Reverberation mapping estimates the size and kinematics of broad line regions (BLR) in Quasars and type I AGNs. It yields size-luminosity relation, to make QSOs standard cosmological candles, and mass-luminosity relation to study the evolution of bla
ck holes and galaxies. The accuracy of these relations is limited by the unknown geometry of the BLR clouds distribution and velocities. We analyze the independent BLR structure constraints given by super-resolving differential interferometry. We developed a three-dimensional BLR model to compute all differential interferometry and reverberation mapping signals. We extrapolate realistic noises from our successful observations of the QSO 3C273 with AMBER on the VLTI. These signals and noises quantify the differential interferometry capacity to discriminate and measure BLR parameters including angular size, thickness, spatial distribution of clouds, local-to-global and radial-to-rotation velocity ratios, and finally central black hole mass and BLR distance. A Markov Chain Monte Carlo model-fit, of data simulated for various VLTI instruments, gives mass accuracies between 0.06 and 0.13 dex, to be compared to 0.44 dex for reverberation mapping mass-luminosity fits. We evaluate the number of QSOs accessible to measures with current (AMBER), upcoming (GRAVITY) and possible (OASIS with new generation fringe trackers) VLTI instruments. With available technology, the VLTI could resolve more than 60 BLRs, with a luminosity range larger than four decades, sufficient for a good calibration of RM mass-luminosity laws, from an analysis of the variation of BLR parameters with luminosity.
Classical Be stars are hot non-supergiant stars surrounded by a gaseous circumstellar disk that is responsible for the observed infrared (IR) excess and emission lines. The influence of binarity on these phenomena remains controversial. We followed t
he evolution of the environment surrounding the binary Be star $delta$ Scorpii one year before and one year after the 2011 periastron to check for any evidence of a strong interaction between its companion and the primary circumstellar disk. We used the VLTI/AMBER spectro-interferometric instrument operating in the K band in high (12000) spectral resolution to obtain information on both the disk geometry and kinematics. Observations were carried out in two emission lines: Br$gamma$ (2.172,$mu$m) and $ion{He}{i}$ (2.056,$mu$m). We detected some important changes in $delta$ Scorpiis circumstellar disk geometry between the first observation made in April 2010 and the new observation made in June 2012. During the last two years the disk has grown at a mean velocity of 0.2,km,s$^{-1}$. This is compatible with the expansion velocity previously found during the 2001-2007 period. The disk was also found to be asymmetric at both epochs, but with a different morphology in 2010 and 2012. Considering the available spectroscopic data showing that the main changes in the emission-line profiles occurred quickly during the periastron, it is probable that the differences between the 2010 and 2012 disk geometry seen in our interferometric data stem from a disk perturbation caused by the companion tidal effects. However, taking into account that no significant changes have occurred in the disk since the end of the 2011 observing season, it is difficult to understand how this induced inhomogeneity has been frozen in the disk for such a long period.
With the advent of large-collecting-area instruments, the number of objects that can be reached by optical long-baseline interferometry is steadily increasing. We present here a few results on massive binary stars, showing the interest of using this
technique for studying the insight of interactions in these systems. Indeed, many massive stars with extended environments host, or are suspected to host, companion stars. These companions could have an important role in shaping the circumstellar environment of the system. These examples provide a view in which binarity could be an ingredient, among many others, for the activity of these stars.
Context. Classical Be stars are hot non-supergiant stars surrounded by a gaseous circumstellar disk that is responsible for the observed infrared-excess and emission lines. The phenomena involved in the disk formation still remain highly debated. Aim
s. To progress in the understanding of the physical process or processes responsible for the mass ejections and test the hypothesis that they depend on the stellar parameters, we initiated a survey on the circumstellar environment of the brightest Be stars. Methods. To achieve this goal, we used spectro-interferometry, the only technique that combines high spectral (R=12000) and high spatial ($theta_{rm min}$=4,mas) resolutions. Observations were carried out at the Paranal observatory with the VLTI/AMBER instrument. We concentrated our observations on the Br$gamma$ emission line to be able to study the kinematics within the circumstellar disk. Our sample is composed of eight bright classical Be stars : $alpha$ Col, $kappa$ CMa, $omega$ Car, p Car, $delta$ Cen, $mu$ Cen, $alpha$ Ara, and textit{o} Aqr. Results. We managed to determine the disk extension in the line and the nearby continuum for most targets. We also constrained the disk kinematics, showing that it is dominated by rotation with a rotation law close to the Keplerian one. Our survey also suggests that these stars are rotating at a mean velocity of V/V$_{rm c}$,=,0.82,$pm$,0.08. This corresponds to a rotational rate of $Omega/Omega_{rm c}$,=,0.95,$pm$,0.02 Conclusions. We did not detect any correlation between the stellar parameters and the structure of the circumstellar environment. Moreover, it seems that a simple model of a geometrically thin Keplerian disk can explain most of our spectrally resolved K-band data. Nevertheless, some small departures from this model have been detected for at least two objects (i.e, $kappa$ CMa and $alpha$ Col). Finally, our Be stars sample suggests that rotation is the main physical process driving the mass-ejection. Nevertheless, smaller effects from other mechanisms have to be taken into account to fully explain how the residual gravity is compensated.
Classical Be stars are hot non-supergiant stars surrounded by a gaseous circumstellar disk that is responsible for the observed IR-excess and emission lines. The influence of binarity on these phenomena remains controversial. delta Sco is a binary sy
stem whose primary suddently began to exhibit the Be phenomenon at the last periastron in 2000. We want to constrain the geometry and kinematics of its circumstellar environment. We observed the star between 2007 and 2010 using spectrally-resolved interferometry with the VLTI/AMBER and CHARA/VEGA instruments. We found orbital elements that are compatible with previous estimates. The next periastron should take place around July 5, 2011 (+- 4,days). We resolved the circumstellar disk in the HAlpha (FWHM = 4.8+-1.5mas), BrGamma (FWHM = 2.9 0.,mas), and the 2.06$ mu$m HeI (FWHM = 2.4+-0.3mas) lines as well as in the K band continuum (FWHM ~2.4mas). The disk kinematics are dominated by the rotation, with a disk expansion velocity on the order of 0.2km/s. The rotation law within the disk is compatible with Keplerian rotation. As the star probably rotates at about 70% of its critical velocity the ejection of matter doesnt seems to be dominated by rotation. However, the disk geometry and kinematics are similar to that of the previously studied quasi-critically rotating Be stars, namely Alpha Ara, Psi Per and 48 Per.
HD 50138 is a southern star that presents the B[e] phenomenon, but its evolutionary stage is still not well known. This object presents spectral variability, which can be explained by outbursts or shell phases and spectropolarimetric observations hav
e shown the presence of a non-spherically symmetric circumstellar environment that is responsible for the B[e] phenomenon. Based on recent optical long baseline interferometric observations from the VLTI/MIDI and VLTI/AMBER, and also from the Keck segment-tilting experiment, we study the structure of the circumstellar environment of HD 50138, through a geometrical analytical modeling, also using the recent LITpro software and considering a large space of parameters. We resolve and describe its circumstellar geometry for the first time in detail. The presence of a dusty circumstellar disk with an orientation onto the sky-plane of 71+-7 degrees, which is perpendicular to the polarimetric measurements from the literature, was derived. We also derived that HD 50138 is seen under an intermediate angle related to the line of sight, 56+-4 degrees. In addition, the structure of the disk and the flux contributions of the gas and dust components is discussed.
Context. To progress in the understanding of evolution of massive stars one needs to constrain the mass-loss and determine the phenomenon responsible for the ejection of matter an its reorganization in the circumstellar environment Aims. In order to
test various mass-ejection processes, we probed the geometry and kinematics of the dust and gas surrounding the A[e] supergiant HD 62623. Methods. We used the combined high spectral and spatial resolution covered by the VLTI/AMBER instrument. Thanks to a new multiwavelength optical/IR interferometry imaging technique, we reconstructed the first velocity-resolved images with a milliarcsecond resolution in the infrared domain. Results. We managed to disentangle the dust and gas emission in the HD 62623 circumstellar disc.We measured the dusty disc inner inner rim, i.e. 6 mas, constrained the inclination angle and the position angle of the major-axis of the disc.We also measured the inner gaseous disc extension (2 mas) and probed its velocity field thanks to AMBER high spectral resolution. We find that the expansion velocity is negligible, and that Keplerian rotation is a favoured velocity field. Such a velocity field is unexpected if fast rotation of the central star alone is the main mechanism of matter ejection. Conclusions. As the star itself seems to rotate below its breakup-up velocity, rotation cannot explain the formation of the dense equatorial disc. Moreover, as the expansion velocity is negligible, radiatively driven wind is also not a suitable explanation to explain the disc formation. Consequently, the most probable hypothesis is that the accumulation of matter in the equatorial plane is due to the presence of the spectroscopic low mass companion.
We study the Be star $delta$ Cen circumstellar disk using long-baseline interferometry which is the only observing technique capable of resolving spatially and spectroscopically objects smaller than 5 mas in the H and K b and. We used the VLTI/AMBER
instrument on January 6, 8, and 9, 2008, in the H and K bands to complete low (35) and medium (150 0) spectral resolution observations. We detected an oscillation in the visibility curve plotted as a function of the spatial frequency which is a clear signat ure of a companion around $delta$ Cen. Our best-fit soltution infers a binary separation of 68.7 mas, a companion flux co ntribution in the K band of about 7% of the total flux, a PA of 117.5 $degr$, and an envelope flux around the Be primary that contributes up to about 50 % of the total flux, in agreement with our Spectral Energy Distribution (SED) fit. The e nvelope size is estimated to be 1.6 mas in K but no departure from spherical symmetry is detected.
