astronomers discover new ultracompact am cvn

Astronomers Discover New Ultracopact AM CVn Binary with Rare Outbursts-TCP J07222683+6220548 Revealed

Introduction to the New Ultracompact binary System

Astronomers from across the world have detected a fresh ultracompact binary system of the AM CVn variety, which displays occasional outbursts. Full details of TCP J07222683+6220548 were released on 27 May in a paper on the arXiv preprint server.

Understanding Cataclysmic Variables (CVs)

Cataclysmic Variables (CVs) are binary systems comprising a white dwarf and an ordinary stellar companion, from which the former draws in material. Their luminosity has been observed to surge erratically before settling back into a dormant phase.

The AM CVn Class

The AM CVn Class—taking its name from AM Canum Venaticorum—comprises a rare breed of cataclysmic variable. Here, a white dwarf in helium-dominated, hydrogen-scarce material from a closely orbiting companion. Their orbits are notably brief, lasting between five minutes and around sixty minutes.

Discovery of the New AM CVn System

A team of astronomers headed by Alexander Tarasenkov of the Russion Academy of Sciences has announced the discovery of anew AM CVn system, observed on 20 January 2025 during the New Milky Way (NMW) survey. The object exhibited a seven-day outburst, followed by several episodes of rebrightening from January through March. Subsequent observation confirmed its classification as an AM CVn.

Characteristics of TCP J07222683+6220548 (J0722)

Location and Spectral Profile

The study notes that TCP J07222683+6220548, referred to as J0722, lies at an approximate distance of 1,874 light years. Its spectral profile features a blue continuum with distinct broad helium absorption lines, absent of Balmer hydrogen lines—hallmarks of an AM CVn system undergoing outburst.

Outburst Brightness and Accretion Disc Orientation

J0722's outburst reached a peak brightness of 12.45 magnitude, ranking it among the most luminous AM CVn events recorded to date. The absolute magnitude, measured at 3.4 implies the accretion disc is likely being observed nearly face-on, enhancing its perceived luminosity.

Observations of Photometric Variations

Periodic Modulation and Positive Superhumps

Researchers observed a recurring modulation in J0722's light curve, with a period of roughly 46.87 minutes. This variation is believed to signify positive superhumps, a photometric feature common to certain dwarf novae and similar systems.

Superhums During Re-brightening

The scientists observed that superhumps became distinctly apparent during J0722's first re-brightening phase, occurring between days 18 and 24 post-outburst. They reported no significant variation in the superhump period.

Summary and Future Directions

summarizing their results, the team noted the strong similarity between J0722's outburst pattern and those of long-period AM CVn binaries, reinforcing the call for further observational campaigns.

Importance of Follow-Up Monitoring

According to the scientists, AM CVn systems without thorough post-outburst monitoring could remain hidden within the latest catalogue of cataclysmic variables.

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