Search

We describe the design and initial results from a visible-light Lyot coronagraph for SCExAO/VAMPIRES. The coronagraph is comprised of four hard-edged, partially transmissive focal plane masks with inner working angles of 36 mas, 55 mas, 92 mas, and 129 mas, respectively. The Lyot stop is a reflective, undersized design with a geometric throughput of 65.7%. Our preliminary on-sky contrast is 1e-2 at 0.1" to 1e-4 at 0.75" for all mask sizes. The coronagraph was deployed in early 2022 and is available for open use., Comment: Proceedings of SPIE 2022 Astronomical Instrumentation and Telescopes conference (#12184-163) more...

We present deep imaging of Sirius B, the closest and brightest white dwarf, to constrain post-main-sequence planetary evolution in the Sirius system. We use Keck/NIRC2 in L'-band (3.776 $\mu$m) across three epochs in 2020 using the technique of angular differential imaging. Our observations are speckle-limited out to 1 AU and background-limited beyond. The 5$\sigma$ detection limits from our best performing epoch are 17 to 20.4 L' absolute magnitude. We consider multiple planetary formation pathways in the context of Sirius B's evolution to derive mass sensitivity limits, and achieve sub-Jupiter sensitivities at sub-AU separations, reaching 1.6 $\mathrm{M_J}$ to 2.4 $\mathrm{M_J}$ at 0.5 AU down to a sensitivity of 0.7 $\mathrm{M_J}$ to 1.2 $\mathrm{M_J}$ at >1 AU. Consistent with previous results, we do not detect any companions around Sirius B. Our strong detection limits demonstrate the potential of using high-contrast imaging to characterize nearby white dwarfs., Comment: 16 pages, 13 figures, accepted by the Astronomical Journal, code and extra figures available at https://github.com/mileslucas/sirius-b more...

We report here time domain infrared spectroscopy and optical photometry of the HD145263 silica-rich circumstellar disk system taken from 2003 through 2014. We find an F4V host star surrounded by a stable, massive 1e22 - 1e23 kg (M_Moon to M_Mars) dust disk. No disk gas was detected, and the primary star was seen rotating with a rapid ~1.75 day period. After resolving a problem with previously reported observations, we find the silica, Mg-olivine, and Fe-pyroxene mineralogy of the dust disk to be stable throughout, and very unusual compared to the ferromagnesian silicates typically found in primordial and debris disks. By comparison with mid-infrared spectral features of primitive solar system dust, we explore the possibility that HD 145263's circumstellar dust mineralogy occurred with preferential destruction of Fe-bearing olivines, metal sulfides, and water ice in an initially comet-like mineral mix and their replacement by Fe-bearing pyroxenes, amorphous pyroxene, and silica. We reject models based on vaporizing optical stellar megaflares, aqueous alteration, or giant hypervelocity impacts as unable to produce the observed mineralogy. Scenarios involving unusually high Si abundances are at odds with the normal stellar absorption near-infrared feature strengths for Mg, Fe, and Si. Models involving intense space weathering of a thin surface patina via moderate (T < 1300 K) heating and energetic ion sputtering due to a stellar superflare from the F4V primary are consistent with the observations. The space weathered patina should be reddened, contain copious amounts of nanophase Fe, and should be transient on timescales of decades unless replenished., 41 Pages, 5 Figures, 5 Tables, Accepted for publication in the Astrophysical Journal more...

Orhan, Zeynep Celik/0000-0002-9424-2339; Serenelli, Aldo/0000-0001-6359-2769; Monteiro, Mario J. P. F. G./0000-0003-0513-8116; Huber, Daniel/0000-0001-8832-4488; Adibekyan, Vardan/0000-0002-0601-6199; Reffert, Sabine/0000-0002-0460-8289; Stock, Stephan/0000-0002-1166-9338; Stassun, Keivan/0000-0002-3481-9052; Cunha, Margarida/0000-0001-8237-7343; Kuszlewicz, James/0000-0002-3322-5279; Lund, Mikkel Norup/0000-0001-9214-5642; Mathur, Savita/0000-0002-0129-0316; Nielsen, Martin Bo/0000-0001-9169-2599; Mosser, Benoit/0000-0002-7547-1208; Pereira, Filipe/0000-0002-2157-7146; Lucas, Miles/0000-0001-6341-310X; miglio, andrea/0000-0001-5998-8533; Ball, Warrick/0000-0002-4773-1017; Basu, Sarbani/0000-0002-6163-3472; Veras, Dimitri/0000-0001-8014-6162; Handberg, Rasmus/0000-0001-8725-4502; Christensen-Dalsgaard, Jorgen/0000-0001-5137-0966; Delgado Mena, Elisa/0000-0003-4434-2195, WOS: 000498546800001, The Transiting Exoplanet Survey Satellite (TESS) is performing a near all-sky survey for planets that transit bright stars. in addition, its excellent photometric precision enables asteroseismology of solar-type and red-giant stars, which exhibit convection-driven, solar-like oscillations. Simulations predict that TESS will detect solar-like oscillations in nearly 100 stars already known to host planets. in this paper, we present an asteroseismic analysis of the known red-giant host stars HD;212771 and HD;203949, both systems having a long-period planet detected through radial velocities. These are the first detections of oscillations in previously known exoplanet-host stars by TESS, further showcasing the mission?s potential to conduct asteroseismology of red-giant stars. We estimate the fundamental properties of both stars through a grid-based modeling approach that uses global asteroseismic parameters as input. We discuss the evolutionary state of HD;203949 in depth and note the large discrepancy between its asteroseismic mass (M-* = 1.23 0.15 MM* = 1.00 0.16 M if in the clump) and the mass quoted in the discovery paper (M-* = 2.1 0.1 M), implying a change >30% in the planet?s mass. Assuming HD;203949 to be in the clump, we investigate the planet?s past orbital evolution and discuss how it could have avoided engulfment at the tip of the red-giant branch. Finally, HD;212771 was observed by K2 during its Campaign 3, thus allowing for a preliminary comparison of the asteroseismic performances of TESS and K2. We estimate the ratio of the observed oscillation amplitudes for this star to be, NASA Explorer ProgramNational Aeronautics & Space Administration (NASA); ESA PRODEXEuropean Space Agency [PEA 4000119301]; Stellar Astrophysics Centre (SAC) - Danish National Research Foundation [DNRF106]; European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grantEuropean Union (EU) [792848, 664931]; FCT/MCTESPortuguese Foundation for Science and Technology [UID/FIS/04434/2019]; FCTPortuguese Foundation for Science and Technology [PTDC/FIS-AST/30389/2017, PTDC/FIS-AST/28953/2017, PTDC/FIS-AST/32113/2017, CEECIND/02619/2017, IF/00650/2015/CP1273/CT0001, IF/00028/2014/CP1215/CT0002]; FEDER through COMPETE2020 [POCI-01-0145-FEDER-030389, POCI-01-0145-FEDER-028953, POCI-01-0145-FEDER-032113]; National Science Foundation under the Kavli Institute for Theoretical Physics program "Better Stars, Better Planets" [NSF PHY-1748958]; European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant [338251]; ESA PRODEX programme; CNES through the PLATO grants; Spanish GovernmentSpanish Government [ESP2017-82674-R]; Generalitat de CatalunyaGeneralitat de Catalunya [2017-SGR-1131]; STFC via an Ernest Rutherford Fellowship [ST/P003850/1]; NSFNational Science Foundation (NSF) [AST-1514676]; NASANational Aeronautics & Space Administration (NASA) [NNX16AI09G]; Spanish Ministry through the Ramon y Cajal fellowship [RYC-2015-17697]; NYUAD Institute [G1502]; DFGGerman Research Foundation (DFG) [SPP 1992, RE 2694/5-1]; Scientific and Technological Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [TUBITAK:118F352]; National Aeronautics and Space Administration through the TESS Guest Investigator Program [80NSSC18K1585, 80NSSC19K0379]; European Social Fund via the Lithuanian Science Council [09.3.3-LMT-K-712-01-0103], This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. Funding for the TESS Asteroseismic Science Operations Center at Aarhus University is provided by ESA PRODEX (PEA 4000119301) and Stellar Astrophysics Centre (SAC), funded by the Danish National Research Foundation (Grant agreement No.: DNRF106). the project leading to this publication has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No..792848 (PULSATION). This work was supported by FCT/MCTES through national funds (UID/FIS/04434/2019). This work was supported by FCT through national funds (PTDC/FIS-AST/30389/2017, PTDC/FIS-AST/28953/2017, and PTDC/FIS-AST/32113/2017) and by FEDER through COMPETE2020 (POCI-01-0145-FEDER-030389, POCI-01-0145-FEDER-028953, and POCI-01-0145-FEDER-032113). This research was supported in part by the National Science Foundation under grant No.NSF PHY-1748958 through the Kavli Institute for Theoretical Physics program "Better Stars, Better Planets". the research leading to the presented results has received funding from the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement No..338251 (StellarAges). E.C.is funded by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No..664931. M.N.L.acknowledges support from the ESA PRODEX programme. B.M.and R.A.G. acknowledge the support received from CNES through the PLATO grants. A. S.is partially supported by grants ESP2017-82674-R (Spanish Government) and 2017-SGR-1131 (Generalitat de Catalunya). D.V.gratefully acknowledges the support of the STFC via an Ernest Rutherford Fellowship (grant ST/P003850/1). V. A.and S.G.S. acknowledge support from FCT through Investigador FCT contracts No..IF/00650/2015/CP1273/CT0001 and No..IF/00028/2014/CP1215/CT0002, respectively. S. B. acknowledges NSF grant AST-1514676 and NASA grant NNX16AI09G. S.M..acknowledges support from the Spanish Ministry through the Ramon y Cajal fellowship No. RYC-2015-17697. M.B.N..acknowledges support from NYUAD Institute grant G1502. S.R..acknowledges support from the DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets (RE 2694/5-1)". M.Y., Z.C.O., and S. O. acknowledge the Scientific and Technological Research Council of Turkey (TUBITAK:118F352). D.H. acknowledges support by the National Aeronautics and Space Administration (80NSSC18K1585, 80NSSC19K0379) awarded through the TESS Guest Investigator Program. M.S.C. is supported in the form of a work contract funded by FCT (CEECIND/02619/2017). H.K. acknowledges support from the European Social Fund via the Lithuanian Science Council grant No. 09.3.3-LMT-K-712-01-0103. more...

Presentation given for an Iowa State University Department of Physics and Astronomy astronomy seminar. The content covers the statistical treatment of stellar spectra using the Starfish methodology. more...

This is my final presentation for my NRAO REU in 2018. It focuses on the methods and metrics for combining interferometer and single-dish radio data. It also describes the pipeline for open-source use to test combination methods on their own data. more...