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Keaton Bell

@astrokeat.bsky.social

180 followers 210 following 37 posts

astronomer to the stars

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Keaton Bell @astrokeat.bsky.social · Feb 23

Preprint of a chapter "White Dwarf Variability" that will appear in the forthcoming Encyclopedia of Astrophysics: arxiv.org/abs/2502.13258

White Dwarf Variability

There are a few different mechanisms that can cause white dwarf stars to vary in brightness, providing opportunities to probe the physics, structures, and formation of these compact stellar remnants. ...

Keaton Bell @astrokeat.bsky.social · Aug 22

My Python environment.

Keaton Bell @astrokeat.bsky.social · Jul 30

Great to revisit this photo! Many people I now know in the field whom I don't recall meeting at this, one of my first real science meetings.

Keaton Bell @astrokeat.bsky.social · Jul 30

RIP to Bill Paxton, lead developer of MESA. I feel privileged to have learned from the man himself at the 2012 MESA Summer School. #stellarastro #astrocode

Keaton Bell @astrokeat.bsky.social · Jul 9

A minor update to Pyriod is now available (v0.3.3), addressing some pesky depreciation warnings that would crop up. pypi.org/project/Pyri...

Keaton Bell @astrokeat.bsky.social · Jul 9

Also another notebook showing how to automate prewhitening analysis (I will try to build more convenience functions into Pyriod for this soon). github.com/keatonb/Pyri...

Keaton Bell @astrokeat.bsky.social · Jul 9

For this presentation, I have also uploaded a demonstration of how to use Pyriod to measure O-C diagrams to track timing variations of a signal. github.com/keatonb/Pyri...

Keaton Bell @astrokeat.bsky.social · Jul 9

At the 9th TESS/16th Kepler Asteroseismic Science Consortium Workshop this week in Vienna. I'm presenting this poster on my code Pyriod for pre-whitening frequency analysis of astronomical time series data. #astromethods

Reposted by Keaton Bell

NSF–DOE Rubin Observatory @vrubinobs.bsky.social · Jun 23

Here it is: the first set of riches from Rubin's Cosmic Treasure Chest!

Introducing NSF–DOE Rubin Observatory's first wide and deep view of the cosmos, the southern region of the Virgo Cluster.

Rubin produced this image in just 10.5 hours over parts of 7 nights! 🔭🧪

youtu.be/Gitit3LwQ20

Keaton Bell @astrokeat.bsky.social · Jun 9

I present the #astrocode Pyriod for interactive or scripted pre-whitening frequency analysis of astronomical time series data. See the demo of #stellarastro #TESS data analysis of a pulsating white dwarf star. Check it out at github.com/keatonb/Pyriod/.

Keaton Bell @astrokeat.bsky.social · Jun 9

Had to withdraw my #AAS246 poster due to COVID, but let me demo "Pyriod: Interactive Pre-Whitening Frequency Analysis in Python." Here is a quick guide to reproducing the analysis of TESS data on a pulsating white dwarf from Bell et al. (2019, ui.adsabs.harvard.edu/abs/2019A%26A...632A..42B).

Keaton Bell @astrokeat.bsky.social · Jun 9

Check out the #AAS246 iPoster "White Dwarf Asteroseismology in the Age of Gaia Astrometry" from Andrew Dublin, Agnes Bischoff-Kim and myself: aas246-aas.ipostersessions.com/Default.aspx...

#stellarastro

aas (iPosterSessions - an aMuze! Interactive system)

aas246-aas.ipostersessions.com

Keaton Bell @astrokeat.bsky.social · Jun 9

Check out the #AAS246 iPoster "TESS CROWDSAP Errors from White Dwarf Observations" from Nikoo Hosseininezhad and myself: aas246-aas.ipostersessions.com/default.aspx...

#stellarastro

aas (iPosterSessions - an aMuze! Interactive system)

aas246-aas.ipostersessions.com

Keaton Bell @astrokeat.bsky.social · Jun 9

Fun article!

Keaton Bell @astrokeat.bsky.social · Jun 9

The development of Pyriod is supported by the National Science Foundation under Grant No. AST-2406917.

Keaton Bell @astrokeat.bsky.social · Jun 9

Learn more at github.com/keatonb/Pyriod, install for yourself with "pip install Pyriod", or try it first in your browser with Binder mybinder.org/v2/gh/keaton... (no download, but a bit slow).

GitHub - keatonb/Pyriod: Python implementation of basic period detection and fitting routines for astronomical time series.

Python implementation of basic period detection and fitting routines for astronomical time series. - keatonb/Pyriod

Keaton Bell @astrokeat.bsky.social · Jun 9

The interface works in Jupyter, and it can also be scripted for automated analysis. We are grateful to lightkurve, astropy, lmfit, qgrid, and qgridnext, which make Pyriod work. I am working to improve tutorials and documentation. Submit issues/feature requests at github.com/keatonb/Pyriod

GitHub - keatonb/Pyriod: Python implementation of basic period detection and fitting routines for astronomical time series.

Python implementation of basic period detection and fitting routines for astronomical time series. - keatonb/Pyriod

Keaton Bell @astrokeat.bsky.social · Jun 9

Pyriod is inspired by Period04 (www.period04.net), aiming to provide a similar interactive data analysis experience for the modern Python workflow, with open-source code, and with a faster periodogram better-suited for the big data era.

Period04 - Homepage

www.period04.net

Keaton Bell @astrokeat.bsky.social · Jun 9

Our reward for completing this process is a table of signal frequencies, amplitudes, and phases, with estimated uncertainties. These measurements of resonant frequencies of a white dwarf star are published and interpreted in Bell et al. (2019, ui.adsabs.harvard.edu/abs/2019A%26A...632A..42B).

Keaton Bell @astrokeat.bsky.social · Jun 9

The fit to the light curve reveals the complex variability that we otherwise couldn't visibly see for all the measurement noise, shown here for one day of the TESS light curve.

Keaton Bell @astrokeat.bsky.social · Jun 9

Pyriod can enforce strict relationships between combination frequencies and independent frequencies when they are identified by their arithmetic relations. We proceed to pre-whiten all significant signals, with combinations marked with gold diamonds.

Keaton Bell @astrokeat.bsky.social · Jun 9

Three signals down, but the next three are "combination frequencies" that appear at precise sums, multiples, and differences of frequencies. If the first three signals are f0, f1, and f2, this next cluster of peaks are f0+f1, 2*f0, and f0+f2.

Keaton Bell @astrokeat.bsky.social · Jun 9

We then identify additional signals from the periodogram of fit residuals (the "pre-whitened" data). Pyriod displays the periodogram of the residuals in blue (highest peak marked). The model is displayed in green. In practice, we move significant peaks from blue to green.

Keaton Bell @astrokeat.bsky.social · Jun 9

We "pre-whiten" signals by fitting and subtracting sinusoids from the light curve. We currently fit the frequency, amplitude, and phase of one sinusoidal signal. The data may be noisy, but TESS collected enough that we detect this signal to high significance.

Keaton Bell @astrokeat.bsky.social · Jun 9

The periodogram displays the frequency content of the light curve, and we identify significant signals as having amplitudes well above the noise floor. The red curve gives an approximate significance threshold, and Pyriod marks the highest peak for inclusion in the model. Let's add it.

Keaton Bell @astrokeat.bsky.social · Jun 9

The pre-whitening algorithm is a method for measuring sinusoidal signals in time series data. It is best suited for signals that are coherent for the duration of the observations. We start with the periodogram of the TESS Sector 3 light curve of the pulsating white dwarf WD 0158-160.

Keaton Bell @astrokeat.bsky.social · Jun 9

Had to withdraw my #AAS246 poster due to COVID, but let me demo "Pyriod: Interactive Pre-Whitening Frequency Analysis in Python." Here is a quick guide to reproducing the analysis of TESS data on a pulsating white dwarf from Bell et al. (2019, ui.adsabs.harvard.edu/abs/2019A%26A...632A..42B).