Adina D. Feinstein

I received by B.S. in Astrophysics and a minor in English from Tufts University in 2018. I applied to 15 Ph.D. programs as a senior undergraduate student and was not admitted to any. Instead, I joined the one-year Masters Program in Physical Sciences program at the University of Chicago. I graduated with my M.S. in 2019 before joining the Ph.D. program at the University of Chicago in the Department in Astronomy and Astrophysics. I successfully defended my Ph.D. thesis in March, 2023. From 2023 - 2024, I was a NASA Sagan Postdoctoral Fellow at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder. Thanks to the flexibility of the NASA Sagan Fellowship, I was able to move my second year of funding to my current institution: Michigan State University.

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Outside of the office,

Undergraduate Students

Undergraduate students at MSU are welcome to contact me about potential research opportunities. In the contact email, interested undergraduate students should note the following:

An unofficial transcript

A brief description* describing why you want to pursue research in astronomy and your career goals

A brief description* describing your interest in stars and/or exoplanets, and what you hope to learn from a research project

A brief description* of previous research experience (if applicable)

Undergraduate students are welcome to contact me at any point throughout the academic year. However, to secure potential funding for the academic year and/or the summer, it would be best to reach out during the Fall semester.
* A brief description = 3-4 sentences.

Graduate Students

I am looking to recruit one or two new graduate students during the 2025 application cycle. If you are interested in pursuing stellar and/or exoplanet research for your Ph.D., I would encourage you to apply! For inquiries about potential projects, please email me (adina [at] msu [dot] edu) before December 9, 2024.

The application for a the Ph.D. program in Astrophysics and Astronomy consists of six parts:

Online application form

Academic records (unofficial transcripts are acceptable)

Curriculum Vitae (including publications, talks, and/or posters)

Personal statement

Academic statement

Three letters of recommendation

For more information about what should be included in the personal and academic statements, please see our department website. Our website includes several questions which should be addressed in each statement.

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Graduate School Application Example

Applying to graduate school can be challenging to navigate. I seek to make this process more transparent and equitable to undergraduate students who wish to pursue a Ph.D. in astronomy/astrophysics. Our department website hosts a number of great questions to answer when applying to our program, as well as other Ph.D. programs. As an additional example of ways to go abour writing the academic or research statement, here is an example of one of my own from 2018.

Postdoctoral Researchers

Applications are invited for a postdoctoral position at Michigan State University working with Prof. Adina Feinstein on infrared transmission spectra of young planet atmospheres. This study is funded by the JWST KRONOS (Keys to Revealing the Origin and Nature Of sub-neptune Systems) program - a team of US and international collaborators focused on understanding how planetary atmospheres evolve. The objective of the study will be to reduce and analyze JWST and complimentary ground-based transit observations of planets with ages between 23-200 Myr to determine the near-primordial composition of exoplanet atmospheres. We encourage applications from candidates with diverse expertise, including - but not limited to - studies of exoplanet atmospheres, starspot properties, and/or stellar flares, and reduction or analysis of transit observations at any wavelength (including optical, UV, and IR).

Application Requirements:
- One page cover letter
- CV. Be sure to highlight leadership experience and community service, in addition to academic record
- Brief statement of research interests (3 pages, including figures and excluding references)
- Contact information for 3 peoeple who will provide reference letters upon request

Deadline: January 23, 2025.

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Postdoc Application Examples

I seek to make the postdoctoral application process more transparent and equitable to graduate students who wish to continue pursuing a career in academia. Below, I link a handful of my own applications to various fellowships, with the hopes that these examples can act as guides to those applying to postdoctoral positions.

Please do not rehost or redistribute these application materials, in whole or in part, without the express permission of the original author. You are welcome to share links to the original application bank. Reading old applications is useful for understanding how to write clearly and persuasively, but it is unacceptable to copy text, figures, or research project ideas. The content of your application must be original.

These applications do not necessarily represent the full breadth of research areas supported by the fellowship program or the only possible successful strategies.

Fellowship Name	Materials
Simons Society of Fellows (Columbia University)	All application materials
MIT Pappalardo Fellowship	All application materials
NASA Hubble Fellowship Program	All application materials
51 Pegasi b Fellowship	Previous work Research proposal DEI statement

Evolution of Flare Activity in GKM Stars Younger Than 300 Myr over Five Years of TESS Observations

Stellar flares are short-duration (< hours) bursts of radiation associated with surface magnetic reconnection events. Stellar magnetic activity generally decreases as a function of both the age and Rossby number, R0, a measure of the relative importance of the convective and rotational dynamos. Young stars (< 300 Myr) have typically been overlooked in population-level flare studies due to challenges with flare-detection methods. Here, we select a sample of stars that are members of 26 nearby moving groups, clusters, or associations with ages < 300 Myr that have been observed by the Transiting Exoplanet Survey Satellite at 2 minute cadence. We identified 26,355 flares originating from 3160 stars and robustly measured the rotation periods of 1847 stars. We measure and find the flare frequency distribution slope, α, saturates for all spectral types at α ∼ −0.5 and is constant over 300 Myr. Additionally, we find that flare rates for stars tage = 50–250 Myr are saturated below R0 < 0.14, which is consistent with other indicators of magnetic activity. We find evidence of annual flare rate variability in eleven stars, potentially correlated with long-term stellar activity cycles. Additionally, we crossmatch our entire sample with the Galaxy Evolution Explorer and find no correlation between flare rate and far- and near-ultraviolet flux. Finally, we find the flare rates of planet-hosting stars are relatively lower than comparable, larger samples of stars, which may have ramifications for the atmospheric evolution of short-period exoplanets.

The project was written and compiled using showyourwork!. The data and Python scripts for this project can be found on GitHub.

Summary in Progress Read the Paper

HST Far-ultraviolet Transit Observations of Two Neptune Progenitors Younger than 30 Myr

Photoevaporation is believed to dominate the removal of planetary atmospheres when they are young (< 100 Myr). Signatures of atmospheric mass-loss can be observed in the ultraviolet (UV) through the near-infrared. We present Far-UV transit observations of AU Mic b (∼22 Myr) and V1298 Tau c (∼28 Myr) with the Hubble Space Telescope. We search for evidence of escaping metals in the C II, Si II, and Si III emission lines and compare their behavior to tracers of stellar activity. We detect no evidence of atmospheric mass loss, and place upper limits on the radii of AU Mic b and V1298 Tau c.

Summary in Progress Read the Paper

Early Release Science of the exoplanet WASP-39b with JWST NIRISS

The Saturn-mass exoplanet WASP-39b has been the subject of extensive efforts to determine its atmospheric properties using transmission spectroscopy. However, these efforts have been hampered by modelling degeneracies between composition and cloud properties that are caused by limited data quality. Here we present the transmission spectrum of WASP-39b obtained using the Single-Object Slitless Spectroscopy (SOSS) mode of the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument on the JWST. This spectrum spans 0.6–2.8 μm in wavelength and shows several water-absorption bands, the potassium resonance doublet and signatures of clouds. The precision and broad wavelength coverage of NIRISS/SOSS allows us to break model degeneracies between cloud properties and the atmospheric composition of WASP-39b, favouring a heavy-element enhancement (‘metallicity’) of about 10–30 times the solar value, a sub-solar carbon-to-oxygen (C/O) ratio and a solar-to-super-solar potassium-to-oxygen (K/O) ratio. The observations are also best explained by wavelength-dependent, non-grey clouds with inhomogeneous coverageof the planet’s terminator.

The code for this project can be found on GitHub and the data can be found on Zenodo.

Summary in Progress Read the Paper

AU Microscopii in the Far-UV: Observations in Quiescence, during Flares, and Implications for AU Mic b and c

High-energy X-ray and ultraviolet (UV) radiation from young stars impacts planetary atmospheric chemistry and mass loss. The active ∼22 Myr M dwarf AU Mic hosts two exoplanets orbiting interior to its debris disk. Therefore, this system provides a unique opportunity to quantify the effects of stellar X-ray and UV irradiation on planetary atmospheres as a function of both age and orbital separation. In this paper, we present over 5 hr of far-UV (FUV) observations of AU Mic taken with the Cosmic Origins Spectrograph (COS; 1070-1360 Å) on the Hubble Space Telescope (HST). We provide an itemization of 120 emission features in the HST/COS FUV spectrum and quantify the flux contributions from formation temperatures ranging from 10⁴ to 10⁷ K. We detect 13 flares in the FUV white-light curve with energies ranging from 10²⁹ to 10³¹ erg s. The majority of the energy in each of these flares is released from the transition region between the chromosphere and the corona. There is a 100× increase in flux at continuum wavelengths λ < 1100 Å in each flare, which may be caused by thermal Bremsstrahlung emission. We calculate that the baseline atmospheric mass-loss rate for AU Mic b is ∼10⁸ g s⁻¹, although this rate can be as high as ∼10¹⁴ g s−1 during flares with L_flare >= 10³³ erg s−1. Finally, we model the transmission spectra for AU Mic b and c with a new panchromatic spectrum of AU Mic and motivate future JWST observations of these planets.

The code for this project can be found on GitHub and the data can be found on Zenodo.

Read the Summary Read the Paper

Testing Self-organized Criticality across the Main Sequence Using Stellar Flares from TESS

Self-organized criticality describes a class of dynamical systems that maintain themselves in an attractor state with no intrinsic length or timescale. Fundamentally, this theoretical construct requires a mechanism for instability that may trigger additional instabilities locally via dissipative processes. This concept has been invoked to explain nonlinear dynamical phenomena such as featureless energy spectra that have been observed empirically for earthquakes, avalanches, and solar flares. If this interpretation proves correct, it implies that the solar coronal magnetic field maintains itself in a critical state via a delicate balance between the dynamo-driven injection of magnetic energy and the release of that energy via flaring events. All-sky high-cadence surveys like the Transiting Exoplanet Survey Satellite (TESS) provide the necessary data to compare the energy distribution of flaring events in stars of different spectral types to that observed in the Sun. We identified ∼10⁶ flaring events on ∼10⁵ stars observed by TESS at a 2 minute cadence. By fitting the flare frequency distribution for different mass bins, we find that all main-sequence stars exhibit distributions of flaring events similar to that observed in the Sun, independent of their mass or age. This may suggest that stars universally maintain a critical state in their coronal topologies via magnetic reconnection events. If this interpretation proves correct, we may be able to infer properties of magnetic fields, interior structure, and dynamo mechanisms for stars that are otherwise unresolved point sources.

Read the Summary Read the Paper

H-Alpha and Ca II Infrared Triplet Variations During a Transit of the 23 Myr Planet V1298 Tau c

Young transiting exoplanets (< 100 Myr) provide crucial insight into atmospheric evolution via photoevaporation. However, transmission spectroscopy measurements to determine atmospheric composition and mass loss are challenging due to the activity and prominent stellar disk inhomogeneities present on young stars. We observed a full transit of V1298 Tau c, a 23 Myr, 5.59 R⊕ planet orbiting a young K0-K1.5 solar analog with GRACES on Gemini North. We were able to measure the Doppler tomographic signal of V1298 Tau c using the Ca II infrared triplet (IRT) and find a projected obliquity of λ = 5° ± 15°. The tomographic signal is only seen in the chromospherically driven core of the Ca II IRT, which may be the result of star-planet interactions. Additionally, we find that excess absorption of the Hα line decreases smoothly during the transit. While this could be a tentative detection of hot gas escaping the planet, we find this variation is consistent with similar timescale observations of other young stars that lack transiting planets over similar timescales. We show this variation can also be explained by the presence of starspots with surrounding facular regions. More observations both in and out of the transits of V1298 Tau c are required to determine the nature of the Ca II IRT and Hα line variations.

The data and Python scripts affiliated with this publication can be found on Zenodo.

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Flare Statistics for Young Stars from a Convolutional Neural Network Analysis of TESS Data

All-sky photometric time-series missions have allowed for the monitoring of thousands of young (t_age < 800 Myr) stars in order to understand the evolution of stellar activity. Here, we developed a convolutional neural network (CNN), stella, specifically trained to find flares in Transiting Exoplanet Survey Satellite (TESS) short-cadence data. We applied the network to 3200 young stars in order to evaluate flare rates as a function of age and spectral type. The CNN takes a few seconds to identify flares on a single light curve. We also measured rotation periods for 1500 of our targets and find that flares of all amplitudes are present across all spot phases, suggesting high spot coverage across the entire surface. Additionally, flare rates and amplitudes decrease for stars t_age > 50 Myr across all temperatures T_eff ≥ 4000 K, while stars from 2300 ≤ T_eff < 4000 K show no evolution across 800 Myr. Stars of T_eff ≤ 4000 K also show higher flare rates and amplitudes across all ages. We investigate the effects of high flare rates on photoevaporative atmospheric mass loss for young planets. In the presence of flares, planets lose 4%–7% more atmosphere over the first 1 Gyr. stella is an open-source Python toolkit hosted on GitHub and PyPI.

Read the Summary Read the Paper

Presented by Darryl Seligman at Extreme Solar Systems V in Christchurch, New Zealand (March, 2024).

Presented at Extreme Solar Systems V in Christchurch, New Zealand (March, 2024).

Presented at Cool Stars 21 in Toulouse, France (July, 2022).

Presented at the virtual Sagan Summer Workshop (July, 2021).

Presented at the virtual Cool Stars 20.5 (March, 2021).

Presented at the 233^rd American Astronomical Soceity meeting in Seattle, WA (January, 2018).

Presented at the 233^rd American Astronomical Soceity meeting in Seattle, WA (January, 2018).

Presented at The 4^th AstroCon DC Meeting at George Washington University (August, 2017).

Email: adina [at] msu [dot] edu