From Gemini Observatory: “Gemini Confirms a New Class of Variable Stars”

NOAO

Gemini Observatory
Gemini Observatory

This post is dedicated to J.G. at WPRB for his kindness to me in my hours of need. I am very grateful for his remarks today.

August 2, 2017

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Gemini South spectra for three BLAPs. Best fits of stellar atmosphere models are shown with red lines. Effective temperatures, surface gravities, and helium abundances derived for these stars are similar to the values obtained from spectra for the prototype object previously studied. This shows that all the newly discovered variables form a homogeneous class of objects. Credit: Gemini Observatory/AURA/NSF


Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

Gemini confirms a new class of variable stars called Blue Large-Amplitude Pulsators. They are significantly bluer than main sequence stars of the same luminosity demonstrating that they are relatively hot. The new pulsating stars vary with periods ranging from 20 to 40 minutes and amplitudes spanning 0.2 – 0.4 magnitude. These characteristics have not been observed in any known hot pulsators.

Astronomers using the Multi-Object Spectrograph (GMOS) on the Gemini South telescope have confirmed a new class of variable stars called Blue Large-Amplitude Pulsators (BLAPs). Pawel Pietrukowicz (Warsaw University Observatory, Poland) led the study as part of the Optical Gravitational Lensing Experiment (OGLE), a variability sky survey conducted on the 1.3-meter Warsaw Telescope at Las Campanas Observatory, Chile.

1.3 meter OGLE Warsaw Telescope at the Las Campanas Observatory in Chile

Gemini Observatory GMOS on Gemini South

Following up on the team’s discovery of 14 candidate stars the team used GMOS to obtain spectra for three of the candidates. The Gemini data confirmed these stars have helium-rich atmospheres and high surface temperatures of about 30,000 K, comparable with hot subdwarfs. Nevertheless, Pietrukowicz concludes that the luminosity of these two classes of hot stars differ significantly, with BLAPs having much higher luminosity and much lower gravity than hot subdwarfs. “We found that the new stars are low-mass giants, which vary with exceptionally high amplitudes. This excludes the possibility that they are hot oscillating subdwarfs, leading to the conclusion that BLAPs form a new class of variable stars,” says Pietrukowicz.

This work is published in the journal Nature Astronomy. The article is also on astro-ph with a .pdf.

See the full article here .

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Gemini/North telescope at Mauna Kea, Hawaii, USA
Gemini/North telescope at Mauna Kea, Hawaii, USA

Gemini South
Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile

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Gemini’s mission is to advance our knowledge of the Universe by providing the international Gemini Community with forefront access to the entire sky.

The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai’i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country’s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

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