” SALT and the super-hot zombie stars.”

SYNOPSIS

We are using the Southern African Large Telescope to carry out a survey of chemically-peculiar hot subdwarfs. Several of the stars observed could not be classified as conventional hot subdwarfs. Eight of these turned out to be extremely hot stars  with surface temperatures between 110,000 K and 180,000 K. One is a white dwarf, the remainder are pre-white dwarfs; that is they are contracting towards the hot end of the white dwarf sequence.

Follow-up photometry showed that two are pulsating GW Vir stars. One is the central star of a previously unknown planetary nebula (JeWeKi 1). Four are record-breakers: the hottest DO white dwarf, the two hottest GW Vir stars, and thehottest `naked’ O(H) star.

My talk will describe the background to the survey, the observations being carried out with SALT and the new discoveries. It will attempt to explain how these stars fit into the big picture of how stars approach their final fate and how some are – indeed – dead stars reborn. 

BIO: Simon Jeffery

Simon’s astronomical life started at the Royal Observatory, Edinburgh, and has taken him via a Physics degree at Imperial College, London, to St Andrews, Scotland and Kiel, Germany, before finally moving to the Armagh Observatory and Planetarium in Northern Ireland, where he works as a senior research astronomer. He has held positions as adjunct Professor of Physics at Trinity College Dublin and a Visiting Byfellowship at Churchill College, Cambridge. He is a past president of IAU Commission G4 on Pulsating Stars and is currently president of IAU Commission G5 on Stellar and Planetary Atmospheres.

Pursuing a lifelong interest in how stars work and how they vary over time, Simon’s PhD in theoretical stellar structure and evolution was followed by observational and theoretical work on stellar pulsations and atmospheres. Most stars never fully exhaust their initial hydrogen store, but retain a hydrogen surface to the very end. However, in rare and extreme cases, some stars become true ‘helium’ stars. Simon’s goal is to demonstrate their elusive origins. The surprising conclusion is that the great majority appear to have formed from the merger of two very old and faint stars … a double white dwarf. His favourite is the pulsating V652 Herculis — the ‘born-again rocket star’.

Simon would like to spend more time dinghy racing, sings baritone, and hunts wild life and seascapes with a camera.

“Diving Deeper into the Radio Sky” – Solar, Stellar and Galactic Astronomy with the LOw Frequency ARray, by Jeremy Rigney, DIAS & AOP.

Synopsis: Radio astronomy has developed at an ever-accelerating rate in the past decade. With the construction of the Low Frequency Array, the largest and most sensitive low frequency radio telescope in the world, a new window into the universe has been opened. This has revealed jets from distant galaxies, new stars, and massive bursts from our Sun in higher detail than ever before.

Ireland plays a large role in the LOFAR consortium, providing the most westerly station for the telescope array and further improving its sensitivity and resolution. I will talk about the science being achieved with I-LOFAR since its construction in 2017, and my own research on other stars within our galaxy and the search for other planets with the potential to host life.

Biography:
Jeremy Rigney is a Lindsay PhD Scholar at DIAS & Armagh Observatory, linked with QUB.

Jeremy graduated from University College Dublin with a degree in Physics with Astronomy and Space Science. He is currently the Eric Lindsay Phd Scholar based jointly between the Dublin Institute for Advanced Studies and Armagh Observatory. He is registered as a PhD researcher at Queen’s University Belfast. Jeremy’s research focuses on simultaneous optical and radio signatures of dwarf stars to examine the potential impact on orbiting exoplanets. He also observes the sun at radio wavelengths to compare its emission to other stars.

ADMISSION FREE, including light refreshments – All welcome!