Aims . HD 96446 is a magnetic B2p He-strong star that has been reported to be a β Cep pulsator. We present a detailed spectroscopic analysis of this object based on an intensive observational data set obtained in a multisite campaign with the spectrographs CORALIE, FEROS, and HARPS (La Silla); UVES (Paranal); HERCULES (Mt. John Observatory); and GIRAFFE (SAAO). Methods . Radial velocities were measured by cross-correlations and analysed to detect periodic variations. On the other hand, the mean spectrum was fit with spectral synthesis to derive atmospheric parameters and chemical abundances. Results . From the analysis of radial velocities, HD 96446 was found to be a spectroscopic binary with a period of 799 days. The stellar companion, which contributes only ∼5% of the total flux, is an A0-type star. A frequency analysis of the radial velocities allowed us to detect two pulsational modes with periods 2.23 h and 2.66 h. The main mode is most probably a low-inclination, dipole mode ( l , m ) = (1, 0), and the second pulsation mode corresponds to ( l , m ) = (2, 2) or to a pole-on ( l , m ) = (3, 2) configuration. In addition to radial velocities, the main pulsation mode is evidenced through small variations in the spectral morphology (temperature variations) and the light flux. The rotation period of 23.4 d, was detected through the variation in line intensities. Chemical abundances are unevenly distributed over the stellar surface, with helium concentrated at the negative magnetic pole and most metals strengthened at lower latitudes. The mean chemical abundance of helium is strongly abnormal, reaching a value of 0.60 (number fraction).
We present the PLANET photometric data set for the binary-lens microlensing event MACHO 97-BLG-28, consisting of 696 I- and V-band measurements, and analyze it to determine the radial surface brightness profile of the Galactic bulge source star. The microlensed source, demonstrated to be a K giant by our independent spectroscopy, crossed an isolated cusp of the central caustic of the lensing binary, generating a sharp peak in the light curve that was well-resolved by dense (3-30 minute) and continuous monitoring from PLANET sites in Chile, South Africa, and Australia. This is the first time that such a cusp crossing has been observed. Analysis of the PLANET data set has produced a measurement of the square-root limb-darkening coefficients of the source star in the I and V bands; the resulting stellar profiles are in excellent agreement with those predicted by stellar atmospheric models for K giants. The limb-darkening coefficients presented here are the first derived from microlensing. They are also among the first found for normal giants by any technique and the first for any star as distant as the Galactic bulge. Modeling of our light curve for MACHO 97-BLG-28 indicates that the lensing binary has a mass ratio q = 0.23 and an (instantaneous) separation in units of the angular Einstein ring radius of d = 0.69. For a lens in the Galactic bulge, this corresponds to a typical stellar binary with a projected separation between 1 and 2 AU. If the lens lies closer (i.e., in the Galactic disk), the separation is smaller, and one or both of the lens objects is in the brown dwarf regime. Assuming that the source is a bulge K2 giant at 8 kpc, the relative lens-source proper motion is μ = 19.4 ± 2.6 km s-1 kpc-1, consistent with a disk or bulge lens. If the nonlensed blended light is due to a single star, it is likely to be a young white dwarf in the bulge, consistent with the blended light coming from the lens itself.
To develop reference ranges for the ductus venosus (DV) and tricuspid valve (TV) waveforms at 11–14 weeks to define auditable standards to assess operator measurement performance. A single operator utilising the FMF criteria, prospectively obtained quantitative measurements for DV (pulsatility index for veins [PIV], pre-load index [PLI] and peak velocity for veins [PVIV]) and TV (E-wave peak velocity [EWPV], A-wave peak velocity [AWPV] and E-A ratio) to develop medians and 90% reference intervals. Measurement agreement studies between two experienced operators were also performed. The measurement bias of 3 additional operators was subsequently assessed using these auditable standards. Doppler measurements were obtained in 292 patients (DV) and 321 patients (TV). Highly correlated DV indices indicated that only one reference range (for PIV) was necessary with a mean PIV measurement of 1.06 (90% RI 0.86 - 1.23). As both EWPV and AWPV changed reliably over gestation, only the E-A ratio reference range was computed. Intra-observer and inter-observer studies on 30 additional patients of the DV PI and TV E-A ratio showed the within-operator agreement was almost perfect for DV PIV (ICC 0.82 - 0.86) and strong for TV E-A ratio (ICC 0.68 - 0.78) whilst the between-operator agreement was good for both DV PIV and TV E-A ratio measurements (ICC 0.46 for both). Preliminary audit using central tendency and dispersion of the measurements by 3 trained operators showed a tendency to over-estimate DV PI (0.97, 1.07 and 1.09 MoM respectively; SD log PI 0.03-0.06) whilst the TV E-A ratio distribution met expectation (0.97, 0.98 and 0.98 MoM respectively; SD log E-A ratio 0.04 - 0.1). Measurements of DV PIV and TV E-A ratio by experienced operators were found to be reproducible. Development of local reference ranges enabled the definition of quantitative auditable standards that can be utilized in assessment of operator training and ongoing Doppler measurement quality assurance.
ABSTRACT We present spectroscopy with resolution R ∼ 33 000 of the circumstellar Ca ii H&K absorptions in the star β Pictoris during 1997 and 1998. From 1997 April onwards, both lines were observed simultaneously. A total of 688 spectra were obtained over 95 nights in order to characterize the lines’ behaviour. Near-continuous Falling Evaporating Body (FEB) variable absorption activity was seen, including additional strong, blueshifted features besides the one on 1997 June 19–20 already reported by others. Temporal coverage is more even than in the HARPS spectra from 2004–11 that have been analysed for FEB orbital parameters via a model of FEB evaporation. Our observations likely encompass the 1997–98 Hill-sphere transit by β Pic b, but we have found no clear signature of transiting material. Lower velocity FEB absorptions tend to be deeper, narrower and longer lived, in confirmation of earlier studies. The ratio of line strengths for one absorption on 1998 November 27 is evocative of the variations expected for a single FEB making a transit perpendicular to the stellar rotation axis. Analysis with the evaporation model produces similar distributions of orbital parameters to those obtained from the HARPS observations, but when the derived orbital parameters are fed into a model based solely on gravitational dynamics of point masses, the predicted FEB accelerations do not agree with observed values. More sophisticated modelling is called for. There is no convincing intrinsic variation in the central circumstellar absorption such as might be expected if an H i ring is responsible for the confinement of circumstellar Ca+ ions. Our observations are available electronically for further analysis by others.
In order to obtain a census of planets with masses in the range of Earth to Jupiter, eight telescopes are being used by the combined microlensing campaign of the PLANET and RoboNet collaborations for high-cadence photometric round-the-clock follow-up of ongoing events, alerted by the OGLE and MOA surveys. In 2005 we detected a planet of 5.5 Earth masses at 2.6 AU from its parent 0.22 MA M star. This object is the first member of a new class of cold telluric planets. Its detection confirms the power of this method and, given our detection efficiency, suggests that these recently-detected planets may be quite common around M stars, as confirmed by subsequent detection of a ~ 13 Earth-mass planet. Using a network of dedicated 1 2-m-class telescopes, we have entered a new phase of planet discovery, and will be able to provide constraints on the abundance of frozen Super-Earths in the near future.
We present PLANET observations of OGLE-1999-BUL-23, a binary-lens microlensing event toward the Galactic bulge. PLANET observations in the I and V bands cover the event from just before the first caustic crossing until the end of the event. In particular, a densely sampled second caustic crossing enables us to derive the linear limb-darkening coefficients of the source star: cV = 0.786 and cI = 0.632. Combined analysis of the light curve and the color-magnitude diagram suggests that the source star is a G/K subgiant in the Galactic bulge (Teff ≃ 4800 K). The resulting linear limb-darkening coefficient of the source is consistent with theoretical predictions, although it is likely that nonlinearity of the stellar surface brightness profile complicates the interpretation, especially for the I band. The global light curve fit to the data indicates that the event is due to a binary lens of a mass ratio q ≃ 0.39 and a projected separation d ≃ 2.42. The lens/source relative proper motion is (22.8 ± 1.5) km s-1 kpc-1, typical of bulge/bulge or bulge/disk events.
Classical novae are thermonuclear explosions that occur on the surfaces of white dwarf stars in interacting binary systems (Bode & Evans 2008). It has long been thought that the luminosity of classical novae is powered by continued nuclear burning on the surface of the white dwarf after the initial runaway (Gallaher & Starrfield 1978). However, recent observations of GeV $\gamma$-rays from classical novae have hinted that shocks internal to the nova ejecta may dominate the nova emission. Shocks have also been suggested to power the luminosity of events as diverse as stellar mergers (Metzger & Pejcha 2017), supernovae (Moriya et al. 2018), and tidal disruption events (Roth et al. 2016), but observational confirmation has been lacking. Here we report simultaneous space-based optical and $\gamma$-ray observations of the 2018 nova V906 Carinae (ASASSN-18fv), revealing a remarkable series of distinct correlated flares in both bands. The optical and $\gamma$-ray flares occur simultaneously, implying a common origin in shocks. During the flares, the nova luminosity doubles, implying that the bulk of the luminosity is shock-powered. Furthermore, we detect concurrent but weak X-ray emission from deeply embedded shocks, confirming that the shock power does not appear in the X-ray band and supporting its emergence at longer wavelengths. Our data, spanning the spectrum from radio to $\gamma$-ray, provide direct evidence that shocks can power substantial luminosity in classical novae and other optical transients.
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