arXiv subjects

S. Goodsell

Publications and source records attributed to S. Goodsell.

4 recordsLinked to original sources

arXiv2019

Probing the Time Domain with High Spatial Resolution

Two groundbreaking new facilities will commence operations early in the 2020s and thereafter define much of the broad landscape of US optical-infrared astronomy in the remaining decade. The Large Synoptic Survey Telescope (LSST), perched atop Cerro Pachon in the Chilean Andes, will revolutionize the young field of Time Domain Astronomy through its wide-field, multi-band optical imaging survey. At the same time, the James Webb Space Telescope (JWST), orbiting at the Sun-Earth L2 Lagrange point, will provide stunningly high-resolution views of selected targets from the red end of the optical spectrum to the mid-infrared. However, the spatial resolution of the LSST observations will be limited by atmospheric seeing, while JWST will be limited in its time-domain capabilities. This paper highlights the scientific opportunities lying between these two landmark missions, i.e., science enabled by systems capable of astronomical observations with both high cadence in the time domain and high resolution in the spatial domain. The opportunities range from constraining the late phases of stellar evolution in nearby resolved populations to constraining dark matter distributions and cosmology using lensed transient sources. We describe a system that can deliver the required capabilities.

astro-ph.IM↗

arXiv2016

An M-dwarf star in the transition disk of Herbig HD 142527; Physical parameters and orbital elements

HD 142527A is one of the most studied Herbig Ae/Be stars with a transitional disk, as it has the largest imaged gap in any protoplanetary disk: the gas is cleared from 30 to 90 AU. The HD142527 system is also unique in that it has a stellar companion with a small mass compared to the mass of the primary star. This factor of ~20 in mass ratio between the two objects makes this binary system different from any other YSO. The HD142527 system could therefore provide a valuable test bed. This low-mass stellar object may be responsible for both the gap and dust trapping observed by ALMA at longer distances. We observed this system with the NACO and GPI instruments using the aperture masking technique. Aperture masking is ideal for providing high dynamic range even at very small angular separations. We present the spectral energy distribution for HD142527A and B. Brightness of the companion is now known from the R band up to the M' band. We also followed the orbital motion of HD 142527B over a period of more than two years. The SED of the companion is compatible with a T=3000+/-100K object in addition to a 1700K blackbody environment (likely a circus-secondary disk). From evolution models, we find that it is compatible with an object of mass 0.13+/-0.03Msun, radius 0.90+/-0.15Rsun, and age $1.0^{+1.0}_{-0.75}$Myr. This age is significantly younger than the age previously estimated for HD142527A. Computations to constrain the orbital parameters found a semi major axis of $140^{+120}_{-70}$mas, an eccentricity of 0.5+/-0.2, an inclination of 125+/-15 degrees, and a position angle of the right ascending node of -5+/-40 degrees. Inclination and position angle of the ascending node are in agreement with an orbit coplanar with the inner disk, not coplanar with the outer disk. Despite its high eccentricity, it is unlikely that HD142527B is responsible for truncating the inner edge of the outer disk.

astro-ph.SR↗

arXiv2015

Discovery and spectroscopy of the young Jovian planet 51 Eri b with the Gemini Planet Imager

Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric composition and luminosity, which is influenced by their formation mechanism. Using the Gemini Planet Imager, we discovered a planet orbiting the \$sim$20 Myr-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water vapor absorption. Modeling of the spectra and photometry yields a luminosity of L/LS=1.6-4.0 x 10-6 and an effective temperature of 600-750 K. For this age and luminosity, "hot-start" formation models indicate a mass twice that of Jupiter. This planet also has a sufficiently low luminosity to be consistent with the "cold- start" core accretion process that may have formed Jupiter.

astro-ph.EP↗

arXiv2013

Final A&T Stages of the Gemini Planet Finder

The Gemini Planet Imager (GPI) is currently in its final Acceptance & Testing stages. GPI is an XAO system based on a tweeter & woofer architecture (43 & 9 actuators respectively across the pupil), with the tweeter being a Boston Michromachines $64^2$ MEMS device. The XAO AO system is tightly integrated with a Lyot apodizing coronagraph. Acceptance testing started in February 2013 at the University of California, Santa Cruz. A conclusive acceptance review was held in July 2013 and the instrument was found ready for shipment to the Gemini South telescope on Cerro Pachon, Chile. Commissioning at the telescope will take place by the end of 2013, matching the summer window of the southern hemisphere. According to current estimates the 3 year planet finding campaign (890 allocated hours) might discover, image, and spectroscopically analyze 20 to 40 new exo-planets. Final acceptance testing of the integrated instrument can always bring up surprises when using cold chamber and flexure rig installations. The latest developments are reported. Also, we will give an overview of GPI's lab performance, the interplay between subsystems such as the calibration unit (CAL) with the AO bench. We report on-going optimizations on the AO controller loop to filter vibrations and last but not least achieved contrast performance applying speckle nulling. Furthermore, we will give an outlook of possible but challenging future upgrades as the implementation of a predictive controller or exchanging the conventional 48x48 SH WFS with a pyramid. With the ELT era arising, GPI will proof as a versatile and path-finding testbed for AO technologies on the next generation of ground-based telescopes.

astro-ph.IM↗