UMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)

Permanent URI for this collectionhttp://hdl.handle.net/11603/7798

The Center for Space Sciences and Technology (CSST) is the administrative unit for UMBC’s participation in the CRESST consortium. The NASA Goddard Space Flight Center (NASA/GSFC), The University of Maryland College Park (UMCP), Catholic University, Howard University and Southeastern Universities Research Association (SURA) are our partners in the consortium.

The Center for Research and Exploration in Space Science & Technology (CRESST), is a cooperative agreement between the partner institutions. The CRESST consortium currently has over 120 PhD astronomers and astrophysicists working within the Astrophysics Science Division at GSFC.

CSST was formed in 2006 and currently has over 20 UMBC research faculty, several of which are affiliated to the physics department. The research conducted by the members of CSST focuses on (i) Astrophysical Data Reduction, Interpretation & Archiving, (ii) Space Science Technology: Development & Calibration, and (iii) Theoretical Astrophysics: Simulations & Software.

CSST maintains close relations with (and is housed within) the Physics Department at UMBC. Combined, UMBC astrophysics faculty and CSST scientists contribute to the Undergraduate & Graduate activities (including the Undergrad & Grad internships) by teaching & mentoring students.

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Observable-based reformulation of time-delay interferometry
(2025-02-16) Yamamoto, Kohei; Reinhardt, Jan Niklas; Hartwig, Olaf
Spaceborne gravitational-wave observatories utilize a post-processing technique known as time-delay interferometry (TDI) to reduce the otherwise overwhelming laser frequency noise by around eight orders of magnitude. While, in its traditional form, TDI considers the spacecraft as point masses, recent studies have enhanced this simplified scenario by incorporating more realistic metrology chain models, which include onboard optical, electronic, and digital delays. These studies have updated the TDI algorithm to include onboard delays obtained from pre-launch and in-flight calibrations. Conversely, the processing scheme presented in this article naturally treats onboard delays as part of the TDI combinations: instead of having separate calibration stages, it directly expresses all delays appearing in the algorithm in terms of onboard measurements, especially pseudo-random-noise ranging (PRNR) measurements. The only onboard delays that need to be corrected in our processing scheme are PRNR delays in the digital domain, which are determined by commandable digital-signal-processing parameters; hence, they can be easily managed in post-processing. Furthermore, our processing scheme does not require a prior interspacecraft clock synchronization, and it automatically corrects for potential relative drifts between the clocks driving local phase measurement systems. The proposed observable-based processing scheme significantly strengthens the bond between TDI and the real metrology system.
NASA Innovative Advanced Concepts Phase I Final Report -- A Lunar Long-Baseline UV/Optical Imaging Interferometer: Artemis-enabled Stellar Imager (AeSI)
(2025-03-03) Carpenter, Kenneth G.; Boyajian, Tabetha; Buzasi, Derek; Clark, Jim; Creech-Eakman, Michelle; Dean, Bruce; Elliott, Ashley; Foster, Julianne; Gong, Qian; Karovska, Margarita; Kim, David; Hulberg, Jon; Leisawitz, David; Maher, Mike; Morse, Jon; Mozurkewich, Dave; Peacock, Sarah; Petro, Noah; Rau, Gioia; Scowen, Paul; Seals, Len; Smith, Walter; Smuda, Max; Sitarski, Breann; Taylor, Buddy; van Belle, Gerard; Wilkinson, Erik
This report presents the findings of a NIAC Phase I feasibility study for the Artemis-enabled Stellar Imager (AeSI), a proposed high-resolution, UV/Optical interferometer designed for deployment on the lunar surface. Its primary science goal is to image the surfaces and interiors of stars with unprecedented detail, revealing new details about their magnetic processes and dynamic evolution and enabling the creation of a truly predictive solar/stellar dynamo model. This capability will transform our understanding of stellar physics and has broad applicability across astrophysics, from resolving the cores of Active Galactic Nuclei (AGN) to studying supernovae, planetary nebulae, and the late stages of stellar evolution. By leveraging the stable vacuum environment of the Moon and the infrastructure being established for the Artemis Program, AeSI presents a compelling case for a lunar-based interferometer. In this study, the AeSI Team, working with the NASA Goddard Space Flight Center's Integrated Design Center (IDC), has firmly established the feasibility of building and operating a reconfigurable, dispersed aperture telescope (i.e., an interferometer) on the lunar surface. The collaboration produced a credible Baseline design featuring 15 primary mirrors arranged in an elliptical array with a 1 km major axis, with the potential to expand to 30 mirrors and larger array sizes through staged deployments. Additionally, this study identified numerous opportunities for optimization and the necessary trade studies to refine the design further. These will be pursued in follow-up investigations, such as a NIAC Phase II study, to advance the concept toward implementation.
Nano-Newton electrostatic force actuators for femto-Newton-sensitive measurements: System performance test in the LISA Pathfinder mission
(APS, 2024-05-22) LISA Pathfinder Collaboration; Armano, M.; Audley, H.; Baird, J.; Bassan, M.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Castelli, Eleonora; Cavalleri, A.; Cesarini, A.; Chiavegato, V.; Cruise, A. M.; Dal Bosco, D.; Danzmann, K.; De Deus Silva, M.; De Rosa, R.; Di Fiore, L.; Diepholz, I.; Dixon, G.; Dolesi, R.; Ferraioli, L.; Ferroni, V.; Fitzsimons, E. D.; Freschi, M.; Gesa, L.; Giardini, D.; Gibert, F.; Giusteri, R.; Grado, A.; Grimani, C.; Grzymisch, J.; Harrison, I.; Hartig, M. S.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hoyland, D.; Hueller, M.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Johlander, B.; Karnesis, N.; Kaune, B.; Korsakova, N.; Killow, C. J.; Liu, L.; Lobo, J. A.; López-Zaragoza, J. P.; Maarschalkerweerd, R.; Mance, D.; Martín, V.; Martin-Polo, L.; Martin-Porqueras, F.; Martino, J.; McNamara, P. W.; Mendes, J.; Mendes, L.; Meshksar, N.; Moerschell, J.; Nofrarias, M.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Plagnol, E.; Praplan, C.; Ramos-Castro, J.; Reiche, J.; Rivas, F.; Robertson, D. I.; Russano, G.; Sala, L.; Sarra, P.; Schule-Walewski, S. L.; Slutsky, J.; Sopuerta, C. F.; Stanga, R.; Sumner, T.; ten Pierick, J.; Texier, D.; Thorpe, J. I.; Vetrugno, D.; Vitale, S.; Wanner, G.; Ward, H.; Wass, P. J.; Weber, W. J.; Wissel, L.; Wittchen, A.; Zanoni, C.; Zweifel, P.
Electrostatic force actuation is a key component of the system of geodesic reference test masses (TM) for the LISA orbiting gravitational wave observatory and in particular for performance at low frequencies, below 1 mHz, where the observatory sensitivity is limited by stray force noise. The system needs to apply forces of order 10?9 N while limiting fluctuations in the measurement band to levels approaching 10?15 N/Hz1/2. We present here the LISA actuation system design, based on audio-frequency voltage carrier signals, and results of its in-flight performance test with the LISA Pathfinder test mission. In LISA, TM force actuation is used to align the otherwise free-falling TM to the spacecraft-mounted optical metrology system, without any forcing along the critical gravitational wave-sensitive interferometry axes. In LISA Pathfinder, on the other hand, the actuation was used also to stabilize the TM along the critical ?? axis joining the two TM, with the commanded actuation force entering directly into the mission’s main differential acceleration science observable. The mission allowed demonstration of the full compatibility of the electrostatic actuation system with the LISA observatory requirements, including dedicated measurement campaigns to amplify, isolate, and quantify the two main force noise contributions from the actuation system, from actuator gain noise and from low frequency “in band” voltage fluctuations. These campaigns have shown actuation force noise to be a relevant, but not dominant, noise source in LISA Pathfinder and have allowed performance projections for the conditions expected in the LISA mission.
Magnetic-Induced Force Noise in LISA Pathfinder Free-Falling Test Masses
(APS, 2025-02-18) Armano, M.; Audley, H.; Baird, J.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Castelli, Eleonora; Cavalleri, A.; Cesarini, A.; Cruise, A. M.; Danzmann, K.; de Deus Silva, M.; Diepholz, I.; Dixon, G.; Dolesi, R.; Ferraioli, L.; Ferroni, V.; Fitzsimons, E. D.; Freschi, M.; Gesa, L.; Giardini, D.; Gibert, F.; Giusteri, R.; Grimani, C.; Grzymisch, J.; Harrison, I.; Hartig, M.-S.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hoyland, D.; Hueller, M.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Karnesis, N.; Kaune, B.; Korsakova, N.; Killow, C. J.; Liu, L.; Lobo, J. A.; López-Zaragoza, J. P.; Maarschalkerweerd, R.; Mance, D.; Martín, V.; Martin-Polo, L.; Martin-Porqueras, F.; Martino, J.; McNamara, P. W.; Mendes, J.; Mendes, L.; Meshksar, N.; Nofrarias, M.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Pivato, P.; Plagnol, E.; Ramos-Castro, J.; Reiche, J.; Rivas, F.; Robertson, D. I.; Russano, G.; Sala, L.; Serrano, D.; Slutsky, J.; Sopuerta, C. F.; Sumner, T.; Texier, D.; Thorpe, J. I.; Vetrugno, D.; Vitale, S.; Wanner, G.; Ward, H.; Wass, P. J.; Weber, W. J.; Wissel, L.; Wittchen, A.; Zweifel, P.
LISA Pathfinder was a mission designed to test key technologies required for gravitational wave detection in space. Magnetically driven forces play a key role in the instrument sensitivity in the low-frequency regime, which corresponds to the measurement band of interest for future space-borne gravitational wave observatories. Magnetically induced forces couple to the test mass motion, introducing a contribution to the relative acceleration noise between the free-falling test masses. In this Letter we present the first complete estimate of this term of the instrument performance model.
In-depth analysis of LISA Pathfinder performance results: Time evolution, noise projection, physical models, and implications for LISA
(APS, 2024-08-21) LISA Pathfinder Collaboration; Armano, M.; Audley, H.; Baird, J.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Castelli, Eleonora; Cavalleri, A.; Cesarini, A.; Chiavegato, V.; Cruise, A. M.; Dal Bosco, D.; Danzmann, K.; De Deus Silva, M.; Diepholz, I.; Dixon, G.; Dolesi, R.; Ferraioli, L.; Ferroni, V.; Fitzsimons, E. D.; Freschi, M.; Gesa, L.; Giardini, D.; Gibert, F.; Giusteri, R.; Grimani, C.; Grzymisch, J.; Harrison, I.; Hartig, M. S.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hoyland, D.; Hueller, M.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Johlander, B.; Karnesis, N.; Kaune, B.; Korsakova, N.; Killow, C. J.; Lobo, J. A.; López-Zaragoza, J. P.; Maarschalkerweerd, R.; Mance, D.; Martín, V.; Martin-Polo, L.; Martin-Porqueras, F.; Martino, J.; McNamara, P. W.; Mendes, J.; Mendes, L.; Meshksar, N.; Nofrarias, M.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Plagnol, E.; Ramos-Castro, J.; Reiche, J.; Rivas, F.; Robertson, D. I.; Russano, G.; Sala, L.; Slutsky, J.; Sopuerta, C. F.; Sumner, T.; Texier, D.; Thorpe, J. I.; Vetrugno, D.; Vitale, S.; Wanner, G.; Ward, H.; Wass, P.; Weber, W. J.; Wissel, L.; Wittchen, A.; Zanoni, C.; Zweifel, P.
We present an in-depth analysis of the LISA Pathfinder differential acceleration performance over the entire course of its science operations, spanning approximately 500 days. We find: (1) The evolution of the Brownian noise that dominates the acceleration amplitude spectral density (ASD), for frequencies 𝑓≳1 mHz, is consistent with the decaying pressure due to the outgassing of a single gaseous species. (2) Between 𝑓=36 μ⁢Hz and 1 mHz, the acceleration ASD shows a 1/𝑓 tail in excess of the Brownian noise of almost constant amplitude, with ≃20% fluctuations over a period of a few days, with no particular time pattern over the course of the mission. (3) At the lowest considered frequency of 𝑓=18 μ⁢Hz, the ASD significantly deviates from the 1/𝑓 behavior, because of temperature fluctuations that appear to modulate a quasistatic pressure gradient, sustained by the asymmetries of the outgassing pattern. We also present the results of a projection of the observed acceleration noise on the potential sources for which we had either a direct correlation measurement or a quantitative estimate from dedicated experiments. These sources account for approximately 40% of the noise power in the 1/𝑓 tail. Finally, we analyze the possible sources of the remaining unexplained fraction and identify the possible measures that may be taken to keep those under control in LISA.
Extracting gravitational wave signals from LISA data in the presence of artifacts
(IOP Publishing, 2025-03-06) Castelli, Eleonora; Baghi, Quentin; Baker, John G.; Slutsky, Jacob; Bobin, Jérôme; Karnesis, Nikolaos; Petiteau, Antoine; Sauter, Orion; Wass, Peter; Weber, William J.
The Laser Interferometer Space Antenna (LISA) mission is being developed by ESA with NASA participation. As it has recently passed the Mission Adoption milestone, models of the instruments and noise performance are becoming more detailed, and likewise prototype data analyses must as well. Assumptions such as Gaussianity, stationarity, and data continuity are unrealistic, and must be replaced with physically motivated data simulations, and data analysis methods adapted to accommodate such likely imperfections. To this end, the LISA Data Challenges have produced datasets featuring time-varying and unequal constellation armlength, and measurement artifacts including data interruptions and instrumental transients. In this work, we assess the impact of these data artifacts on the inference of galactic binary and massive black hole properties. Our analysis shows that the treatment of noise transients and gaps is necessary for effective parameter estimation, as they substantially corrupt the analysis if unmitigated. We find that straightforward mitigation techniques can significantly if imperfectly suppress artifacts. For the Galactic Binaries, mitigation of glitches was essentially total, while mitigations of the data gaps increased parameter uncertainty by approximately 10%. For the massive black hole binaries the particularly pernicious glitches resulted in a 30% uncertainty increase after mitigations, while the data gaps can increase parameter uncertainty by up to several times. Critically, this underlines the importance of early detection of transient gravitational waves to ensure they are protected from planned data interruptions.
Artifact: Defining and Analyzing Smart Device Passive Mode
(HAL, 2025-03-17) Badolato, Christian; Kullman, Kaur; Papadakis, Nikolaos; Bhatt, Manav; Bouloukakis, Georgios; Engel, Don; Yus, Roberto
This artifact paper presents a guide for the Smart Home IoT Passive Mode Analysis tool and dataset to perform network traffic analysis (NTA) on smart home IoT devices in passive mode. The repository includes: 1) scripts and configurations for processing network traffic capture files and extracting the relevant information; 2) output data files for the experiments conducted; and 3) a link to the raw network capture dataset. The dataset contains 12GB of passive mode traffic from 32 devices across 3 testbeds; between 71 and 196 hours of traffic is present for each device.
The X-ray Integral Field Unit at the end of the Athena reformulation phase
(Springer, 2025-03-04) Peille, Philippe; Barret, Didier; Cucchetti, Edoardo; Albouys, Vincent; Piro, Luigi; Simionescu, Aurora; Cappi, Massimo; Bellouard, Elise; Cénac-Morthé, Céline; Daniel, Christophe; Pradines, Alice; Finoguenov, Alexis; Kelley, Richard; Mas-Hesse, J. Miguel; Paltani, Stéphane; Rauw, Gregor; Rozanska, Agata; Svoboda, Jiri; Wilms, Joern; Audard, Marc; Bozzo, Enrico; Costantini, Elisa; Dadina, Mauro; Dauser, Thomas; Decourchelle, Anne; den Herder, Jan-Willem; Goldwurm, Andrea; Jonker, Peter; Markowitz, Alex; Mendez, Mariano; Miniutti, Giovanni; Molendi, Silvano; Nicastro, Fabrizio; Pajot, François; Pointecouteau, Etienne; Pratt, Gabriel W.; Schaye, Joop; Vink, Jacco; Webb, Natalie; Bandler, Simon; Barbera, Marco; Ceballos, Maria Teresa; Charles, Ivan; den Hartog, Roland; Doriese, W. Bertrand; Duval, Jean-Marc; Gatti, Flavio; Jackson, Brian; Kilbourne, Caroline; Macculi, Claudio; Martin, Sylvain; Parot, Yann; Porter, Frederick; Prêle, Damien; Ravera, Laurent; Smith, Stephen; Soucek, Jan; Thibert, Tanguy; Tuominen, Eija; Acero, Fabio; Ettori, Stefano; Grosso, Nicolas; Kaastra, Jelle; Mazzotta, Pasquale; Miller, Jon; Sciortino, Salvatore; Beaumont, Sophie; D’Andrea, Matteo; de Plaa, Jelle; Eckart, Megan; Gottardi, Luciano; Leutenegger, Maurice; Lotti, Simone; Molin, Alexei; Natalucci, Lorenzo; Adil, Muhammad Qazi; Argan, Andrea; Cavazzuti, Elisabetta; Fiorini, Mauro; Khosropanah, Pourya; Medinaceli Villegas, Eduardo; Minervini, Gabriele; Perry, James; Pinsard, Frederic; Raulin, Desi; Rigano, Manuela; Roelfsema, Peter; Schwander, Denis; Terron, Santiago; Torrioli, Guido; Ullom, Joel; Zuchniak, Monika; Chaoul, Laurence; Torrejon, Jose Miguel; Brachet, Frank; Cobo, Beatriz; Durkin, Malcolm; Fioretti, Valentina; Geoffray, Hervé; Jacques, Lionel; Kirsch, Christian; Lo Cicero, Ugo; Adams, Joseph; Gloaguen, Emilie; Gonzalez, Manuel; Hull, Samuel; Jellyman, Erik; Kiviranta, Mikko; Sakai, Kazuhiro; Taralli, Emanuele; Vaccaro, Davide; van der Hulst, Paul; van der Kuur, Jan; van Leeuwen, Bert-Joost; van Loon, Dennis; Wakeham, Nicholas; Auricchio, Natalia; Brienza, Daniele; Cheatom, Oscar; Franssen, Philippe; Julien, Sabine; Le Mer, Isabelle; Moirin, David; Silva, Vitor; Todaro, Michela; Clerc, Nicolas; Coleiro, Alexis; Ptak, Andy; Puccetti, Simonetta; Surace, Christian; Abdoelkariem, Shariefa; Adami, Christophe; Aicardi, Corinne; André, Jérôme; Angelinelli, Matteo; Anvar, Shebli; Arnaldi, Luis Horacio; Attard, Anthony; Audley, Damian; Bancel, Florian; Banks, Kimberly; Bernard, Vivian; Bij de Vaate, Jan Geralt; Bonino, Donata; Bonnamy, Anthony; Bonny, Patrick; Boreux, Charles; Bounab, Ayoub; Brigitte, Maïmouna; Bruijn, Marcel; Brysbaert, Clément; Bulgarelli, Andrea; Calarco, Simona; Camus, Thierry; Canourgues, Florent; Capobianco, Vito; Cardiel, Nicolas; Celasco, Edvige; Chen, Si; Chervenak, James; Chiarello, Fabio; Clamagirand, Sébastien; Coeur-Joly, Odile; Corcione, Leonardo; Coriat, Mickael; Coulet, Anais; Courty, Bernard; Coynel, Alexandre; D’Ai, Antonino; Dambrauskas, Eugenio; D’anca, Fabio; Dauner, Lea; De Gerone, Matteo; DeNigris, Natalie; Dercksen, Johannes; de Wit, Martin; Dieleman, Pieter; DiPirro, Michael; Doumayrou, Eric; Duband, Lionel; Dubbeldam, Luc; Dupieux, Michel; Dupourqué, Simon; Durand, Jean Louis; Eckert, Dominique; Ferrando, Philippe; Ferrari Barusso, Lorenzo; Finkbeiner, Fred; Fiocchi, Mariateresa; Fossecave, Hervé; Gabici, Stefano; Gallucci, Giovanni; Gant, Florent; Gao, Jian-Rong; Gastaldello, Fabio; Genolet, Ludovic; Ghizzardi, Simona; Giovannini, Elisa; Giustini, Margherita; Givaudan, Alain; Godet, Olivier; Gomez, Alicia; Gonzalez, Raoul; Gozaliasl, Ghassem; Grandsire, Laurent; Granena, David; Gros, Michel; Guerin, Corentin; Guilhem, Emmanuel; Guizzo, Gian Paolo; Gu, Liyi; Irwin, Kent; Jacquey, Christian; Janiuk, Agnieszka; Jaubert, Jean; Jolly, Antoine; Jourdan, Thierry; Knödlseder, Jürgen; König, Ole; Korb, Andrew; Kreykenbohm, Ingo; Lafforgue, David; Lan, Radek; Larrieu, Maélyss; Laudet, Philippe; Laurent, Philippe; Laurent, Sylvain; Laurenza, Monica; Le Cam, Maël; Lesrel, Jean; Ligori, Sebastiano; Lorenz, Maximilian; Luminari, Alfredo; Madsen, Kristin; Maisonnave, Océane; Marelli, Lorenzo; Marty, Wilfried; Massida, Zoé; Massonet, Didier; Maussang, Irwin; Merino Alonso, Pablo Eleazar; Mesquida, Jean; Mineo, Teresa; Montinaro, Nicola; Murat, David; Nagayoshi, Kenichiro; Nazé, Yaël; Noguès, Loïc; Nouals, François; Ortega, Cristina; Panessa, Francesca; Parodi, Luigi; Piconcelli, Enrico; Pinto, Ciro; Porquet, Delphine; Prouvé, Thomas; Punch, Michael; Rioland, Guillaume; Riollet, Marc-Olivier; Rodriguez, Louis; Roig, Anton; Roncarelli, Mauro; Roucayrol, Lionel; Roudil, Gilles; Ruiz de Ocenda, Lander; Sciortino, Luisa; Simonella, Olivier; Sordet, Michael; Taubenschuss, Ulrich; Terrasa, Guilhem; Terrier, Régis; Ubertini, Pietro; Uhlir, Ludek; Uslenghi, Michela; van Weers, Henk; Varisco, Salvatore; Varniere, Peggy; Volpe, Angela; Walmsley, Gavin; Wise, Michael; Wolnievik, Andreas; Wo?niak, Grzegorz
The Athena mission entered a redefinition phase in July 2022, driven by the imperative to reduce the mission cost at completion for the European Space Agency below an acceptable target, while maintaining the flagship nature of its science return. This notably called for a complete redesign of the X-ray Integral Field Unit (X-IFU) cryogenic architecture towards a simpler active cooling chain. Passive cooling via successive radiative panels at spacecraft level is now used to provide a 50 K thermal environment to an X-IFU owned cryostat. 4.5 K cooling is achieved via a single remote active cryocooler unit, while a multi-stage Adiabatic Demagnetization Refrigerator ensures heat lift down to the 50 mK required by the detectors. Amidst these changes, the core concept of the readout chain remains robust, employing Transition Edge Sensor microcalorimeters and a SQUID-based Time-Division Multiplexing scheme. Noteworthy is the introduction of a slower pixel. This enables an increase in the multiplexing factor (from 34 to 48) without compromising the instrument energy resolution, hence keeping significant system margins to the new 4 eV resolution requirement. This allows reducing the number of channels by more than a factor two, and thus the resource demands on the system, while keeping a 4’ field of view (compared to 5’ before). In this article, we will give an overview of this new architecture, before detailing its anticipated performances. Finally, we will present the new X-IFU schedule, with its short term focus on demonstration activities towards a mission adoption in early 2027
Tilt-to-length coupling in LISA Pathfinder: Long-term stability
(APS, 2024-09-03) Armano, M.; Audley, H.; Baird, J.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Castelli, Eleonora; Cavalleri, A.; Cesarini, A.; Cruise, A. M.; Danzmann, K.; de Deus Silva, M.; Diepholz, I.; Dixon, G.; Dolesi, R.; Ferraioli, L.; Ferroni, V.; Fitzsimons, E. D.; Freschi, M.; Gesa, L.; Giardini, D.; Gibert, F.; Giusteri, R.; Grimani, C.; Grzymisch, J.; Harrison, I.; Hartig, M.-S.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hoyland, D.; Hueller, M.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Johann, U.; Johlander, B.; Karnesis, N.; Kaune, B.; Killow, C. J.; Korsakova, N.; Lobo, J. A.; López-Zaragoza, J. P.; Maarschalkerweerd, R.; Mance, D.; Martín, V.; Martin-Polo, L.; Martin-Porqueras, F.; Martino, J.; McNamara, P. W.; Mendes, J.; Mendes, L.; Meshksar, N.; Nofrarias, M.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Plagnol, E.; Ramos-Castro, J.; Reiche, J.; Rivas, F.; Robertson, D. I.; Russano, G.; Sanjuan, J.; Slutsky, J.; Sopuerta, C. F.; Sumner, T.; Texier, D.; Thorpe, J. I.; Vetrugno, D.; Vitale, S.; Wanner, G.; Ward, H.; Wass, P. J.; Weber, W. J.; Wissel, L.; Wittchen, A.; Zweifel, P.
The tilt-to-length coupling during the LISA Pathfinder mission has been numerically and analytically modeled for particular time spans. In this work, we investigate the long-term stability of the coupling coefficients of this noise. We show that they drifted slowly (by 1 ?m/rad and 6 ×10?6 in 100 days) and were strongly correlated to temperature changes within the satellite (8 ?m/rad/K and 30×10?6/K). Based on analytical tilt-to-length coupling models, we attribute the temperature-driven coupling changes to rotations of the test masses and small distortions in the optical setup. Particularly, our findings lead to the conclusion that LISA Pathfinder’s optical baseplate was bent during the cooldown experiment, which started in late 2016 and lasted several months.
The temperature and metallicity distributions of the ICM: insights with TNG-Cluster for XRISM-like observations
(2025-03-03) Chatzigiannakis, Dimitris; Pillepich, Annalisa; Simionescu, Aurora; Truong, Nhut; Nelson, Dylan
The new era of high-resolution X-ray spectroscopy will significantly improve our understanding of the intra-cluster medium (ICM) by providing precise constraints on its underlying physical properties. However, spectral fitting requires reasonable assumptions on the thermal and chemical distributions of the gas. We use the output of TNG-Cluster, the newest addition to the IllustrisTNG suite of cosmological magnetohydrodynamical simulations, to provide theoretical expectations for the multi-phase nature of the ICM across hundreds of z=0 clusters (M$_{500c}$ = 10$^{14.0-15.3}$ M$_\odot$) based upon a realistic model for galaxy formation and evolution. We create and analyse, in an observer-like manner, end-to-end XRISM/Resolve mock observations towards cluster centres. We then systematically compare the intrinsic properties of the simulated gas with the inferred ones from spectral fitting via a variety of commonly used spectral-emission models. Our analysis suggests that models with a distribution of temperatures, such as bvlognorm and bvgadem, better describe the complex thermal structure of the ICM, as predicted by TNG-Cluster, but incur biases of 0.5-2 keV (16th-84th percentiles). The 1T bvapec is too simplistic for the predicted broad temperature distributions, while a 2T double bvapec model systematically fails to capture the input temperature structure. However, all spectral emission models systematically underestimate the Fe abundance of the central ICM by ~0.1 Solar (~ 20 per cent) primarily due to projection effects. Selecting only strong cool core clusters leads to minor improvements on inference quality, removing the majority of outliers but maintaining similar overall biases and cluster-to-cluster scatter.
The Proxima Centauri Campaign—First Constraints on Millimeter Flare Rates from ALMA
(AAS, 2025-03-17) Burton, Kiana; MacGregor, Meredith A.; Osten, Rachel A.; Howard, Ward S.; Weinberger, Alycia J.; Shkolnik, Evgenya; Wilner, David J.; Forbrich, Jan; Barclay, Thomas
Proxima Centauri (Cen) has been the subject of many flaring studies due to its proximity and potential to host habitable planets. The discovery of millimeter flares from this M dwarf with Atacama Large Millimeter/submillimeter Array (ALMA) has opened a new window into the flaring process and the space-weather environments of exoplanets like Proxima b. Using a total of 50 hr of ALMA observations of Proxima Cen at 1.3 mm (233 GHz), we add a new piece to the stellar flaring picture and report the first cumulative flare frequency distribution (FFD) at millimeter wavelengths of any M dwarf. We detect 463 flares ranging from energies 1024 to 1027 erg. The brightest and most energetic flare in our sample reached a flux density of 119 ± 7 mJy, increasing by a factor of 1000× the quiescent flux, and reaching an energy of 1027 erg in the ALMA bandpass, with t1/2 ? 16 s. From a log–log linear regression fit to the FFD, we obtain a power-law index of ?FFD = 2.92 ± 0.02, much steeper than ?FFD values ( 2) observed at X-ray to optical wavelengths. If millimeter flare rates are predictive of flare rates at extreme-UV wavelengths, the contribution of small flares to the radiation environment of Proxima b may be much higher than expected based on the shallower power-law slopes observed at optical wavelengths.
The Pandora SmallSat: A Low-Cost, High Impact Mission to Study Exoplanets and Their Host Stars
(2025-02-13) Barclay, Thomas; Quintana, Elisa V.; Colón, Knicole; Hord, Benjamin J.; Mosby, Gregory; Schlieder, Joshua E.; Zellem, Robert T.; Karburn, Jordan; Simms, Lance M.; Heatwole, Peter F.; Hedges, Christina L.; Dotson, Jessie L.; Greene, Thomas P.; Foote, Trevor O.; Lewis, Nikole K.; Rackham, Benjamin V.; Morris, Brett M.; Gilbert, Emily A.; Kostov, Veselin B.; Rowe, Jason F.; Wiser, Lindsay S.
The Pandora SmallSat is a NASA flight project aimed at studying the atmospheres of exoplanets -- planets orbiting stars outside our Solar System. Pandora will provide the first dataset of simultaneous, multiband (visible and NIR), long-baseline observations of exoplanets and their host stars. Pandora is an ambitious project that will fly a 0.44 m telescope in a small form factor. To achieve the scientific goals, the mission requires a departure from the traditional cost-schedule paradigm of half-meter-class observatories. Pandora achieves this by leveraging existing capabilities that necessitate minimal engineering development, disruptive and agile management, trusted partnerships with vendors, and strong support from the lead institutions. The Pandora team has developed a suite of high-fidelity parameterized simulation and modeling tools to estimate the performance of both imaging channels. This has enabled a unique bottom-up approach to deriving trades and system requirements. Pandora is a partnership between NASA and Lawrence Livermore National Laboratory. The project completed its Critical Design Review in October 2023 and is slated for launch into Sun-synchronous, low-Earth orbit in Fall 2025.
Precision measurements of the magnetic parameters of LISA Pathfinder test masses
(APS, 2025-02-18) Armano, M.; Audley, H.; Baird, J.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Castelli, Eleonora; Cavalleri, A.; Cesarini, A.; Cruise, A. M.; Danzmann, K.; de Deus Silva, M.; Diepholz, I.; Dixon, G.; Dolesi, R.; Ferraioli, L.; Ferroni, V.; Fitzsimons, E. D.; Freschi, M.; Gesa, L.; Giardini, D.; Gibert, F.; Giusteri, R.; Grimani, C.; Grzymisch, J.; Harrison, I.; Hartig, M.-S.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hoyland, D.; Hueller, M.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Karnesis, N.; Kaune, B.; Korsakova, N.; Killow, C. J.; Liu, L.; Lobo, J. A.; López-Zaragoza, J. P.; Maarschalkerweerd, R.; Mance, D.; Martín, V.; Martino, J.; Martin-Polo, L.; Martin-Porqueras, F.; Meshksar, N.; McNamara, P. W.; Mendes, J.; Mendes, L.; Nofrarias, M.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Pivato, P.; Plagnol, E.; Ramos-Castro, J.; Reiche, J.; Robertson, D. I.; Rivas, F.; Russano, G.; Sala, L.; Serrano, D.; Slutsky, J.; Sopuerta, C. F.; Sumner, T.; Texier, D.; Thorpe, J. I.; Vetrugno, D.; Vitale, S.; Wanner, G.; Ward, H.; Wass, P. J.; Weber, W. J.; Wissel, L.; Wittchen, A.; Zweifel, P.
A precise characterization of the magnetic properties of LISA Pathfinder free falling test-masses is of special interest for future gravitational wave observatory in space. Magnetic forces have an important impact on the instrument sensitivity in the low frequency regime below the millihertz. In this paper we report on the magnetic injection experiments performed throughout LISA Pathfinder operations. We show how these experiments allowed a high precision estimate of the instrument magnetic parameters. The remanent magnetic moment was found to have a modulus of (0.245±0.081) nAm², the x-component of the background magnetic field within the test masses position was measured to be (414±74) nT and its gradient had a value of (−7.4±2.1) μ⁢T/m. Finally, we also measured the test mass magnetic susceptibility at 5 mHz to be (−3.3723±0.0069)×10⁻⁵. All results are in agreement with on-ground estimates.
Outflowing photoionized plasma in Circinus X-1 using the high-resolution X-ray spectrometer Resolve onboard XRISM and the radiative transfer code cloudy
(2025-03-11) Tsujimoto, Masahiro; Enoto, Teruaki; Trigo, María Díaz; Hell, Natalie; Chakraborty, Priyanka; Leutenegger, Maurice A.; Loewenstein, Michael; Pradhan, Pragati; Shidatsu, Megumi; Takahashi, Hiromitsu; Yaqoob, Tahir
High-resolution X-ray spectroscopy is a key to understanding the mass inflow and outflow of compact objects. Spectral lines carry information about the ionization, density, and velocity structures through their intensity ratios and profiles. They are formed in non-local thermodynamic equilibrium conditions under the intense radiation field from the compact objects, thus radiative transfer (RT) calculation is a requisite for proper interpretations. We present such a study for a low-mass X-ray binary, Circinus X-1, from which the P Cygni profile was discovered using the X-ray grating spectrometer onboard Chandra. We observed the source using the X-ray microcalorimeter onboard XRISM at an orbital phase of 0.93-0.97 and revealed many spectral features unidentified before; the higher series transitions (n to 1; n > 2) of highly-ionized (H- and He-like) S, Ca, Ar, and Fe in emission and absorption, the Fe K{\alpha} and K\b{eta} inner-shell excitation absorption of mildly-ionized (O- to Li-like) Fe, and resolved fine-structure level transitions in the Fe Ly{\alpha} and He{\alpha} complexes. They blend with each other at different velocity shifts on top of apparently variable continuum emission that changed its flux by an order of magnitude within a 70 ks telescope time. Despite such complexity in the observed spectra, most of them can be explained by a simple model consisting of the photoionized plasma outflowing at ~300 km s-1 and the variable blocking material in the line of sight of the incident continuum emission from the accretion disk. We demonstrate this with the aid of the RT code cloudy for the line ratio diagnostics and spectral fitting. We further constrain the physical parameters of the outflow and argue that the outflow is launched close to the outer edge of the accretion disk and can be driven radiatively by being assisted by the line force calculated using the RT simulation.
An X-ray view of the Cataclysmic Variable V902 Mon: Discovery of an X-ray eclipse
(2025-02-14) Islam, Nazma; Mukai, Koji
V902 Mon is one of a few eclipsing Intermediate Polars (IPs), and show deep eclipses in the optical lightcurves. The presence of a strong Fe Kα fluorescence line in its X-ray spectrum and its low X-ray flux compared to other IPs suggests significant absorption, most likely from an accretion disk. In an observation carried out using the Nuclear Spectroscopic Telescope Array (NuSTAR), we confirm the presence of an X-ray eclipse in the energy resolved lightcurves, coincident with the optical AAVSO/CV-band lightcurves. Broadband X-ray spectral analysis using NuSTAR and XMM-Newton observations confirm a strong absorption N H ∼10 ²³ cm⁻² local to the source, along with a high equivalent width of about 0.7 keV for a Fe Kα fluorescence line. We interpret this using a model similar to an Accretion Disk Corona source, which have a very high inclination and the compact object is heavily obscured by the body of the accretion disk. We propose that the primary X-rays from the accretion column in V902 Mon is hidden from our direct view at all times by the accretion disk. In this scenario, the observed scattered X-rays indicate substantial absorption of direct X-rays by the accretion disk. Additionally, a strong Fe fluorescence line suggests reprocessing of the radiation by a more extended region, such as the pre-shock region, which could be located a few white dwarf radii above the orbital plane.
The bulk motion of gas in the core of the Centaurus galaxy cluster
(Nature, 2025-02) Audard, Marc; Awaki, Hisamitsu; Ballhausen, Ralf; Bamba, Aya; Behar, Ehud; Boissay-Malaquin, Rozenn; Brenneman, Laura; Brown, Gregory V.; Corrales, Lia; Costantini, Elisa; Cumbee, Renata; Done, Chris; Dotani, Tadayasu; Ebisawa, Ken; Eckart, Megan E.; Eckert, Dominique; Enoto, Teruaki; Eguchi, Satoshi; Ezoe, Yuichiro; Foster, Adam; Fujimoto, Ryuichi; Fujita, Yutaka; Fukazawa, Yasushi; Fukushima, Kotaro; Furuzawa, Akihiro; Gallo, Luigi; García, Javier A.; Gu, Liyi; Guainazzi, Matteo; Hagino, Kouichi; Hamaguchi, Kenji; Hatsukade, Isamu; Hayashi, Katsuhiro; Hayashi, Takayuki; Hell, Natalie; Hodges-Kluck, Edmund; Hornschemeier, Ann; Ichinohe, Yuto; Ishida, Manabu; Ishikawa, Kumi; Ishisaki, Yoshitaka; Kaastra, Jelle; Kallman, Timothy; Kara, Erin; Katsuda, Satoru; Kanemaru, Yoshiaki; Kelley, Richard; Kilbourne, Caroline; Kitamoto, Shunji; Kobayashi, Shogo; Kohmura, Takayoshi; Kubota, Aya; Leutenegger, Maurice; Loewenstein, Michael; Maeda, Yoshitomo; Markevitch, Maxim; Matsumoto, Hironori; Matsushita, Kyoko; McCammon, Dan; McNamara, Brian; Mernier, François; Miller, Eric D.; Miller, Jon M.; Mitsuishi, Ikuyuki; Mizumoto, Misaki; Mizuno, Tsunefumi; Mori, Koji; Mukai, Koji; Murakami, Hiroshi; Mushotzky, Richard; Nakajima, Hiroshi; Nakazawa, Kazuhiro; Ness, Jan-Uwe; Nobukawa, Kumiko; Nobukawa, Masayoshi; Noda, Hirofumi; Odaka, Hirokazu; Ogawa, Shoji; Ogorzalek, Anna; Okajima, Takashi; Ota, Naomi; Paltani, Stephane; Petre, Robert; Plucinsky, Paul; Porter, Frederick Scott; Pottschmidt, Katja; Sato, Kosuke; Sato, Toshiki; Sawada, Makoto; Seta, Hiromi; Shidatsu, Megumi; Simionescu, Aurora; Smith, Randall; Suzuki, Hiromasa; Szymkowiak, Andrew; Takahashi, Hiromitsu; Takeo, Mai; Tamagawa, Toru; Tamura, Keisuke; Tanaka, Takaaki; Tanimoto, Atsushi; Tashiro, Makoto; Terada, Yukikatsu; Terashima, Yuichi; Trigo, María Díaz; Tsuboi, Yohko; Tsujimoto, Masahiro; Tsunemi, Hiroshi; Tsuru, Takeshi G.; Uchida, Hiroyuki; Uchida, Nagomi; Uchida, Yuusuke; Uchiyama, Hideki; Ueda, Yoshihiro; Uno, Shinichiro; Vink, Jacco; Watanabe, Shin; Williams, Brian J.; Yamada, Satoshi; Yamada, Shinya; Yamaguchi, Hiroya; Yamaoka, Kazutaka; Yamasaki, Noriko Y.; Yamauchi, Makoto; Yamauchi, Shigeo; Yaqoob, Tahir; Yoneyama, Tomokage; Yoshida, Tessei; Yukita, Mihoko; Zhuravleva, Irina; Kondo, Marie; Werner, Norbert; Plšek, Tomáš ; Sun, Ming; Hosogi, Kokoro; Majumder, Anwesh; XRISM collaboration
Galaxy clusters contain vast amounts of hot ionized gas known as the intracluster medium (ICM). In relaxed cluster cores, the radiative cooling time of the ICM is shorter than the age of the cluster. However, the absence of line emission associated with cooling suggests heating mechanisms that offset the cooling, with feedback from active galactic nuclei (AGNs) being the most likely source1,2. Turbulence and bulk motions, such as the oscillating (‘sloshing’) motion of the core gas in the cluster potential well, have also been proposed as mechanisms for heat distribution from the outside of the core3,4. Here we present X-ray spectroscopic observations of the Centaurus galaxy cluster with the X-Ray Imaging and Spectroscopy Mission satellite. We find that the hot gas flows along the line of sight relative to the central galaxy, with velocities from 130 km s⁻¹ to 310 km s⁻¹ within about 30 kpc of the centre. This indicates bulk flow consistent with core gas sloshing. Although the bulk flow may prevent excessive accumulation of cooled gas at the centre, it could distribute the heat injected by the AGN and bring in thermal energy from the surrounding ICM. The velocity dispersion of the gas is found to be only ≲120 km s⁻¹ in the core, even within about 10 kpc of the AGN. This suggests that the influence of the AGN on the surrounding ICM motion is limited in the cluster.
Your smart home exchanged 3M messages: defining and analyzing smart device passive mode
(HAL, 2025-03) Badolato, Christian; Kullman, Kaur; Papadakis, Nikolaos; Bhatt, Manav; Bouloukakis, Georgios; Engel, Don; Yus, Roberto
The constant connectedness of smart home devices and their sensing capabilities pose a unique threat to individuals’ privacy. While users may expect devices to exhibit minimal activity while they are not performing their intended functions, this is not necessarily the case, and traditional idle mode designations are insufficient to address the current landscape of smart home devices. To address this we propose a passive mode designation based on a comprehensive categorization of smart home devices. We then measure the network traffic of thirty-two devices in their respective passive modes. We find that 97% of the devices exhibit near-constant network activity in these modes (exchanging over 3M messages in 24 hours), with many of the devices initiating and responding to LAN communications with other devices, which potentially exposes users to privacy leakages.
Detection of X-ray Emission from a Bright Long-Period Radio Transient
(2024-11-26) Wang, Ziteng; Rea, Nanda; Bao, Tong; Kaplan, David L.; Lenc, Emil; Wadiasingh, Zorawar; Hare, Jeremy; Zic, Andrew; Anumarlapudi, Akash; Bera, Apurba; Beniamini, Paz; Cooper, A. J.; Clarke, Tracy E.; Deller, Adam T.; Dawson, J. R.; Glowacki, Marcin; Hurley-Walker, Natasha; McSweeney, S. J.; Polisensky, Emil J.; Peters, Wendy M.; Younes, George; Bannister, Keith W.; Caleb, Manisha; Dage, Kristen C.; James, Clancy W.; Kasliwal, Mansi M.; Karambelkar, Viraj; Lower, Marcus E.; Mori, Kaya; Ocker, Stella Koch; Pérez-Torres, Miguel; Qiu, Hao; Rose, Kovi; Shannon, Ryan M.; Taub, Rhianna; Wang, Fayin; Wang, Yuanming; Zhao, Zhenyin; Bhat, N. D. R.; Dobie, Dougal; Driessen, Laura N.; Murphy, Tara; Jaini, Akhil; Deng, Xinping; Jahns-Schindler, Joscha N.; Lee, Y. W. J.; Pritchard, Joshua; Tuthill, John; Thyagarajan, Nithyanandan
Recently, a class of long-period radio transients (LPTs) has been discovered, exhibiting emission on timescales thousands of times longer than radio pulsars. Several models had been proposed implicating either a strong magnetic field neutron star, isolated white dwarf pulsar, or a white dwarf binary system with a low-mass companion. While several models for LPTs also predict X-ray emission, no LPTs have been detected in X-rays despite extensive searches. Here we report the discovery of an extremely bright LPT (10-20 Jy in radio), ASKAP J1832-0911, which has coincident radio and X-ray emission, both with a 44.2-minute period. The X-ray and radio luminosities are correlated and vary by several orders of magnitude. These properties are unique amongst known Galactic objects and require a new explanation. We consider a ≳ 0.5 Myr old magnetar with a ≳ 10¹³ G crustal field, or an extremely magnetised white dwarf in a binary system with a dwarf companion, to be plausible explanations for ASKAP J1832-0911, although both explanations pose significant challenges to formation and emission theories. The X-ray detection also establishes a new class of hour-scale periodic X-ray transients of luminosity ~10³³ erg/s associated with exceptionally bright coherent radio emission.
Shockingly Bright Warm Carbon Monoxide Molecular Features in the Supernova Remnant Cassiopeia A Revealed by JWST
(AAS, 2024-06-24) Rho, J.; Park, S.-H.; Arendt, Richard; Matsuura, M.; Milisavljevic, D.; Temim, T.; De Looze, I.; Blair, W. P.; Rest, A.; Fox, O.; Ravi, A. P.; Koo, B.-C.; Barlow, M.; Burrows, A.; Chevalier, R.; Clayton, G.; Fesen, R.; Fransson, C.; Fryer, C.; Gomez, H. L.; Janka, H.-T.; Kirchschlager, F.; Laming, J. M.; Orlando, S.; Patnaude, D.; Pavlov, G.; Plucinsky, P.; Posselt, B.; Priestley, F.; Raymond, J.; Sartorio, N.; Schmidt, F.; Slane, P.; Smith, N.; Sravan, N.; Vink, J.; Weil, K.; Wheeler, J.; Yoon, S. C.
We present JWST NIRCam (F356W and F444W filters) and MIRI (F770W) images and NIRSpec Integral Field Unit (IFU) spectroscopy of the young Galactic supernova remnant Cassiopeia A (Cas A) to probe the physical conditions for molecular CO formation and destruction in supernova ejecta. We obtained the data as part of a JWST survey of Cas A. The NIRCam and MIRI images map the spatial distributions of synchrotron radiation, Ar-rich ejecta, and CO on both large and small scales, revealing remarkably complex structures. The CO emission is stronger at the outer layers than the Ar ejecta, which indicates the re-formation of CO molecules behind the reverse shock. NIRSpec-IFU spectra (3–5.5 μm) were obtained toward two representative knots in the NE and S fields that show very different nucleosynthesis characteristics. Both regions are dominated by the bright fundamental rovibrational band of CO in the two R and P branches, with strong [Ar vi] and relatively weaker, variable strength ejecta lines of [Si ix], [Ca iv], [Ca v], and [Mg iv]. The NIRSpec-IFU data resolve individual ejecta knots and filaments spatially and in velocity space. The fundamental CO band in the JWST spectra reveals unique shapes of CO, showing a few tens of sinusoidal patterns of rovibrational lines with pseudocontinuum underneath, which is attributed to the high-velocity widths of CO lines. Our results with LTE modeling of CO emission indicate a temperature of ∼1080 K and provide unique insight into the correlations between dust, molecules, and highly ionized ejecta in supernovae and have strong ramifications for modeling dust formation that is led by CO cooling in the early Universe.
Hydrogen escaping from a pair of exoplanets smaller than Neptune
(Nature, 2025-02) Loyd, R. O. Parke; Schreyer, Ethan; Owen, James E.; Rogers, James G.; Broome, Madelyn I.; Shkolnik, Evgenya L.; Murray-Clay, Ruth; Wilson, David J.; Peacock, Sarah; Teske, Johanna; Schlichting, Hilke E.; Duvvuri, Girish M.; Youngblood, Allison; Schneider, P. Christian; France, Kevin; Giacalone, Steven; Batalha, Natasha E.; Schneider, Adam C.; Longo, Isabella; Barman, Travis; Ardila, David R.
Exoplanet surveys have shown a class of abundant exoplanets smaller than Neptune on close, <100-day orbits1,2,3,4. These planets form two populations separated by a natural division at about 1.8 R⊕ termed the radius valley. It is uncertain whether these populations arose from separate dry versus water-rich formation channels, evolved apart because of long-term atmospheric loss or a combination of both5,6,7,8,9,10,11,12,13,14. Here we report observations of ongoing hydrogen loss from two sibling planets, TOI-776 b (1.85 ± 0.13 R⊕) and TOI-776 c (2.02 ± 0.14 R⊕), the sizes of which near the radius valley and mature (1–4 Gyr) age make them valuable for investigating the origins of the divided population of which they are a part. During the transits of these planets, absorption appeared against the Lyman-α emission of the host star, compatible with hydrogen escape at rates equivalent to 0.03–0.6% and 0.1–0.9% of the total mass per billion years of each planet, respectively. Observations of the outer planet, TOI-776 c, are incompatible with an outflow of dissociated steam, suggesting both it and its inner sibling formed in a dry environment. These observations support the strong role of hydrogen loss in the evolution of close-orbiting sub-Neptunes5,6,7,8,15,16.

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