Title:Recycled pulsar-like white dwarfs in close binaries AE Aquarii, AR Scorpii and LAMOST J024048.51+195226.9

Speaker: Nazar Ikhsanov (Pulkovo Observatory (RAS), Saint-Petersburg, Russia)

Time: 15:00, Thursday, 22 October 2026

Tencent Meeting: 46822606747 password: 6360

Location: Lecture Hall, 3rd floor

Invited by: Minfeng Gu

Abstract：

The problem caused by the inconsistency between the age and spin-down time scale of the white dwarfs in the systems AE Aquarii and AR Scorpii is discussed within the hypothesis of their accretion-driven spin-up during a previous epoch. Considering a scenario of accretion from a Keplerian disk, we conclude that the white dwarfs in these systems could be spun-up to the currently observed periods provided the radius of their magnetospheres at the end of the spin-up epoch was comparable to the Bohm radius, which is substantially smaller than the conventional Alfven radius. In this case the spin-up of the white dwarfs in the systems under consideration can be described within a model of stationary accretion from the Keplerian disk at an average rate of 10−9−10−8 solar mass per year without any additional assumptions about the evolution of the intrinsic magnetic field of the white dwarfs during the spin-up epoch. An application of the proposed spin-up scenario to the white dwarf in the close binary system LAMOST J024048.51+195226.9 allows us to explain its extremely short spin period (25 seconds) provided the surface magnetic field of the white dwarf is about 35 MG. Under these conditions, in the current epoch the white dwarf would operate as a recycled spin-powered pulsar spinning-down at a rate of about 2 × 10−14 s/s.

References

1. Ikhsanov, N.R. 1998, Astron. Astrophys. 338, 521-526;

2. Ikhsanov, N.R. 1999, Astron. Astrophys. 347, 915-918;

3. Ikhsanov, N.R. 2000, Astron. Astrophys. 358, 201-207;

4. Ikhsanov, N.R., Neustroev, V.V. and Beskrovnaya, N.G. 2004, Astron. Astrophys. 421, 1131-1142; DOI: 10.1051/0004-6361:20040319

5. Ikhsanov, N.R. and Beskrovnaya, N.G. 2012, Astronomy Reports, 56, No. 8, 595-608;

DOI: 10.1134/S1063772912070025

6. Beskrovnaya, N.G., and Ikhsanov, N.R. 2024, Astrophysical Bulletin, 79, No. 1, pp. 104-110;

DOI: 10.1134/S1990341323600254

7. Beskrovnaya, N.G., Ikhsanov, N.R. 2025, Moscow University Physics Bulletin, 80, Suppl. 1, pp. S221-S223; DOI: 10.3103/S0027134925701942

8. Ikhsanov, N.R. and Beskrovnaya, N.G. 2025, Publications of the Pulkovo Observatory, 238, pp. 51-59; DOI:10.31725/0367-7966-2025-238-51-59

CV：Nazar Ikhsanov is the Director of the Central Astronomical Observatory of the Russian Academy of Sciences at Pulkovo (Pulkovo Observatory, Saint-Petersburg, Russia). MS (the Leningrad State University in 1986) and PhD (the Pulkovo Observatory in 1989). Career milestones: an Alexander von Humboldt Fellow at the Ludwig-Maximilian University  (Munich, Germany) and at the Max Planck Institute for Radioastronomy (Bonn, Germany); a Research Fellow at the Korea Astronomy and Space Science Institute (Daejeon, South Korea); Maria Curie Fellow at the Institute of Astronomy of the University of Cambridge (Cambridge, UK); NPP Program Senior Fellow at the Marshal Space Flight Center (Huntsville, AL, US). In 2011-2016 is a Head of the Stellar Evolution Dept. of Pulkovo Observatory and a Professor of Astronomy of the Saint-Petersburg State University. From 2016 is the Director of Pulkovo Observatory. Main topics of research are magneto-rotational evolution of degenerate stars, accretion in close binaries and AGNs and flaring activity of astrophysical objects.