Searching for Exoplanets Using a Microresonator Astrocomb.

Orbiting planets induce a weak radial velocity (RV) shift in the host star that provides a powerful method of planet detection. Importantly, the RV technique provides information about the exoplanet mass, which is unavailable with the complementary technique of transit photometry. However, RV detection of an Earth-like planet in the 'habitable zone'1 requires extreme spectroscopic precision that is only possible using a laser frequency comb (LFC)2. Conventional LFCs require complex filtering steps to be compatible with astronomical spectrographs, but a new chip-based microresonator device, the Kerr soliton microcomb3-8, is an ideal match for astronomical spectrograph resolution and can eliminate these filtering steps. Here, we demonstrate an atomic/molecular line-referenced soliton microcomb as a first in-the-field demonstration of microcombs for calibration of astronomical spectrographs. These devices can ultimately provide LFC systems that would occupy only a few cubic centimetres9,10, thereby greatly expanding implementation of these technologies into remote and mobile environments beyond the research lab.

Demonstration of a near-IR line-referenced electro-optical laser frequency comb for precision radial velocity measurements in astronomy.

An important technique for discovering and characterizing planets beyond our solar system relies upon measurement of weak Doppler shifts in the spectra of host stars induced by the influence of orbiting planets. A recent advance has been the introduction of optical frequency combs as frequency references. Frequency combs produce a series of equally spaced reference frequencies and they offer extreme accuracy and spectral grasp that can potentially revolutionize exoplanet detection. Here we demonstrate a laser frequency comb using an alternate comb generation method based on electro-optical modulation, with the comb centre wavelength stabilized to a molecular or atomic reference. In contrast to mode-locked combs, the line spacing is readily resolvable using typical astronomical grating spectrographs. Built using commercial off-the-shelf components, the instrument is relatively simple and reliable. Proof of concept experiments operated at near-infrared wavelengths were carried out at the NASA Infrared Telescope Facility and the Keck-II telescope.

A New Supernova Remnant Coincident with the Slow X-Ray Pulsar AX J1845-0258.

We report on Very Large Array observations in the direction of the recently discovered slow X-ray pulsar AX J1845-0258. In the resulting images, we find a 5&arcmin; shell of radio emission; the shell is linearly polarized with a nonthermal spectral index. We classify this source as a previously unidentified, young (<8000 yr) supernova remnant (SNR), G29.6+0.1, which we propose is physically associated with AX J1845-0258. The young age of G29.6+0.1 is then consistent with the interpretation that anomalous X-ray pulsars (AXPs) are isolated, highly magnetized neutron stars ("magnetars"). Three of the six known AXPs can now be associated with SNRs; we conclude that AXPs are young ( less, similar10,000 yr) objects and that they are produced in at least 5% of core-collapse supernovae.

A Giant Glitch in the Energetic 69 Millisecond X-Ray Pulsar AXS J161730-505505.

We present new results on the recently discovered 69 ms X-ray pulsar AXS J161730-505505, the sixth youngest example of a rotation-powered pulsar. We have undertaken a comprehensive X-ray-observing campaign of AXS J161730-505505 with the ASCA, BeppoSAX, and RXTE observatories and follow its long-term spin-down history between 1989 and 1999 using these observations and archival Ginga and ASCA data sets. The spin-down is not simply described by a linear function as originally thought, but instead we find evidence of a giant glitch (DeltaP&solm0;P greater, similar10-6) between 1993 August and 1997 September, perhaps the largest yet observed from a young pulsar. The glitch is well described by steps in P and P&d2; accompanied by a persistent P&d3; similar to those seen in the Vela pulsar. The pulse profile of AXS J161730-505505 presents a single asymmetric peak that is maintained over all observation epochs. The energy spectrum is also steady over time, characterized by a highly absorbed power law with a photon index Gamma=1.4+/-0.2, consistent with that found for other young rotation powered pulsars.