arXiv subjects

Susanne M Hoffmann

Publications and source records attributed to Susanne M Hoffmann.

11 recordsLinked to original sources

arXiv2025

Was there a (super)nova in 1408?

The 1408 CE "guest star" recorded in Chinese historical texts presents a compelling case for identifying a historical stellar transient. While previous studies debated its nature as a meteor, comet, or nova, we re-evaluate the event using original Ming Dynasty records, including a newly found memorial from the imperial court. The object, described as stationary for over ten days, yellow, and luminous (resembling a "Zhou Bo virtue star"), is inconsistent with cometary behavior. Positional analysis locates it near the Niandao asterism (modern Cygnus-Vulpecula region) within the Milky Way, with a derived brightness of -4 to 0 mag. Light-curve stability over ten days and color descriptions align with a slow nova or a supernova. We cross-correlated the historical coordinates with modern catalogs and found a few possible counterparts. Among them, CK Vul - a luminous red nova remnant from 1670 to 1672 - is the most interesting candidate. Could its progenitor system have experienced a precursor classical nova eruption circa 1408 prior to the merger ~200 years later? We also examine cataclysmic variables and planetary nebulae within the 100 square-degree search field, though most lack sufficient brightness or age characteristics. This study emphasizes the value of integrating detailed historical records with contemporary astrophysical data to resolve long-standing controversies over ancient transients. The 1408 event likely represents a rare, well-documented nova, offering insights into pre-modern stellar phenomena and their modern counterparts.

astro-ph.SR↗

arXiv2024

Identification of Z Cam's Historical Counterpart: The Quest for an Ancient Nova

In recent astronomical discussions, attempts have been made to link the known dwarf nova Z Cam to historical celestial events, particularly the "guest star" phenomenon reported in China in 77 BCE. Despite other suggestions and the problems with regard to the location of the event in 77 BCE, its identification with Z Cam is used in the Variable Star IndeX (VSX) of the AAVSO and in several research papers that aim to derive knowledge on the evolution of cataclysmic variables. Through the reconstruction of the super-constellation of the Purple Palace in the Han Dynasty, we found that Z Cam is actually located outside this enclosure, contradicting the records of the 77 BCE guest star being "within the Purple Palace". With newly found text versions of the guest star in 77 BCE, we narrowed down the position given therein. Combined with a new analysis of accompanying divination text leads to the conclusion that this guest star was actually a comet. Finally, through meticulous examination and comparison, we conclude that the guest star of 369 CE appears the most plausible candidate for Z Cam's historical counterpart, aligning with both textual evidence and modern astronomical observations.

astro-ph.IM↗

arXiv2021

A Search for recurrent novae among Far Eastern guest stars

According to recent theoretical studies, classical novae are expected to erupt every ~$10^5$ years, while the recurrence time scale of modern recurrent novae (N_r) stars ranges from 10 to ~100 years. To bridge this huge gap in our knowledge (three orders of magnitude in time scales), it appears attractive to consider historical data: In Far Eastern sources, we searched for brightening events at different epochs but similar positions that possibly refer to recurrent nova eruptions. Probing a sample of ~185 Asian observations from ~500 BCE to 1700 CE, we present a method to systematically filter possible events. The result are a few search fields with between 2 and 5 flare ups and typical cadences between $10^2$ and $10^3$ years. For most of our recurrence candidates, we found possible counterparts among known cataclysmic variables in the corresponding search areas. This work is based on an interdisciplinary approach, combining methods from digital humanities and computational astrophysics when applying our previously developed methods in searches for classical novae among Far Eastern guest stars. A first and rather preliminary comparison of (possible) historical and (well known) modern recurrent novae reveals first tentative hints on some of their properties, stimulating further studies in this direction.

astro-ph.SR↗

arXiv2021

The Simulated Sky: Stellarium for Cultural Astronomy Research

For centuries, the rich nocturnal environment of the starry sky could be modelled only by analogue tools such as paper planispheres, atlases, globes and numerical tables. The immersive sky simulator of the twentieth century, the optomechanical planetarium, provided new ways for representing and teaching about the sky, but the high construction and running costs meant that they have not become common. However, in recent decades, "desktop planetarium programs" running on personal computers have gained wide attention. Modern incarnations are immensely versatile tools, mostly targeted towards the community of amateur astronomers and for knowledge transfer in transdisciplinary research. Cultural astronomers also value the possibilities they give of simulating the skies of past times or other cultures. With this paper, we provide an extended presentation of the open-source project Stellarium, which in the last few years has been enriched with capabilities for cultural astronomy research not found in similar, commercial alternatives.

astro-ph.IM↗

arXiv2020

Accuracy of magnitudes in pre-telescopic star catalogues

Historical star magnitudes from catalogues by Ptolemy (137 AD), as-Sufi (964) and Tycho Brahe (1602/27) are converted to the Johnson V-mag scale and compared to modern day values from the HIPPARCOS catalogue. The deviations (or "errors") are tested for dependencies on three different observational influences. The relation between historical and modern magnitudes is found to be linear in all three catalogues as it had previously been shown for the Almagest data by Hearnshaw (1999). A slight dependency on the colour index (B-V) is shown throughout the data sets and as-Sufi's as well as Brahe's data also give fainter values for stars of lower culmination height (indicating extinction). In all three catalogues, a star's estimated magnitude is influenced by the brightness of its immediate surroundings. After correction for the three effects, the remaining variance within the magnitude errors can be considered as approximate accuracy of the pre-telescopic magnitude estimates. The final converted and corrected magnitudes are available via the Vizier catalogue access tool (Ochsenbein, Bauer, & Marcout, 2000).

astro-ph.IM↗

arXiv2020

A Search for the modern counterparts of the Far Eastern guest stars 369 CE, 386 CE, and 393 CE

In this study, we apply our previously developed method to investigate ancient transient sightings in order to derive consequences for modern astrophysical problems.We present case studies of three observations of so called 'guest stars' in the 4th century CE which lasted several months each. These three observations had been suggested and discussed as possible supernovae but slow novae are also viable alternatives. Our careful re-interpretation of the historical texts and the currently known objects in the given fields shed new light on this topic. In particular, for the two events in 386 and 393 CE we suggest possible supernova identifications, while in all three cases there are interesting candidates for past classical or recurrent nova eruptions among known cataclysmic variables (CVs) and/or symbiotic stars. The transient of 369, we suggest to explain as classical and possibly recurrent nova instead of a supernova. The most plausible candidates are BZ Cam, a CV with a possible nova shell, or CQ Dra, a naked eye multiple system perhaps able to permit an overwhelmingly bright nova with day-time visibility.

astro-ph.HE↗

arXiv2020

The genesis of Hippachus' celestial globe

This paper summarises briefly and in English some of the results of the book Hoffmann: Hipparchs Himmelsglobus, Springer, 2017 that had to be written in German. The globe of Hipparchus is not preserved. For that reason, it has been a source of much speculation and scientific inquiry during the last few centuries. This study presents a new analysis of the data given in the commentary on Aratus' poem by Hipparchus, in comparison with other contemporary Babylonian and Greek astronomical data, as well as their predecessors in the first millennium and their successors up to Ptolemy. The result of all these studies are the following: i) although the data of Ptolemy and Hipparchus are undoubtedly correlated, it is certainly also wrong to accuse Ptolemy having simply copied and transformed it without correct citation; ii) although Hipparchus presumably observed most of his star catalogue with his own instruments, we cannot neglect Babylonian influences. Hipparchus was educated in Greek astronomy but, in his time, there are traces of Babylonian influences since at least two centuries. Since we are unable to definitely prove that Hipparchus used Babylonian data, we are not sure if there are direct Babylonian influences in his time or as a consequence of his education only. Finally, we present a virtual 3D-image showing what the globe of Hipparchus might have looked like.

physics.hist-ph↗

arXiv2020

Counterparts of Far Eastern Guest Stars: Novae, supernovae, or something else?

Historical observations of transients are crucial for studies of their long-term evolution. This paper forms part of a series of papers in which we develop methods for the analysis of ancient data of transient events and their usability in modern science. Prior research on this subject by other authors has focused on looking for historical supernovae and our earlier work focused on cataclysmic binaries as classical novae. In this study we consider planetary nebulae, symbiotic stars, supernova remnants and pulsars in the search fields of our test sample. We present the possibilities for these object types to flare up visually, give a global overview on their distribution and discuss the objects in our search fields individually. To summarise our results, we provide a table of the most likely identifications of the historical sightings in our test sample and outline our method in order to apply it to further historical records in future works. Highlights of our results include a re-interpretation of two separate sightings as one supernova observation from May 667 to June 668 CE, the remnant of which could possibly be SNR G160.9+02.6. We also suggest the recurrent nova U Sco as a candidate for the appearance observed between Scorpius and Ophiuchus in 891, which could point towards a long-term variability of eruption amplitudes. In addition, we find that the `shiny bright' sighting in 1431 can be linked to the symbiotic binary KT Eri, which erupted as a naked eye classical nova in 2009.

astro-ph.SR↗

arXiv2020

Cataclysmic variables as possible counterparts of ancient Far Eastern guest stars

Continuing our efforts to select possible classical nova candidates among Far Eastern guest stars and to identify them with modern cataclysmic variables (CVs), we present a search for counterparts in 24 promising areas of the sky corresponding to ancient observations between 204 BCE and 1690 CE. These areas have been derived by us in a previous paper. Based on physical entities of the CVs in our areas and reasonable magnitude limits compatible with the distribution of known eruption amplitudes of telescopic classical novae, we present a catalogue of a total of 80 CVs and related targets which could possibly have caused the historical sightings. This list could potentially be reduced by additionally discussing further information more vaguely given in the text. In some cases, we present a detailed discussion of the interpretation of ancient sources confronting them with properties of the brightest CVs in the field. In order to estimate whether this list is representative, we discuss the distribution of CV types in our catalogue of counterparts for the historical events. Compared to the entire sky, the surface density of most CV subtypes in our search fields reveals similar values, except for polars and intermediate polars, i. e. strongly magnetic CVs, for which a significant excess in our search fields was detected. Finally, we give an outlook towards future research in this topic, and add in an Appendix a complete atlas of the celestial maps of all 24 guest star events, displaying the search areas and locations of CVs within them.

astro-ph.SR↗

arXiv2019

A new approach to generate a catalogue of potential historical novae

Ancient Chinese, Korean and Vietnamese observers left us records of celestial sightings, the so-called `guest stars' dated up to $\sim2500$ years ago. Their identification with modern observable targets could open interesting insights into the long-term behavior of astronomical objects, as shown by the successful identification of 8 galactic supernovae (SNe). Here we evaluate the possibility to identify ancient classical novae with presently known cataclysmic variables (CVs). For this purpose, we have developed a method which reconsiders in detail positions and sizes of ancient asterisms, in order to define areas on the sky that should be used for a search of modern counterparts. These areas range from a few to several hundred square degrees, depending on the details given in ancient texts; they should replace the single coordinate values given by previous authors. Any appropriate target (CVs, X-ray binaries etc.) within these areas can be considered as a valid candidate for identification with the corresponding ancient event. Based on the original descriptions of several hundred old events, we selected those without movement and without a tail (to exclude comets) and which did not only visible within a certain hour (to exclude meteors). This way, we present a shortlist of 24 most promising events which could refer to classical nova eruptions. Our method is checked by applying it to the known SN identifications, leading to a margin of error between 0 and 4.5 degrees, meaning that some SN remnants lay exactly inside the areas given by the historical reports while in some other cases they are laying at considerable distances.

astro-ph.IM↗

arXiv2019

Which information can we derive from historical Far Eastern guest stars for modern research on novae and cataclysmic variables?

Recently, there have been several studies on the evolution of binary systems using historical data treated as facts in the chain of arguments. In this paper we discuss six case studies of modern dwarf novae with suggested historical counterpart from the historical point of view as well as the derived consequences for the physics of close binary systems (the dwarf novae Z Cam and AT Cnc, the nebula in M22, and the possible Nova 101, Nova 483, and Nova 1437). We consider the historical Far Eastern reports and after a careful re-reading of the text we map the given information on the sky. In some cases, the positions given in modern lists of classical nova-guest star-pairs turn out to be wrong, or they have to be considered highly approximate: The historical position, in most cases, should be transformed into areas at the celestial sphere and not into point coordinates. Based on the correct information we consider the consequences concerning the evolution of close binary systems. However, the result is that none of the cases of cataclysmic variables suggested to have a historical counterpart can be (fully) supported. As the identification of the historical record of observation with the CVs known today turns out to be always uncertain, a potential historical observation alone may not be relied on to draw conclusions on the evolution of binaries. The evolution scenarios should be derived from astrophysical observation and modelling only.

astro-ph.SR↗