Spectroscopic Period Research Articles

Dynamical Evidence for a Black Hole in the Microquasar XTE J1550−564

Optical spectroscopic observations of the companion star (type G8IV to K4III) in the microquasar system XTE J1550-564 reveal a radial velocity curve with a best fitting spectroscopic period of P_sp = 1.552 +/- 0.010 days and a semiamplitude of K_2 = 349 +/- 12 km/s. The optical mass function is f(M) = 6.86 +/- 0.71 solar masses (1 sigma). We tentatively measure the rotational velocity of the companion star to be V_rot*sin(i) = 90 +/- 10 km/s, which when taken at face value implies a mass ratio of Q = M_1/M_2 = 6.6 (+2.5 / -1.6) (1 sigma), using the above value of K_2. We derive constraints on the binary parameters from simultaneous modelling of the ellipsoidal light and radial velocity curves. We find the most likely value of the mass of the compact object is 9.41 solar masses with a 1 sigma range of 8.36 < M_1 < 10.76 solar masses. If we apply our tentative value of V_rot*sin(i) = 90 +/- 10 km/s as an additional constraint in the ellipsoidal modelling, we find the most likely value of the mass of the compact object is 10.56 solar masses with a 1 sigma range of 9.68 < M_1 < 11.58 solar masses. In either case the mass of the compact object is well above the maximum mass of a stable neutron star, and we therefore conclude XTE J1550-564 contains a black hole.

The long-period orbit of the dwarf nova V630 Cassiopeiae

We present extensive spectroscopy and photometry of the dwarf nova V630 Cassiopeiae. A late-type (K4-5) absorption spectrum is easily detectable, from which we derive the orbital parameters. We find a spectroscopic period of P=2.56387 +/- (4 times 10^{-5}) days and a semiamplitude of K_2=132.9 +/- 4.0 km/s. The resulting mass function, which is a firm lower limit on the mass of the white dwarf, is then f(M)=0.624 +/- 0.056 solar masses. The secondary star is a ``stripped giant'', and using relations between the core mass and the luminosity and the core mass and the radius we derive a lower limit of M_2 > 0.165 solar masses for the secondary star. The rotational velocity of the secondary star is not resolved in our spectra and we place a limit of V_rot*sin(i) 0.165 solar masses and V_rot*sin(i) < 40 km/s yields a white dwarf mass of M_1=0.977^{+0.168}_{-0.098} solar masses and a secondary star mass of M_2=0.172^{+0.029}_{-0.012} solar masses (90 per cent confidence limits). Our findings confirm the suggestion of Warner (1994), namely that V630 Cas is rare example of a dwarf nova with a long orbital period.

Low-frequency variability and binarity of theδScuti star XX Pyx

We analyse 147 h of single-site CCD time series photometry of the multiperiodic low-amplitude δ Scuti star XX Pyx with the aim of investigating variability at low frequencies. Part of the data were obtained in the context of the 1998 multisite campaign on XX Pyx, the results of which were described by Handler et al. We find that periodic low-frequency variations are present in the XX Pyx light curves, and we detect two frequencies at fA=0.8695 cycle d−1 and fB=1.7352 cycle d−1, respectively, with amplitudes of 4.5 and 5.4 mmag. The low-frequency variability is intrinsic to XX Pyx, and cannot be attributed to instrumental or atmospheric effects. The near 2:1 ratio of the frequencies leads us to suggest that XX Pyx is a δ Scuti star in a binary system, with a possible binary period of 27.6 h. This is strongly supported by the detection of radial velocity variations from the re-analysis of echelle spectra obtained by Handler et al. However, in the absence of a spectroscopic period, alternative explanations of the photometric variability involving pulsation are also possible; the variations occur close to possible combination frequencies of the short-period (δ Scuti) variations, but high Q values of 0.57 and 0.28 d suggest that the variations are not a result of normal (p-)modes. They could possibly be due to g-modes excited to observable amplitudes as a result of resonance effects. Surface features (spots) are unlikely to be the cause of the variations. We searched for combination frequencies ( fi−fj), f being the normal δ Scuti frequencies detected by Handler et al., but failed to detect any.

The dwarf nova WX Cet: a clone of WZ Sge or a pretender?

We present charge-coupled device (CCD) photometry of WX Cet in quiescence. Apart from the flickering which is characteristic to cataclysmic binaries, our data also reveal the periodic modulation of the brightness of WX Cet with a period of 0.058 27±0.000 02, with further restrictions on it. This period is derived from our data alone, but it agrees, within errors, with the spectroscopic period of Thorstensen et al. Hence the most likely spectroscopic and photometric periods are identical and correspond to the orbital motion. Our data were obtained during two observational seasons in 1990 and 1998. In the former season we observed what appears to be the ordinary orbital hump. However, in 1998 we observed both single- and double-hump orbital modulation. Several authors have noted the similarities between WX Cet and WZ Sge: the occurrence of rare, large-amplitude, long-lasting superoutbursts with superhump modulation, and the slow rate of decline. Both stars have similar, extremely short orbital periods. We recorded further similarities: the orbital modulation of brightness, with switching between single- and double-hump light curves. Patterson noticed that superhump excesses in WX Cet and WZ Sge are different in that they may fall on different evolutionary branches (pre-period minimum versus post-period minimum). We demonstrate that the masses of their white dwarfs differ by a factor of two.

Multimode Detections from Surveys

AbstractIn this study we present an overview of the search for multiple frequencies in variable Be stars from surveys. We review the recent ground-based photometric surveys and conclude from them that multiperiodicity is not detected. The photometric experiment on board Hipparcos, on the other hand, does allow us to derive multiple periods for a few Be stars. We present the results of our frequency searches in the Hipparcos data for 50 λ Eri stars.Further we review the recent spectroscopic campaigns dedicated to some stars. It seems that all of these campaigns point to multiperiodic phenomena, although for most of them the time base is insufficient to derive the periods with high accuracy. Moreover, the spectroscopic periods are often not the same as those found from the photometry. This clearly demonstrates the necessity of long-term simultaneous photometric and spectroscopic campaigns. We present the preliminary results of such a campaign for the λ Eri star HD 105382.We close with reflections on the cause of the variability observed in the λ Eri stars and on the best viewpoint for further research in this area.

Simultaneous photometry and spectroscopy of the Be star 28 ( ) CMa -- I. Observational evidence of the periodic components of rapid variability

We analyse the periodic variability of the Be star 28 (ω) CMa. The data consist of 275 new He i 6678 line profiles of high spectral and temporal resolution, and new Strömgren and Geneva photometry. The photometric analysis has been extended by including previously published data to cover an interval of 16 yr. The principal spectroscopic period of 1.37 d is confirmed by analysis of He i 6678 modes and moments. There is evidence to show that a single period is insufficient to explain the variation in the line wings. In particular, the variation of the second moment, which samples the line wings, is best described when a second period is included. The photometric data have been divided into 10 sets in which the time is sufficiently contiguous for period analysis. These sets have been smoothed to remove as well as possible the long-term irregular variations which are always present in Be stars. The residuals have then been analysed for coherent periodicities using several techniques. Evidence for one or the other of the two known spectroscopic periods can be found in individual data sets. By an analysis in which two periods are assumed, it is possible to recover both the principal spectroscopic period and the satellite period of 1.46 d. Unlike in the He i 6678 line profiles, the latter period seems to be most often present in the light variations. The amplitude of the periodic components of the light variation is only a few millimagnitudes, in contrast to the very large radial velocity amplitude. We find that the photometric amplitudes of the two periodic components, and their ratio, vary smoothly on a time-scale of years. The amplitudes are larger in seasons when the mean brightness is higher.

The new intermediate polar RX J1238 – 38: a system below the period gap?

We present optical observations of the recently discovered ROSAT source RX J1238 ‒ 38, which is a new member of the intermediate polar class of asynchronous magnetic cataclysmic variables (CVs). Optical photometry reveals two coherent periodicities at 1860 and 2147 s respectively, with similar amplitudes of ∼8 per cent. Infrared (J-band) intensity variations are detected only at the 1860-s period, at an amplitude of ∼15 per cent. The initial hypothesis, that these two periods were the spin and synodic (i.e., beat) period respectively, appears not to be supported by the spectroscopic data. The emission lines vary on the longer photometric period, and radial velocity variations are detected at this period and at a longer period of ∼5300 s, which we identify as the spin and orbital periods respectively. The most likely explanation for the 1860-s period is that it is the first harmonic of the ω − Ω sideband, leading to an improved determination of the orbital period as 5077 s (= 84 min). If this interpretation is correct, RX J1238 − 38 joins EX Hya as the only other intermediate polar below the 2‒3 h period gap, and with an orbital period close to the minimum for CVs with non-degenerate secondaries. The spin-modulated emission-line radial velocities and widths appear to be anticorrelated, with maximum width occurring at maximum blueshift. Such an anticorrelation is expected for aspect changes of accretion curtains. Polarimetric observations of RX J1238 − 38 were inconclusive, although we can put a limit of 0.4 per cent on any variability on the circular polarization, and certainly there is no indication of variations at the photometric or spectroscopic periods.

Simultaneous WBVR observations and interpretations of the light curves of TT ARI and V603 AQL

Abstract Four-colour photometric observations of TT Ari and V603 Aql in 1994–1995 are presented. Both stars show photometric periodicities in their light curves, 3.2 h and 3.5 h respectively. But their colours sometimes also vary with spectroscopic periods for both stars equal to 3.3 h, and W–B of TT Ari varies with half the photometric period. In the TT Ari light curves quasi-periodic oscillations (QPO) are found in a wide range of periods, from 47 to 16 minutes, and they changed from night to night. The 60 minutes oscillations and their harmonics are presented on V603 Aql light curves. A new model of the oblique processing accretion disk together with reflection from a secondary or hot spot is suggested to allow for the photometric variability of these stars. The theoretical light curves of TT Ari in the framework of this model are calculated. It is proposed that QPO is connected with orbiting blobs in the disk.

Multicolour Photometry of AM Her During 1994 96

Multicolour photometry of the polar AM Her was obtained during 3 observational seasons (1994/95/96). The star was in its high state for most of the observations. It was in its low state in '96 April. It was established that these two states differ not only in the average light level but in the larger amplitudes of variations at low state than at high state. Moreover the energy distributions of the two states differ in the stronger dependence of the flux on ν at high state than at low state. The Fourier analysis of the photometric data shows variability with the spectroscopic (orbital) period. The amplitudes of this variability in all colours are about two times bigger at low state than at high state. An attempt to explain the photometric behaviour of AM Her by a model of dominant emission of two hot spots at the magnetic poles of the white dwarf was made and the spot parameters were determined.

High-Speed BVRI Photometry of SS Cyg at Quiescence and at Outburst

BVRI photometry of SS Cyg from the end of 1996 and the beginning of 1997 is presented. The star underwent an eruption around December 11. The amplitude of which was slightly bigger than those of observed earlier eruptions. We saw some indication of the future outburst in the decreasing of brightness in all colours by about 0.4 mag during the last two weeks before the event. The emission of the system moved strongly to the shorter wavelengths at outburst. Our multicolour data confirm the existence of a light variability with the orbital (spectroscopic) period at quiescence. Moreover we found for the first time that this variability exists also at outburst but its amplitude is 3–5 times smaller. Whereas the amplitudes of the orbital variability at quiescence decrease to the longer wavelengths, they increase at outburst to the longer wavelengths. The orbital folded curve at quiescence has two-wave shape and was fitted well by the different visibility of two diametrical opposite hot spots (210000 K) with angular size 100 on the magnetic poles of the white dwarf. An analogy between the two basic states of the U Gem-star SS Cyg, the polar AM Her and Z Cam-star RX And was found.

Optical Observations of GRO J1655−40 in Quiescence. I. A Precise Mass for the Black Hole Primary

We report photometric and spectroscopic observations of the black hole binary GRO J1655-40 in complete quiescence. In contrast to the 1995 photometry, the light curves from 1996 are almost completely dominated by ellipsoidal modulations from the secondary star. Model fits to the light curves, which take into account the temperature profile of the accretion disk and eclipse effects, yield an inclination of i = 6950 ? 008 and a mass ratio of Q = M1/M2 = 2.99 ? 0.08. The precision of our determinations of i and Q allow us to determine the black hole mass to an accuracy of ? 4% (M1 = 7.02 ? 0.22 M?). The secondary star's mass is M2 = 2.34 ? 0.12 M?. The position of the secondary on the Hertzsprung-Russell diagram is consistent with that of a ? 2.3 M? star that has evolved off the main sequence and is halfway to the start of the giant branch. Using the new spectra, we present an improved value of the spectroscopic period (P = 262157 ? 000015), radial velocity semiamplitude (K = 228.2 ? 2.2 km s-1), and mass function [f(M) = 3.24 ? 0.09 M?]. Based on the new spectra of the source and spectra of several MK spectral type standards, we classify the secondary star as F3 IV-F6 IV. Evolutionary models suggest an average mass transfer rate for such a system of ${u{M}{705F}}$ --> -->2=3.4?10 -->?9 M? yr-1 = 2.16 ? 1017 g s-1, which is much larger than the average mass transfer rates implied in the other six transient black hole systems but is still barely below the critical mass transfer rate required for stability.

Multicolour Photometry of RX and During 1994/95

The cataclysmic star RX And was observed in the states standstill and quiescence. They differed not only in the light level but in the type of variations around this level. The standstill observed by us turned out quite near to the maximum light and its duration was unusually long. The energy distribution of RX And at the standstill seemed similar to the spectrum of an accretion disk. Two variabilities with periods 3 h 43 min and 1 h 26 min were found at the standstill but only the second of them was present at quiescence too. The star did not show light variability with the spectroscopic period. We tried to interpret some of the results by the supposition that the Z Cam-stars are an intermediate subtype of the cataclysmic stars evolving from UX UMa-subtype to U Gem-subtype and that probably RX And presents a pattern of Z Cam-star that is very near to the U Gem-subtype.

The Nature of the Supersoft X-Ray Source RX J0513-69

We present spectroscopy and photometry of the LMC supersoft binary system RX~J0513.9-6951. We derive a refined spectroscopic period of P$=0.761\pm0.004$~d, which is consistent with the value obtained from long term photometric monitoring (P$=0.76278\pm0.00005$~d). We see bipolar outflow components of He{\sc ii} and H$\beta$, with velocities of $\sim 3800$\,km\,s$^{-1}$, strongly suggesting that the compact object is a white dwarf. Using all the available optical and X-ray data, we construct a theoretical model to explain the principal features of the unusual variability of this source. In particular, we note that X-ray outbursts have only been seen at times of optical minima. From this, we conclude that the most likely cause of the X-ray outbursts is a photospheric contraction during a nuclear shell burning phase, rather than a thermonuclear flash or shocked emission. The system probably comprises a relatively massive white dwarf accreting at a high rate ($\sim 10^{-6} M_{\odot}~{\rm yr}^{-1}$) from an evolved donor star, and is observed close to pole-on.

Identification of the Soft X-Ray Source WGA J1802.1+1804 with a New Magnetic Cataclysmic Variable

We have discovered a bright (V ~ 14.5) cataclysmic variable during observations of the soft X-ray sources in the list of Singh et al. The optical source, which is coincident with the X-ray position of WGA J1802.1+1804, shows all the characteristics of a magnetic AM Herculis-type system: circular polarization, He II strength greater than Hβ, multiple line components, and a consistent photometric, polarimetric, spectroscopic, and X-ray period of 113 minutes. The X-ray spectrum shows a dominant soft blackbody (kT = 20-45 eV) and a weaker bremsstrahlung component (kT > 1 keV), while the circular polarization is relatively low (4% in the red).

ITAL]ROSAT[/ITAL] Observation of the Old Classical Nova CP Puppis

We present X-ray observation of the old nova CP Puppis obtained by the ROSAT Position Sensitive Proportional Counter in 1993 April. The source is detected with a count rate of 0.067 ± 0.004 counts s-1. The total observed X-ray flux between 0.1 and 2.4 keV is ~3 × 10-12 ergs s-1 cm-2. The spectrum of the source is best fit by a thermal bremsstrahlung emission model with temperature ≥1 keV. The X-ray count rates are modulated with the previously known spectroscopic period ~00614 (~88.4 minutes) of the system at the 3 σ confidence level. The hard X-ray flux and the detected X-ray modulations suggest that CP Puppis is an intermediate polar system.

CCD photometry of BM Orionis and other trapezium stars

New light curves have been obtained for the eclipsing binary BM Orionis in theuvbyRI filter regions. The observations were made from 1988 to 1990 using the CCD photometer of the Behlen Observatory of the University of Nebraska. Reduction of all image data to magnitudes for BM Orionis and for each of the five other brightest stars in the Θ1 Orionis group known as the Trapezium was accomplished by use of Stetson's DAOPHOT crowded-field photometry program. Differential magnitudes and light curves for BM Orionis and V1016 Orionis have been constructed using star D of the group as the primary comparison star. Possible indications of variability have also been looked for in the member stars C, E, and F with negative results for stars C and F and positive results for star E. The same CCD frames also contained the stars Θ2 Orionis A and B. A light curve of the possibly-eclipsing spectroscopic binary Θ2 Orionis A folded on its spectroscopic period does show some variability, but no obvious eclipses.

Evidence for Accretion Disk Precession in the Cataclysmic Binary AM Canum Venaticorum

view Abstract Citations (64) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evidence for Accretion Disk Precession in the Cataclysmic Binary AM Canum Venaticorum Patterson, Joseph ; Halpern, Jules ; Shambrook, Anouk Abstract We have found a 13.38 hr period in the helium absorption-line profiles of the cataclysmic variable AM Canum Venaticorum. The lines display blue and red troughs which alternate in depth on this period. Comparison of the data with theoretical line profiles of elliptical accretion disks suggests that this is the signature of an elliptical disk, with the line of apsides advancing slowly around the white dwarf. This interpretation of the 13.38 hr spectroscopic period as apsidal precession of the disk supports the idea that the familiar 1051 s photometric signal is the orbital frequency's precessional sideband, which is also believed to be present in the "superhumps" of dwarf novae. The exact orbital period is inferred to be 1028s.77 + _{0 }. 18. More important, this kinematic evidence for accretion disk precession in a noneruptive star strongly suggests that superhumps and tidal instabilities may be a very widespread and essentially permanent feature of the accretion disks in many CVs. The variation in the skewness of the absorption lines is best seen near line center, as expected since low velocities tend to arise in the outer disk, where tidal effects are more important. But the same periodic signal is found in the wings of the absorption lines, with a phase displaced by 120°. This unexpected phase shift may arise from a dependence of tidal lag on orbital radius in the disk. Publication: The Astrophysical Journal Pub Date: December 1993 DOI: 10.1086/173532 Bibcode: 1993ApJ...419..803P full text sources ADS | data products SIMBAD (4)

CP Puppis - No ordinary old nova

We present spectrophotometric data for the old nova CP Puppis (Nova Puppis 1942) that demonstrates the simultaneous existence of two distinct periods for the system. We find that the photometric period of 0.06834(7) day is 11 percent longer than the spectroscopic period. We also present Doppler tomographic images of CP Pup that indicate the existence of an accretion disk in the system. Finally, we interpret the observational evidence in terms of a DQ Herculis model and an SU Ursae Majoris model for CP Pup. While the evidence mildly supports both interpretations, it is insufficient for us to conclusively classify CP Pup as either a DQ Her system or an SU UMa system.

RAPID OSCILLATIONS IN CATACLYSMIC VARIABLES. X. TW PICTORIS (= H0534-581)

ABSTRACT Photometry of the X-ray selected cataclysmic variable TW Pictoris (= H0534-581) reveals a periodic signal at P = 6.1 hours, which is approximately the orbital period of the binary. In addition, a highly probable signal is found at P = 119.76 ± 0.09 minutes. Coupled with the high excitation, the high LX/Lopt ratio, and the probable detection of a similar spectroscopic period, this makes it likely that the star belongs to the "DQ Herculis" class of cataclysmic variables--in which the stable short period is the spin period of an accreting magnetic white dwarf. Theory suggests that TW Pic is a particularly attractive candidate for showing circular polarization at visual or near-infrared wavelengths.

A 4.86-h periodic modulation in the UV resonance lines of the cataclysmic variable V795 Herculis

Low-resolution IUE spectroscopy of V795 Her secured in 1992 August is used to authenticate the presence of a approximately 4.86-h periodic variation in the mainly wind-formed Si IV lambda 1400 and C IV lambda 1 549 resonance lines. The modulation is demonstrated to be coherent across a 3-yr time-span, and is discordant with the mooted orbital (optical spectroscopic) period of approximately 2.60 h. Constraints are discussed for some possible configurations of the system that introduce asymmetries and can potentially yield modulated profile variability. The first ROSAT X-ray detection of V795 Her is also described.