iiinova — where your digital self keeps evolving

Jonatan Rudrasingam @astrojonatan.bsky.social · 24/09/2026

Overall, this study highlighted the advantage and need to compare asteroseismic results for main-sequence stars with non-seismic results. Other binary candidates, such as the bright star Procyon, can be amenable to similar analysis in the future (9/9)

000

Jonatan Rudrasingam @astrojonatan.bsky.social · 24/09/2026

Using 9 different asteroseismic modelling pipelines, we can compare the model masses and radii. Although most models have large mass uncertainties, all model masses are lower than our fitted mass. However, it is too early to assess the significance (8/9)

A plot comparing the Keplerian-derived mass and the interferometry-derived radius, and the asteroseismic model mass and radius, from 9 different model pipelines. The red vertical shaded area is the 1σ region of the Keplerian mass, while the blue shaded horizontal area is the 1σ region of the interferometric radius. The gray shaded area is the mass and radius calculated from our derived νmax, a proxy for the frequency at maximum amplitude. The model masses are slightly lower than our derived values; however, their uncertainties are also larger.

100

Jonatan Rudrasingam @astrojonatan.bsky.social · 24/09/2026

Using interferometry with the PAVO instrument at CHARA, we determined the radius of oscillating χ Draconis A. Combined with the mass, this establishes the star as a benchmark star. (7/9)

The squared visibility curve of χ Draconis from CHARA interferometry. The shape of this curves can tell us how large the star is.

100

Jonatan Rudrasingam @astrojonatan.bsky.social · 24/09/2026

Here is a figure showing the radial velocity orbital curve for both components. Because of the number of high-precision measurements, we obtain a mass precision of 0.4%, comparable to that for α Cen. (6/9)

Upper panel: Radial velocity curves for both binary components. Bottom panel: An observed minus calculated (O-C) plot showing how well our fitted model compares to observations. Because of the large number of high-precision radial velocity measurements, we obtained high mass precision for both components in the system.

100

Jonatan Rudrasingam @astrojonatan.bsky.social · 24/09/2026

Using 618 spectra obtained with the SONG telescope at Tenerife and historical astrometric measurements, we determined the mass of both components using Kepler's 3rd law (5/9)

110

Jonatan Rudrasingam @astrojonatan.bsky.social · 24/09/2026

Here is a Fourier transform of the star's TESS light curve. The peaks are oscillating modes travelling inside the star, which we can use to infer the star's interior properties. These modes enable us to estimate the star's properties such as its mass, radius, and age (4/9)

A power spectral density (Fourier transform) of the TESS light curve of χ Draconis A. The peaks are the observed modes, which are color marked by their angular degrees.

100

Jonatan Rudrasingam @astrojonatan.bsky.social · 24/09/2026

Here we present χ Draconis A, the main-sequence massive component of a binary system in the northern TESS continuous viewing zone, enabling long, continuous observation and, therefore, asteroseismology. It is also in the proposed PLATO northern FoV (3/9)

The position of χ Draconis in Galactic coordinates. The TESS continous viewing zone is shown as a red circle. Both the Kepler and the proposed northern PLATO field are also shown.

110

Jonatan Rudrasingam @astrojonatan.bsky.social · 24/09/2026

However, the accuracy of asteroseismology is not always reliable and needs anchoring with benchmark stars, stars which have asteroseismically independent masses and/or radii. In practice, almost all of these stars are red giants (2/9)

100

Reposted by Jonatan Rudrasingam

MAST - Mikulski Archive for Space Telescopes @mast-news.bsky.social · 12/03/2026

New HLSP: HALO-TESS provides custom light curves for 98 saturated stars in TESS Full Frame Images. The team presents 411 light curves from Sectors 1-93, of which 77 are identified as variables! archive.stsci.edu/hlsp/halo-tess

An HR diagram from the Hipparcos-Tycho catalog. The stars in the HALO-TESS sample are color-coded by the number of available TESS sectors, with their sizes indicating their apparent V-band magnitudes. The y-axis plots absolute V magnitude ranging from 6 to -9, the x-axis plots B-V color ranging from -0.5 to 2.0. A majority of the HALO-TESS targets land from absolute V magnitudes of 2.5 to -6 and B-V colors from -0.5 to 0.25, although a few targets populate unique areas of parameter space.

001

Jonatan Rudrasingam @astrojonatan.bsky.social · 28/02/2026

There are many more stars in our sample. All light curves will soon be available on MAST, and we encourage anyone interested to have a look at them (9/9)

020

Jonatan Rudrasingam @astrojonatan.bsky.social · 28/02/2026

ε Car is a binary star consisting of a red giant star and a smaller blue star. From the light curve, two signals are visible, each coming from both stars. The longer period signal originates from the red giant, while the shorter period signal originates from the blue companion (8/9)

120

Jonatan Rudrasingam @astrojonatan.bsky.social · 28/02/2026

α Cep was suspected to show oscillations since 1971! However, until now, no one has been able to detect variation in the star. The Fourier spectrum shows many peaks, characteristic of a Delta Scuti variable, confirming the earlier prediction (7/9)

120

Jonatan Rudrasingam @astrojonatan.bsky.social · 28/02/2026

Here is the Fourier spectrum of Pollux. Pollux shows intrinsic variability similar to that of the Sun. From the oscillations, we can derive the star's mass and radius! (6/9)

120

Jonatan Rudrasingam @astrojonatan.bsky.social · 28/02/2026

I will now go through a small subset of stars from my total sample. Here is a light curve of the newly discovered eclipsing binary γ And! γ And is a multi-star system consisting of 5 stars. Two of these stars are oriented in just the right way to be eclipsing (5/9)

120

Jonatan Rudrasingam @astrojonatan.bsky.social · 28/02/2026

Among the sample are the brightest variable stars, including eclipsing binaries and intrinsic oscillating stars. Many oscillate in specific waves due to starquakes, and like earthquakes on Earth, starquakes can be used to tell us about their interiors. (4/9)

120

Jonatan Rudrasingam @astrojonatan.bsky.social · 28/02/2026

Halo photometry works by ignoring oversaturated pixels and weighting unsaturated pixels to extract optimal light curves for each star. The weighting works by minimizing the flux between each consecutive epoch (3/9)

130

Jonatan Rudrasingam @astrojonatan.bsky.social · 28/02/2026

However, with careful statistical weighting and the unsaturated "halo" pixels, we can overcome this problem and obtain high-quality data for these stars. In this paper, I used "halo photometry" to extract high-quality data for 98 of the brightest stars in the night sky observed by TESS (2/9)

130

Jonatan Rudrasingam @astrojonatan.bsky.social · 28/02/2026

My first scientific paper is now public on arXiv! TESS struggles with the brightest stars due to saturation from overexposure. This is unfortunate, because these are the stars that are amenable to photon-hungry follow-up methods, such as spectroscopy or interferometry (1/9) arxiv.org/abs/2602.22472

arxiv.org

Halo Photometry and Asteroseismology for 98 of the Brightest Stars Observed by TESS

The Transiting Exoplanet Survey Satellite (TESS) mission has facilitated studies of asteroseismology, eclipsing binaries, and transits in many stars. However, the brightest stars saturate TESS, yet th...

1154