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IoA Institute of Astronomy Talk Lists

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This is a List of Talks Lists that is a List of all IoA Seminars, Colloquia, Extra talks, IoA Stellar Pops and Extragalactic Gathering, etc. It is used as a feed for the IOA website and Digital Display screens. Individual Talks should NOT be added to this Talk lists. They should be added to one of the series that feed this list.
URL: https://talks.cam.ac.uk/show/index/13724
Updated: 1 hour 21 min ago

Tue 13 Feb 13:00: Disc evolution in young intermediate-mass stars

Mon, 05/02/2024 - 09:05
Disc evolution in young intermediate-mass stars

Planets are born from circumstellar discs and the evolution of these discs determines the final architecture of planetary systems. The stellar mass range between 1.5 and 3.5 solar masses presents a particularly interesting circumstellar disc evolution; most notably, it is dominated by the EUV /FUV photoevaporation regime on the pre-main sequence, it contains the majority of gaseous debris discs, and it also shows the highest giant planet frequency. In our recent spectroscopic VLT /X-Shooter survey (UV to nIR), combined with WISE data (nIR to mIR), we identified 135 pre-main sequence (PMS) intermediate mass stars (IMSs) in the Southern sky. This is the first unbiased sample of IMSs in the PMS , allowing a study of disc evolution. Our sample, encompassing protoplanetary and debris discs, also revealed a significant number of discs between these two evolutionary stages. We find that the IR excess evolution of IMSs differs from that seen for low-mass stars (LMSs), exemplified by samples drawn from nearby star forming regions. We observe that, in IMSs, the inner disc regions are vacated in their entirety, in contrast to the LMSs where we note a more gradual inside-out dissipation. We also investigated the presence of gas absorption features in our sample via optical high-resolution spectroscopy to identify gas-bearing debris discs. This requires detailed comparisons to spectra of nearby stars to eliminate objects with foreground cloud absorption as cause of the absorption features. In particular, we apply this effective method to one such disc, eta Tel, discarding the earlier claim of disc wind as the origin for the absorption features. Finally, we discuss our several ongoing and future surveys investigating the nature of circumstellar discs around IMSs.

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Fri 09 Feb 11:30: The quest for the earliest black holes: a theoretical perspective

Sat, 03/02/2024 - 12:41
The quest for the earliest black holes: a theoretical perspective

Abstract not available

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Thu 08 Feb 11:30: Problems with (our) galaxy formation simulations and some new angles

Thu, 01/02/2024 - 14:26
Problems with (our) galaxy formation simulations and some new angles

Stellar feedback is a crucial component in controlling the baryon cycle in galaxies. However, it is not very clear how this can be done without assuming exotic models of stellar feedback. In this talk I will first discuss why we have not been very successful in producing realistic galaxies in our simulations, and present some attempts to solve this problem. I will also discuss how Lyman alpha profiles can potentially be used to place some constraints on cosmological simulations with cosmic ray feedback. This talk is intended to be thought-provoking rather than a collection of success stories.

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Fri 28 Jun 11:30: Title to be confirmed

Wed, 31/01/2024 - 16:38
Title to be confirmed

Abstract not available

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Fri 19 Apr 11:30: Title to be confirmed

Wed, 31/01/2024 - 12:24
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Fri 12 Apr 11:30: Title to be confirmed

Wed, 31/01/2024 - 12:23
Title to be confirmed

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Tue 06 Feb 13:00: Photoevaporation from Exoplanet Atmospheres: Understanding the Role of Stellar Winds and Considering Water-rich Atmospheres Room changed

Tue, 30/01/2024 - 10:54
Photoevaporation from Exoplanet Atmospheres: Understanding the Role of Stellar Winds and Considering Water-rich Atmospheres

The atmospheres of close-in exoplanets are extremely vulnerable to the effects of stellar UV to X-ray radiation. Photoevaporation can significantly alter planetary atmospheres or even strip them entirely, potentially rendering a planet uninhabitable. Understanding how these atmospheres evolve, persist, or fade away remains a fundamental challenge. In this talk, I will discuss two distinct but interconnected areas of photoevaporative research.

Firstly, I will discuss the interaction between the stellar wind and photoevaporating atmospheres. I will present 3D magnetohydrodynamic simulations of the interaction between the stellar wind and the photoevaporating outflow of a planet orbiting an M dwarf. This analysis reveals a diverse range of magnetosphere morphologies and plasma distributions due to the wind-outflow interaction. I consider how these changing morphologies might impact observable hydrogen Lyman-alpha signatures during planetary transits.

In the second part, I will delve into our current understanding of photoevaporation from water-rich atmospheres. Conventional analytic approaches often oversimplify the process, assuming two scenarios: the escape of only lighter hydrogen, or the dragging of oxygen along with escaping hydrogen. These two scenarios lead to two end cases: a planet that has retained its water-rich atmosphere or a planet which has lost its atmosphere, becoming dry and desiccated. I will challenge these oversimplifications by presenting results from a novel 1D multifluid hydrodynamic model of photoevaporation from a water-rich atmosphere, which shows oxygen escape should no longer be described by a simple on/off switch but instead requires careful modelling.

Room changed

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Fri 17 May 11:30: Title to be confirmed

Mon, 29/01/2024 - 09:56
Title to be confirmed

Abstract not available

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Fri 01 Mar 11:30: Title to be confirmed

Fri, 26/01/2024 - 23:12
Title to be confirmed

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Fri 16 Feb 11:30: TBD

Fri, 26/01/2024 - 23:08
TBD

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Fri 15 Mar 11:30: Title to be confirmed

Fri, 26/01/2024 - 23:08
Title to be confirmed

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Fri 22 Mar 11:30: Title to be confirmed

Fri, 26/01/2024 - 23:04
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Tue 20 Feb 13:00: TBC

Fri, 26/01/2024 - 11:20
TBC

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Fri 08 Mar 11:30: Title to be confirmed

Fri, 26/01/2024 - 09:41
Title to be confirmed

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Wed 14 Feb 14:00: Unlocking the Power of Transfer Learning: Meeting the Challenge of Mobile App Predictions in Data-Scarce Environments

Mon, 22/01/2024 - 11:52
Unlocking the Power of Transfer Learning: Meeting the Challenge of Mobile App Predictions in Data-Scarce Environments

We’ll explore the world of predictive modelling at Bending Spoons. In our suite of apps, each with distinct traits, accurate predictions on user renewals drive rapid app improvement and translate into increased profits. However, for some apps we don’t have sufficient data to make reliable predictions. Transfer learning is a technique that can allow predictive models to learn generic features of all apps, and fine-tune those models on the unique behaviour of each app. I’ll delve into the problems and potential solutions that empower us to acquire and rapidly scale new apps to their full potential.

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Wed 07 Feb 14:00: All molecules are interesting

Sun, 21/01/2024 - 21:00
All molecules are interesting

Abstract not available

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Tue 12 Mar 13:00: TBC

Mon, 15/01/2024 - 14:03
TBC

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Tue 05 Mar 13:00: TBC

Mon, 15/01/2024 - 14:02
TBC

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Tue 27 Feb 13:00: TBC

Mon, 15/01/2024 - 14:02
TBC

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Fri 23 Feb 11:30: Decoding the Gravitational-Wave Biographies of Binary Black Holes

Thu, 11/01/2024 - 11:26
Decoding the Gravitational-Wave Biographies of Binary Black Holes

With the fourth observing run of the LIGO -Virgo-KAGRA detector network ongoing, the number of detections of gravitational waves from binary black hole mergers is rapidly reaching into the hundreds. However, despite this wealth of detections, it is still unclear how black holes become bound into tight binaries that merge within the age of the Universe. Binaries that form and merge in isolation are predicted to have different parameters than those that form under the influence of dynamical interactions with other objects. Traditionally, we have looked to the masses and spins of these binaries to teach us about their formation. However, arguably the most robust indication of dynamical evolution is orbital eccentricity: while isolated binaries will have essentially circular orbits at detection, a fraction of dynamically-formed binaries should have measurably non-zero eccentricity. Gravitational waves from eccentric binaries have historically been challenging to detect and analyse. Yet in the last few years, a handful of the signals reported by the LIGO -Virgo-KAGRA collaboration, including that from the unusually massive binary GW190521 , have been claimed by multiple groups to contain tantalising hints of orbital eccentricity. In this talk, I will demonstrate how evidence of eccentricity in gravitational-wave signals can be decoded and harnessed to reveal details of a binary’s history, and even to probe the identities of external influences to its evolution. I will also discuss what we can learn about our population of binary black holes when we combine observations of their masses, spins, and eccentricity.

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