{"id":68,"date":"2019-01-20T08:32:29","date_gmt":"2019-01-20T13:32:29","guid":{"rendered":"https:\/\/sites.bu.edu\/smallstars\/?page_id=68"},"modified":"2026-01-09T03:43:57","modified_gmt":"2026-01-09T08:43:57","slug":"projects","status":"publish","type":"page","link":"https:\/\/sites.bu.edu\/smallstars\/projects\/","title":{"rendered":"Research Projects and Papers"},"content":{"rendered":"

All refereed publications on ADS.<\/a><\/h4>\n

Atmospheres of Brown Dwarfs and Rogue Planets<\/h4>\n

We are part of an international collaboration investigating the atmospheres of “planetary mass objects” (also called “rogue planets”) and brown dwarfs: celestial objects without the necessary mass for sustained hydrogen fusion in their cores.\u00a0 We use ground and space-based telescopes to measure brightness variations as the objects rotate, revealing their atmospheric surfaces.\u00a0 By observing brightness variations at different wavelengths, we probe different layers of their atmospheres.\u00a0 See the following links to papers and press releases:<\/p>\n

NASA’s Webb Exposes Complex Atmosphere of Starless Super-Jupiter<\/a><\/p>\n

The JWST Weather Report from the Isolated Exoplanet Analog SIMP 0136+0933: Pressure-dependent Variability Driven by Multiple Mechanisms<\/a><\/p>\n

The JWST weather report from the nearest brown dwarfs I: multiperiod JWST NIRSpec + MIRI monitoring of the benchmark binary brown dwarf WISE 1049AB<\/a><\/p>\n

Multiple Patchy Cloud Layers in the Planetary-mass Object SIMP 0136+0933<\/a><\/p>\n

PINES: The Perkins INfrared Exosatellite Survey<\/h4>\n
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Our logo, designed by P. Tamburo<\/figcaption><\/figure>\n

Project website: https:\/\/pines.bu.edu<\/a><\/p>\n

PINES is a search for exosatellites transiting the nearest L and T dwarfs. \u00a0L and T dwarfs can be either hydrogen-fusing stars, brown dwarfs or planetary-mass objects. \u00a0Objects that orbit L and T dwarfs could be classified as either exoplanets or exomoons, depending on the host, so we prefer the more general term exosatellite<\/em>. \u00a0We are currently searching for exosatellites orbiting L and T dwarfs via the transit method<\/a>\u00a0with the Mimir infrared camera<\/a> on Boston University’s 1.83-meter Perkins Telescope<\/a>. \u00a0For the survey design, please see this paper led by current PhD student Patrick Tamburo:<\/p>\n

Tamburo, P., & Muirhead, P. S. “Design Considerations for a Ground-based Search for Transiting Planets around L and T Dwarfs”, 2019, Publications of the Astronomical Society of the Pacific,131, 114401.\u00a0<\/a><\/p>\n

The following two papers discuss our initial results and our first exosatellite candidate:<\/p>\n

Tamburo, P., Muirhead, P. S., McCarthy, A. M., Hart, M., Gracia, D., Vos, J. M., Bardalez Gagliuffi, D. C., Faherty, J., Theissen, C., Agol, E., Skinner, J. N., & Sagear, S. “The Perkins INfrared Exosatellite Survey (PINES) I. Survey Overview, Reduction Pipeline, and Early Results”, 2022, The Astronomical Journal,163, 253.<\/a><\/p>\n

Tamburo, P., Muirhead, P. S., McCarthy, A. M., Hart, M., Vos, J. M., Agol, E., Theissen, C., Gracia, D., Bardalez Gagliuffi, D. C., & Faherty, J. “The Perkins INfrared Exosatellite Survey (PINES). II. Transit Candidates and Implications for Planet Occurrence around L and T Dwarfs”, 2022, The Astronomical Journal,164, 252.<\/a><\/p>\n

The PINES name was inspired by the ponderosa pine trees that surround the Perkins Telescope. \u00a0PINES is a collaboration between Boston University (PI: P. Muirhead),\u00a0\u00a0the American Museum of Natural History, the University of Washington and UC San Diego. \u00a0Support for this project is provided by NASA’s Exoplanet Research Program.<\/p>\n

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Animation showing the Perkins Telescope and surrounding ponderosa pine trees during an observing run.<\/figcaption><\/figure>\n

<\/h4>\n

Brief but Spectacular: New Windows in the Physics of Common Envelope Evolution<\/h4>\n

Funded by two NSF awards, the Low-mass Star Group is partnering with the Rochester Institute of Technology and the University of Toronto to investigate the common envelope (CE) phase of binary stars. \u00a0The CE phase of binary star evolution is short lived: only about 1000 years. \u00a0As such, we are very unlikely to witness the common envelope phase of a binary star, given astronomical time scales. \u00a0However, post-common envelope (post-CE) systems are relatively common, consisting of a white dwarf and (typically) an M dwarf star. \u00a0In this project, we will identify and investigate post-CE systems in clusters, measuring the stellar masses, radii and luminosities. \u00a0Combined with cluster ages, we aim to flesh out the physics of this “brief but spectacular” phase of stellar evolution. \u00a0Our first paper, led by Steffani Grondin (UT PhD -> Postdoc at UCSD ) is here:<\/p>\n

Grondin, S. M., Drout, M. R., Nordhaus, J., Muirhead, P. S., Speagle, J. S., & Chornock, R. “The First Catalog of Candidate White Dwarf\u2500Main-sequence Binaries in Open Star Clusters: A New Window into Common Envelope Evolution”, 2024, The Astrophysical Journal,976, 102.<\/a><\/p>\n

A Fresh Look at M Dwarfs<\/h4>\n

Funded by the NSF, we are partnering with Arizona State University and the University of California Santa Cruz to develop new techniques for modeling the spectra of M dwarf stars.\u00a0 Specifically, we are applying “atmospheric retrieval” methods that typically used on brown dwarfs to M dwarf stars.\u00a0 See the following papers, led Aishwarya Iyer (ASU PhD -> NPP at NASA Goddard):<\/p>\n

Iyer, A. R., Line, M. R., Muirhead, P. S., Fortney, J. J., & Gharib-Nezhad, E. “The SPHINX M-dwarf Spectral Grid. I. Benchmarking New Model Atmospheres to Derive Fundamental M-dwarf Properties”, 2023, The Astrophysical Journal,944, 41.<\/a><\/p>\n

Iyer, A. R., Line, M. R., Muirhead, P. S., Fortney, J. J., & Faherty, J. K. “The SPHINX M dwarf Spectral Grid. II. New Model Atmospheres and Spectra to Derive Fundamental Properties of mid-to-late type M-dwarfs”, 2026, The Astrophysical Journal in press<\/em>.<\/a><\/p>\n

Chemical Ages of M Dwarf Stars<\/h4>\n

It is particularly challenging to measure the ages of M dwarf stars. \u00a0Recently, we developed new techniques to estimate M dwarf ages based on their abundances, specifically their \u03b1-element enhancement over iron, or [\u03b1\/Fe]. \u00a0 Iron and \u03b1-elements are dispersed into the Galaxy by different types of supernovae, which occur at different rates in the past. \u00a0The ratio of \u03b1-elements to iron in a star can tell us the gas content of the Milky Way\u00a0when<\/em>\u00a0and where<\/em>\u00a0the star formed.<\/p>\n

Recent group member Mark Veyette (BU PhD ’18) developed a technique to measure Ti48<\/sup> and Fe abundances of M dwarf stars using their absorption lines in high-resolution Y-band spectra obtained at Keck Observatory<\/a>. \u00a0Though not technically an \u03b1-element,\u00a0Ti48<\/sup> is a rapid decay product of Cr48<\/sup>, a true\u00a0\u03b1-element.<\/p>\n

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Figure from Veyette et al. (2017) showing Keck-NIRSPEC spectra of M dwarfs in Y-band. Green bands correspond to Ti lines and purple bands correspond to Fe lines.<\/figcaption><\/figure>\n

Using these data, we can now infer ages of M dwarf stars by their\u00a0\u03b1-element enhancement over iron. \u00a0For the final chapter of Mark’s thesis, he determined the ages of canonical M dwarf stars that host planets. \u00a0He found that planets orbiting M dwarf stars can remain in eccentric orbits for billions of years. \u00a0For papers related to this work, please see:<\/p>\n

Veyette, M. J. & Muirhead, P. S. “Chemo-kinematic Ages of Eccentric-planet- hosting M Dwarf Stars”, 2018, The Astrophysical Journal,863, 166.\u00a0<\/a><\/p>\n

Veyette, M. J., Muirhead, P. S., Mann, A. W., Brewer, J. M., Allard, F. & Homeier, D. “A Physically Motivated and Empirically Calibrated Method to Measure the Effective Temperature, Metallicity, and Ti Abundance of M Dwarfs”, 2017, The Astrophysical Journal,851, 26.\u00a0<\/a><\/p>\n

Veyette, M. J., Muirhead, P. S., Mann, A. W. & Allard, F. “The Physical Mechanism Behind M Dwarf Metallicity Indicators and the Role of C and O Abundances”, 2016, The Astrophysical Journal,828, 95.\u00a0<\/a><\/p>\n

Support for this project is provided by the National Science Foundation’s Astronomy and Astrophysics Research Grants program.<\/p>\n

Magnetic Inflation and Stellar Mass<\/h4>\n

For several decades there has been a mismatch between the observed sizes of M dwarf stars and predictions for stellar models. \u00a0There are several proposals to explain the discrepancy, and in this program we are aiming to determine specifically the cause of the mismatch. \u00a0We are using the\u00a0Discovery Channel Telescope<\/a>\u00a0and NASA’s Infrared Telescope Facility<\/a> to measure precise and accurate masses and radii of M dwarfs. \u00a0This work is the primary effort of current PhD student Eunkyu Han:<\/p>\n

 <\/p>\n

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Figure from Han et al. (2019) showing masses and radii of M dwarf stars in eclipsing binary systems, and predictions from evolutionary models.<\/p>\n

For papers related to this work, please see:<\/p>\n

Muirhead, P. S., Veyette, M. J., Newton, E. R., Theissen, C. A., & Mann, A. W. “Magnetic Inflation and Stellar Mass. V. Intensification and saturation of M dwarf absorption lines with Rossby number”, 2019, arXiv e-prints, arXiv:1912.01004.<\/a><\/p>\n

Han, E., Muirhead, P. S., & Swift, J. J. “Magnetic Inflation and Stellar Mass. IV. Four Low-mass Kepler Eclipsing Binaries Consistent with Non-magnetic Stellar Evolutionary Models”, 2019, The Astronomical Journal,158, 111.\u00a0<\/a><\/p>\n

Healy, B. F., Han, E., Muirhead, P. S., Skiff, B., Polakis, T., Rilinger, A., & Swift, J. J. “Magnetic Inflation and Stellar Mass. III. Revised Parameters for the Component Stars of NSVS 07394765”, 2019, The Astronomical Journal,158, 89.\u00a0<\/a><\/p>\n

Kesseli, A. Y., Muirhead, P. S., Mann, A. W. & Mace, G. “Magnetic Inflation and Stellar Mass. II. On the Radii of Single, Rapidly Rotating, Fully Convective M-Dwarf Stars”, 2018, The Astronomical Journal,155, 225.\u00a0<\/a><\/p>\n

Han, E., Muirhead, P. S., Swift, J. J., Baranec, C., Law, N. M., Riddle, R., Atkinson, D., Mace, G. N. & DeFelippis, D. “Magnetic Inflation and Stellar Mass. I. Revised Parameters for the Component Stars of the Kepler Low-mass Eclipsing Binary T-Cyg1-12664”, 2017, The Astronomical Journal,154, 100.\u00a0<\/a><\/p>\n

Support for this project was provided by NASA’s Exoplanet Research Program.<\/p>\n

The Transiting Exoplanet Survey Satellite (TESS)<\/h4>\n

In support of NASA’s TESS Mission (lead institution: MIT), we developed a catalog of cool dwarf stars for inclusion into the Candidate Target List, a prioritized list of stars for short-cadence observations. \u00a0The following paper describes the first Cool Dwarf Catalog, with the second paper currently\u00a0in prep<\/em>:<\/p>\n

Muirhead, P. S., Dressing, C. D., Mann, A. W., Rojas-Ayala, B., L\u00e9pine, S., Paegert, M., De Lee, N., & Oelkers, R. “A Catalog of Cool Dwarf Targets for the Transiting Exoplanet Survey Satellite”, 2018, The Astronomical Journal,155, 180.<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

All refereed publications on ADS. Atmospheres of Brown Dwarfs and Rogue Planets We are part of an international collaboration investigating the atmospheres of “planetary mass objects” (also called “rogue planets”) and brown dwarfs: celestial objects without the necessary mass for sustained hydrogen fusion in their cores.\u00a0 We use ground and space-based telescopes to measure brightness […]<\/p>\n","protected":false},"author":7725,"featured_media":0,"parent":0,"menu_order":5,"comment_status":"closed","ping_status":"closed","template":"page-templates\/no-sidebars.php","meta":[],"_links":{"self":[{"href":"https:\/\/sites.bu.edu\/smallstars\/wp-json\/wp\/v2\/pages\/68"}],"collection":[{"href":"https:\/\/sites.bu.edu\/smallstars\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sites.bu.edu\/smallstars\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sites.bu.edu\/smallstars\/wp-json\/wp\/v2\/users\/7725"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.bu.edu\/smallstars\/wp-json\/wp\/v2\/comments?post=68"}],"version-history":[{"count":48,"href":"https:\/\/sites.bu.edu\/smallstars\/wp-json\/wp\/v2\/pages\/68\/revisions"}],"predecessor-version":[{"id":662,"href":"https:\/\/sites.bu.edu\/smallstars\/wp-json\/wp\/v2\/pages\/68\/revisions\/662"}],"wp:attachment":[{"href":"https:\/\/sites.bu.edu\/smallstars\/wp-json\/wp\/v2\/media?parent=68"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}