988 DOI: 10.1086/185157 Bibcode: 1988ApJ...328L..45O Keywords: Magnetic Stars; Stellar Mass Accretion; White Dwarf Stars; X Ray Binaries; X Ray Sources; Exosat Satellite; Modulation; Stellar Luminosity; Astrophysics; STARS: ACCRETION; STARS: INDIVIDUAL ALPHANUMERIC: EXO 033319-2554.2; STARS: MAGNETIC; STARS: WHITE DWARFS; X-RAYS: BINARIES; X-RAYS: SOURCES full text sources ADS | data products SIMBAD (5)

Phase-resolved IUE observations of AM Herculis system E1405-451

The first phase-resolved IUE observations of the AM Herculis system E1405-451 is reported. The spectra show bright emission lines from N V, C IV, and He II, whose centroids vary drastically during the 101.5 minute period. The radial velocities measured from the line centroids show a sinusoidal variation with a semiamplitude of 300 km/s. An explanation for the observed emission line velocities is considered using a model for the system having inclination i = 60 deg and magnetic colatitude Delta = 20 deg.

2.3 metre multi-colour photometry of a new AM Herculis variable

AbstractWe present UBVRI photometry of the faint and highly erratic cataclysmic variable discovered by Hawkins (1983) from a sequence of U.K. Schmidt plates. Observations using the ANU 2.3 m telescope over two nights in September 1986 show pronounced and repeatable modulation at a binary period of 108.6 min. Dramatic colour differences are evident in the folded UBVRI light curves: in the U band, a single sinusoidal peak is present, while at longer wavelengths, a second red peak dominates at a phase separation of Δϕ = 0.5. This behaviour is strongly suggestive of cyclotron emission from two magnetic accretion funnels in an AM Herculis binary system. Furthermore, the binary period lies in the narrow range of 100-115 minutes that characterizes most of the AM Herculis variables lying on the short side of the 2-3 hour period gap. We conclude therefore that the object is almost certainly a new AM Herculis system, and develop a model in which the blue and red components originate from two non-diametrically opposed cyclotron regions that are characterized by differing electron temperatures and opacities. Predictions are made regarding the linear and circular polarization properties of this important new magnetic variable.

An Emission Line Model for AM Herculis Systems: Application to E1405-451

AbstractThe optical spectra of the AM Herculis binaries are characterized by extremely complex emission lines whose profiles can be resolved into at least three components which are formed in different regions of the accretion stream leading from the companion star towards the magnetic white dwarf. We present a theoretical model which localizes the formation region of the broad emission line component and provides information regarding the structure of this emitting region. In our model the particle trajectories are integrated in a Roche potential and the volume between the white dwarf and the companion has been divided into two different regimes of motion. In one region the gas escapes from the secondary near the inner Lagrange point and is accelerated along a straight line towards the white dwarf. In the other region the magnetic field is strong enought to divert the gas out of the orbital plane and to channel it towards the white dwarfs surface. The model has been used to interpret radial velocity and velocity dispersion data from the AM Herculis system E1405-451.

Time-resolved spectrophotometry of the AM Herculis system E2003 + 225

Time-resolved, medium-resolution photometry is reported for the binary system E2003 + 225 over a complete orbital period in 1984. The object was 1.5-2 mag fainter than when viewed earlier in 1984. The fluxes, equivalent widths and full widths at FWHM for dominant lines are presented for four points in the cycle. A coincidence of emission lines and a 4860 A continuum line was observed for the faster component, which had a 500 km/sec velocity amplitude that was symmetric around the zero line. An aberrant emission line component, i.e., stationary narrow emission lines displaced about 9 A from the rest wavelengths, is modeled as Zeeman splitting of emission from material close to the primary.

Gravitational light deflection effects in eclipsing binary pulsars

A study of the general relativistic deflection of light in an idealized eclipsing binary pulsar system is performed, which indicates that the pulse train of the pulsar is differentially delayed through the course of the orbit in a way distinct from other observed delays. The effect is calculated for the Hercules X-1-HZ Herculis system because it most closely resembles the idealized system used to solve the problem. It is shown to be marginally detectable at present for Her X-1, and may possibly be more evident in other eclipsing X-ray binary pulsars.

On the carbon composition of the ejecta of DQ Herculis

view Abstract Citations (8) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the carbon composition of the ejecta of DQ Her. Ferland, G. J. ; Truran, J. W. Abstract Existing spectrophotometric data for Nova DQ Herculis 1934, spanning virtually its entire postoutburst history, reveal a time dependence of the inferred nebular composition. The observed trends may suggest that the intrinsic carbon abundance is log C/H approximately equal to -1.7, and that the nebula has grown progressively cooler over the past 45 yr. The presence of a source of hard radiation in the DQ Herculis system is suggested. Publication: The Astrophysical Journal Pub Date: September 1980 DOI: 10.1086/158265 Bibcode: 1980ApJ...240..608F Keywords: Carbon Stars; Chemical Composition; Ejecta; Novae; Stellar Mass Ejection; Abundance; Heavy Elements; Stellar Radiation; Time Dependence; Astrophysics full text sources ADS | data products SIMBAD (5)

Masses of the Dwarf M Stars in the MU Herculis System.

Masses of the Dwarf M Stars in the MU Herculis System.