About

Sarbani Basu is a Professor of Astronomy at Yale University, affiliated with the Yale Center for Astronomy and Astrophysics. Her professional address is at Kline Tower 617. The provided page does not include specific details about her research focus, background, or key contributions.

Research topics

• Computer Science
• Astrophysics
• Physics
• Remote sensing
• Geology
• Astronomy
• Meteorology
• Geography

Selected publications

• Anti-Solar Differential Rotation May Have Revived Magnetic Braking in the Subgiant 31 Aquilae

  ArXiv.org · 2026-03-17

  articleOpen access

  Recent observations have shown that sufficiently slow rotation disrupts the organization of large-scale magnetic field in older main-sequence stars, leading to weakened magnetic braking (WMB) and a collapse in the efficiency of the global stellar dynamo. Recent simulations predict a shift from solar-like to anti-solar differential rotation (DR) at slower rotation rates, which typically do not occur on the main-sequence due to WMB. However, physical expansion on the subgiant branch can eventually slow the stellar rotation beyond this threshold, yielding a non-cycling large-scale field that revives magnetic braking. We combine asteroseismology from the Transiting Exoplanet Survey Satellite (TESS) with spectropolarimetry from the Large Binocular Telescope (LBT) to test these predictions in the old metal-rich subgiant 31 Aql. The LBT observations reveal a strong large-scale magnetic field in this star, and archival measurements of its chromospheric emission over 50 years confirm that it is non-cycling, as predicted. The star exhibits a variety of rotation periods during different observing seasons, consistent with DR but with no means of distinguishing between solar-like and anti-solar patterns. We incorporate the TESS observations to estimate the current wind braking torque of 31 Aql, demonstrating that it supports revived magnetic braking in this old subgiant. We also use rotational evolution modeling to place a preliminary constraint on the stellar Rossby number for the transition to anti-solar DR. Future refinements in both asteroseismic observations and rotational modeling may yield improvements to this initial analysis.

  PublisherOA PDF

• A Test of Substellar Evolutionary Models with High-precision Ages from Asteroseismology and Gyrochronology for the Benchmark System HR 7672AB

  The Astrophysical Journal · 2026-04-21

  articleOpen access

  Abstract We present high-precision measurements for HR 7672AB, composed of a Sun-like (G0V) star and an L dwarf companion. Three nights of precise (70 cm s −1 ) radial velocity (RV) asteroseismology with the Keck Planet Finder clearly detect 5 minute oscillations from the primary, HR 7672A, and modeling of the frequency spectrum yields an asteroseismic age of 1.87 ± 0.65 Gyr. We also determine a gyrochronological age of 2.58 ± 0.47 Gyr, and we combine these two results for a final age of 2.26 ± 0.40 Gyr. In addition, we obtained new RVs for HR 7672A and new astrometry for the companion HR 7672B. From a joint orbit fit, we measured a dynamical mass of 1.111 ± 0.017 M ⊙ for HR 7672A and 75.39 ± 0.67 M Jup for HR 7672B. This places the companion near the stellar/substellar boundary and is thus particularly sensitive to differences in model predictions. The joint precision in host star age (18% uncertainty) and companion mass (0.9% uncertainty) makes HR 7672AB an exceptional substellar benchmark. Combined with the companion’s luminosity, we use these measurements to test predictions from six brown dwarf cooling models. The best agreement occurs with the G. Chabrier et al. models, which incorporate a new equation of state, resulting in predictions that agree within <0.3 σ with all the observations. The other five sets of models agree at the 1 σ –3 σ level, depending on the particular test, and some models struggle to predict a sufficiently low luminosity for HR 7672B at any age given its dynamical mass. We also detected a weak seismic signal in near-simultaneous TESS photometry of HR 7672A, with the resulting RV-to-photometry oscillation amplitude ratio consistent with solar values.

  PublisherDOI

• Anti-Solar Differential Rotation May Have Revived Magnetic Braking in the Subgiant 31 Aquilae

  arXiv (Cornell University) · 2026-03-17

  preprintOpen access

  Recent observations have shown that sufficiently slow rotation disrupts the organization of large-scale magnetic field in older main-sequence stars, leading to weakened magnetic braking (WMB) and a collapse in the efficiency of the global stellar dynamo. Recent simulations predict a shift from solar-like to anti-solar differential rotation (DR) at slower rotation rates, which typically do not occur on the main-sequence due to WMB. However, physical expansion on the subgiant branch can eventually slow the stellar rotation beyond this threshold, yielding a non-cycling large-scale field that revives magnetic braking. We combine asteroseismology from the Transiting Exoplanet Survey Satellite (TESS) with spectropolarimetry from the Large Binocular Telescope (LBT) to test these predictions in the old metal-rich subgiant 31 Aql. The LBT observations reveal a strong large-scale magnetic field in this star, and archival measurements of its chromospheric emission over 50 years confirm that it is non-cycling, as predicted. The star exhibits a variety of rotation periods during different observing seasons, consistent with DR but with no means of distinguishing between solar-like and anti-solar patterns. We incorporate the TESS observations to estimate the current wind braking torque of 31 Aql, demonstrating that it supports revived magnetic braking in this old subgiant. We also use rotational evolution modeling to place a preliminary constraint on the stellar Rossby number for the transition to anti-solar DR. Future refinements in both asteroseismic observations and rotational modeling may yield improvements to this initial analysis.

  PublisherDOI

• Prosthetic Stuck Valve Presentation and Management

  Heart Lung and Circulation · 2025-08-01

  articleOpen access
  PublisherOA PDFDOI

• Projection-angle effects when "observing" a turbulent magnetized collapsing molecular cloud. II. Magnetic field

  ArXiv.org · 2025-03-03

  preprintOpen access

  Interstellar magnetic fields are thought to play a fundamental role in the evolution of star-forming regions. Polarized thermal dust emission serves as a key probe for understanding the structure of the POS component of the magnetic field. However, inclination effects can significantly influence the apparent morphology of the magnetic field and lead to erroneous conclusions regarding its dynamical importance. Our aim is to investigate how projection-angle effects impact dust polarization maps and to explore new ways for accessing the inclination angle of the mean component of the magnetic field with respect to the POS. We post-processed a 3D ideal MHD simulation of a turbulent collapsing molecular cloud and produced synthetic dust polarization measurements under various projection angles, ranging from "face-on" (i.e., viewed along the mean magnetic field direction) to "edge-on" (perpendicular to the mean magnetic field direction). Additionally, we used synthetic PPV data cubes from the CO (J = 1-0) transition, presented in a companion paper. The projected magnetic-field morphology is found to be highly affected by the projection angle with the hourglass morphology being clearly visible only for projection angles close to edge-on. We find that the direction of the apparent "flow" between successive velocity channels in the simulated PPV data cubes shows an increasing correlation with the synthetic dust polarization observations, as the cloud is observed closer to an edge-on orientation. Based on this property, we developed a new method to probe the inclination angle of the magnetic field relative to the POS. We validated our approach by generating additional synthetic data (PPV cubes and polarization maps) at an earlier stage of the cloud's evolution and demonstrated an excellent quantitative agreement between the derived inclination angle and the true observational angle.

  PublisherOA PDF

• Projection-angle effects when "observing" a turbulent magnetized collapsing molecular cloud. I. Chemistry and line transfer

  ArXiv.org · 2025-03-03

  preprintOpen access

  Most of our knowledge regarding molecular clouds and the early stages of star formation stems from molecular spectral-line observations. However, the various chemical and radiative-transfer effects, in combination with projection effects, can lead to a distorted view of molecular clouds. Our objective is to simultaneously study all of these effects by creating synthetic spectral-line observations based on a chemo-dynamical simulation of a collapsing molecular cloud. We performed a 3D ideal MHD simulation of a supercritical turbulent collapsing molecular cloud where the dynamical evolution was coupled to a nonequilibrium gas-grain chemical network consisting of 115 species, the evolution of which was governed by >1600 chemical reactions. We post-processed this simulation with a multilevel non-LTE radiative-transfer code to produce synthetic PPV data cubes of the CO, HCO+, HCN, and N2H+ (J = 1-0) transitions under various projection angles with respect to the mean component of the magnetic field. We find that the chemical abundances of various species in our simulated cloud tend to be over-predicted in comparison to observationally derived abundances and attribute this discrepancy to the fact that the cloud collapses rapidly and therefore the various species do not have enough time to deplete onto dust grains. This suggests that our initial conditions may not correspond to the initial conditions of real molecular clouds and cores. We show that the projection angle has a notable effect on the moment maps of the species for which we produced synthetic observations. Specifically, the integrated emission and velocity dispersion of CO, HCO+, and HCN are higher when the cloud is observed "face on" compared to "edge on," whereas column density maps exhibit an opposite trend. Finally, we show that only N2H+ is an accurate tracer of the column density of the cloud across all projection angles.

  PublisherOA PDF

• Structure and Dynamics of the Sun’s Interior Revealed by the Helioseismic and Magnetic Imager

  Solar Physics · 2025-05-01 · 10 citations

  articleOpen access

  Abstract High-resolution helioseismology observations with the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) provide a unique three-dimensional view of the solar interior structure and dynamics, revealing a tremendous complexity of the physical processes inside the Sun. We present an overview of the results of the HMI helioseismology program and discuss their implications for modern theoretical models and simulations of the solar interior.

  PublisherOA PDFDOI

• The PLATO mission

  Experimental Astronomy · 2025-04-21 · 124 citations

  articleOpen access

  Abstract PLATO (PLAnetary Transits and Oscillations of stars) is ESA’s M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to &lt;2R $$_\textrm{Earth}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mtext>Earth</mml:mtext> <mml:mrow/> </mml:mmultiscripts> </mml:math> ) around bright stars (&lt;11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5%, 10%, 10% for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO‘s target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile towards the end of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases.

  PublisherDOI

• Ensemble seismic study of the properties of the core of Red Clump stars

  DIGITAL.CSIC (Spanish National Research Council (CSIC)) · 2025-10-07 · 1 citations

  preprintOpen access

  Red clump stars still pose open questions regarding several physical processes, such as the mixing around the core, or the nuclear reactions, which are ill-constrained by theory and experiments. The oscillations of red clump stars, which are of mixed gravito-acoustic nature, allow us to directly investigate the interior of these stars and thereby better understand their physics. In particular, the measurement of their period spacing is a good probe of the structure around the core. We aim to explain the distribution of period spacings in red clump stars observed by Kepler by testing different prescriptions of core-boundary mixing and nuclear reaction rate. Using the MESA stellar evolution code, we computed several grids of core-helium burning tracks, with varying masses and metallicities. Each of these grids have been computed assuming a certain core boundary mixing scheme, or carbon-alpha reaction rate. We then sampled these grids, in a Monte-Carlo fashion, using observational spectroscopic metallicities and seismic masses priors, in order to retrieve a period spacing distribution that we compared to the observations. We found that the best fitting distribution was obtained when using a "maximal overshoot" core-boundary scheme, which has similar seismic properties as a model whose modes are trapped outside a semi-convective region, and which does not exhibit core breathing pulses at the end of the core-helium burning phase. If no mode trapping is assumed, then no core boundary mixing scheme is compatible with the observations. Moreover, we found that extending the core with overshoot worsens the fit. Additionally, reducing the carbon-alpha reaction rate (by around 15%) improves the fit to the observed distribution. Finally, we noted that an overpopulation of early red clump stars with period spacing values around 250s is predicted by the models but not found in the observations.

  PublisherDOI

• Ensemble seismic study of the properties of the core of red clump stars

  Astronomy and Astrophysics · 2025-12-01

  articleOpen access

  Context. Red clump (RC) stars still pose open questions regarding several physical processes, such as the mixing around the core or the nuclear reactions, which are ill-constrained by theory and experiments. The oscillations of RC stars, which are of a mixed gravito-acoustic nature, allow us to directly investigate the interior of these stars and thereby better understand their physics. In particular, the measurement of their period spacing is a good probe of the structure around the core. Aims. We aim to explain the distribution of period spacings in RC stars observed by Kepler by testing different prescriptions of core-boundary mixing and the nuclear reaction rate. Methods. Using the MESA stellar evolution code, we computed several grids of core-helium-burning tracks, with varying masses and metallicities. Each of these grids has been computed assuming a certain core boundary mixing scheme, or 12 C( α , γ ) 16 O reaction rate. We then sampled these grids, in a Monte-Carlo fashion, using observational spectroscopic metallicity and seismic mass priors, in order to retrieve a period spacing distribution, which we compared to the observations. Results. We find that the best-fitting distribution is obtained when using a “maximal overshoot” core-boundary scheme, which has similar seismic properties as a model whose modes are trapped outside a semi-convective region, and which does not exhibit core-breathing pulses at the end of the core-helium-burning phase. If no mode trapping is assumed, then no core boundary mixing scheme is compatible with the observations. Moreover, we find that extending the core with overshoot worsens the fit. Additionally, reducing the 12 C( α , γ ) 16 O reaction rate (by around 15%) improves the fit to the observed distribution. Finally, we note that an overpopulation of early RC stars with period spacing values around 250 s is predicted by the models but not found in the observations. Conclusions. Assuming a semi-convective region and mode trapping, along with a slightly lower than nominal 12 C( α , γ ) 16 O rate, allowed us to reproduce most of the features of the observed period spacing distribution, except for those of early RC stars.

  PublisherOA PDFDOI

Recent grants

• Journey to the Centre of Stars: Testing Stellar Evolution with Asteroseismology

  NSF · $345k · 2011–2015

• Asteroseismic analyses of the physics red-giant interiors

  NSF · $449k · 2022–2025

• Helioseismology and Solar Magnetic Fields: Studying the Forward Problem

  NSF · $399k · 2008–2011

• Decreasing Systematic Errors in Estimates of Stellar Ages

  NSF · $434k · 2015–2019

• CAREER: Solar Variability in the Classroom and in Research

  NSF · $597k · 2004–2011

Frequent coauthors

• R. A. García

  532 shared

• W. J. Chaplin

  University of Birmingham

  276 shared

• B. Mosser

  Laboratoire d’études spatiales et d’instrumentation en astrophysique

  276 shared

• S. Hekker

  250 shared

• J. Christensen‐Dalsgaard

  184 shared

• Daniel Huber

  University of Hawaii System

  159 shared

• Dennis Stello

  UNSW Sydney

  148 shared

• H. M. Antia

  Center for Excellence in Basic Sciences

  146 shared

Education

• Ph.D., Theoretical Astrophysics Group

  Tata Institute of Fundamental Research

  1993

• M.Sc., Physics

  University of Pune

  1988

• B.Sc., Physics

  Women's Christian College

  1986