QS Telescopii is a faint, well‑studied cataclysmic variable star system (a binary) located in the southern constellation Telescopium. The system consists of a magnetic white dwarf primary and a low‑mass main‑sequence donor star (spectral type M4–M5) that fill their Roche lobes and transfer material directly onto the white dwarf. Because of the white dwarf’s strong magnetic field (≈ 50–80 megagauss), the accretion flow is funneled along magnetic field lines onto one or both magnetic poles, preventing the formation of an accretion disk. Such systems are classified as polars or AM Herculis stars.
Astrometric and Physical Properties
- Coordinates (J2000.0): Right ascension 19 h 38 m 35.816 s, Declination −46° 12′ 57.11″.
- Parallax: 5.3378 ± 0.0834 mas (Gaia DR2), yielding a distance of ≈ 187 pc (≈ 611 ly).
- Proper motion: +35.150 mas yr⁻¹ (RA), −25.496 mas yr⁻¹ (Dec).
- Orbital period: 2.33 h, in a circular orbit (eccentricity ≈ 0).
- White dwarf mass: ≈ 0.71 M☉; effective temperature ≈ 17,500 K.
- Donor star: Red dwarf of approximate mass ≈ 0.15 M☉ (spectral type M4.5 ± 0.5).
Variability and Accretion Behavior
QS Telescopii exhibits rapid changes between high‑ and low‑accretion states, accompanied by variations in its optical and X‑ray brightness. The system can switch between single‑pole and two‑pole accretion configurations; the dominant pole is partially self‑eclipsing. Photometric observations have revealed quasi‑periodic oscillations with timescales of 6–10 minutes during certain states.
Discovery and Designations
The object was first identified as an extreme‑ultraviolet source (RE 1938‑461) in ROSAT and EUVE surveys. In 1991, David A. H. Buckley and collaborators recognized it as a variable star, and it received the variable‑star designation QS Telescopii in 1995 (Kazarovets & Samus, 1995). Other catalog identifiers include EUVE J1938‑46.2, RE 1938‑461, and AAVSO 1931‑46.
Observational Studies
QS Telescopii has been the subject of multi‑wavelength campaigns, including:
- X‑ray observations with XMM‑Newton, revealing a soft X‑ray component characteristic of polars (Traulsen et al., 2011).
- Optical/UV spectroscopy and polarimetry, documenting changes in the accretion geometry and magnetic field orientation (Rosen et al., 1996; de Martino et al., 1998).
- Long‑term photometric monitoring, establishing the pattern of high/low states and the presence of quasi‑periodic oscillations (Gerke et al., 2006).
Significance
As a relatively bright (V ≈ 15) polar located in the “period gap” of cataclysmic variables (orbital periods between 2–3 h where few systems are found), QS Telescopii provides a valuable laboratory for studying magnetic accretion processes, the interaction between white dwarf magnetic fields and donor star mass transfer, and the mechanisms driving state changes in polars.
References
- Rosen, S. R. et al. (1996). “Accretion mode changes in QS Tel (RE 1938‑461): EUVE, ROSAT and optical observations.” MNRAS, 280, 1121‑1142.
- Traulsen, I. et al. (2011). “XMM‑Newton observations of the X‑ray soft polar QS Telescopii.” A&A, 529, A116.
- Gerke, J. R. et al. (2006). “Polars Changing State: Multiwavelength Long‑Term Photometry and Spectroscopy of QS Telescopii, V834 Centauri, and BL Hydri.” PASP, 118, 678‑686.
- Buckley, D. A. et al. (1993). “Discovery of an EUV‑bright polar in the period gap from the ROSAT Wide Field Camera sky survey.” MNRAS, 262, 93‑108.
(All data retrieved from the Wikipedia article “QS Telescopii” and associated scholarly references.)