astrobites 2017

Find out the latest thinking about our universe.
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A Survey of Stellar Activity

Post by bystander » Sat Dec 30, 2017 8:10 pm

A Survey of Stellar Activity
astrobites | 2017 Dec 27
Jamila Pegues wrote:
The search for life as we know it on Earth-like, rocky exoplanets has been a driving force for many telescope missions of the new century. And, as today’s authors point out, M-Dwarfs seem more and more like great places to look.

M-Dwarfs (aka Red Dwarfs) are typically really dim, lightweight stars (relative to the Sun), which seem to account for most of the stars in the universe. Because M-Dwarfs are so small and faint, the signs that planets are orbiting them show up more clearly than for planets orbiting Sun-like stars. ...

That’s where today’s authors come in. By mapping the distributions of various stellar cycles for a survey of M-Dwarfs, the authors aim to make it easier to distinguish between signals of stellar activity and signals of orbiting planets. ...

HADES RV Programme with HARPS-N at TNG. VII. Rotation and Activity of M-Dwarfs from
Time-Series High-Resolution Spectroscopy of Chromospheric Indicators
- A. Suárez Mascareño et al
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bystander
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Something bizarre is happening in stars

Post by bystander » Sat Dec 30, 2017 8:14 pm

Something bizarre is happening in stars
astrobites | 2017 Dec 28
Zephyr Penoyre wrote:
The stars are out of tune.

The sky is falling, the sea is boiling, and the miner bird has stopped its song. Metaphorically. Because something very strange is happening. The stars are vibrating in a way they just should not. ...

High Order Harmonics in Light Curves of Kepler Planets - Caden Armstrong, Hanno Rein
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

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Hanbury Brown-Twiss Revival

Post by bystander » Sat Dec 30, 2017 8:26 pm

Hanbury Brown-Twiss Revival
astrobites | 2017 Dec 29
Philipp Plewa wrote:
In 1956, R. Hanbury Brown and R. Q. Twiss (HBT) tested a new type of interferometer, by accurately measuring the angular diameter of the star Sirius A, which is just about 6 milliarcseconds. An astronomical interferometer, which combines the light collected by two or more separated telescopes pointing at the same target, can be used to measure such tiny angles on the sky because its maximum angular resolution is determined by the maximum separation of the constituent telescopes, not mirror size. But constructing and operating an interferometer at visible wavelengths is technically more challenging than at longer (radio) wavelengths, for example. HBT mitigated some of these challenges by inventing a design for an optical interferometer that does not require bringing together and combining light beams from different telescopes by means of optics, but requires only to record the light intensity electronically at each telescope.

In the years following the pioneering work of HBT, the angular diameters of several more bright stars were successfully measured using this technique, yet it was eventually all but abandoned in astrophysics due to limited sensitivity. However, by taking advantage of modern technological developments in photonics and digital electronics, the authors of today’s paper demonstrate a renewed relevance of intensity interferometry, mainly for studying astronomical phenomena at sub-milliarcsecond angular resolution. ...

Temporal intensity interferometry: photon bunching on three bright stars - W. Guerin et al
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor