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Tue 20 May 13:00: On Activity and Planets of Low-Mass Stars: Towards the Tenth Anniversary of CARMENES

IoA Institute of Astronomy Talk Lists - Thu, 15/05/2025 - 20:14
On Activity and Planets of Low-Mass Stars: Towards the Tenth Anniversary of CARMENES

It has been almost ten years since CARMENES opened its two spectroscopic eyes at the Calar-Alto observatory. Here’s an up-to-date account of the findings: more than 40 new planets in a sample of 354 M dwarfs; mass estimates of 32 transiting planets; and more than 120 papers, also covering topics such as stellar magnetic activity, binaries, and atmospheric characterization of exoplanets. So, what’s next? Stellar activity is still the main factor limiting the detection of many more planets or estimating the mass of transiting planets around low-mass stars. But for CARMENES , stellar activity is a signal, not just correlated noise. In its spectroscopic time series, it is manifested as a quasiperiodic wavelength-dependent variability, which induces activity-related radial velocity (ARV) variations of at least 2 m/s. For many stars, ARV variability is >10 m/s. Fortunately, ARV variability differs from Doppler shifts: it is usually incoherent, wavelength-dependent, and accompanied by spectral shape variations. These differences can help us distinguish between activity-related and planetary signals and model both phenomena simultaneously.

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The vertical structure of debris discs and the role of disc gravity

Stars and stellar evolution - Thu, 15/05/2025 - 10:56
arXiv:2505.09578v1 Announce Type: new Abstract: Debris discs provide valuable insights into the formation and evolution of exoplanetary systems. Their structures are commonly attributed to planetary perturbations, serving as probes of as-yet-undetected planets. However, most studies of planet-debris disc interactions ignore the disc's gravity, treating it as a collection of massless planetesimals. Here, using an analytical model, we investigate how the vertical structure of a back-reacting debris disc responds to secular perturbations from an inner, inclined planet. Considering the disc's axisymmetric potential, we identify two dynamical regimes: planet-dominated and disc-dominated, which may coexist, separated by a secular-inclination resonance. In the planet-dominated regime ($M_d/m_p\ll1$), we recover the classical result: a transient warp propagates outward until the disc settles into a box-like structure centered around the planetary orbit's initial inclination $I_p(0)$, with a distance-independent aspect ratio $\mathcal{H}(R)\approx I_p(0)$. In contrast, in the disc-dominated regime ($M_d/m_p\gtrsim1$), the disc exhibits dynamical rigidity, remaining thin and misaligned, with significantly suppressed inclinations and a sharply declining aspect ratio, $\mathcal{H}(R)\propto I_p(0)R^{-7/2}$. In the intermediate regime ($M_d/m_p\lesssim1$), the system exhibits a secular-inclination resonance, leading to long-lived, warp-like structures and a bimodal inclination distribution, containing both dynamically hot and cold populations. We provide analytic formulae describing these effects as a function of system parameters. We also find that the vertical density profile is intrinsically non-Gaussian and recommend fitting observations with non-zero slopes of $\mathcal{H}(R)$. Our results may be used to infer planetary parameters and debris disc masses based on observed warps and scale heights, as demonstrated for HD110058 and $\beta$ Pic.

The vertical structure of debris discs and the role of disc gravity

Planetary systems - Thu, 15/05/2025 - 10:56
arXiv:2505.09578v1 Announce Type: new Abstract: Debris discs provide valuable insights into the formation and evolution of exoplanetary systems. Their structures are commonly attributed to planetary perturbations, serving as probes of as-yet-undetected planets. However, most studies of planet-debris disc interactions ignore the disc's gravity, treating it as a collection of massless planetesimals. Here, using an analytical model, we investigate how the vertical structure of a back-reacting debris disc responds to secular perturbations from an inner, inclined planet. Considering the disc's axisymmetric potential, we identify two dynamical regimes: planet-dominated and disc-dominated, which may coexist, separated by a secular-inclination resonance. In the planet-dominated regime ($M_d/m_p\ll1$), we recover the classical result: a transient warp propagates outward until the disc settles into a box-like structure centered around the planetary orbit's initial inclination $I_p(0)$, with a distance-independent aspect ratio $\mathcal{H}(R)\approx I_p(0)$. In contrast, in the disc-dominated regime ($M_d/m_p\gtrsim1$), the disc exhibits dynamical rigidity, remaining thin and misaligned, with significantly suppressed inclinations and a sharply declining aspect ratio, $\mathcal{H}(R)\propto I_p(0)R^{-7/2}$. In the intermediate regime ($M_d/m_p\lesssim1$), the system exhibits a secular-inclination resonance, leading to long-lived, warp-like structures and a bimodal inclination distribution, containing both dynamically hot and cold populations. We provide analytic formulae describing these effects as a function of system parameters. We also find that the vertical density profile is intrinsically non-Gaussian and recommend fitting observations with non-zero slopes of $\mathcal{H}(R)$. Our results may be used to infer planetary parameters and debris disc masses based on observed warps and scale heights, as demonstrated for HD110058 and $\beta$ Pic.

The vertical structure of debris discs and the role of disc gravity

Recent IoA Publications - Thu, 15/05/2025 - 10:56
arXiv:2505.09578v1 Announce Type: new Abstract: Debris discs provide valuable insights into the formation and evolution of exoplanetary systems. Their structures are commonly attributed to planetary perturbations, serving as probes of as-yet-undetected planets. However, most studies of planet-debris disc interactions ignore the disc's gravity, treating it as a collection of massless planetesimals. Here, using an analytical model, we investigate how the vertical structure of a back-reacting debris disc responds to secular perturbations from an inner, inclined planet. Considering the disc's axisymmetric potential, we identify two dynamical regimes: planet-dominated and disc-dominated, which may coexist, separated by a secular-inclination resonance. In the planet-dominated regime ($M_d/m_p\ll1$), we recover the classical result: a transient warp propagates outward until the disc settles into a box-like structure centered around the planetary orbit's initial inclination $I_p(0)$, with a distance-independent aspect ratio $\mathcal{H}(R)\approx I_p(0)$. In contrast, in the disc-dominated regime ($M_d/m_p\gtrsim1$), the disc exhibits dynamical rigidity, remaining thin and misaligned, with significantly suppressed inclinations and a sharply declining aspect ratio, $\mathcal{H}(R)\propto I_p(0)R^{-7/2}$. In the intermediate regime ($M_d/m_p\lesssim1$), the system exhibits a secular-inclination resonance, leading to long-lived, warp-like structures and a bimodal inclination distribution, containing both dynamically hot and cold populations. We provide analytic formulae describing these effects as a function of system parameters. We also find that the vertical density profile is intrinsically non-Gaussian and recommend fitting observations with non-zero slopes of $\mathcal{H}(R)$. Our results may be used to infer planetary parameters and debris disc masses based on observed warps and scale heights, as demonstrated for HD110058 and $\beta$ Pic.

A 70 pc-Diameter Nova Super-remnant Surrounding the Recurrent Nova RS Ophiuchi

Stars and stellar evolution - Thu, 15/05/2025 - 10:55
arXiv:2505.09510v1 Announce Type: new Abstract: Recurrent novae undergo thermonuclear-powered eruptions separated by less than 100 years, enabled by subgiant or red giant donors transferring hydrogen-rich matter at very high rates onto their massive white dwarf companions. The most-rapidly moving parts of envelopes ejected in successive recurrent nova events are predicted to overtake and collide with the slowest ejecta of the previous eruption, leading to the buildup of vast (~ 10 - 100 parsec) super-remnants surrounding all recurrent novae; but only three examples are currently known. We report deep narrowband imaging and spectroscopy which has revealed a ~ 70-parsec-diameter shell surrounding the frequently recurring nova RS Ophiuchi. We estimate the super-remnant mass to be ~ 20 - 200 solar masses, expanding at a few tens of km/s, with an age of order 50-100 kyr. Its extremely low surface brightness and large angular size help explain the hitherto surprising absence of nova super-remnants. Our results support the prediction that ALL recurrent novae are surrounded by similar extended structures.

A 70 pc-Diameter Nova Super-remnant Surrounding the Recurrent Nova RS Ophiuchi

Recent IoA Publications - Thu, 15/05/2025 - 10:55
arXiv:2505.09510v1 Announce Type: new Abstract: Recurrent novae undergo thermonuclear-powered eruptions separated by less than 100 years, enabled by subgiant or red giant donors transferring hydrogen-rich matter at very high rates onto their massive white dwarf companions. The most-rapidly moving parts of envelopes ejected in successive recurrent nova events are predicted to overtake and collide with the slowest ejecta of the previous eruption, leading to the buildup of vast (~ 10 - 100 parsec) super-remnants surrounding all recurrent novae; but only three examples are currently known. We report deep narrowband imaging and spectroscopy which has revealed a ~ 70-parsec-diameter shell surrounding the frequently recurring nova RS Ophiuchi. We estimate the super-remnant mass to be ~ 20 - 200 solar masses, expanding at a few tens of km/s, with an age of order 50-100 kyr. Its extremely low surface brightness and large angular size help explain the hitherto surprising absence of nova super-remnants. Our results support the prediction that ALL recurrent novae are surrounded by similar extended structures.

NASA Awards Launch Service Task Order for Aspera’s Galaxy Mission

Astronomy News - Thu, 15/05/2025 - 10:33
Credit: NASA

NASA has selected Rocket Lab USA Inc. of Long Beach, California, to launch the agency’s Aspera mission, a SmallSat to study galaxy formation and evolution, providing new insights into how the universe works.

The selection is part of NASA’s Venture-Class Acquisition of Dedicated and Rideshare (VADR) launch services contract. This contract allows the agency to make fixed-price indefinite-delivery/indefinite-quantity launch service task order awards during VADR’s five-year ordering period, with a maximum total contract value of $300 million.

Through the observation of ultraviolet light, Aspera will examine hot gas in the space between galaxies, called the intergalactic medium. The mission will study the inflow and outflow of gas from galaxies, a process thought to contribute to star formation.

Aspera is part of NASA’s Pioneers Program in the Astrophysics Division at NASA Headquarters in Washington, which funds compelling astrophysics science at a lower cost using small hardware and modest payloads. The principal investigator for Aspera is Carlos Vargas at the University of Arizona in Tucson. NASA’s Launch Services Program, based at the agency’s Kennedy Space Center in Florida, manages the VADR contract.

To learn more about NASA’s Aspera mission and the Pioneers Program, visit:

https://go.nasa.gov/42U1Wkn

-end-

Joshua Finch / Tiernan Doyle
Headquarters, Washington
202-358-1600
joshua.a.finch@nasa.gov / tiernan.doyle@nasa.gov

Patti Bielling
Kennedy Space Center, Florida
321-501-7575
patricia.a.bielling@nasa.gov

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Black hole fly-by modelled with landmark precision

Astronomy News - Thu, 15/05/2025 - 10:33

Nature, Published online: 14 May 2025; doi:10.1038/d41586-025-01339-x

A prediction of the gravitational waves produced by interacting black holes achieves high precision and demonstrates the link between general relativity and geometry.

Black hole flings out clumps of gas

Astronomy News - Thu, 15/05/2025 - 10:32

Nature, Published online: 14 May 2025; doi:10.1038/d41586-025-01421-4

Measurements of wind in a luminous galactic core reveal dense pockets of gas — a finding that calls for a rethink of how black holes interact with their host galaxies.

Thermal asymmetry in the Moon’s mantle inferred from monthly tidal response

Astronomy News - Thu, 15/05/2025 - 10:32

Nature, Published online: 14 May 2025; doi:10.1038/s41586-025-08949-5

Data from the NASA GRAIL spacecraft recover the lunar gravity field suggesting preservation of a predominantly thermal anomaly in the nearside mantle, which could influence the spatial distribution of deep moonquakes.

Water ice in the debris disk around HD 181327

Astronomy News - Thu, 15/05/2025 - 10:32

Nature, Published online: 14 May 2025; doi:10.1038/s41586-025-08920-4

The James Webb Space Telescope has detected water ice in the cold debris disk (analogous to the Kuiper belt) around the star HD 181327.

Emergence of Calabi–Yau manifolds in high-precision black-hole scattering

Astronomy News - Thu, 15/05/2025 - 10:32

Nature, Published online: 14 May 2025; doi:10.1038/s41586-025-08984-2

A new, highest-precision analytical result for solving the gravitational two-body problem of black hole or neutron star scattering reveals the emergence of Calabi–Yau manifolds in the solution to the radiated energy in these encounters.

One half of the moon is hotter than the other

Astronomy News - Thu, 15/05/2025 - 10:30

Anomalies in the moon’s gravitational field suggest our satellite’s insides are warmer on one side than the other – which means that its interior is asymmetric

2025 Gruber Cosmology Prize awarded to Max Pettini and Ryan Cooke

Latest News - Thu, 15/05/2025 - 09:36

The 2025 Gruber Cosmology Prize has been awarded to Professor Max Pettini (IoA) and Professor Ryan Cooke (who is currently faculty at Durham, and was an IoA PhD student 2008-2011). The collaboration that would eventually receive the 2025 Gruber Cosmology Prize coalesced over the course of a short car ride. In early 2009...

Tue 20 May 13:00: Cosmology with the ACT DR6 data release

Next External Talks - Wed, 14/05/2025 - 17:49
Cosmology with the ACT DR6 data release

In March 2025, the Atacama Cosmology Telescope (ACT) released its last cosmological analysis along with a new cosmic microwave background (CMB) dataset. The sixth data release (DR6), including data collected from 2017 to 2022, covers 40% of the sky at arcminute resolution providing the most precise maps of CMB temperature and polarization. In this talk, I will give an overview of the challenges faced during the ACT DR6 analysis and describe its constraints on fundamental assumptions of the standard cosmological model and extensions to it.

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Categories: Talks

Thu 22 May 11:30: Baryon Acoustic Oscillations from a Different Angle KICC Special Seminar

IoA Institute of Astronomy Talk Lists - Wed, 14/05/2025 - 12:35
Baryon Acoustic Oscillations from a Different Angle

The Dark Energy Spectroscopic Instrument (DESI) has published BAO measurements from one year of data (DR1) in 2024 and 3 years of data (DR2) in 2025. The DESI collaboration argue that their measurements suggest that dark energy is evolving and that this evidence is stronger using the DR2 data. This result would have major implications for fundamental physics if true. I will present a new way of looking at BAO data which shows that the DR2 data are more consistent with the Planck LCDM cosmology than the DR1 data. The evidence for evolving dark energy from DESI BAO has therefore weakened as the data have improved. I will also discuss the impact of systematic errors if DESI BAO data are combined with Type Ia supernovae. In summary, I find very little evidence to suggest that dark energy is evolving.

KICC Special Seminar

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Neutron-Capture Element Signatures in Globular Clusters: Insights from the Gaia-ESO Survey

Stars and stellar evolution - Wed, 14/05/2025 - 12:03
arXiv:2505.08399v1 Announce Type: new Abstract: Globular clusters (GCs) are key to understanding the formation and evolution of our Galaxy. While the abundances of light and Fe-peak elements in GCs have been widely studied, investigations into heavier, neutron-capture elements -- and their connection to multiple stellar populations and GC origins -- remain limited. In this work, we analysed the chemical abundances of neutron-capture elements in GCs to trace the Galactic halo and to explore possible links to the MP phenomenon. Our goal is to better constrain the nature of the polluters responsible for intracluster enrichment and to distinguish the origin of GCs through the chemical signature of neutron-capture elements. We examined 14 GCs from the Gaia-ESO Survey, spanning a wide metallicity range, [Fe/H] from -0.40 to -2.32, using a homogeneous methodology. We focused on the abundances of Y, Zr, Ba, La, Ce, Nd, Pr, and Eu, derived from FLAMES-UVES spectra. These were compared with predictions from a stochastic Galactic chemical evolution model. With the exception of Zr, the model broadly reproduces the observed trends in neutron-capture elements. In some GCs, we found strong correlations between hot H-burning products (Na, Al) and s-process elements, pointing to a shared nucleosynthesis site, e.g., asymptotic giant branch stars of different masses and/or fast-rotating massive stars. We also detect a distinct difference in [Eu/Mg] ratio between in-situ ($\langle$[Eu/Mg]$\rangle$ = 0.14 dex) and ex-situ ($\langle$[Eu/Mg]$\langle$ = 0.32 dex) GCs, highlighting their different enrichment histories. Finally, on average, Type II GCs (NGC 362, NGC 1261, and NGC 1851) showed a s-process element spread ratio between second- and first-generations about twice as large as those seen in Type I clusters.

Neutron-Capture Element Signatures in Globular Clusters: Insights from the Gaia-ESO Survey

Recent IoA Publications - Wed, 14/05/2025 - 12:03
arXiv:2505.08399v1 Announce Type: new Abstract: Globular clusters (GCs) are key to understanding the formation and evolution of our Galaxy. While the abundances of light and Fe-peak elements in GCs have been widely studied, investigations into heavier, neutron-capture elements -- and their connection to multiple stellar populations and GC origins -- remain limited. In this work, we analysed the chemical abundances of neutron-capture elements in GCs to trace the Galactic halo and to explore possible links to the MP phenomenon. Our goal is to better constrain the nature of the polluters responsible for intracluster enrichment and to distinguish the origin of GCs through the chemical signature of neutron-capture elements. We examined 14 GCs from the Gaia-ESO Survey, spanning a wide metallicity range, [Fe/H] from -0.40 to -2.32, using a homogeneous methodology. We focused on the abundances of Y, Zr, Ba, La, Ce, Nd, Pr, and Eu, derived from FLAMES-UVES spectra. These were compared with predictions from a stochastic Galactic chemical evolution model. With the exception of Zr, the model broadly reproduces the observed trends in neutron-capture elements. In some GCs, we found strong correlations between hot H-burning products (Na, Al) and s-process elements, pointing to a shared nucleosynthesis site, e.g., asymptotic giant branch stars of different masses and/or fast-rotating massive stars. We also detect a distinct difference in [Eu/Mg] ratio between in-situ ($\langle$[Eu/Mg]$\rangle$ = 0.14 dex) and ex-situ ($\langle$[Eu/Mg]$\langle$ = 0.32 dex) GCs, highlighting their different enrichment histories. Finally, on average, Type II GCs (NGC 362, NGC 1261, and NGC 1851) showed a s-process element spread ratio between second- and first-generations about twice as large as those seen in Type I clusters.

Hints of Disk Substructure in the First Brown Dwarf with a Dynamical Mass Constraint

Recent IoA Publications - Wed, 14/05/2025 - 11:52
arXiv:2505.08107v1 Announce Type: new Abstract: We present high-resolution ALMA observations at 0.89 mm of the Class II brown dwarf 2MASS J04442713+2512164 (2M0444), achieving a spatial resolution of 0$.\!\!^{\prime\prime}$046 ($\sim$6.4 au at the distance to the source). These observations targeted continuum emission together with $^{12}$CO (3-2) molecular line. The line emission traces a Keplerian disk, allowing us to derive a dynamical mass between 0.043-0.092 M${_{\odot}}$ for the central object. We constrain the gas-to-dust disk size ratio to be $\sim$7, consistent with efficient radial drift. However, the observed dust emission suggest that a dust trap is present, enough to retain some dust particles. We perform visibility fitting of the continuum emission, and under the assumption of annular substructure, our best fit shows a gap and a ring at 98.1$^{+4.2}_{-8.4}$ mas ($\sim$14 au) and 116.0$^{+4.2}_{-4.8}$ mas ($\sim$16 au), respectively, with a gap width of 20 mas ($\sim$3 au). To ensure robustness, the data were analyzed through a variety of methods in both the image and uv plane, employing multiple codes and approaches. This tentative disk structure could be linked to a possible planetary companion in the process of formation. These results provide the first dynamical mass of the lowest mass object to date, together with the possible direct detection of a substructure, offering new insights into disk dynamics and planet formation in the very low-mass regime. Future higher spatial resolution ALMA observations will be essential to confirm these findings and further investigate the link between substructures and planet formation in brown dwarf disks.

Hints of Disk Substructure in the First Brown Dwarf with a Dynamical Mass Constraint

Stars and stellar evolution - Wed, 14/05/2025 - 11:51
arXiv:2505.08107v1 Announce Type: new Abstract: We present high-resolution ALMA observations at 0.89 mm of the Class II brown dwarf 2MASS J04442713+2512164 (2M0444), achieving a spatial resolution of 0$.\!\!^{\prime\prime}$046 ($\sim$6.4 au at the distance to the source). These observations targeted continuum emission together with $^{12}$CO (3-2) molecular line. The line emission traces a Keplerian disk, allowing us to derive a dynamical mass between 0.043-0.092 M${_{\odot}}$ for the central object. We constrain the gas-to-dust disk size ratio to be $\sim$7, consistent with efficient radial drift. However, the observed dust emission suggest that a dust trap is present, enough to retain some dust particles. We perform visibility fitting of the continuum emission, and under the assumption of annular substructure, our best fit shows a gap and a ring at 98.1$^{+4.2}_{-8.4}$ mas ($\sim$14 au) and 116.0$^{+4.2}_{-4.8}$ mas ($\sim$16 au), respectively, with a gap width of 20 mas ($\sim$3 au). To ensure robustness, the data were analyzed through a variety of methods in both the image and uv plane, employing multiple codes and approaches. This tentative disk structure could be linked to a possible planetary companion in the process of formation. These results provide the first dynamical mass of the lowest mass object to date, together with the possible direct detection of a substructure, offering new insights into disk dynamics and planet formation in the very low-mass regime. Future higher spatial resolution ALMA observations will be essential to confirm these findings and further investigate the link between substructures and planet formation in brown dwarf disks.