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Six New Variable Stars Discovered from Ground-Based Photometry and Characterized with TESS Data

This paper reports the discovery and TESS-based characterization of six new variable stars found through ground-based photometry using a small telescope and CMOS camera, while also detailing the author's custom data analysis workflow and software tools.

Original authors: Maksym Yu. Pyatnytskyy

Published 2026-05-01

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Maksym Yu. Pyatnytskyy

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the night sky as a massive, bustling city. For a long time, astronomers have been using giant, automated "security cameras" (like the Gaia satellite and TESS) to scan this city, cataloging millions of stars and noting which ones blink or change brightness. Because these cameras are so powerful, it has become very hard for a single person with a small telescope to find a new blinking star; most of the obvious ones have already been caught.

However, this paper tells the story of how one amateur astronomer, Maksym Yu. Pyatnytskyy, managed to find six new "blinkers" right from his backyard in Kyiv, Ukraine. Here is how he did it, explained simply:

1. The Setup: A Small Camera in a Bright City

The author didn't use a massive observatory. He used a modest telescope (about the size of a large kitchen trash can) and a sensitive digital camera, all set up in a neighborhood with significant light pollution (like a city street with streetlights). It's like trying to hear a whisper in a busy café.

To make the data useful, he didn't just take pictures; he built his own "kitchen tools" (software scripts) to clean the images, remove the glare from the city lights, and organize the data. He treated hundreds of stars at once, creating a "light curve" for each one—a graph that shows how bright the star is over time, like a heartbeat monitor for the sky.

2. The Detective Work: Finding the New Stars

By looking at these graphs, the author spotted six stars that were behaving strangely. They weren't in the official "missing persons" lists of known variable stars.

The Ground Team: He found them first using his backyard telescope.
The Space Team: To understand what these stars were, he called in the big guns: the TESS satellite. TESS is like a high-definition drone that flies over the city and takes incredibly detailed, continuous photos of these specific stars.

3. The New Tools: The "Light Curve Viewer"

The author realized that the existing software for analyzing these star patterns was a bit old and slow (like using a 1990s calculator for complex math). So, he wrote two new programs:

LCV (Light Curve Viewer): A fast, modern tool to crunch the numbers and find the rhythm (period) of the stars.
VS-fit: A tool to fine-tune the rhythm, making sure the timing is perfect.

4. The Six New Characters

Here is what the author discovered about these six new stars, using the TESS data to give them their "personality":

The Shapeshifter (PMAK V147): This star changes brightness because it is being stretched and squeezed by a partner, like a piece of dough being kneaded. It's an "ellipsoidal" variable.
The Spinning Top (PMAK V148): This star is simply rotating. As it spins, dark spots (like sunspots) on its surface come and go, making it look like it's blinking.
The Rapid Heartbeat (PMAK V149): This is a "pulsating" star that expands and contracts incredibly fast—more than 19 times a day! It's like a star with a very fast heartbeat.
The Double-Act (PMAK V150): This is the most complex character. It is a binary system (two stars orbiting each other).
- First, they eclipse each other (one blocks the other) every 41 days.
- Second, one of the stars is pulsating (beating) rapidly every few hours.
- The author had to prove these changes came from the target star and not its neighbors by using a "pixel-by-pixel" camera trick, ensuring the signal wasn't a mix-up.
The Slow Dancer (PMAK V151): A "Slowly Pulsating B" star. It breathes in and out slowly, changing brightness over a few days.
The Masked Dancer (PMAK V152): This is an eclipsing binary where the stars pass in front of each other. However, the light curve is messy because the stars are covered in huge spots, making the brightness wobble even when they aren't eclipsing. It's like a dancer wearing a mask that changes shape while they spin.

5. Why This Matters

The paper concludes that even with a small telescope in a light-polluted city, you can still find new stars if you have the right "detective tools" (software) and the patience to cross-reference your findings with space data.

Two of these stars are particularly special:

The Double-Act (PMAK V150): Because it both eclipses and pulsates, it offers a rare chance to measure the star's size and internal structure very precisely.
The Masked Dancer (PMAK V152): It shows how active and "spot-covered" binary stars can be, which helps scientists understand how stars interact with their partners.

In short, this paper is a demonstration that a small, dedicated observer with custom software can still make new discoveries in an era dominated by giant automated surveys.

1. Problem Statement

The discovery of new variable stars has become increasingly challenging due to the saturation of automated sky surveys (e.g., Gaia DR3, which contains ~10 million classified variables). While these surveys are powerful, they may miss specific targets due to selection biases, data gaps, or the limitations of automated pipelines in complex fields.
The author aims to demonstrate the viability of small-aperture, ground-based telescopes in urban environments (Bortle class 7) for detecting variable stars. Furthermore, the paper addresses the need for robust, open-source tools to analyze these discoveries, specifically bridging the gap between initial ground-based detection and detailed characterization using space-based data (TESS).

2. Methodology

The research employs a hybrid workflow combining custom ground-based observations with space-based data analysis and proprietary software tools.

A. Observations and Data Reduction

Site & Equipment: Observations were conducted from the "Osokorky" private observatory in Kyiv, Ukraine (Bortle class 7). Equipment included a 150mm Newtonian telescope (f=750mm), a ZWO ASI183MM Pro cooled CMOS camera, and a filter wheel.
Target Fields: Three star fields were observed over multiple sessions (totaling ~3.5–3.8 hours per field) using clear and Johnson V filters.
Calibration: A custom command-line toolkit (MaxFITStoolkit) was used for standard calibration (dark, flat, dark-flat). Images were binned 2x to reduce size.
Photometry:
- AstroImageJ: Used for aperture photometry of hundreds of objects simultaneously.
- Custom Python Scripts:
  - apgen.py: Uses the DAOStarFinder algorithm (via Photutils) to generate source lists and coordinate files.
  - aijplot.py: Visualizes light curves in HTML format, allowing for rapid visual inspection of short-period variables.

B. Data Analysis & Software Development

To overcome limitations in existing software (e.g., the older MCV program lacking multiprocessing), the author developed two new open-source tools:

LCV (Light Curve Viewer):
- Function: Periodogram analysis and light curve modeling.
- Algorithm: Approximates light curves using a combination of algebraic and trigonometric polynomials:
  $y_c(t) = \sum_{\alpha=0}^{r} C_{1\alpha}t^\alpha + \sum_{\beta=1}^{s} [C_{2\beta}\sin(\beta\omega t) + C_{3\beta}\cos(\beta\omega t)]$
- Optimization: Utilizes the Intel oneMKL library for high-speed computation and supports multiprocessing.
- Metric: Calculates a power statistic $S(f)$ based on the reduction of residual variance ( $O-C$ ).
VS-fit:
- Function: Period refinement.
- Algorithm: Uses scipy.optimize to refine periods for combinations of up to nine trigonometric polynomials plus an optional algebraic term. It addresses the inability of LCV to refine periods during the initial approximation phase.

C. TESS Data Integration

Source: TESS data was retrieved via the Lightkurve package.
Strategy: Pre-calculated light curves (SPOC/QLP) were used where available. For fainter stars or those not in target lists, light curves were extracted directly from Full Frame Images (FFIs) using aperture photometry.
Validation: For crowded fields, one-pixel aperture photometry was performed to distinguish the target from neighbors.

3. Key Contributions

Discovery of Six New Variables: Identification of six periodic variable stars (designated PMAK V147 through V152) that were missed by automated surveys.
Software Suite: Release of LCV and VS-fit, providing the community with modern, high-performance tools for periodogram analysis and complex light curve modeling (handling mixed algebraic/trigonometric fits).
Workflow Demonstration: A proven pipeline showing how urban-based amateur/small-scale observatories can contribute to professional astronomy by acting as a discovery filter for TESS data.

4. Results

Six new variable stars were characterized. Their properties are summarized below:

TIC ID	VSX Name	Type	Period (days)	Key Characteristics
174042954	PMAK V147	ELL (Rotating Ellipsoidal)	0.3150	Amplitude 0.03 mag.
79234006	PMAK V148	ROT (Rotational)	0.4249	Amplitude 0.11 mag.
79234043	PMAK V149	DSCT (δ Scuti)	0.0506	Multi-periodic pulsator; 4 distinct periods identified.
269112631	PMAK V150	EA + BCEP (Eclipsing + β Cephei)	41.04 (EA) 0.1329 (BCEP)	Complex System: Eclipsing binary with superimposed pulsations. Neighbors confirmed via 1-pixel aperture photometry. Spectral type B, $T_{eff} \approx 13,300$ K.
269809093	PMAK V151	SPB (Slowly Pulsating B)	0.3680	Complex light curve shape; spectral type B.
269112450	PMAK V152	EA/RS (Eclipsing + RS CVn)	1.1231	Total eclipses with significant rotational modulation (starspots) dominating the light curve shape.

Specific Highlights:

TIC 269112631: A rare combination of an Algol-type eclipsing binary and a β Cephei pulsator. The author confirmed the variability originates from the target (not neighbors) using single-pixel photometry on TESS FFIs.
TIC 269112450: An example where starspot modulation is comparable to or exceeds the eclipse depth, making it a candidate for studying active binary systems.

5. Significance

Astrophysical Value: The discovery of TIC 269112631 is particularly significant. As an eclipsing binary with pulsations, it offers a unique laboratory to simultaneously constrain fundamental stellar parameters (mass, radius) and internal structure (via asteroseismology).
Methodological Impact: The paper validates that small telescopes in light-polluted urban areas can still yield new scientific discoveries when paired with rigorous data analysis and space-based follow-up.
Tool Accessibility: By open-sourcing LCV and VS-fit, the author provides the astronomical community with efficient, modern alternatives to legacy software for analyzing complex, multi-periodic variable stars.
Future Research: The identified systems, particularly the active binary TIC 269112450 and the pulsating eclipsing binary TIC 269112631, are proposed as prime targets for further detailed study to understand binary evolution and stellar interiors.