VLBA observations reveal complex nature of classical novae

During an American Astronomical Society press conference held in Albuquerque, New Mexico, groundbreaking findings were presented regarding classical novae, which may have been previously misunderstood. A graduate researcher utilizing the National Radio Astronomy Observatory’s Very Long Baseline Array (VLBA) made a significant discovery that challenges the conventional view of these celestial objects. By studying V1674 Herculis, the fastest classical nova known, the researcher, Montana Williams, detected unexpected non-thermal emissions from the system. This revelation has profound implications and sheds light on the complex dynamics occurring within classical novae, disproving the notion that they are merely heat-induced explosions.

Classical novae have long been perceived as simple events primarily characterized by thermal energy release. However, recent observations conducted with the Fermi Large Area Telescope indicated that this traditional model was incomplete. Williams and the team were able to obtain highly detailed insights into one crucial aspect of classical novae complexity: non-thermal emissions. Such detections using Very Long Baseline Interferometry (VLBI) techniques, particularly in novae with dwarf companions like V1674Her, are exceedingly rare. In fact, there has been only one previous report of resolved radio synchrotron components in a similar detection, emphasizing the infrequency of these occurrences. The scarcity of such observations can be attributed, at least in part, to the presumed simplistic nature of classical novae.

This breakthrough in understanding classical novae challenges existing theories and opens up new avenues of research. It underscores the need to revise the prevailing notion of these events as straightforward explosions and prompts a reevaluation of the mechanisms at play within these celestial systems. The graduate researcher’s work with the VLBA and the unveiling of non-thermal emissions from V1674 Herculis heralds a significant paradigm shift in our comprehension of classical novae.

Scientists studying the classical nova V1674Her have confirmed the presence of non-thermal emissions. The nova, which was discovered in 2021, is the fastest classical nova on record. This side-by-side shows the difference in brightness over just four days. Credit: M. Williams/New Mexico Tech, B. Saxton (NRAO/AUI/NSF)

According to Williams, the ability to detect novae using Very Long Baseline Interferometry (VLBI) has only recently become feasible due to advancements in VLBI techniques. These improvements primarily involve enhancing instrument sensitivity and expanding the bandwidth, allowing for a greater range of recorded frequencies. Previously, classical novae were not considered optimal subjects for VLBI investigations due to prevailing theories that categorized them as simplistic events. However, recent multi-wavelength observations have revealed a more intricate scenario, dispelling the previous misconceptions and demonstrating the value of VLBI studies in unraveling the enigmatic nature of classical novae.

Given the scarcity of such observations, the team’s recent findings hold significant importance. They represent a crucial step forward in comprehending the concealed dynamics of classical novae and gaining insights into the underlying factors that trigger their explosive behavior. By shedding light on the hidden lives of these celestial phenomena, the team’s work paves the way for a deeper understanding of classical novae as complex and dynamic cosmic events.

V1674Her is a classical nova located in the constellation Hercules. Credit: IAU/Sky & Telescope

Williams explained that their research involved analyzing images from the VLBA and comparing them to observations obtained from other telescopes such as the Very Large Array (VLA), Fermi-LAT, Nu-Star, and NASA-Swift. This comprehensive approach allowed them to investigate the possible causes of the non-thermal emission and refine the existing simplistic model. The team is currently focused on determining whether the non-thermal energy arises from interactions between clumps of gas, resulting in shockwaves, or if there are other contributing factors at play.

V1674Her was an ideal candidate for study due to indications from previous Fermi-LAT and Nu-Star observations that suggested the presence of non-thermal emissions. Confirming or refuting these findings became a primary objective for the team. Moreover, Williams finds the system particularly captivating, describing it as “interesting” or even “cute.” This is attributed to its remarkably rapid evolution, unlike supernovae that result in the destruction of the host system. In the case of V1674Her, the host system remains almost entirely intact and unchanged after the explosion, making it a unique and intriguing object of study.

Williams further emphasized the dynamic nature of classical novae, highlighting that many astronomical sources exhibit minimal changes over long periods of time, spanning years or even centuries. However, V1674Her experienced an astonishing 10,000-fold increase in brightness within a single day, only to return to its normal state in approximately 100 days. This hyper-fast evolution, coupled with the potential for recurrent eruptions, offers researchers multiple opportunities to gain deeper insights into the mechanisms driving these events.

By delving into the mysteries of V1674Her and other classical novae, scientists hope to unravel the underlying causes and mechanisms governing their behavior, leading to a more comprehensive understanding of these captivating astronomical phenomena.

Source: National Radio Astronomy Observatory

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