Multi-band Photometric and spectroscopic analysis of the dwarf novae IU Leo

TL;DR

IU Leo is a dwarf nova CV with a circumbinary envelope, and the paper couples multi-band photometry (K2, TESS, AAVSO) and spectroscopy (LAMOST LRS/MRS, HST) with MESA binary evolution to constrain system parameters. The analysis yields an orbital period of $P_{orb} \approx 0.3763$ d, donor and accretor masses of roughly $M_1 \approx 0.982\,M_{sun}$ and $M_2 \approx 0.835\,M_{sun}$, and a circumbinary envelope with $T_{eff}$ of a few hundred Kelvin; three outbursts with ~61-day recurrence are observed. LAMOST and HST data reveal Balmer, He, and metal lines, along with UV emission features, enabling velocity measurements and line diagnostics that support disk-instability physics. The results are broadly consistent with prior work and illustrate the value of combining multi-band photometry and spectroscopy with stellar-evolution modeling to study CV evolution and circumbinary environments.

Abstract

IU Leo was first identified as a cataclysmic variable star in 2006. Based on an image data and a distance value, we derived that the circumbinary envelope of IU Leo was $\sim$3,745\,AU on the optical band. According the multi-band photometric data, we calculated a $T_{eff}$ of a few hundred Kelvin for the circumbinary envelope of IU Leo. We reviewed the physical parameters of IU Leo and simulated the evolution process using a stellar evolution code MESA with $M_{1}$=0.982\,$M_{\bigodot}$, $M_{2}$=0.835\,$M_{\bigodot}$, and an orbital period of 0.376308\,days. The evolved other parameters are basically consistent with the parameters in the literatures. Based on the quiescence Kepler Mission 2.0 light curve, the quiescence Transiting Exoplanet Survey Satellite light curve, and 89 Large Sky Area Multi-Object Fiber Spectroscopic Telescope medium resolution spectra, we derived an orbital period of 0.376307 $\pm$ 0.000004\,days, 0.3762 $\pm$ 0.0001\,days, and 0.3763\,days for IU Leo respectively. These orbital periods are basically consistent with the results of previous studies. According to light curve of IU Leo from American Association of Variable Star Observers, we reported three new outburst spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope low resolution catalogue with part Balmer emission lines overlap on their absorption lines. Many H, He, C, N, O, Na, Mg, Si, and Ca neutral and ionized lines are identified, which are produced by different mechanisms. In the future, we will conduct more comprehensive and in-depth research on CVs based on multi-band photometric and spectroscopic data.

Figures (9)

• Figure 1: The image data for IU Leo from SDSS_DR15. The image was observed on March 12, 2002, corresponding to a MJD of 52,345.
• Figure 2: High-precision light curves for IU Leo from K2 and TESS. The lower panel shows observations that began on June 1, 2017 and lasted for nearly 80 days by K2. The upper panel shows observations that began on November 7, 2021 and lasted for approximately 25 days by TESS.
• Figure 3: The variations in apparent magnitude of IU Leo from AAVSO. The observed time is from March 13, 2012 to May 26, 2025.
• Figure 4: The magnified figure of variations in apparent magnitude of IU Leo from AAVSO. The 4 vertical dashed lines correspond to the detailed observation times of the low resolution spectra released by LAMOST. The spectra were observed on January 1, 2015, February 19, 2020, March 27, 2022, and March 26, 2023 respectively.
• Figure 5: The two low resolution spectra for IU Leo released by LAMOST corresponding to the vertical dashed lines in the two upper panels in Fig. 4.