Author Archives: Alexandra Zvia Greenbaum

Announcement of post-doctoral fellowship opportunities in Exoplanet Research

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Now is a great time to study exoplanets at the University of Michigan. We are looking to hire multiple postdoctoral scholars, to work with Professors Michael Meyer, John Monnier, and Emily Rauscher on various aspects of exoplanet research. Specifically, we are targeting the areas of:

The University of Michigan hosts a vibrant astrophysics research community within the Astronomy and Physics Departments, as well as significant expertise in planetary sciences within the Earth & Environmental Sciences and Climate & Space Sciences Departments. We are particularly strong in the interrelated study of stars, planets, and their formation (https://lsa.umich.edu/astro/research/stars-exoplanets.html). A postdoctoral researcher in our department can apply as PI to any of our telescope facility partnerships, currently including the Magellan Telescopes in Chile, the MDM Observatory in Arizona, the CHARA Interferometer, the SWIFT space telescope, and the NOEMA mm array. Significant computing resources are available through the Department and through the University of Michigan. The Michigan Institute for Research in Astrophysics funds cross-disciplinary efforts, including a series of intellectually stimulating conferences.

The University of Michigan is recognized as a top academic employer and Ann Arbor, Michigan is routinely celebrated for its high quality of life. We are a department that values diversity, equity, and inclusion as essential to scientific excellence (https://sites.google.com/umich.edu/astro-dei/home) and encourage applications from those with identities underrepresented in astronomy.

Please share this information with potentially interested persons, and do not hesitate to contact individual staff members conducting each individual search.

Sincerely,
Michael Meyer, John Monnier, and Emily Rauscher

Press release: VLT/SPHERE confirmation image of a newborn exoplanet

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ESO’s VLT/SPHERE announced today the confirmation images of an exoplanet inside the gap of the PDS 70 proto-planetary disk. Michael Meyer is part of the SPHERE consortium that has made this exciting discovery. Detailed results were released today in two manuscripts: discovery & confirmation paper, and characterization paper.

Detection of a planet caught in formation discovered by VLT/SPHERE from the ESO press release: https://www.eso.org/public/news/eso1821/

You can see the ESO press release here: https://www.eso.org/public/news/eso1821/

New paper on spectroscopy of HR 8799 planets c d and e

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Alex Greenbaum, along with the GPI team, has had a paper accepted to the Astronomical Journal presenting new IFU spectroscopy of three planets around HR 8799 using the Gemini Planet Imager. The paper uses a forward modeling algorithm first presented in Pueyo et al. (2016) to account for self-subtraction effects common to PCA-style stellar PSF subtraction algorithms. This was especially valuable for obtaining robust results for the innermost planet e.

Documentation for the software used in this paper is available here.

Images of the HR 8799 system with the stellar PSF subtracted via the KLIP algorithm (Soummer et al. 2012) using the PyKLIP open source package. (Figure taken from Greenbaum et al. 2018, https://arxiv.org/abs/1804.07774). The central part of the image is blocked for clarity. The top and bottom panels are reduced with different algorithm parameters, as described in the text. Planet e has moved noticeably along its orbit between the 2013 and 2016 observations.

A comparison of the three planets’ spectra to a few different atmospheric models show that multiple physical mechanisms (e.g., non-equilibrium chemistry, clouds) can reproduce the emission. In addition the paper does a statistical comparison of the three spectra showing clear differences between HR 8799 c and d.

A preprint is available on the arXiv: GPI spectra of HR 8799 c, d, and e from 1.5 to 2.4μm with KLIP Forward Modeling

Document on Thermal-IR Opportunity with ELTs answers call for Exoplanet Science Strategy Papers

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Recently the National Academy of Sciences put out a call for papers addressing strategies for pursuing exoplanet science in the coming decade. Michael Meyer is lead author on white paper, “Finding and Characterizing Other Worlds: the Thermal-IR ELT Opportunity.” The document outlines the opportunity for imaging terrestrial and super-Earth planets with thermal-IR imaging on next generation ELTs.

You can read the paper by clicking here.

Press release on JWST programs to study brown dwarfs

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NGC 1333 will be a target of an upcoming JWST Guaranteed time program that our group is involved in. Credits: NASA/CXC/JPL

NASA has put out a press release detailing the plan to study very low mass brown dwarfs with JWST though time guaranteed to the instrument teams. From our group, Michael Meyer is a member of the NIRISS and NIRCam instrument teams and is co-Investigator on these exciting programs. Alexandra Greenbaum is part of the NIRISS AMI working group, and is Co-I to a program that will use interferometric methods to search for binaries around a few very low mass objects.

To see the press release: https://www.nasa.gov/feature/goddard/2018/nasa-s-webb-telescope-to-investigate-mysterious-brown-dwarfs

A related program on NIRCam led by our group will search for very low mass free floating objects in NGC 2024, taking advantage of the low thermal background provided by JWST. Veenu Suri from our group will be presenting a poster based on his work from the past year at the American Astronomical Society winter meeting this Thurs Jan 11 (2018). His poster is number 355.10.  Veenu explored various combinations of filters on NIRCam that would provide the most information for distinguishing young, low gravity objects, from line-of-sight field objects.

Successful Early Science Release Proposal for JWST

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This week came with the announcement of selected Early Release Science (ERS) programs for the James Webb Space Telescope as a part of the Director’s Discretionary Time. ERS programs are an opportunity for investigators to have access to the earliest science data and test out various instrument modes. In turn the successful ERS teams deliver science-enabling products to the community, a set of software tools, data reduction procedures, and/or performance assessments. These are to facilitate future observation cycles and subsequent data reduction. Several University of Michigan affiliates are investigators of selected ERS programs including professors, research staff, and graduate students.

 

From our group Prof. Michael Meyer and Dr. Alexandra Greenbaum are Co-Is for the “High Contrast Imaging of Exoplanets and Exoplanetary Systems with JWST” program (PI: Sasha Hinkley — U. Exeter). The 39-hour program includes high contrast imaging of a known exoplanetary system and a circumstellar debris disk, as well as spectroscopic characterization of a wide-separation planetary mass companion from 2-28 micron. The program with utilize NIRCam, NIRSpec, NIRISS, and MIRI. The abstract can be accessed here. Dr. Greenbaum is co-lead of the NIRISS Aperture Masking Interferometry (AMI) sub-program to place upper limits on the presence of bright companions close in to a known imaged exoplanet host and and to characterize the contrast limit of this imaging mode. JWST is scheduled to Launch in the spring of 2019 and ERS observations are expected to start towards the end of the year.

The Origins of Volatiles in Habitable Planets Meeting

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Image Credit: Amaury Triaud

Over Monday and Tuesday of this week, we (collaboration between UM faculty in Astronomy and Earth & Environmental Sciences) finished hosting a special interdisciplinary workshop through the Michigan Institute for Research in Astrophysics. This workshop, “The Origins of Volatiles in Habitable Planets: The Solar System and Beyond,” had a great mix of astronomers, planetary scientists, and geologists, as well as many scientists who straddle the intersections of these disciplines. Two days of talks emphasized the big questions in early solar system chemistry, delivery and retention of volatiles, and the measurements that put our theories to the test.

Our group was involved in the scientific and local organizing committees. Felicity presented a poster on her latest results of high contrast imaging around proxima Cen to rule out the presence of gas giants.

SPHERE Discovery of a Jupiter-like planet

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An international team of astronomers, using the SPHERE instrument on the European Southern Observatory’s Very Large Telescope have discovered a planetary mass companion orbiting a nearby star.  Prof. Michael Meyer is a member of the team and comments on the discovery in this Michigan News press release.

Image of the planet HIP 65426b (bottom left), produced with the SPHERE instrument. SPHERE has physically blocked out light from the central star (blocked-out region marked by circle) in order for the planets much weaker light to become detectable. The light received from the planet allows deductions about its properties – in this case the presence of water vapor and reddish clouds. Image: Chauvin et al. / SPHERE

The preprint article is out today: https://arxiv.org/abs/1707.01413

A quick visit to the lab

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Today in place of our usual weekly group meeting we all took a walk over to the Physics Department to have a look at our (empty) new lab. In this photo you can see our clean enclosure where we’ll set up our experiments to characterize new IR detectors.

While it’s not much to look at yet, having the lab construction done makes the upcoming projects feel more real and we are excited to get the rest of the lab set up over the next year. We look forward to sharing pictures when the lab is no longer empty!

Johannes Sahlmann visits for NIRISS-AMI pipeline development & shares his work on high precision astrometry

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Dr. Johannes Sahlmann, an instrument support scientist at the Space Telescope Science Institute, visited our group early last week. Part of his visit was to support his collaboration on the data analysis pipeline for the Aperture Masking Interferometry (AMI) mode on NIRISS. Johannes is involved in helping to understand and predict performance with AMI preceding the first JWST data. He is working closely with Alexandra to improve the data pipeline and set up simulations ahead of the real calibration data. The pipeline is being developed as a community tool.

Artist impression of Gaia. Copyright: ESA/ATG medialab from http://sci.esa.int/gaia/28820-summary/

Johannes also gave a talk at the Stars, Planets, and Formation group, describing his work combining high precision astrometry with radial velocities and imaging. Of particular interest was Gaia performance on nearby stars (in which Johannes has had an important role) and the timeline for obtaining a new sample of astrometry-detected planets with Gaia. He concluded by looking ahead to how Gaia will help prepare target lists for WFIRST direct imaging observations and for other future missions.