- ID:
- ivo://CDS.VizieR/J/A+A/639/L6
- Title:
- HERMES spectra of LS V +22 25
- Short Name:
- J/A+A/639/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The intriguing binary LS V +22 25 (LB-1) has drawn much attention following claims of it being a single-lined spectroscopic binary with a 79-day orbit comprising a B-type star and a ~70M_{sun}_ black hole - the most massive stellar black hole reported to date. Subsequent studies demonstrated a lack of evidence for a companion of such great mass. Recent analyses have implied that the primary star is a stripped He-rich star with peculiar sub-solar abundances of heavy elements, such as Mg and Fe. However, the nature of the secondary, which was proposed to be a black hole, a neutron star, or a main sequence star, remains unknown. Based on 26 newly acquired spectroscopic observations secured with the HERMES and FEROS spectrographs covering the orbit of the system, we perform an orbital analysis and spectral disentangling of LB-1 to elucidate the nature of the system. To derive the radial velocity semi-amplitude K2 of the secondary and extract the spectra of the two components, we used two independent disentangling methods: the shift-and-add technique and Fourier disentangling with FDBinary. We used atmosphere models to constrain the surface properties and abundances. Our disentangling and spectral analysis shows that LB-1 contains two components of comparable brightness in the optical. The narrow-lined primary, which we estimate to contribute 55% in the optical, has spectral properties that suggest that it is a stripped star: it has a small spectroscopic mass (~1M_{sun}_) for a B-type star and it is He- and N-rich. Unlike previous reports, the abundances of heavy elements are found to be solar. The 'hidden' secondary, which contributes about 45% of the optical flux, is a rapidly rotating (vsini~300km/s) B3 V star with a decretion disk - a Be star. As a result of its rapid rotation and dilution, the photospheric absorption lines of the secondary are not readily apparent in the individual observations.We measure a semi-amplitude for this star of K2=11.2+/-1.0km/s and adopting a mass of M2=72M_{sun}_ typical for B3 V stars, we derive an orbital mass for the stripped primary of M1=1.5+/-0.4 M_{sun}_. The orbital inclination of 394 implies a near-critical rotation for the Be secondary (v_eq_~470km/s). LB-1 does not contain a compact object. Instead, it is a rare Be binary system consisting of a stripped star (the former mass donor) and a Be star rotating at near its critical velocity (the former mass accretor). This system is a clear example that binary interactions play a decisive role in the production of rapid stellar rotators and Be stars.
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- ID:
- ivo://CDS.VizieR/J/ApJ/719/1293
- Title:
- High precision orbits of 5 SB2 stars
- Short Name:
- J/ApJ/719/1293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-precision radial velocities (RVs) of double-lined spectroscopic binary stars HD78418, HD123999, HD160922, HD200077, and HD210027. They were obtained based on the high-resolution echelle spectra collected with the Keck I/HIRES, Shane/CAT/Hamspec, and TNG/Sarge telescopes/spectrographs over the years 2003-2008 as part of the TATOOINE search for circumbinary planets. The RVs were computed using our novel iodine cell technique for double-line binary stars, which relies on tomographically disentangled spectra of the components of the binaries. The precision of the RVs is of the order of 1-10m/s, and to properly model such measurements one needs to account for the light-time effect within the binary's orbit, relativistic effects, and RV variations due to tidal distortions of the components of the binaries. With such proper modeling, our RVs combined with the archival visibility measurements from the Palomar Testbed Interferometer (PTI) allow us to derive very precise spectroscopic/astrometric orbital and physical parameters of the binaries.
- ID:
- ivo://CDS.VizieR/J/A+AS/135/503
- Title:
- Hipparcos southern B8-F2 stars radial velocities
- Short Name:
- J/A+AS/135/503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocities have been determined for a sample of B8-F2 type stars observed by the Hipparcos satellite. Observations were obtained within the framework of an ESO key-program. Radial velocities have been measured using a cross-correlation method, the templates being a grid of synthetic spectra. The obtained precision depends on effective temperature and projected rotational velocity of the star as well as on a possible asymmetry of the correlation peak generally due to secondary components. New spectroscopic binaries have been detected from these a symmetries and the variability of the measured radial velocity. Simulations of binary and triple systems have been performed. For binaries our results have been compared with Hipparcos binary data. Adding the variable radial velocities, the minimum binary fraction has been found 60% for physical systems. Radial velocities have been determined for 581 B8-F2 stars, 159 being new. Taking into account published radial velocities, 39% south A-type stars with V magnitude lower than 7.5 have a radial velocity.
- ID:
- ivo://CDS.VizieR/J/ApJ/695/1527
- Title:
- HR 8257: orbit and basic properties
- Short Name:
- J/ApJ/695/1527
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used interferometric and spectroscopic observations of HR 8257 to determine a three-dimensional orbit of the system. The orbit has a period of 12.21345 days and an eccentricity of 0.2895. The masses of the F0 and F2 dwarf components are 1.56 and 1.38M_{sun}_, respectively, with fractional errors of 1.4%. Our orbital parallax of 13.632+/-0.095mas, corresponding to a distance of 73.4+/-0.6pc, differs from the Hipparcos result by just 2% and has a significantly smaller uncertainty. From our spectroscopic observations and spectral energy distribution modeling we determine the component effective temperatures and luminosities to be T_eff_(A)=7030+/-200K and T_eff_(B)=6560+/-200K and L_A_=9.4+/-0.3L_{sun}_ and L_B_=4.7+/-0.2L_{sun}_. The primary rotates pseudosynchronously, while the secondary is not far from its pseudosynchronous rotational velocity. Although both early-F stars are slowly rotating, neither component of this close binary is an Am star. A comparison with evolutionary tracks indicates that the stars are slightly metal poor, and although the components have evolved away from the zero-age main sequence, they are both still dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A167
- Title:
- Hubble spectroscopy of LB-1 (LS V +22 25)
- Short Name:
- J/A+A/649/A167
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- LB-1 has variously been proposed as either an X-ray dim B-type star plus black hole (B+BH) binary, or a Be star plus an inflated stripped star (Be+Bstr) binary. The Space Telescope Imaging Spectrograph (STIS) on board HST was used to obtain a flux-calibrated spectrum that is compared with non-LTE spectral energy distributions (SED) and line profiles for the proposed models. The Hubble data, together with the Gaia EDR3 parallax, provide tight constraints on the properties and stellar luminosities of the system. In the case of the Be+Bstr model we adopt the published flux ratio for the Be and Bstr stars, re-determine the Teff of the Bstr using the silicon ionization balance, and infer Teff for the Be star from the fit to the SED. We derive stellar parameters consistent with previous results, but with greater precision enabled by the Hubble SED. While the Be+Bstr model is a better fit to the HeI lines and cores of the Balmer lines in the optical, the B+BH model provides a better fit to the SiIV resonance lines in the UV. The analysis also implies that the Bstr star has roughly twice solar silicon abundance, which is difficult to reconcile with a stripped star origin. The Be star on the other hand has a rather low luminosity, and a spectroscopic mass inconsistent with its possible dynamical mass. The fit to the UV can be significantly improved by reducing the Teff and radius of the Be star, though at the expense of leading to a different mass ratio. In the B+BH model, the single B-type spectrum is a good match to the UV spectrum. Adopting a mass ratio of 5.1+/-0.1 (Liu et al., 2020ApJ...900...42L) implies a BH mass of 21^+9^_-8_ solar masses.
- ID:
- ivo://CDS.VizieR/J/AJ/116/2549
- Title:
- HW Per UBV differential photometry
- Short Name:
- J/AJ/116/2549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A complete photometric analysis for the eclipsing binary candidate HW Persei is presented. The UBV observations were taken at Lowell Observatory in 1996 January. Three epochs of minimum light were determined, and an improved linear ephemeris was calculated. The O-C residuals, spanning some 60 years, show no evidence of a period change. Standard magnitudes are given, and reddening estimates are made. The first published synthetic light curve solutions of HW Per reveal that it is near a state of critical contact, which we define as both components exactly filling their respective Roche lobes. The primary component is of A8 spectral type, and the secondary component is a K3-K4 spectral type. The nature of the model is discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/334/863
- Title:
- II Peg radial velocities
- Short Name:
- J/A+A/334/863
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A detailed model atmosphere analysis of high-resolution and high S/N CCD spectra of IIPeg has yielded for the first time a self-consistent set of fundamental parameters of the primary component: T_eff_=4600K, logg=3.2, [M/H]=-0.4, {xi}_t_=2.0km/s. In addition, 121 new high quality radial velocity measurements allowed us to determine improved orbital parameters, resulting in a new orbital ephemeris of T_conj_=2449582.9268+6.724333E. The position of the primary of II Peg in the HR diagram with the new parameters corresponds to a K2 IV star with mass =~0.8M_{sun}_. The evolved character of the star is confirmed by the C/N ratio, which is reduced significantly relative to the solar value. The unspotted V magnitude of the star of 6.9mag is estimated from the observed variations of the TiO bands and quasi-simultaneous photometry. The blend of LiI 6707{AA} is suspected to vary in equivalent width due to spot modulation. The lithium abundance for the unspotted star, Li/H=1.0+/-0.1, is found to be consistent with other post-main sequence chromospherically active stars. Combining all parameters, the radius R=~3.4R_{sun}_ and the inclination i=~60{deg} of the primary are estimated with the assumption that its rotational axis is perpendicular to the orbital plane. The secondary is probably a M0-M3 V star with a mass of about 0.4M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AJ/144/55
- Title:
- Infrared spectroscopy of NTTS 155808-2219
- Short Name:
- J/AJ/144/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young, low-mass, triple system NTTS 155808-2219 (ScoPMS 20) was previously identified as a ~17day period single-lined spectroscopic binary (SB) with a tertiary component at 0.21arcsec. Using high-resolution infrared spectra, acquired with NIRSPEC on Keck II, both with and without adaptive optics (AO), we measured radial velocities (RVs) of all three components. Reanalysis of the single-lined visible light observations, made from 1987 to 1993, also yielded RV detections of the three stars. Combining visible light and infrared data to compute the orbital solution produces orbital parameters consistent with the single-lined solution and a mass ratio of q=0.78+/-0.01 for the SB. We discuss the consistency between our results and previously published data on this system, our RV analysis with both observed and synthetic templates, and the possibility that this system is eclipsing, providing a potential method for the determination of the stars' absolute masses. Over the ~20year baseline of our observations, we have measured the acceleration of the SB's center of mass in its orbit with the tertiary. Long-term, AO imaging of the tertiary will eventually yield dynamical data useful for component mass estimates.
- ID:
- ivo://CDS.VizieR/J/AJ/152/213
- Title:
- Interferometry and spectroscopy of sigma Orionis
- Short Name:
- J/AJ/152/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present interferometric observations of the {sigma} Orionis triple system using the CHARA Array, NPOI, and VLTI. Using these measurements, we spatially resolve the orbit of the close spectroscopic binary (Aa,Ab) for the first time and present a revised orbit for the wide pair (A,B). Combining the visual orbits with previously published radial velocity measurements and new radial velocities measured at CTIO, we derive dynamical masses for the three massive stars in the system of M_Aa_=16.99+/-0.20M_{Sun}_, M_Ab_=12.81+/-0.18M_{Sun}_, and M_B_=11.5+/-1.2M_{Sun}_. The inner and outer orbits in the triple are not coplanar, with a relative inclination of 120{deg}-127{deg}. The orbital parallax provides a precise distance of 387.5+/-1.3pc to the system. This is a significant improvement over previous estimates of the distance to the young {sigma} Orionis cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/393/965
- Title:
- Intrinsic frequencies of slowly pulsating B stars
- Short Name:
- J/A+A/393/965
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of detailed frequency analyses of a sample of thirteen confirmed slowly pulsating B stars. Our analysis is based on a combination of elaborate photometric and spectroscopic data-sets. The original sample consists of a mixture of five confirmed slowly pulsating B stars and twelve candidate slowly pulsating B stars discovered thanks to the photometric measurements of the HIPPARCOS satellite. HD 55522 and HD 131120 turn out to be chemically peculiar stars. HD 169978 and HD 69144 are two ellipsoidal variables for which no intrinsic variability is found. At least nine of the thirteen studied slowly pulsating B stars are multi-periodic. We here present the observed amplitudes, phases and their corresponding standard errors of the variations with the accepted intrinsic frequencies in the first three normalised velocity moments of the SiII 413.0nm line profiles, in the seven filters of the Geneva photometric system, and in the Hp filter of the HIPPARCOS photometric system. They are determined by fitting the data with a superposition of sinusoidal models with reference epoch HJD=2450000. For the higher order moments, the appropriate interaction terms are also taken into account (see Mathias et al., 1994A&A...283..813M). We use the same notations as in Aerts (1996A&A...314..115A) and Aerts (2000, Cat. <J/A+A/361/245>) for the amplitudes of respectively the velocity moments and the variations in the Geneva data.
