Hodari-Sadiki Hubbard-James
Assistant Professor of Astronomy
Agnes Scott College
Research Interests: Stellar Age & Activity, Exoplanet Atmospheres, and Astrobiology.
About Me
As an Assistant Professor of Astronomy at Agnes Scott College, my work builds upon a strong foundation in astrophysical research and collaboration with the RECONS group. My career has progressed from advanced research using the CHIRON echelle spectrometer at the SMARTS 1.5m telescope in Cerro Tololo, Chile, to a role where I combine my research expertise with a deep commitment to teaching.
My research aims to find the Best Stellar Hosts for Life in the Solar Neighborhood. 
. To achieve this, I conduct spectroscopic analysis of K dwarf stars located within 100 light-years, examining their age, activity, temperature, and metallicity. Recently, I have expanded this exploration into high-energy UV and X-ray spectroscopy, which has broadened my investigation into the complexities of stellar astronomy.
Teaching is a vital part of my work. In the classroom, I'm passionate about integrating coding and data science with stellar astronomy, advocating for hands-on learning. My goal is to give students real-world experience in astronomical research methods . Beyond academia, I'm engaged in K-12 outreach, striving to spark a lifelong interest in astronomy among young students and contributing to the growth of the scientific community.
Compilation of Spectral Line Diagnostics
for Benchmark Sample
Left: A compilation of 10 K dwarf (B p − R p between 1.2 and 1.5) spectra from all 5 benchmark age groups, focusing on a 15 Å window around the Na I Doublet at at 5889.95 Å & 5895.92 Å. Middle: A compilation of 10 K dwarf (B p − R p between 1.2 and 1.5) spectra from all 5 benchmark age groups, focusing on a 10 Å window around the Hα 6563 Å line. Right: A compilation of 10 K dwarf (B p − R p between 1.2 and 1.5) spectra from all 5 benchmark age groups, focusing on a 15 Å window around the Li I 6707.7 Å feature. Benchmark groups included in plots: β Pic (blue), Tuc-Hor (green), AB Dor (red), Hyades cluster (black), K field dwarfs (yellow). Stars included: (a) CD-26 13904, (b) AO Men, (c) BD-15 705, (d) CD-78 24, (e) HD 201919, (f) BD+20 1790, (g) HD 285828, (h) HD 285507, (i) GJ0250A, and (j) eps Ind. Spectral types taken from the Simbad database.
Takeaways:
• The Li I 6707.7 Å line decreases with the increasing age of moving associations.
• The Hα 6563 Å core emission decreases with the increasing age of moving associations.
Equivalent Width Trend
Activity (Hα) vs Youth (Li I)
Left Figure: Plot of EW[Hα] vs. EW[Li I] for benchmark members (n=36). Dashed black box in the bottom left highlights K dwarfs present in the old locus.
Right Figure: Plot Plot of EW[Hα] vs. EW[Li I] for the benchmark members (n=36) with the addition of 140 K dwarfs within 20 pc.
Takeaways:
• Left plot shows "Old Locus" of K dwarfs (dashed box) with younger (<120 MYR) stars radiating away.
• Right plot shows activity and youth relation for 140 field K dwarfs (orange crosses) within 20 pc.
7% of K field stars identified as either young or active.
K Dwarf Stellar Properties using
Empirical SpecMatch
Figure above of metallicity ([Fe/H]) plotted against effective temperature (Teff) for 140 K dwarfs (orange dots) within 20 pc, with confirmed host stars from the NASA Exoplanet Archive circled (blue circle), and SpecMatch library stars (black x’s) shown in the background.
Takeaways:
• Low number of metal poor ([Fe/H]<-0.5) stars in the solar neighborhood
• No trend observed between confirmed exoplanet host stars and metallicity [Fe/H].
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