Sky coverage and tip/tilt error analysis for TMT

A Monte Carlo sky coverage model for laser guide star adaptive optics systems is presented. This model provides fast Monte Carlo simulations of the tip/tilt (TT) wavefront error calculated with minimum variance estimators over natural guide star constellations generated from star models. With this simulation code we are able to generate a TT error budget for the Thirty Metre Telescope (TMT) facility Narrow Field Infra-Red Adaptive Optics System (NFIRAOS), and perform several design trade studies. With the current NFIRAOS design, the median TT error at the galactic pole with median seeing is calculated to be 65 nm or 1.8 mas

High-resolution imaging at the SOAR telescope

Bright single and binary stars were observed at the 4.1-m telescope with a fast electron-multiplication camera in the regime of partial turbulence correction by the visible-light adaptive optics system. We compare the angular resolution achieved by simple averaging of AO-corrected images (long-exposure), selection and re-centering (shift-and-add or "lucky" imaging) and speckle interferometry. The effect of partial AO correction, vibrations, and image post-processing on the attained resolution is shown. Potential usefulness of these techniques is evaluated for reaching the diffraction limit in ground-based optical imaging. Measurements of 75 binary stars obtained during these tests are given and objects of special interest are discussed. We report tentative resolution of the astrometric companion to Zeta Aqr B. A concept of advanced high-resolution camera is outlined.Comment: Accepted for publication in PASP. 14 pages, 9 figures, 2 tabl

Giant Planet Companion to 2MASSW J1207334-393254

We report new VLT/NACO imaging observations of the young, nearby brown dwarf 2MASSW J1207334-393254 and its suggested planetary mass companion (2M1207 b). Three epochs of VLT/NACO measurements obtained over nearly one year show that the planetary mass companion candidate shares the same proper motion and, with a high confidence level, is not a stationary background object. This result confirms the status of 2M1207 b as of planetary mass (5 times the mass of Jupiter) and the first image of a planetary mass companion in a different system than our own. This discovery offers new perspectives for our understanding of chemical and physical properties of planetary mass objects as well as their mechanisms of formation.Comment: 4 pages, 2 figures. accepted in Astronomy & Astrophysic

Five new very low mass binaries

We report the discovery of companions to 5 nearby late M dwarfs (>M5), LHS1901, LHS4009, LHS6167, LP869-26 and WT460, and we confirm that the recently discovered mid-T brown dwarf companion to SCR1845-6357 is physically bound to that star. These discoveries result from our adaptive optics survey of all M dwarfs within 12 pc. The new companions have spectral types M5 to L1, and orbital separations between 1 and 10 AU. They add significantly to the number of late M dwarfs binaries in the immediate solar neighbourhood, and will improve the multiplicity statistics of late M dwarfs. The expected periods range from 3 to 130 years. Several pairs thus have good potential for accurate mass determination in this poorly sampled mass range.Comment: 5 pages, 2 figures, submitted to Astronomy & Astrophysic

NFIRAOS: TMT facility adaptive optics with conventional DMs

Although many of the instruments planned for the TMT (Thirty Meter Telescope) have their own closely-coupled adaptive optics systems, TMT will also have a facility Adaptive Optics (AO) system feeding three instruments on the Nasmyth platform. For this Narrow-Field Infrared Adaptive Optics System, NFIRAOS (pronounced nefarious), the TMT project considered two architectures. One, described in this paper, employs conventional deformable mirrors with large diameters of about 300 mm and this is the reference design adopted by the TMT project. An alternative design based on MEMS was also studied, and is being presented separately in this conference. The requirements for NFIRAOS include 0.8-5 microns wavelength range, 30 arcsecond diameter output field of view (FOV), excellent sky coverage, and diffraction- limited atmospheric turbulence compensation (specified at 133 nm RMS including residual telescope and science instrument errors.) The reference design for NFIRAOS includes multiple sodium laser guide stars over a 70 arcsecond FOV, and an infrared tip/tilt/focus/astigmatism natural guide star sensor within instruments. Larger telescopes require greater deformable mirror (DM) stroke. Although initially NFIRAOS will correct a 10 arcsecond science field, it uses two deformable mirrors in series, partly to provide sufficient stroke for atmospheric correction over the 30 m telescope aperture, but mainly to partially correct a 2 arcminute diameter "technical" field to sharpen near-IR natural guide stars and improve sky coverage. The planned upgrade to full performance includes replacing the groundconjugated DM with a higher actuator density, and using a deformable telescope secondary mirror as a "woofer." NFIRAOS incorporates an instrument rotator and selection of three live instruments: a near-Infrared integral field Imaging spectrograph, a near-infrared echelle spectrograph, and after upgrading NFIRAOS to full multi-conjugation, a wide field (30 arcsecond) infrared camera

Adaptive optics imaging survey of the Tucana-Horologium association

We present the results of an adaptive optics (AO) imaging survey of the common associations of Tucana and Horologium, carried out at the ESO 3.6m telescope with the ADONIS/SHARPII system. Based on our observations of two dozen probable association members, HIP 1910 and HIP 108422 appear to have low-mass stellar companions, while HIP 6856 and GSC 8047-0232 have possible sub-stellar candidate companions. Astrometric measurements, performed in November 2000 and October 2001, indicate that HIP 1910 B likely is bound to its primary, but are inconclusive in the case of the candidate companion to HIP 6856. Additional observations are needed to confirm the HIP 6856 companionship as well as for HIP 108422 and GSC 8047-0232.Comment: 7 pages, 4 figures postscript. A&A accepte

A companion to AB Pic at the planet/brown dwarf boundary

We report deep imaging observations of the young, nearby star AB Pic, a member of the large Tucana-Horologium as sociation. We have detected a faint, red source 5.5" South of the star with JHK colors compatible with that of a young substellar L dwarf. Follow-up observations at two additional epochs confirm, with a confidence level of 4.7sigma, that the faint red object is a companion to AB Pic rather than it being a stationary background object. A low resolution K-band spectrum indicates an early-L spectral type for the companion. Finally, evolutionary model predictions based on the JHK photometry of AB Pic b indicate a mass of 13 to 14 MJup if its age is ~30Myr. Is AB Pic b a massive planet or a minimum mass brown dwarf?Comment: 4 pages, 3 figures. accepted in Astronomy & Astrophysic

Adaptive optics imaging of the MBM 12 association

We report adaptive optics (AO) observations of the young and nearby association MBM 12 obtained with the Canada-France-Hawaii Telescope. Our main observational result is the discovery of six new binary systems, LkHa 264, E 0255+2018, RX J0255.4+2005, S18, MBM 12-10, RX J0255.3+1915, and the confirmation of HD 17332, already known as a binary. We also detected a possible quadruple system. It is composed of the close binary LkHa 263 AB (separation of 0.41 ''), of LkH\alpha 262 located 15.25 '' from LkHa 263 A, and of LkHa 263 C, located 4.1 '' from LkH\alpha 263 A. A preliminary study of the binary fraction suggests a binary excess in the MBM 12 association as compared to the field and IC 348. Because of the high binarity rate, previous estimations of spectral types and measurements of IR excesses for several candidate members of MBM 12 have to be revised. LkH\alpha 263 C is a nebulous object that we interpret as a disk oriented almost perfectly edge-on and seen in scattered light. This object has already been reported by Jayawardhana et al. (2002). Scattered light models allow us to estimate some of the structural parameters (i.e. inclination, diameter and to a lesser extent dust mass) of the circumstellar disk. We find an inclination of 89^o and a outer radius for the disk, 165 AU if the distance to MBM 12 is 275 pc. With the present data set, we do not attempt to re-assess the distance to MBM 12. We estimate however that the distance to the candidate member RX J0255.3+1915 is d > 175 pc.Comment: 9 pages, 1 figure postscript, 6 figures .gi

NFIRAOS: TMT facility adaptive optics with conventional DMs

Although many of the instruments planned for the TMT (Thirty Meter Telescope) have their own closely-coupled adaptive optics systems, TMT will also have a facility Adaptive Optics (AO) system feeding three instruments on the Nasmyth platform. For this Narrow-Field Infrared Adaptive Optics System, NFIRAOS (pronounced nefarious), the TMT project considered two architectures. One, described in this paper, employs conventional deformable mirrors with large diameters of about 300 mm and this is the reference design adopted by the TMT project. An alternative design based on MEMS was also studied, and is being presented separately in this conference. The requirements for NFIRAOS include 0.8-5 microns wavelength range, 30 arcsecond diameter output field of view (FOV), excellent sky coverage, and diffraction- limited atmospheric turbulence compensation (specified at 133 nm RMS including residual telescope and science instrument errors.) The reference design for NFIRAOS includes multiple sodium laser guide stars over a 70 arcsecond FOV, and an infrared tip/tilt/focus/astigmatism natural guide star sensor within instruments. Larger telescopes require greater deformable mirror (DM) stroke. Although initially NFIRAOS will correct a 10 arcsecond science field, it uses two deformable mirrors in series, partly to provide sufficient stroke for atmospheric correction over the 30 m telescope aperture, but mainly to partially correct a 2 arcminute diameter "technical" field to sharpen near-IR natural guide stars and improve sky coverage. The planned upgrade to full performance includes replacing the groundconjugated DM with a higher actuator density, and using a deformable telescope secondary mirror as a "woofer." NFIRAOS incorporates an instrument rotator and selection of three live instruments: a near-Infrared integral field Imaging spectrograph, a near-infrared echelle spectrograph, and after upgrading NFIRAOS to full multi-conjugation, a wide field (30 arcsecond) infrared camera

New neighbours. III. 21 new companions to nearby dwarfs, discovered with adaptive optics

We present some results of a CFHT adaptive optics search for companions to nearby dwarfs. We identify 21 new components in solar neighbourhood systems, of which 13 were found while surveying a volume-limited sample of M dwarfs within 12pc. We are obtaining complete observations for this subsample, to derive unbiased multiplicity statistics for the very-low-mass disk population. Additionally, we resolve for the first time 6 known spectroscopic or astrometric binaries, for a total of 27 newly resolved companions. A fair fraction of the new binaries has favourable parameters for accurate mass determinations. The newly resolved companion of Gl120.1C had an apparent spectroscopic minimum mass in the brown-dwarf range (Duquennoy & Mayor 1991) and it contributed to the statistical evidence that a few percent of solar type stars might have close-in brown-dwarf companions. We find that Gl~120.1C actually is an unrecognised double-lined spectroscopic pair. Its radial-velocity amplitude had therefore been strongly underestimated by Duquennoy & Mayor, and it does not truly belong to their sample of single-lined systems with minimum spectroscopic mass below the substellar limit. We also present the first direct detection of Gl~494B, an astrometric brown-dwarf candidate. Its luminosity does straddle the substellar limit, and it is a brown dwarf if its age is less than 300Myr. A few more years of observations will ascertain its mass and status from first principles.Comment: Accepted by Astronomy & Astrophysic