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Superhumps in active dwarf novae. Part I: ER Ursae Majoris

K. Bakowska, B. Kirpluk, P. Zielinski, M. Motylinski, A. Gurgul, J. Golonka, K. Szyszka

TL;DR

ER UMa is a highly active SU UMa-type dwarf nova whose long-term behavior and superhump evolution are analyzed by combining ground-based photometry with TESS data. Using period analyses and O-C diagrams across multiple well-sampled superoutbursts, the study derives a consistent period excess of $\epsilon \approx 3.0\%$ and a mass ratio of $q \approx 0.14$, arguing that ER UMa follows standard CV evolutionary tracks. The supercycle length shows a substantial increase from roughly $42$ to $60$ days over three decades, indicating a gradual decline in the mean mass-transfer rate, while outburst amplitudes remain broadly constant. The work clarifies previous discrepancies in P_sc measurements and establishes a detailed framework for future, multi-season analyses of ER UMa and analogous systems (Part II).

Abstract

We report photometry results of a frequently outbursting dwarf nova, ER Ursae Majoris. To measure the outburst parameters of the system, we carried out analyses of the light curve, periodograms, and O-C diagrams. We investigated the system's behaviour using the ground-based optical data and the Transiting Exoplanet Survey Satellite data. During these observation runs, we scrutinised three superoutbursts and several normal outbursts. We detected ordinary and late superhumps during each of the investigated superoutbursts. We derived the period excess value $ε\approx 3.0(1)\% $. This suggests that over the last 30 years, ER UMa has not shifted on the evolutionary path toward period-bounce objects. Between 1992 and 2022, the interval between two successive superoutbursts (the supercycle length) changed significantly from 42.1 days to 59.6 days, which indicates that the mean mass-transfer rate of ER UMa has been decreasing over this period.

Superhumps in active dwarf novae. Part I: ER Ursae Majoris

TL;DR

ER UMa is a highly active SU UMa-type dwarf nova whose long-term behavior and superhump evolution are analyzed by combining ground-based photometry with TESS data. Using period analyses and O-C diagrams across multiple well-sampled superoutbursts, the study derives a consistent period excess of and a mass ratio of , arguing that ER UMa follows standard CV evolutionary tracks. The supercycle length shows a substantial increase from roughly to days over three decades, indicating a gradual decline in the mean mass-transfer rate, while outburst amplitudes remain broadly constant. The work clarifies previous discrepancies in P_sc measurements and establishes a detailed framework for future, multi-season analyses of ER UMa and analogous systems (Part II).

Abstract

We report photometry results of a frequently outbursting dwarf nova, ER Ursae Majoris. To measure the outburst parameters of the system, we carried out analyses of the light curve, periodograms, and O-C diagrams. We investigated the system's behaviour using the ground-based optical data and the Transiting Exoplanet Survey Satellite data. During these observation runs, we scrutinised three superoutbursts and several normal outbursts. We detected ordinary and late superhumps during each of the investigated superoutbursts. We derived the period excess value . This suggests that over the last 30 years, ER UMa has not shifted on the evolutionary path toward period-bounce objects. Between 1992 and 2022, the interval between two successive superoutbursts (the supercycle length) changed significantly from 42.1 days to 59.6 days, which indicates that the mean mass-transfer rate of ER UMa has been decreasing over this period.
Paper Structure (18 sections, 13 equations, 14 figures, 13 tables)

This paper contains 18 sections, 13 equations, 14 figures, 13 tables.

Table of Contents

  1. Introduction
  2. Observations and data reduction
  3. Light curves
  4. Global photometric behaviour
  5. Publicly available observations
  6. Observations from the Piwnice Observatory
  7. TESS satellite data
  8. Period analysis
  9. Superoutbursts
  10. Normal outbursts
  11. Quiescence
  12. O-C Diagrams for superhumps
  13. The 2020 February Superoutburst
  14. The 2022 February Superoutburst
  15. The 2024 February Superoutburst
  16. ...and 3 more sections

Figures (14)

  • Figure 1: Finding chart of ER UMa, marked as T1. The positions of three comparison stars are also shown as C2, C3 and C4, respectively. The field of view is about 5'$\times$ 5'. North is left, and east is down.
  • Figure 2: Global photometric behavior of ER UMa. Top panels: Light curves from the AAVSO, bottom panel: data from the Piwnice Observatory.
  • Figure 3: Global photometric behavior of ER UMa, where data were provided by the TESS mission in four sectors: 21, 48, 74 and 75, shown on the subsequent panels.
  • Figure 4: Periodograms of the ER UMa superoutbursts calculated based on the following datasets: top left: AAVSO, top right: Piwnice, middle left: TESS, sec. 21, middle right: TESS, sec. 48, and bottom: TESS, sec. 75.
  • Figure 5: Superhumps observed during the 2022 Feb superoutburst of ER UMa (TESS, sec. 48).
  • ...and 9 more figures