The EXPRES Stellar Signals Project II. State of the Field in Disentangling Photospheric Velocities

Measured spectral shifts due to intrinsic stellar variability (e.g., pulsations, granulation) and activity (e.g., spots, plages) are the largest source of error for extreme-precision radial-velocity (EPRV) exoplanet detection. Several methods are designed to disentangle stellar signals from true center-of-mass shifts due to planets. The Extreme-precision Spectrograph (EXPRES) Stellar Signals Project (ESSP) presents a self-consistent comparison of 22 different methods tested on the same extreme-precision spectroscopic data from EXPRES. Methods derived new activity indicators, constructed models for mapping an indicator to the needed radial-velocity (RV) correction, or separated out shape- and shift-driven RV components. Since no ground truth is known when using real data, relative method performance is assessed using the total and nightly scatter of returned RVs and agreement between the results of different methods. Nearly all submitted methods return a lower RV rms than classic linear decorrelation, but no method is yet consistently reducing the RV rms to sub-meter-per-second levels. There is a concerning lack of agreement between the RVs returned by different methods. These results suggest that continued progress in this field necessitates increased interpretability of methods, high-cadence data to capture stellar signals at all timescales, and continued tests like the ESSP using consistent data sets with more advanced metrics for method performance. Future comparisons should make use of various well-characterized data sets—such as solar data or data with known injected planetary and/or stellar signals—to better understand method performance and whether planetary signals are preserved

TOI-4010: A System of Three Large Short-Period Planets With a Massive Long-Period Companion

We report the confirmation of three exoplanets transiting TOI-4010 (TIC-352682207), a metal-rich K dwarf observed by TESS in Sectors 24, 25, 52, and 58. We confirm these planets with HARPS-N radial velocity observations and measure their masses with 8 - 12% precision. TOI-4010 b is a sub-Neptune ($P = 1.3$ days, $R_{p} = 3.02_{-0.08}^{+0.08}~R_{\oplus}$, $M_{p} = 11.00_{-1.27}^{+1.29}~M_{\oplus}$) in the hot Neptune desert, and is one of the few such planets with known companions. Meanwhile, TOI-4010 c ($P = 5.4$ days, $R_{p} = 5.93_{-0.12}^{+0.11}~R_{\oplus}$, $M_{p} = 20.31_{-2.11}^{+2.13}~M_{\oplus}$) and TOI-4010 d ($P = 14.7$ days, $R_{p} = 6.18_{-0.14}^{+0.15}~R_{\oplus}$, $M_{p} = 38.15_{-3.22}^{+3.27}~M_{\oplus}$) are similarly-sized sub-Saturns on short-period orbits. Radial velocity observations also reveal a super-Jupiter-mass companion called TOI-4010 e in a long-period, eccentric orbit ($P \sim 762$ days and $e \sim 0.26$ based on available observations). TOI-4010 is one of the few systems with multiple short-period sub-Saturns to be discovered so far.Comment: 26 pages, 16 figures, published in A

A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780

We present the confirmation of two new planets transiting the nearby mid-M dwarf LTT 3780 (TIC 36724087, TOI-732, $V=13.07$, $K_s=8.204$, $R_s$=0.374 R$_{\odot}$, $M_s$=0.401 M$_{\odot}$, d=22 pc). The two planet candidates are identified in a single TESS sector and are validated with reconnaissance spectroscopy, ground-based photometric follow-up, and high-resolution imaging. With measured orbital periods of $P_b=0.77$ days, $P_c=12.25$ days and sizes $r_{p,b}=1.33\pm 0.07$ R$_{\oplus}$, $r_{p,c}=2.30\pm 0.16$ R$_{\oplus}$, the two planets span the radius valley in period-radius space around low mass stars thus making the system a laboratory to test competing theories of the emergence of the radius valley in that stellar mass regime. By combining 63 precise radial-velocity measurements from HARPS and HARPS-N, we measure planet masses of $m_{p,b}=2.62^{+0.48}_{-0.46}$ M$_{\oplus}$ and $m_{p,c}=8.6^{+1.6}_{-1.3}$ M$_{\oplus}$, which indicates that LTT 3780b has a bulk composition consistent with being Earth-like, while LTT 3780c likely hosts an extended H/He envelope. We show that the recovered planetary masses are consistent with predictions from both photoevaporation and from core-powered mass loss models. The brightness and small size of LTT 3780, along with the measured planetary parameters, render LTT 3780b and c as accessible targets for atmospheric characterization of planets within the same planetary system and spanning the radius valley.Comment: Accepted to AJ. 8 figures, 6 tables. CSV file of the RV measurements (i.e. Table 2) are included in the source cod

Precise radial velocities and simultaneous magnetic flux estimates from intensity spectra

The Radial Velocity (RV) community has made tremendous leaps forward in the past decades detecting and characterising ever smaller and lighter exoplanets. In recent years, this trend has been broken as planet-induced RV signals smaller than 1 m/s are drowned out by the stars' activity. The detection of Earth analogues causing an RV effect of about 10 cm/s is, therefore, out of reach at the time of writing. A few avenues are being explored to resume the trend to detect ever lighter planets. These include improving (a) instruments, (b) observation strategies, (c) RV extraction techniques, (d) the monitoring of stellar activity, and (e) the stellar activity models. This thesis is subdivided into three interconnected topics. First, I present my contribution to problem (c). I implemented a technique called Least-Squares Deconvolution (LSD) to estimate precise stellar RVs. Instead of using a template-based mask, I inferred the average stellar line profile based on laboratory data and extracted the RV from this profile. I analysed the dependence of the RVs on the quality thresholds and found a suitable optimisation scheme. We call this method the Multi-Mask Least-Squares Deconvolution technique (MM-LSD), and I have made it publicly available on GitHub. MM-LSD can be a valuable tool if observations are spread out over time and have not been reduced with the same pipelines or CCF masks, as can be the case in archival data. I expect the multi-mask approach to be adopted in tandem with the CCF technique, which will then provide more stable RVs, reducing method-induced RV variations. These variations are not the aim of the current modelling efforts focused on mitigating stellar-induced RV variations and are essential to eliminate. The flexibility and transparency of the MM-LSD pipeline enable one to extend it easily. For the second part of my PhD, I have implemented a magnetic flux estimation technique built on MM-LSD. This extension is aimed to contribute to solving the problem (d) above. I modelled the Zeeman effect in intensity spectra for which it can be parameterised in a way suitable for the LSD approach. Through this method, the information contained in thousands of lines can be harnessed simultaneously. This approach suppresses noise within the spectra and leads to the averaging out of many other effects affecting the absorption lines. The approach and the results are published in Lienhard et al. (2023). The extracted indicator shows higher correlations with the RVs than any classical indicators and is thus a very promising tool for mitigating stellar activity in solar-type stars. Lastly, I led the observation campaign for TOI-1774 carried out with the HARPS-N spectrograph. For this star, we initiated a collaboration with CHEOPS to share the data and run a joint analysis on the photometric (CHEOPS) and RV data (HARPS-N). I tested the two approaches above on this target, estimating the planetary mass to 7.14 +/- 2.08 Earth masses and the radius to 2.836 +/- 0.036 Earth radii. The orbital period of this planet was known from the transits observed by TESS and is equal to 16.71 days. Lastly, I assessed the probability of the existence of other planets in the system

Effectiveness of the Call in Beach Volleyball Attacking Play

In beach volleyball the setter has the opportunity to give her or his hitter a “call”. The call intends that the setter suggests to her or his partner where to place the attack in the opponent’s court. The effectiveness of a call is still unknown. We investigated the women’s and men’s Swiss National Beach Volleyball Championships in 2011 and analyzed 2185 attacks. We found large differences between female and male players. While men called in only 38.4% of attacks, women used calls in 85.5% of attacks. If the male players followed a given call, 63% of the attacks were successful. The success rate of attacks without any call was 55.8% and 47.6% when the call was ignored. These differences were not significant (χ2(2) = 4.55, p = 0.103). In women’s beach volleyball, the rate of successful attacks was 61.5% when a call was followed, 35% for attacks without a call, and 42.6% when a call was ignored. The differences were highly significant (χ2(2) = 23.42, p < 0.0005). Taking into account the findings of the present study, we suggested that the call was effective in women’s beach volleyball, while its effect in men’s game was unclear. Considering the quality of calls we indicate that there is a significant potential to increase the effectiveness of a call

Bright and photostable single-photon emitter in silicon carbide

Single-photon sources are of paramount importance in quantum communication, quantum computation, and quantum metrology. In particular, there is great interest in realizing scalable solid-state platforms that can emit triggered photons on demand to achieve scalable nanophotonic networks. We report on a visible-spectrum single-photon emitter in 4H silicon carbide (SiC). The emitter is photostable at room and low temperatures, enabling photon counts per second in excess of 2×10⁶ from unpatterned bulk SiC. It exists in two orthogonally polarized states, which have parallel absorption and emission dipole orientations. Low-temperature measurements reveal a narrow zero phonon line (linewidth 30% of the total photoluminescence spectrum.United States. Air Force Office of Scientific Research (FA9550-14-1-0052