Period Analysis of Eclipsing Cataclysmic Variable Stars

David A. Moffett; Emily S. Hatten; Mennatalla Mahmoud Ellaqany; Mridul Agarwal; Valeria Garcia-Lopez

REVIEW 4 major objections 5 minor 24 references

Period Analysis of Eclipsing Cataclysmic Variable Stars

T0 review · 4 major / 5 minor · reviewed 2026-08-10 · deepseek-v4-flash

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Pith's one-line read This paper reports new orbital period derivatives for seven eclipsing cataclysmic variables from TESS data, including three negative values with no prior comparison.

desk verdict Honest undergraduate TESS O-C study whose new period-derivative claims are undercut by unit inconsistencies and short-baseline systematics. read the letter →

arxiv 2501.12334 v1 pith:W3WESDXN submitted 2025-01-21 astro-ph.SR

Mennatalla Mahmoud Ellaqany , Valeria Garcia-Lopez , Emily S. Hatten , Mridul Agarwal , David A. Moffett This is my paper · ORCID

classification astro-ph.SR

keywords eclipsingcataclysmicvariablesO-CdiagramsorbitalperiodderivativeTESSphotometrydwarfnovaeevolutioneclipsetimingmagneticbraking

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper sets out to measure whether the orbital periods of seven eclipsing cataclysmic variable binaries are changing with time, using TESS two-minute-cadence photometry spanning three to four years. It extracts eclipse times, builds observed-minus-computed (O-C) diagrams, and fits quadratic curves whose curvature yields the period derivative $\dot{P}$. The orbital periods it finds for all seven systems agree with published values; the period derivative it finds for EX Dra agrees with a longer-baseline study, while those for QZ Aur, EX Hya, and AY Psc do not. For DO Leo, GY Cnc, and HBHA 4204-09 it reports negative $\dot{P}$ values with no recent literature values for comparison, making these the paper's most direct new constraints on orbital evolution of these binaries and a possible observational signature of magnetic braking.

What carries the argument

The load-bearing object is the O-C diagram: for each eclipse, the difference between the observed time and the time predicted by a constant-period ephemeris, plotted against eclipse cycle number $E$. Under a constant period derivative, the relation $O-C = \frac{1}{2}P\dot{P}E^2$ holds, so the coefficient of a quadratic fit gives $\dot{P}$. Supporting machinery includes Lomb-Scargle periodograms to set the initial period, Savitzky-Golay filtering to remove outbursts and long-term trends, inverted-Gaussian fits to individual eclipses, and cubic-spline resampling to a 12-second cadence before the eclipse times are extracted.

What would settle it

A direct test would be to extend the O-C baseline for DO Leo, GY Cnc, and HBHA 4204-09 with archival eclipse timings or additional TESS sectors: if the apparent quadratic curvature flattens or reverses as more cycles are added, the negative $\dot{P}$ values are artifacts of the short baseline. An independent re-analysis of the same TESS data using phase-folded eclipse templates should reproduce the quoted $\dot{P}$ values within the stated uncertainties if the measurements are stable.

Watch

Extended reading notes

Core claim

The central claim is that the O-C diagrams of the seven target systems, built from TESS eclipse timings, carry measurable curvature, and that interpreting that curvature as a constant period derivative yields the $\dot{P}$ values in Table 2. For DO Leo, GY Cnc, and HBHA 4204-09 the fitted derivatives are negative: $-5.90(\pm0.88)\times10^{-10}$, $-1.91(\pm3.93)\times10^{-10}$, and $-7.28(\pm5.06)\times10^{-11}$ days/day, respectively, and the paper finds no recent published values to compare against. The paper treats these as evidence that the three orbits are shrinking, likely through magnetic braking, while noting that the same short-baseline analysis disagrees with longer-baseline O-C studies for QZ Aur, EX Hya, and AY Psc.

Load-bearing premise

The analysis assumes that the curvature visible in a three-to-four-year O-C diagram is produced by a steady, linear period derivative and that each inverted-Gaussian eclipse time is accurate enough to trust that curvature; the paper itself notes that low signal-to-noise, outbursts, and accretion-disk contamination can make fitting difficult, and that three of its period derivatives disagree with longer-baseline studies.

Editorial extensions

If this is right

Seven orbital periods are now confirmed against published values, validating the TESS-only processing chain for period measurement.
EX Dra's $\dot{P}$ matches the long-baseline value within one sigma, showing that a three-to-four-year TESS baseline can sometimes recover a known period derivative.
DO Leo, GY Cnc, and HBHA 4204-09 enter the literature with first-time $\dot{P}$ constraints, all negative.
If those negative derivatives are real, the three systems' orbits are shrinking on million-year timescales, and magnetic braking is a viable explanation.
The paper notes that adding more eclipse epochs is needed to improve the results, especially where short-baseline values disagree with longer studies.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

A longer baseline for DO Leo, GY Cnc, and HBHA 4204-09, combining TESS with archival eclipse times, would discriminate between secular shrinking and cyclic period changes; if the quadratic curvature persists over decades, the negative $\dot{P}$ values are real.
The disagreement between short and long baselines in QZ Aur, EX Hya, and AY Psc suggests that some O-C residuals may be dominated by timing jitter or cyclic variations rather than a steady $\dot{P}$; those systems would be good targets for testing whether TESS-only baselines can mislead.
Using phase-folded eclipse templates instead of individual inverted-Gaussian fits would be a testable improvement, since the paper identifies low signal-to-noise and accretion-disk contamination as sources of fitting difficulty.
If magnetic braking is the cause, the three negative derivatives carry information about donor-star magnetic field strengths and mass-loss rates; comparing them to evolutionary models would be a natural next step.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

Short version: this is a transparent undergraduate exercise that confirms seven orbital periods and reports three new Pdot values (DO Leo, GY Cnc, HBHA 4204-09) from 3–4 yr TESS O-C diagrams. The periods are solid; the new Pdot values probably aren't, and the paper itself gives reasons to be cautious. The biggest problem is that the quoted numbers aren't even self-consistent: Table 2 and the text disagree by factors of 10–100 for DO Leo and HBHA 4204-09. Until the units are fixed, the central measurements are not well-defined.

What the paper does well: the methods are described clearly enough to reproduce, the periods match literature values, and the authors explicitly flag where their Pdot values disagree with longer-baseline studies (QZ Aur, EX Hya, AY Psc). That honesty is real. The three new negative Pdot values do not have obvious recent literature comparisons, so if correct they would be a small but real contribution to CV orbital evolution. But the case is not made.

The soft spots are not minor. There is no derivation of the quoted uncertainties, no null test for whether the O-C curvature could arise from timing noise or systematic bias, and no code or data release. The 12-second spline interpolation from 2-minute cadence is a potential source of correlated errors, and the paper admits low S/N and outburst contamination in Section 3.3. More troubling, three of four Pdot values with external checks disagree with long-baseline results, in one case (EX Hya) by sign. That is exactly what you would expect if short-baseline curvature is not a secular period derivative. The three new values are the least protected against this artifact, so they should be treated as provisional at best.

I also cannot overlook the unit inconsistency. Table 2 lists DO Leo as −5.901 × 10⁻⁹ and HBHA 4204-09 as −7.279 × 10⁻⁹, but Sections 4.5 and 4.7 quote −5.90 × 10⁻¹⁰ and −7.279 × 10⁻¹¹. That is a factor of 10–100 mismatch. Before any referee spends time on the astrophysics, the authors need to fix their tables and state units unambiguously.

Who is this for? CV specialists and anyone teaching O-C analysis. It is a useful case study in the pitfalls of short-baseline timing. It deserves peer review, not desk rejection, because the target selection is sensible, the periods are likely correct, and a serious referee can push the authors to add an error analysis and an injection-recovery test. But as submitted, the central Pdot claims are not yet credible.

Referee Report

4 major / 5 minor

Summary. The paper analyzes TESS 2-minute-cadence photometry of seven eclipsing cataclysmic variables. It detrends the light curves, identifies eclipse times by fitting inverted Gaussians, builds O-C diagrams, and fits the quadratic O-C = 0.5 P Pdot E^2 to derive orbital period derivatives. The reported orbital periods agree with earlier literature. For four systems with published Pdot values, three disagree with longer-baseline studies, sometimes in sign. The paper highlights three systems (DO Leo, GY Cnc, HBHA 4204-09) as having negative period derivatives with no recent literature comparison.

Significance. If the reported period derivatives are correct, the paper would add new empirical constraints on the orbital evolution of eclipsing CVs, particularly the three negative Pdot values for DO Leo, GY Cnc, and HBHA 4204-09. The work also demonstrates a reproducible, undergraduate-accessible pipeline for TESS CV analysis, and the authors are transparent in reporting disagreements with longer-baseline studies. However, the central claim is only as strong as the short-baseline quadratic fits, and the manuscript contains internal inconsistencies in the quoted Pdot values and no explicit uncertainty derivation. The significance is therefore conditional on resolving those issues.

major comments (4)

[Table 2 and Sections 4.5, 4.7] The reported Pdot values are not internally consistent by factors of 10-100. In Table 2, DO Leo is listed as -5.901 ± 0.875 × 10^-1 in units of 10^-9 days/day, i.e., approximately -5.9 × 10^-9, while Section 4.5 quotes -5.90(±0.88) × 10^-10. Similarly, HBHA 4204-09 is listed in Table 2 as -7.279 ± 5.059 × 10^-2 in 10^-9 units, roughly -7.3 × 10^-9, while Section 4.7 quotes -7.279(±5.059) × 10^-11. These are not cosmetic unit conventions; they change the claimed physical value by an order of magnitude or more. The central claim of constraining Pdot requires a single, unambiguous set of values.
[Section 3.4] The manuscript does not describe how the uncertainties on Pdot are derived. The text gives formal-looking error bars but no covariance matrix, no confidence-interval construction, and no treatment of correlated uncertainties between P, T0, and Pdot. In GY Cnc the quoted uncertainty is roughly twice the fitted value, and in HBHA 4204-09 the quoted error is close in size to the value, so the statistical meaning of these errors is unclear. A description of the fitting and error-propagation procedure is needed before the values in Table 2 can be assessed.
[Sections 3.1 and 3.3] The pipeline may introduce correlated timing errors that mimic a quadratic O-C trend. Cubic-spline interpolation from 2-minute cadence to 12-second cadence (Section 3.1) and fitting a Gaussian center to each eclipse (Section 3.3) are both susceptible to systematic offsets from eclipse asymmetries, outbursts, or disk contamination, as the paper itself notes in Section 3.3. A null test is missing: no injection-recovery experiment demonstrates that an artificial eclipse sequence with zero Pdot and similar noise yields zero curvature, or that a known Pdot is recovered without bias. Without such a test, a 3-4 year baseline is too short to distinguish a secular Pdot from correlated timing noise.
[Section 4, especially 4.1, 4.3, 4.4] The paper's own comparisons with longer-baseline results undermine the claim that short-baseline quadratic curvature is secular. QZ Aur, EX Hya, and AY Psc all disagree with Schaefer (2024) or Kára et al. (2023), and in the case of EX Hya the sign differs. This is exactly the failure mode expected if the short-baseline curvature is not a true period derivative. The three highlighted new negative Pdot values (DO Leo, GY Cnc, HBHA 4204-09) have no external check, so they are the least protected against this artifact. The conclusion that these are 'most promising' is premature without additional validation or longer baseline data.

minor comments (5)

[Table 2] The units in Table 2 are confusing: the header states Pdot in 10^-9 days/day, but the uncertainty column uses notations like '±0.875×10^-1' and '±5.059×10^-2', which appear to mix scales. Standardize the notation so the value and uncertainty share the same exponent.
[Section 4.3 and Table 2] The orbital period for EX Hya is given as 0.068234 days in Section 4.3 but 0.068228 days in Table 2. Please correct the inconsistency.
[Title and general text] There are typographical errors such as 'V ariable' in the title and 'T able' in table captions. A careful proofreading pass is needed.
[Appendix figures] The appendix figures are not explicitly referenced in the results section for each source; adding explicit references (e.g., 'Figure 32(d)') would improve navigation.
[Data availability] The paper mentions Python code but does not state whether the code or derived eclipse times are publicly available. Providing a repository would strengthen reproducibility, which is important for a methods-oriented paper.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: the Pdot values are inferred from O−C curvature against an independently fitted period and are compared with external long-baseline measurements.

full rationale

The paper's central claim—that O−C diagrams constrain Pdot—is a standard two-step inference, not a circular one. The orbital period P is first obtained from a Lomb-Scargle periodogram of the TESS light curves (Section 3.2). This period is then used to compute predicted eclipse times C = T0 + EP (Section 3.4). The observed-minus-computed eclipse times are fit with a quadratic O−C = (1/2) P Pdot E^2, and the period derivative is extracted from the quadratic curvature. Nothing in this chain defines Pdot in terms of itself, and the fitted P is not derived from the Pdot value being reported. The period derivative is a free parameter of the quadratic fit, not an input, and the sign and magnitude are determined by the data rather than by construction. The paper also provides external benchmarks: for EX Dra it reports agreement with Schaefer (2024), while for QZ Aur, EX Hya, and AY Psc it explicitly notes disagreement with longer-baseline determinations, showing the results are falsifiable and not forced. The references are to independent external authors, not to the present authors' prior work, and no uniqueness theorem or ansatz is imported via self-citation. The internal inconsistencies between Table 2 and the quoted text values (factors of 10–100 for several Pdot entries) are a correctness or presentation issue, not a circularity. Likewise, the caveats about low signal-to-noise and short baselines affect reliability, not circularity. The derivation is self-contained in the sense that the reported Pdot values come from fitting the data, with no fitted input renamed as a prediction.

Assumptions & free parameters 4 free parameters · 4 assumptions · 0 invented entities

The central Pdot claims rest on four domain assumptions about period identification, Gaussian eclipse symmetry, the physical meaning of O-C curvature, and the timing safety of the detrending process. The fitted P, Pdot, and Gaussian initial guesses are empirical fit parameters rather than theory inputs. No new particles, forces, or physical entities are proposed.

free parameters (4)

Orbital period P (per system) = 0.0682 to 0.3575 days
Fitted from the Lomb-Scargle peak and used to fold the light curve and predict eclipse times; the fitted values agree with literature.
Period derivative Pdot (per system) = Table 2; some entries are inconsistent with the text
Quadratic coefficient of the O-C fit; this is the central measured quantity, but it is unverified for three systems and inconsistent with longer-baseline measurements for three others in the paper's own comparison.
Eclipse Gaussian center and width initial guesses = manually selected from one sample chunk
Section 3.3 uses manually chosen initial guesses for the inverted Gaussian fit, so the eclipse times inherit human subjectivity and the uncertainty is not propagated into Pdot.
Savitzky-Golay window and 10 percent periodogram threshold = not stated
Algorithm parameters are chosen by hand in Sections 3.1 and 3.2 without justification, and their effect on the fitted eclipse times is not tested.

assumptions (4)

domain assumption The strongest Lomb-Scargle peak above 10 percent of maximum power identifies the binary orbital period.
Invoked in Section 3.2; no independent verification that alias peaks or harmonics are excluded for every target.
domain assumption An inverted Gaussian is an adequate model of the eclipse shape for all seven systems.
Used in Section 3.3; the authors note contamination can make fitting difficult, but the Gaussian centers are still treated as the observed eclipse times.
domain assumption Quadratic curvature in the O-C diagram over 3 to 4 years arises from a constant period derivative.
Equation in Section 3.4; timing jitter, spot migration, or asymmetric eclipses could masquerade as curvature, and several fitted values conflict with longer-baseline studies.
domain assumption Savitzky-Golay filtering and spline interpolation remove outbursts and sampling gaps without biasing the eclipse timings.
Sections 3.1 and 3.3; window lengths and interpolation parameters are not reported, so the timing-preservation assumption is untested.

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Cite this review

Pith. "Pith review of Period Analysis of Eclipsing Cataclysmic Variable Stars." pith.science (2026). https://pith.science/paper/W3WESDXN

@misc{pith2026250112334,
  author       = {Pith},
  title        = {Pith review of: Period Analysis of Eclipsing Cataclysmic Variable Stars},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/W3WESDXN}},
  note         = {Machine review of arXiv:2501.12334}
}

read the original abstract

We have performed a study of the orbital properties of seven eclipsing cataclysmic variable (CV) binary systems by analyzing photometric time series from the Transiting Exoplanet Survey Satellite (TESS). We employed Python code to determine the eclipse epochs and orbital periods for each system, and constructed O-C diagrams from observed and predicted eclipse epochs. By analyzing the O-C diagrams of our target CVs, we have constrained values for changes in orbital period with time. Our targets include a sample of sources from each class of non-magnetic, eclipsing CVs: dwarf novae variables, Z Cam type, and U Gem subclasses. We include in our study classical novae variables, nova-like variables (including the VY Scl and UX UMa subclasses), and recurrent novae variable stars. We approached this project with goals of developing time series analysis techniques for future undergraduate-level studies of eclipsing CVs, and how they may contribute to the understanding of their orbital evolution.

Figures

Figures reproduced from arXiv: 2501.12334 by the authors.

**Figure 1.** Detrended TESS light curve of Ex Dra. Time is in units of Barycentric Julian Day (BTJD), and amplitude is in units of normalized flux. 3.2. Periodogram Analysis To find the orbital period of the binary star we applied a Lomb-Scargle periodogram to the residual light curve. Once a periodogram is obtained, we further processed it by applying cubic spline interpolation to smooth the power spectrum, making it easier to … view at source ↗

**Figure 2.** Lomb-Scargle periodogram for EX Dra. The highest peak was fitted by a Gaussian function for the orbital period. 3.3. Eclipse time fitting Once we determined the orbital period, we used it to divide the light curve data into one period wide chunks containing the primary and secondary eclipses. We modeled the primary eclipse with an inverted Gaussian. From a sample chunk, we manually select two points in the eclipse p… view at source ↗

**Figure 3.** Sample chunk from EX Dra with inverse Gaussian fit. Time is measured in Barycentric Julian Day (BTJD), and amplitude is expressed in normalized flux. 3.4. O-C Diagrams and Period Derivation After extracting the observed eclipse times (O), we then calculated the predicted (C) eclipse times from the following equation: C = T0 + EP where T0 is the initial time value in the light curve, E is the epoch or cycle number of… view at source ↗

Figures from the paper (13 more)

**Figure 4.** Figure 4: O − C for EX Dra with time measured in epochs. 4. RESULTS AND DISCUSSION We summarize the results of our time series analysis of the target sources in [PITH_FULL_IMAGE:figures/full_fig_p005_4.png]

**Figure 6.** Figure 6 [PITH_FULL_IMAGE:figures/full_fig_p009_6.png]

**Figure 7.** Figure 7: AY Psc [PITH_FULL_IMAGE:figures/full_fig_p009_7.png]

**Figure 9.** Figure 9: GY Cnc [PITH_FULL_IMAGE:figures/full_fig_p009_9.png]

**Figure 12.** Figure 12: QZ Aur [PITH_FULL_IMAGE:figures/full_fig_p010_12.png]

**Figure 15.** Figure 15 [PITH_FULL_IMAGE:figures/full_fig_p010_15.png]

**Figure 16.** Figure 16: GY Cnc [PITH_FULL_IMAGE:figures/full_fig_p010_16.png]

**Figure 19.** Figure 19: QZ Aur [PITH_FULL_IMAGE:figures/full_fig_p011_19.png]

**Figure 21.** Figure 21: AY Psc [PITH_FULL_IMAGE:figures/full_fig_p011_21.png]

**Figure 23.** Figure 23: GY Cnc [PITH_FULL_IMAGE:figures/full_fig_p011_23.png]

**Figure 26.** Figure 26: QZ Aur [PITH_FULL_IMAGE:figures/full_fig_p012_26.png]

**Figure 28.** Figure 28: AY Psc [PITH_FULL_IMAGE:figures/full_fig_p012_28.png]

**Figure 30.** Figure 30: GY Cnc [PITH_FULL_IMAGE:figures/full_fig_p012_30.png]

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

24 extracted references · 19 canonical work pages

[1]

Abbott, T. M. C., Shafter, A. W., Wood, J. H., Tomaney, A. B., & Haswell, C. A. 1990, Publications of the Astronomical Society of the Pacific, 102, 558, 10.1086/132669

work page doi:10.1086/132669 1990
[2]

2024, Ex Hydrae: Variable Star of the Season, https://www.aavso.org/vsots_exhya

American Association of Variable Star Observers (AAVSO) . 2024, Ex Hydrae: Variable Star of the Season, https://www.aavso.org/vsots_exhya

work page 2024
[3]

L., & Breus, V

Andronov, I. L., & Breus, V. V. 2013, Astrophysics, 56, 518–530, 10.1007/s10511-013-9304-7

work page doi:10.1007/s10511-013-9304-7 2013
[4]

1989, in Two Topics in X-Ray Astronomy, ed

Bade, N., Hagen, H.-J., & Reimers, D. 1989, in Two Topics in X-Ray Astronomy, ed. J. Hunt & B. Battrick, ESA SP-296 (Noordwijk: ESA), 883

work page 1989
[5]

2024, NASA - TESS Science Support Center

Barclay, T. 2024, NASA - TESS Science Support Center

work page 2024
[6]

1993, in Compact Stars in Binary Systems, ed

Barwig, H., Fiedler, H., Reimers, D., & Bade, N. 1993, in Compact Stars in Binary Systems, ed. H. van Woerden (Dordrecht: Kluwer), 89

work page 1993
[7]

Bours, M. C. P. 2015. http://webcat.warwick.ac.uk/record=b2844675 S1

work page 2015
[8]

2024, Observation Summary for Variable Star GY CNC, https://britastro.org/vssdb/object_summary.php?object_id=GY

British Astronomical Association . 2024, Observation Summary for Variable Star GY CNC, https://britastro.org/vssdb/object_summary.php?object_id=GY

work page 2024

Show all 24 references

[9]

2024, , 273, 6, 10.3847/1538-4365/ad43ec

Bruch , A. 2024, , 273, 6, 10.3847/1538-4365/ad43ec

2024 doi
[10]

1957, Peremennye Zvezdy, 12

Brun, A., & Petit, M. 1957, Peremennye Zvezdy, 12

1957
[11]

A., Garnavich , P., Littlefield , C., et al

Ca \ n izares , L. A., Garnavich , P., Littlefield , C., et al. 2018, Research Notes of the American Astronomical Society, 2, 184, 10.3847/2515-5172/aae48d

2018 doi
[12]

1995, apj, 440, 336, 10.1086/175275

Campbell, R., & Shafter, A. 1995, apj, 440, 336, 10.1086/175275

1995 doi
[13]

F., Ferguson , D

Green , R. F., Ferguson , D. H., Liebert , J., & Schmidt , M. 1982, , 94, 560, 10.1086/131022

1982 doi
[14]

F., Schmidt , M., & Liebert , J

Green , R. F., Schmidt , M., & Liebert , J. 1986, , 61, 305, 10.1086/191115

1986 doi
[15]

2017, Research in Astronomy and Astrophysics, 17, 056, 10.1088/1674-4527/17/6/56

Han, Z.-T., Qian, S.-B., Voloshina, I., & Zhu, L.-Y. 2017, Research in Astronomy and Astrophysics, 17, 056, 10.1088/1674-4527/17/6/56

2017 doi
[16]

S., Stanek , K

Jayasinghe , T., Kochanek , C. S., Stanek , K. Z., et al. 2018, , 477, 3145, 10.1093/mnras/sty838

2018 doi
[17]

2023, The Astrophysical Journal, 950, 47, 10.3847/1538-4357/accd63

Kára, J., Zharikov, S., Wolf, M., et al. 2023, The Astrophysical Journal, 950, 47, 10.3847/1538-4357/accd63

2023 doi
[18]

P., Rodríguez-Gil, P., Marsh, T

Littlefair, S. P., Rodríguez-Gil, P., Marsh, T. R., Parsons, S. G., & Dhillon, V. S. 2023, Monthly Notices of the Royal Astronomical Society, 527, 4353, 10.1093/mnras/stad3500

2023 doi
[19]

2024, EX Hydrae, https://asd.gsfc.nasa.gov/Koji.Mukai/iphome/systems/exhya.html

Mukai, K. 2024, EX Hydrae, https://asd.gsfc.nasa.gov/Koji.Mukai/iphome/systems/exhya.html

2024
[20]

1975, Information Bulletin on Variable Stars, 1011, 1

Sanduleak, N. 1975, Information Bulletin on Variable Stars, 1011, 1

1975
[21]

Schaefer, B. E. 2024, Evolutionary Period Changes For 52 Cataclysmic Variables, and the Failure For the Most Fundamental Prediction of the Magnetic Braking Model. 2404.12525

2024 arXiv
[22]

2014, Publications of the Astronomical Society of Japan, 66, 41, 10.1093/pasj/psu004

Shi, G., & Qian, S.-B. 2014, Publications of the Astronomical Society of Japan, 66, 41, 10.1093/pasj/psu004

2014 doi
[23]

Y., & Stefanov, A

Stefanov, S. Y., & Stefanov, A. K. 2023, Monthly Notices of the Royal Astronomical Society, 520, 3355–3367, 10.1093/mnras/stad259

2023 doi
[24]

2021, in Photometric study of eclipsing dwarf nova EX Dra, 010, 10.22323/1.368.0010

Voloshina, I., Khruzina, T., & Metlov, V. 2021, in Photometric study of eclipsing dwarf nova EX Dra, 010, 10.22323/1.368.0010

2021 doi

Pith tools

Reviewed August 10, 2026 · model on record in the stance chip above.

[1] [1]

Abbott, T. M. C., Shafter, A. W., Wood, J. H., Tomaney, A. B., & Haswell, C. A. 1990, Publications of the Astronomical Society of the Pacific, 102, 558, 10.1086/132669

work page doi:10.1086/132669 1990

[2] [2]

2024, Ex Hydrae: Variable Star of the Season, https://www.aavso.org/vsots_exhya

American Association of Variable Star Observers (AAVSO) . 2024, Ex Hydrae: Variable Star of the Season, https://www.aavso.org/vsots_exhya

work page 2024

[3] [3]

L., & Breus, V

Andronov, I. L., & Breus, V. V. 2013, Astrophysics, 56, 518–530, 10.1007/s10511-013-9304-7

work page doi:10.1007/s10511-013-9304-7 2013

[4] [4]

1989, in Two Topics in X-Ray Astronomy, ed

Bade, N., Hagen, H.-J., & Reimers, D. 1989, in Two Topics in X-Ray Astronomy, ed. J. Hunt & B. Battrick, ESA SP-296 (Noordwijk: ESA), 883

work page 1989

[5] [5]

2024, NASA - TESS Science Support Center

Barclay, T. 2024, NASA - TESS Science Support Center

work page 2024

[6] [6]

1993, in Compact Stars in Binary Systems, ed

Barwig, H., Fiedler, H., Reimers, D., & Bade, N. 1993, in Compact Stars in Binary Systems, ed. H. van Woerden (Dordrecht: Kluwer), 89

work page 1993

[7] [7]

Bours, M. C. P. 2015. http://webcat.warwick.ac.uk/record=b2844675 S1

work page 2015

[8] [8]

2024, Observation Summary for Variable Star GY CNC, https://britastro.org/vssdb/object_summary.php?object_id=GY

British Astronomical Association . 2024, Observation Summary for Variable Star GY CNC, https://britastro.org/vssdb/object_summary.php?object_id=GY

work page 2024