We are designing and constructing a new SETI (Search for Extraterrestrial Intelligence) instrument to search for direct evidence of interstellar communications via pulsed laser signals at near-infrared wavelengths. The new instrument design builds upon our past optical SETI experiences, and is the first step toward a new, more versatile and sophisticated generation of very fast optical and near-infrared pulse search devices. We present our instrumental design by giving an overview of the opto-mechanical design, detector selection and characterization, signal processing, and integration procedure. This project makes use of near-infrared (950 -1650 nm) discrete amplification Avalanche Photodiodes (APD) that have > 1 GHz bandwidths with low noise characteristics and moderate gain (~10 4 ). We have investigated the use of single versus multiple detectors in our instrument (see Maire et al., this conference), and have optimized the system to have both high sensitivity and low false coincidence rates. Our design is optimized for use behind a 1m telescope and includes an optical camera for acquisition and guiding. A goal is to make our instrument relatively economical and easy to duplicate. We describe our observational setup and our initial search strategies for SETI targets, and for potential interesting compact astrophysical objects.

The near-infrared region offers a compelling window for interstellar communications, energy transfer, and transient detection due to low extinction and low thermal emission from dust. We have conducted a search for near-infrared (950-1650 nm) light pulses having durations less than 50 nanoseconds while observing 1280 astronomical objects which include a wide range of nearby stars, clusters, and galaxies. A field of view of 2 5 × 2 5 for a duration of at least 300 s was observed for each object pointing. These observations were made using the latest Near-InfraRed Optical SETI instrumentation on the Nickel telescope (1 m) at Lick Observatory. Equipped with two detectors collecting photons coming from the same part of the sky, the instrument is aimed at detecting light pulses coincident between them within nanoseconds, as well as periodic signals. While we report on a few notifications from our system, we believe these events were consistent with the statistical noise of our data. No significant evidence for repeated near-infrared nanosecond pulsed signal was found, given the instrumental limit in sensitivity of 63 ph m −2 ns −1 .

Context. It is well known that stellar companions can influence the evolution of a protoplanetary disk. Nevertheless, previous disk surveys did not -and could not -consistently exclude binaries from their samples. Aims. We present a study dedicated to investigating the frequency of ongoing disk accretion around single stars in a star-forming region. Methods. We obtained near-infrared spectroscopy of 54 low-mass stars selected from a high-angular resolution survey in the 2-3 Myrold Chamaeleon I region to determine the presence of Brackett-γ emission, taking the residual chance of undetected multiplicity into account, which we estimate to be on the order of 30%. The result is compared with previous surveys of the same feature in binary stars of the same region to provide a robust estimate of the difference between the accretor fractions of single stars and individual components of binary systems. Results. We find Brγ emission among 39.5 +14.0 −9.9 % of single stars, which is a significantly higher fraction than for binary stars in Chamaeleon I. In particular, close binary systems with separations <100 AU show emission in only 6.5 +16.5 −3.0 % of the cases according to the same analysis. The emitter frequency of wider binaries appears consistent with the single star value. Interpreting Brγ emission as a sign of ongoing accretion and correcting for sensitivity bias, we infer an accretor fraction of single stars of F acc = 47.8 +14.0 −9.9 %. This is slightly higher but consistent with previous estimates that do not clearly exclude binaries from their samples. Conclusions. Through our robust and consistent analysis, we confirm that the fraction of young single stars harboring accretion disks is much larger than that of close binaries at the same age. Our findings have important implications for the timescales of disk evolution and planet formation.

Maximizing the grating efficiency is a key goal for the first light instrument IR.IS (Infrared Imaging Spectrograph) currently being designed to sample the diffraction limit of the TMT (Thirty Meter Telescope). Volume Phase Holographic (VPH) gratings have been shown to offer extremely high efficiencies that approach 100% for high line frequencies (i.e., 600 to 60001/mm), which has been applicable for astronomical optical spectrographs. However, VPH gratings have been less exploited in the near-infrared, particularly for gratings that have lower line frequencies. Given their potential to offer high throughputs and low scattered light, VPH gratings are being explored for IR.IS as a potential dispersing element in the spectrograph. Our team has procured near-infrared gratings from t\¥0 separate vendors. We have t\¥0 gratings with the specifications needed for IR.IS current design: l.5 l-l.82µm (H-band) to produce a spectral resolution of 4000 and 1.19-1.3 7µm (J-band) to produce a spectral resolution of 8000. ' The center wavelengths for each grating are l.629µm and l.27µm, and the groove densities are 1771/mm and 4401/mm for H-band R=4000 and J-band R=8000, respectively. We directly measure the efficiencies in the lab and find that the peak efficiencies of these t\¥0 types of gratings are quite good with a peak efficiency of ~88% at the Bragg angle in both TM and TE modes at H-band, and 90.23% in TM mode, 79.91 % in TE mode at J-band for the best vendor. We determine the drop in efficiency off the Bragg angle, with a 20-23% decrease in efficiency at H-band when 2.5° deviation from the Bragg angle, and 25%-28% decrease at J-band \Vhen 5° dev iation from the Bragg angle.