V1309 Sco Research Articles

Bowen Fluorescence from Companion Stars in X-Ray Binaries

AbstractThis paper will review a new technique of detecting companion stars in LMXBs and X-ray transients in outburst using the Bowen fluorescence NIII lines at 4634-4640. These lines are very efficiently reprocessed in the atmospheres of the companion stars and, thereby, provide estimates of the K2 velocities and mass functions. The method has been applied to Sco X-1, X1822-371 and GX339-4 which, in the latter case, provides dynamical evidence for the presence of an accreting black hole. Preliminary results from a VLT campaign on V801 Ara, V926 Sco and XTE J1814-338 are also presented.

A spectroscopic study of southern binary Cepheids

AbstractHigh-resolution spectroscopic observations have been made of a number of southern binary Cepheids to determine their dynamical masses. The stars are part of a long-term programme to observe southern variable stars for which a valuable long-term database has been obtained. The most recent radial velocities have a precision of ~300ms−1, allowing the detection of velocity differences of ~l kms−1 with confidence. Masses were determined for three systems: the 9-day Cepheid S Mus (6.0±0.4M⊙), the double-mode Cepheid Y Car (4.5±1.8M⊙) and the 5-day Cepheid V350Sgr (6.0±0.9M⊙). For five Cepheids (YZCar, AX Cir, V636 Sco, W Sgr and T Mon) new or improved orbital solutions were found. Line level effects have been observed in several species of lines. Most Cepheids were observed to show the same progression of line level effects. Using non-linear radiative hydrodynamical models, we have compared the results of these models with our observations. These have shown that AX Cir and YZ Car have the following properties: L = 2050 L⊙, M = 4.8 M), Teff = 5900 K and L = 9350 L∩, M = 7.7M∩, Teff = 5590 K. Our models show no strong Shockwaves being produced. Good agreement was found between the observed and modelled spectral lines Fe I 5576Å, Si II 6347Å, Ba II 5853Å and Ca II 8542Å.

Recurrent Novae as a Progenitor System of Type Ia Supernovae. I. RS Ophiuchi Subclass: Systems with a Red Giant Companion

Theoretical light curves of four recurrent novae in outburst are modeled to obtain various physical parameters. They are those with a red giant companion, T CrB, RS Oph, V745 Sco, and V3890 Sgr. Our model includes irradiations of the companion star and the accretion disk together with a shadowing effect on the companion by the accretion disk. The early visual light curves are well reproduced with a thermonuclear runaway model on a very massive white dwarf of 1.37 Mo for T CrB, 1.37 Mo for RS Oph with low metallicity (Z=0.004), 1.35 Mo for V745 Sco, and 1.35 Mo for V3890 Sgr. Each envelope mass at the optical maximum is also estimated to be 3 x 10^{-6}, 2 x 10^{-6}, 5 x 10^{-6}, and 3 x 10^{-6} Mo, indicating an average mass accretion rate of 0.4 x 10^{-7}, 1.2 x 10^{-7}, 0.9 x 10^{-7}, and 1.1 x 10^{-7} Mo/yr during the quiescent phase. Although a large part of the envelope mass is blown in the wind, each WD can retain a substantial part of the envelope mass after hydrogen burning ends. Thus, we have obtained net mass-increasing rates of the WDs as 0.1 x 10^{-7}, 0.12 x 10^{-7}, 0.05 x 10^{-7}, and 0.11 x 10^{-7} Mo/yr. These results strongly indicate that the WDs in the recurrent novae have now grown up to near the Chandrasekhar mass limit and will soon explode as a Type Ia supernova if the WDs consist of carbon and oxygen. We also include a radiation-induced warping instability of the accretion disk to reproduce the second peak of T CrB outbursts. Thus, we have clarified the reason why only T CrB shows a secondary maximum but the other three systems do not.

Optically Thick Wind Solutions for an Extremely Rapid Light Curve of Recurrent Novae

Wind mass-loss solutions and theoretical light curves for rapid outbursts of recurrent novae are presented for a wide range of parameters of white-dwarf masses of 1.2, 1.3, 1.35, and 1.377 M® with envelope compositions of X=0.7, 0.35, and 0.1 and heavy element contents of Z=0.001, 0.004, 0.01, 0.02, 0.05, and 0.1. Very rapid optical decline (£3 < 10 days) is obtained only in very massive white dwarfs ( > 1.35 M® ) for Z=0.02. Systematic differences of evolutionary time-scale and of the wind velocity are predicted between novae of Populations I and II. The light-curve fittings of four recurrent novae U Sco, V394 CrA, T CrB, and V745 Sco, show that these systems contain a very massive white dwarf of mass 1.35–1.38 M®.

The Mass of the Cepheid Binary V636 Scorpii

The mass-luminosity relation for Cepheids depends on the degree of mixing in their main-sequence progenitors. Masses of Cepheids can be inferred by using different aspects of pulsation theory. These methods have in the past led to diverging results, showing that something was wrong in either evolution theory or pulsation theory or both. For some binary Cepheids dynamical masses, which are independent of pulsation and evolution theories, can be determined. V636 Sco is one of a handful of Cepheid binaries whose companions are bright enough in the ultraviolet that orbital radial velocities can be measured. We have here attempted to determine the radial velocity of the companion V636 Sco B to the Cepheid V636 Sco A by means of two Hubble Space Telescope (HST) spectra taken at phases of minimum and maximum Cepheid orbital velocities. The ratio of the orbital velocity of the companion and the Cepheid (which is the inverse of their mass ratio) came out to be 1.25 ± 0.17. V636 Sco B has a spectral type B9.5 V, for which we expect a stellar mass of 2.5 M☉. For the Cepheid we thus determine a mass of 3.1 ± 0.4 M☉, which is surprisingly low. If true, such a low mass would indicate an extremely large amount of excess mixing, which is very unlikely. We discuss the likely possibility that V636 Sco B may itself be a binary with an unseen secondary, in which case the mass derived from the two measurements discussed above is not correct. Although the error limits for the mass of each Cepheid are rather large, the combined mass-luminosity relation for all Cepheids studied by us so far by means of HST spectra indicates excess mixing corresponding to core convective overshoot by 0.25 to about 0.5 pressure scale height in the main-sequence progenitors of the Cepheids.

Infrared observations of the recurrent novae V745 SCO and V3890 SGR

Infrared photometric and spectral observations of the two newly identified recurrent novae V745 Sco and V3890 Sgr are presented. We find that these two objects have late-type giant stars in their systems, allowing us to group them in the RS Oph/T Crb subclass of recurrent novae. We reclassify the secondary of V745 Sco as an M4 III, and classify the secondary of V3890 Sgr as spectral type M5 III. The outburst luminosities of both V745 Sco and V3890 Sgr were similar to the Eddington luminosity for a 1.35 M ○ . white dwarf.

New calibrators for the Cepheid period-luminosity relation

view Abstract Citations (35) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS New Calibrators for the Cepheid Period-Luminosity Relation Evans, Nancy R. Abstract IUE spectra of six Cepheids have been used to determine their absolute magnitudes from the spectral types of their binary companions. The stars observed are U Aql, V659 Cen, Y Lac, S Nor, V350 Sgr, and V636 Sco. The absolute magnitude for V659 Cen is more uncertain than for the others because its reddening is poorly determined and the spectral type is hotter than those of the others. In addition, a reddening law with extra absorption in the 2200 A region is necessary, although this has a negligible effect on the absolute magnitude. For the other Cepheids, and also Eta Aql and W Sgr, the standard deviation from the Feast and Walker period-luminosity-color (PLC) relation is 0.37 mag, confirming the previously estimated internal uncertainty. The absolute magnitudes for S Nor from the binary companion and from cluster membership are very similar. The preliminary PLC zero point is less than 2 sigma (+0.21 mag) different from that of Feast and Walker. The same narrowing of the instability strip at low luminosities found by Fernie is seen. Publication: The Astrophysical Journal Pub Date: April 1992 DOI: 10.1086/171238 Bibcode: 1992ApJ...389..657E Keywords: Cepheid Variables; Stellar Luminosity; Stellar Magnitude; Stellar Oscillations; Ultraviolet Spectra; Binary Stars; Companion Stars; Hertzsprung-Russell Diagram; Iue; Stellar Spectrophotometry; Astrophysics; STARS: BINARIES: SPECTROSCOPIC; STARS: FUNDAMENTAL PARAMETERS; STARS: OSCILLATIONS; STARS: VARIABLES: CEPHEIDS; ULTRAVIOLET: STARS full text sources ADS | data products SIMBAD (10) MAST (1) INES (1)

High Resolution Spectroscopy of Symbiotic Stars

A high resolution spectroscopy survey of symbiotic stars is conducted in the southern hemisphere by the authors, using the Coudé Echelle Spectrograph (CES), equipped with a CCD at the ESO Coudé Auxiliary Telescope (CAT), and concurrently in the northern hemisphere by Bode, Evans, Meaburn and collaborators, using the UK facilities at La Palma. So far, more than 400 spectra of about 70 stars have been obtained, mostly during 1988 and 1989. The southern part of the work will be described below.The discussion of symbiotic stars in the context of novae is not far-fetched. A number of symbiotics are known to have nova-like outbursts, and several novae are not easily distinguished from symbiotic stars. A noteworthy example is the most recently recognized recurrent nova, V745 Sco, first observed by Liller on July 24, 1989. It is described here, both because in late decline it represents a link between novae and symbiotic stars, and because of its current interest.

A Spectroscopic Survey of Recurrent Novae at Minimum

From 1986 to 1988 optical spectroscopy near minimum of all then established recurrent novae (excluding recurrent X-ray novae such as V616 Mon and V404 Cyg) was carried out with the 3.6 m and 1.5 m telescopes of ESO, using EFOSC with CCD and the Cassegrain spectrograph with CCD or IDS, respectively. Flux-calibrated spectra of the six objects are shown in Figs, 1a – f. The most recent recurrent nova, V745 Sco, is included in the present discussion, because 1 month after outburst it had already reached a very late stage of outburst evolution. A spectrum of V745 Sco is shown in Schwarz et al. (1989).

Rapid optical flaring in MXB 1735-444 and an optical burst from GX 17+2

view Abstract Citations (7) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Rapid Optical Flaring in MXB 1735-444 and an Optical Burst from GX 17+2 Imamura, James N. ; Steiman-Cameron, Thomas Y. ; Middleditch, John Abstract The results of high-speed white-light photometry of five low-mass X-ray binaries (LMXB), including MXB 1735-444 (V926 Sco), are reported. It is found that MXB 1735-444 was in a previously unreported state. It showed rapid optical flaring on time scales of 10 s or less to about 20 minutes over the course of a 2 hr observation. During the bursts, the optical luminosity increased by up to a factor of five; the average optical luminosity of MXB 1735-444 was about 2 x 10 to the 34th ergs/s at these times. Qualitatively similar long type II X-ray bursts have been observed from the rapid burster, MXB 1730-335, and long X-ray bursts of undetermined type have been observed from GX 17+2 (4U 1813-14). The detection of an optical burst from the source GX 17+2 is also reported. Optical bursts have not been previously reported in this object. Publication: The Astrophysical Journal Pub Date: September 1987 DOI: 10.1086/184973 Bibcode: 1987ApJ...320L..41I Keywords: Neutron Stars; Stellar Flares; Stellar Spectrophotometry; X Ray Binaries; X Ray Sources; Eddington Approximation; Light Curve; Astrophysics; STARS: BINARIES; STARS: NEUTRON; X-RAYS: BURSTS; X-RAYS: SOURCES full text sources ADS | data products SIMBAD (7)

The Cepheid mass problem and Cepheid binaries

Existing mass determinations for Cepheids with different periods are examined. Wesselink masses are independent of the adopted distance scale. For short periods (less than 6 days) they follow the sequence of evolutionary masses. For periods longer than 10 days they are lower by up to a factor of 2. The lower mass branch joins up with the bump masses. The new pulsational masses agree with the Wesselink masses for periods longer than 6 days. Cepheid masses determined by means of their giant companions also agree with the Wesselink masses and the new pulsational masses. While the error bars are large, the derived dynamical masses determined for S Mus and V636 Sco also agree with the low Wesselink and giant companion masses.

Blueshifted narrow absorption components in the ultraviolet spectrum of the binary V861 Sco (HD 152667)

Blueshifted narrow absorption components in the ultraviolet spectrum of the binary V861 Sco (HD 152667)

Infrared observations and mass loss of the binary system V861 Sco

V 861 Sco (HD 152667) is a well known single line binary(1,2).The proposed association with a variable X-ray source(3,4) has triggered renewed interest in the system. Recent optical, infrared and ultraviolet observations(5 - 12) have provided a better knowledge of its characteristics. A first estimate of the mass loss was given by Hutchings(13).Here we report on a series of photometric observations in the infrared (from 1.25 to 4.8 µ) taken at various orbital phases which improve and extend previous measurements by Tanzi et al.(12)The results give evidence of a phase modulated infrared excess which can be interpreted in terms of a non isotropic mass flow in the system or, alternately, of a contribution from a colder secondary component.

The nature of V861 Sco (=HD 152667)

AbstractThe physical parameters of the components of V861 Sco are derived from light-curve analysis and published spectroscopy. Good agreement with evolutionary models is obtained. The stellar wind is investigated using IUE data; the results include no large phase dependence of the mass loss rate and insensitivity of the velocity of the wind (measured with respect to interstellar lines) to changes in the photospheric velocity, even near the base of the wind. However, small random changes in velocity near the base of the wind are amplified to larger changes further out.

X-ray observations of the OAO1653-40 field

The region of sky containing OAO1653-40 have been observed simultaneously with the Einstein and Copernicus satellites in 1979 August. A best position of RA = 254.318 degrees, Dec = -41.577 degrees (1950) and a period of 38.019 + or - 0.009 sec were obtained for the X-ray pulsar discovered by White and Pravdo. The X-ray spectrum shows considerable photoelectric absorption with an equivalent hydrogen column density of 2.3 x 10 to the 23rd atom per sq cm. An upper limit to any 0.5-3.0 keV flux from V861 Sco of (4 + or - 1) x 10 to the -13th erg /sq cm/sec was also obtained.

Precise positions and optical search for the 38 second X-ray pulsar near OAO 1653-40 and upper limit on X-ray emission from V861 Scorpii

The region of the binary system V861 Scorpii, whose secondary has been suggested as a black hole candidate, was observed with the HEAO 1 X-ray observatory during an 8-hour pointed observation on September 4, 1978. An upper limit of 1.0 micro Jy (within three standard deviations) is placed on X-ray emission from V861 Sco during this observation. This effectively removes the secondary from the list of black hole candidates. The presence of a 38 sec pulsar in the region is confirmed, precise (0.63 sq arcmin) positions are given, and a search for the optical counterpart is described.

The discovery of 38.22 second X-ray pulsations from the vicinity of OAO 1653-40

A 38.22-s X-ray pulsator has been discovered during an 8-hour HEAO 1 pointed observation of the area of sky containing OAO 1653-40. It is found that this pulsing source is not associated with V861 Sco, the proposed optical identification for OAO 1653-40. The spectrum is very hard, the spectral index being about 1.4, with about a 500-eV equivalent width of iron-line emission. No high-energy cutoff is observed.

Simultaneous ultraviolet and X-ray observations of the massive binary V861 Scorpii (=OAO 1653-40)?

Results are reported for simultaneous Copernicus UV and X-ray observations of the massive binary system V861 Sco (possibly associated with the X-ray source OAO 1653-40) over a period of five orbital cycles from April to September 1978. It is found that the UV spectrum of V861 Sco is similar to that of a normal supergiant and that the X-ray flux from OAO 1653-40 is highly variable. A simultaneous change in the C III 1176-A line and the 3.8-8.8-keV X-ray flux is discussed which was detected when V861 Sco was observed in September 1978. The close correlation between the X-ray and UV events is taken to imply that the X-ray source OAO 1653-40 is coincident with V861 Sco. The event energetics and physical conditions in the region responsible for the C III 1176-A emission are considered. It is concluded that the most likely X-ray production mechanism is accretion by a gas stream onto a black hole.

Infrared observations of the black-hole candidate V861 Sco

V861 Sco was found to be an eclipsing binary by Cousins and Lagerwey1 and its radial velocity curve has been determined by Walker2. The primary is a B01 star, and taking suitable values for its mass the radial velocity curve suggests the unidentified secondary has a mass in the range 5–12 M⊙. Recently Polidan et al.3,4 showed that the system may be an X-ray source; it is therefore a black-hole candidate. We therefore thought that observations at other wavelengths would be of interest and we report here IR observations from 1.2 to 3.6 µm.