The PEPSI ultra-high resolution spectral library of M dwarfs Yutong Shan1,2, Mathias Zechmeister1, Ansgar Reiners1, Ilya Ilyin3, Klaus Strassmeier3 yutong.shan@geo.uio.no [1] Reiners, Mrotzek, Lemke, Hinrichs, & Reinsch, 2016, A&A, 587, A56 [2] Strassmeier, Ilyin, & Weber, 2018, A&A, 612, A45 [3] Adibekyan et al., 2020, A&A, 642, A182 [4] Husser et al., 2013, A&A, 553, A6 [5] Zechmeister, Shan, Reiners, Ilyin, & Strassmeier, in prep. [6] Shan et al. 2021, A&A, 654, A118 [7] Nagel et al., 2023, A&A, 680, A73 [8] Blanco-Cuaresma 2019, MNRAS, 486, 2075 [9] Ryabchikova et al., 2015, Physics Scripta, 90, 5 [10] Pakhomov et al., 2019, Astron. Rep., 63, 1010 References Abstract: We present a forthcoming library of M dwarf spectra taken with the ultra-high resolution spectrograph PEPSI (R = 250 000). Our library consists of 7 nearby inactive M dwarfs spanning spectral types M0 to M7, including several known planet hosts. The wavelength coverage (383 — 906 nm) approximately captures the peak of the M dwarf flux density distribution. In particular, the 700 — 900 nm window is information-rich and suitable for chemical abundance measurements. The PEPSI spectral templates will be an invaluable resource for the community by enabling precise radial velocity measurements for exoplanet searches, as well as detailed tests of cool dwarf atmosphere models and refinements of relevant line lists for chemical analysis. 3. The M dwarf sample Our library consists of high-S/N PEPSI spectra for 7 nearby inactive M dwarfs [5]. 1. Why ultra-high resolution? Ultra-high resolution (UHR) stellar spectroscopy encodes information on important stellar properties, including fundamental parameters, chemical compositions, and physical processes in the atmosphere [1, 2, 3]. They also serve as templates for precise radial velocity measurements for exoplanet searches. Cool dwarfs have complicated spectral features that are poorly explained by state-of-the-art models, hampering their interpretation and application. High-quality, UHR spectra can help to map these features and enable detailed refinement of atmosphere models. 1. Institut für Astrophysik und Geophysik, University of Göttingen, Germany; 2. Centre for Planetary Habitability, University of Oslo, Norway; 3. Leibniz-Institut für Astrophysik Potsdam, Germany Star SpT Teff (K) V mag Vrot (km/s) Planet host? S/N @ 830 nm GJ 548A M0V 3985 9.7 0.28 330 GJ 701 M1V 3706 9.4 0.18 380 GJ 226 M2V 3554 10.4 0.46 278 GJ 581 M3V 3500 10.6 0.12 yes 253 Barnard’s Star M4V 3254 9.5 0.06 ? 645 CD Cet M5V 3214 14.0 0.07 yes 92 Teegarden’s Star M7V 3034 15.1 0.06 yes 49 4. Data access Sneak preview: all data and interactive explorer to be made available on the web, similar to [2]. Stay tuned! Acknowledgement: This work has made use of the VALD database, operated at Uppsala University, the Institute of Astronomy RAS in Moscow, and the University of Vienna. 5. Example spectra & science applications The hyperfine structure (HFS) of vanadium [6] is exquisitely resolved. It is remarkably well-described by model spectra that includes HFS components. Also shown: CARMENES spectra [7] and PHOENIX- ACES model spectra [4]. iSpec model is generated with the iSpec code (MARCS + Turbospectrum) [8] and VALD3 line lists [9, 10]. Detailed model comparisons Detection of chemical elements Wavelength segment with various atomic lines and nice pseudo-continuua enable measuring chemical elements like chromium (Cr) and nickel (Ni). Mismatches with state-of-art synthetic spectra model (PHOENIX-ACES [4]) highlight inadequacies in the treatment of molecules, esp. in late-Ms. HARPS CARMENES- VIS ESPRESSSO Wavelength (nm) 380 – 690 520 – 960 380 – 788 383 – 906 Resolution 115,000 90,000 190,000 250,000 Telescope diameter 3.6 m 3.5 m 8.2 m x 4 8.4 m x 2 Location North + South North South North PEPSI = Potsdam Echelle Polarimetric and Spectroscopic Instrument is an ultra high-resolution optical to near infrared wavelength spectrograph on the Large Binocular