A. Carmona

A survey for near-infrared H2 emission in Herbig Ae/Be stars: emission from the outer disks of HD 97048 and HD 100546 ,

We report on a sensitive search for H2 1-0 S(1), 1-0 S(0) and 2-1 S(1) ro-vibrational emission at 2.12, 2.22 and 2.25 μ mi n as ample of 15 Herbig Ae/Be stars employing CRIRES, the ESO-VLT near-infrared high-resolution spectrograph, at R ∼ 90 000. We report the detection of the H2 1-0 S(1) line toward HD 100546 and HD 97048. In the other 13 targets, the line is not detected. The H2 1-0 S(0) and 2-1 S(1) lines are undetected in all sources. These observations are the first detection of near-IR H2 emission in HD 100546. The H2 1-0 S(1) lines observed in HD 100546 and HD 97048 are observed at a velocity consistent with the rest velocity of both stars, suggesting that they are produced in the circumstellar disk. In HD 97048 the emission is spatially resolved and it is observed to extend at least up to 200 AU from the star. We report an increase of one order of magnitude in the H2 1-0 S(1) line flux with respect to previous measurements taken in 2003 for this star, which suggests line variability. In HD 100546 the emission is tentatively spatially resolved and may extend at least up to 50 AU from the star. Modeling of the H2 1-0 S(1) line profiles and their spatial extent with flat Keplerian disks shows that most of the emission is produced at a radius larger than 5 AU. Upper limits to the H2 1-0 S(0)/1-0 S(1) and H2 2-1 S(1)/1-0 S(1) line ratios in HD 97048 are consistent with H2 gas at T > 2000 K and suggest that the emission observed may be produced by X-ray excitation. The upper limits for the line ratios for HD 100546 are inconclusive. Because the H2 emission is located at large radii, for both sources a thermal emission scenario (i.e., gas heated by collisions with dust) is implausible. We argue that the observation of H2 emission at large radii may be indicative of an extended disk atmosphere at radii >5 AU. This may be explained by a hydrostatic disk in which gas and dust are thermally decoupled or by a disk wind caused by photoevaporation.

Fundamental vibrational transition of CO during the outburst of EX Lupi in 2008

We report monitoring observations of the T Tauri star EX Lupi during its outburst in 2008 in the CO fundamental band at 4.6–5.0 μm. The observations were carried out at the Very Large Telescope and the Subaru Telescope at six epochs from 2008 April to August, covering the plateau of the outburst and the fading phase to a quiescent state. The line flux of CO emission declines with the visual brightness of the star and the continuum flux at 5 μm, but composed of two subcomponents that decay with different rates. The narrow-line emission (50 kms^(−1) in FWHM) is near the systemic velocity of EX Lupi. These emission lines appear exclusively in v =1–0. The line widths translate to a characteristic orbiting radius of 0.4 AU. The broad-line component (FWZI ~ 150 km s^(−1)) is highly excited up to v ≤ 6. The line flux of the component decreases faster than the narrow-line emission. Simple modeling of the line profiles implies that the broad-line emitting gas is orbiting around the star at 0.04–0.4 AU. The excitation state, the decay speed of the line flux, and the line profile indicate that the broad-line emission component is physically distinct from the narrow-line emission component, and more tightly related to the outburst event.

New Herbig Ae/Be stars confirmed via high-resolution optical spectroscopy

We present FEROS high-resolution (R ∼ 45 000) optical spectroscopy of 34 Herbig Ae/Be star candidates with previously unknown or poorly constrained spectral types. Within the sample, 16 sources are positionally coincident with nearby (d 700 pc (Hen 2-80, Hen 3-1121 N&S, HD 313571, MWC 953, WRAY 15-1435, and Th 17-35) are inside or close (<5 � ) to regions with extended 8 μm continuum emission and in their 20 � vicinity have astronomical sources characteristic of SFRs (e.g., HII regions, molecular clouds, dark nebulae, masers, young stellar-objects). These 7 sources are likely to be members of SFRs.

On the origin of [Ne II] emission in young stars: mid-infrared and optical observations with the Very Large Telescope

Context. The [Ne II] line 12.81 μm was proposed to be a good tracer of gas in the environments of proto-planetary disks; its origin is explained by different mechanisms: jets in outflows, photo-evaporative disk winds driven by stellar X-rays/EUV or by the X-ray irradiated proto-planetary disk atmosphere. Previous Spitzer studies gave hints toward the neon emitting mechanism by exploring correlations between the line luminosity and properties of the star-disk system. These studies concluded that the origin of the emission is likely related to accretion and outflows, with some influence from X-rays. Aims. We provide direct constraints on the origin of the [Ne II] emission using high-spatial and spectral resolution observations that allow us to study the kinematics of the emitting gas. In addition we compare the [Ne II] line with optical forbidden lines. Methods. We obtained high-resolution ground-based observations with VISIR-VLT for 15 stars and UVES-VLT for three of them. The stars were chosen for having bright neon emission lines detected with Spitzer/IRS. The velocity shifts and profiles are used to disentangle the different emitting mechanisms producing the [Ne II] line. A comparison between results from this study and previous high-resolution studies is also presented. Results. The [Ne II] line was detected in seven stars, among them the first confirmed detection of [Ne II] in a Herbig Be star, V892 Tau. In four cases, the large blueshifted lines indicate an origin in a jet. In two stars, the small shifts and asymmetric profiles indicate an origin in a photo-evaporative wind. CoKu Tau 1, seen close to edge-on, shows a spatially unresolved line centered at the stellar rest velocity, although cross-dispersion centroids move within 10 AU from one side of the star to the other as a function of wavelength. The line profile is symmetric with wings extending up to ~±80 km s-1. The origin of the [Ne II] line is unclear and could either be due to the bipolar jet or to the disk. For the stars with VLT-UVES observations, in several cases, the optical forbidden line profiles and shifts are very similar to the profile of the [Ne II] line, suggesting that the lines are emitted in the same region. A general trend observed with VISIR is a lower line flux when compared with the fluxes obtained with Spitzer. We found no correlation between the line full-width at half maximum and the line peak velocity. The [Ne II] line remains undetected in a large part of the sample, an indication that the emission detected with Spitzer in those stars is likely extended.

Warm gas at 50 AU in the disk around Herbig Be star HD 100546

Context. The disk atmosphere is one of the fundamental elements of theoretical models of a protoplanetary disk. However, the direct observation of the warm gas (≫100 K) at large radius of a disk (≫10 AU) is challenging, because the line emission from warm gas in a disk is usually dominated by the emission from an inner disk. Aims. Our goal is to detect the warm gas in the disk atmosphere well beyond 10 AU from a central star in a nearby disk system of the Herbig Be star HD 100546. Methods. We measured the excitation temperature of the vibrational transition of CO at incremental radii of the disk from the central star up to 50 AU, using an adaptive optics system combined with the high-resolution infrared spectrograph CRIRES at the VLT. Results. The observation successfully resolved the line emission with 0. ′′ 1 angular resolution, which is 10 AU at the distance of HD 100546. Population diagrams were constructed at each location of the disk, and compared with the models calculated taking into account the optical depth effect in LTE condition. The excitation temperature of CO is 400‐500 K or higher at 50 AU away from the star, where the blackbody temperature in equilibrium with the stellar radiation drops as low as 90 K. This is unambiguous evidence of a warm disk atmosphere far away from the central star.

KINEMATICS OF IONIZED GAS AT 0.01 AU OF TW Hya

We report two-dimensional spectroastrometry of Brγ emission of TW Hya to study the kinematics of the ionized gas in the star-disk interface region. The spectroastrometry with the integral field spectrograph SINFONI at the Very Large Telescope is sensitive to the positional offset of the line emission down to the physical scale of the stellar diameter (~0.01 AU). The centroid of Brγ emission is displaced to the north with respect to the central star at the blue side of the emission line, and to the south at the red side. The major axis of the centroid motion is P.A. = –20°, which is nearly equal to the major axis of the protoplanetary disk projected on the sky, previously reported by CO submillimeter spectroscopy (P.A. = –27°). The line-of-sight motion of the Brγ emission, in which the northern side of the disk is approaching toward us, is also consistent with the direction of the disk rotation known from the CO observation. The agreement implies that the kinematics of Brγ emission is accounted for by the ionized gas in the inner edge of the disk. A simple modeling of the astrometry, however, indicates that the accretion inflow similarly well reproduces the centroid displacements of Brγ, but only if the position angles of the centroid motion and the projected disk ellipse are a chance coincidence. No clear evidence of disk wind is found.

Where is the warm H2? A search for H2 emission from disks around Herbig Ae/Be stars

Context. Mid-infrared (mid-IR) emission lines of molecular hydrogen (H2) are useful probes to determine the mass of warm gas present in the surface layers of circumstellar disks. In the past years, numerous observations of Herbig Ae/Be stars (HAeBes) have been performed, but only two detections of H2 mid-IR emission toward HD 97048 and AB Aur have been reported. Aims. We aim at tracing the warm gas in the circumstellar environment of five additional HAeBes with gas-rich environments and/or physical characteristics close to those of AB Aur and/or HD 97048, to discuss whether the detections toward these two objects are suggestive of peculiar conditions for the observed gas. Methods. We search for the H2 S(1) emission line at 17.035 μm using high-resolution mid-IR spectra obtained with VLT/VISIR, and complemented by CH molecule observations with VLT/UVES. We gather the H2 measurements from the literature to put the new results in context and search for a correlation with some disk properties. Results. None of the five VISIR targets shows evidence for H2 emission at 17.035 μm. From the 3σ upper limits on the integrated line fluxes we constrain the amount of optically thin warm (>150 K) gas to be less than ∼1.4 MJup in the disk surface layers. There are now 20 HAeBes observed with VISIR and TEXES instruments to search for warm H2, but only two detections (HD 97048 and AB Aur) were made so far. We find that the two stars with detected warm H2 show at the same time high 30/13 μm flux ratios and large PAH line fluxes at 8.6 and 11.3 μm compared to the bulk of observed HAeBes and have emission CO lines detected at 4.7 μm. We detect the CH 4300.3 A absorption line toward both HD 97048 and AB Aur with UVES .T he CH to H 2 abundance ratios that this would imply if it were to arise from the same component as well as the radial velocity of the CH lines both suggest that CH arises from a surrounding envelope, while the detected H2 would reside in the disk. Conclusions. The two detections of the S(1) line in the disks of HD 97048 and AB Aur suggest either peculiar physical conditions or a particular stage of evolution. New instruments such as Herschel / PACS should bring significant new data for the constraints of thermodynamics in young disks by observing the gas and the dust simultaneously.

HD 144432: A young triple system

We present new imaging and spectroscopic data of the young Herbig star HD 144432 A, which is a well-known binary star with a separation of 1.47 �� . High-resolution NIR imaging data obtained with NACO at the VLT reveal that HD 144432 B itself is a close binary pair with a separation of 0.1 �� . High-resolution optical spectra, acquired with FEROS at the 2.2m MPG/ESO telescope in La Silla, of the primary star and its co-moving companions are used to determine their main stellar parameters, such as effective temperature, surface gravity, radial velocity, and projected rotational velocity by fitting synthetic spectra to the observed stellar spectra. The two companions, HD 144432 B and HD 144432 C, are identified as low-mass T Tauri stars of spectral type K7V and M1V, respectively. From the position in the HRD, the triple system appears to be co-eval with a system age of 6 ± 3M yr.

The young B-star quintuple system HD 155448

Astronomy and Astrophysics 533 (2011): A54 reproduced with permission from Astronomy & Astrophysics

SPIRou @CFHT: full in-lab and on-sky performances

SPIRou is the new high resolution echelle spectropolarimeter and high-precision velocimeter, in the near infra- red, for the 3.6m Canada-France-Hawaii Telescope (CFHT Mauna Kea). This next generation instrument aims at detecting and characterizing Earth-like planets in the habitable zone of low-mass dwarfs and at investigating how magnetic fields impact star and planet formation. SPIRou consists of an achromatic polarimetric module coupled with a fluoride fiber link to a thermally-controlled cryogenic echelle spectrograph, and a Calibration Unit which can fed the light of hollow-cathod lamps, a radial velocity reference (Fabry-Pérot), or a cold source to the polarimeter and/or the spectrograph. Here we present a summary of the full performances obtained in laboratory tests carried in Toulouse (France), and the first results of the on-going commissioning at the CFHT. SPIRou covers a spectral range from 0.96 to 2.48 μm (YJHK domain) in one single exposure at a resolving power of 70 K, providing unpolarized and polarized spectra (with sensitivity 10 ppm) of stars, with a 10 15% peak throughput. Lab tests demonstrate that SPIRou is capable of achieving a relative radial velocity precision better than 0.2 m/s rms on timescales of 24 hr. Science operations of SPIRou are expected to start in 2018 S2, enabling significant synergies with major space and ground instruments such as the JWST, TESS, ALMA and later-on PLATO and the ELT.