arXiv subjects

R. Neuhäuser

Publications and source records attributed to R. Neuhäuser.

At least 19 recordsLinked to original sources

arXiv2025

Challenging historical novae: AT Cnc (1645), Te-11 (483), and M22 (BC 48) revisited

Connections between novae with shells and historical observations are crucial for astrophysical understanding of long-term evolution of shells and cataclysmic variables. Three of five previously considered links are revisited here: extended features in M22 in BC48, Te-11 in 483, and AT Cnc in 1645. We aim to develop a procedure to check whether these links are credible. Literal translations of the Chinese texts, historically based arguments, and close readings are combined with astrophysics, (peak brightness, decay time estimate, shell age expansion model calculation, etc.). (a) Nandou's second star, near which the BC48 `guest star' was reported, is identified as tau Sgr, not lambda Sgr, far from the M22 location. A nova in M22 would peak at only m=6.4 \pm 1.4 mag, and thus a description as a `blue-white' `melon' does not fit; it was likely a comet. (b) The imprecise position (`Shen['s] east') of the `guest star' in 483, its extended (dipper-like) radiance, and the context speak for a bolide. Considering the new (larger) Gaia distance and small extinction towards Te-11 (outside a cloud), its bi-polar morphology and current expansion velocity point to a planetary nebula; as a nova, the shell expansion age is 1100-2000 yr from detailed supersonic expansion calculations. (c) Most certainly, Mars was meant when the source for 1645 reported `a large star entered Yugui'; the verb implies motion. AT Cnc lies neither in Yugui's asterism box nor in the eponymous lunar mansion range. The fluid drag expansion age of AT Cancri's ejecta is 128-631 yr. All three exact ages are unsubstantiated. True novae or nova shells can be connected to historical records only if the position and object type are plausible. Duration, brightness (light curve), and color (evolution) should fit and could provide more astrophysical insight ...

astro-ph.SR↗

arXiv2025

Massive runaway star HD 254577: the pre-supernova binary companion to the progenitor of the supernova remnant IC 443

The secondaries of the massive binary systems can be found as runaway stars after being ejected due to the supernova (SN) of the more massive component. We search for such stars inside the supernova remnants (SNRs), where a recent SN is guaranteed to have happened. In this paper, we present the massive runaway star HD~254577 as the pre-supernova binary companion to the progenitor of the supernova remnant IC~443 and the neutron star (NS) CXOU~J61705.3$+$222127. We performed spectroscopic observations of the runaway star and specified its atmospheric parameters. Together with the precise \textit{Gaia} DR3 astrometry and photometry, we identified the possible birth origin of the runaway star, and by isochrone fitting, we determined the progenitor mass. From the \textit{Gaia} DR3 proper motions, we specified the possible explosion sites and calculated the neutron star (NS) velocity. HD~254577 is a hot and evolved star with an effective temperature of $24000\pm1000$ K (B0.5II) and a surface gravity of $\log({g~\rm[cm/s^2]})=2.75\pm0.25$. It is probably a single star with a peculiar 3-D velocity of $31.3^{+1.2}_{-0.9}$ km~s$^{-1}$, lying at a heliocentric distance of $1701^{+55}_{-54}$ pc. The cometary tail of the NS implies that it is moving away from the same site as the runaway star. From the flight trajectories, we calculated that the NS has typical pulsar velocities such as $254-539$ km~s$^{-1}$ at a distance of $1.7$ kpc for $10-20$ kyr ages. Together with the blue-only shifted interstellar medium lines on its spectrum, HD~254577 must be the pre-supernova binary companion to the progenitor of IC~443. By identifying the pre-supernova companion and the possible parent cluster, we showed that the progenitor zero-age main sequence mass is high: $31-64$ M$_\odot$. We also discuss the expansion dynamics of the SNR due to the highly off-centered explosion site.

astro-ph.SR↗

arXiv2025

Radial Velocity Monitoring and Analysis of Gaia Astrometry of Selected Intermediate Mass Stars to Constrain Their Multiplicity Status

We present new radial velocity measurements of 13 selected intermediate mass stars (2 - 6 M$_\odot$). The measurements were performed between 29 April and 6 September 2024 at the University Observatory Jena using the échelle spectrograph FLECHAS. The radial velocity of eight stars was found to be constant during our spectroscopic monitoring, namely: 17 Dra A, HD 148374, HD 169487 A, 57 Cnc, $γ$ And, HD 11031, $κ$ And, and $λ$ Cas. In contrast, the radial velocity of five stars showed significant variability throughout or spectroscopic observation, namely: 7 CrB A, 7 CrB B, HD 214007, $ι$ Her, and HD 201433 A. In all these cases, Keplerian orbital solutions were fitted to the observational data and the orbital elements of these spectroscopic binary systems were determined. In addition, we searched for wide companions of our targets using the third data release from ESA's Gaia mission, in order to determine the multiplicity status of these stars and contribute to the census of bright, nearby multiple stars.

astro-ph.SR↗

arXiv2025

New Arabic records from Cairo on supernovae 1181 and 1006

The remnant of the historical supernova SN 1181 is under discussion: While the previously suggested G130.7+3.1 (3C58) appears too old (3000-5000 yr), the unusual star IRAS 00500+6713 with a surrounding nebula (Pa-30) has an expansion age not inconsistent with a SN Iax explosion in AD 1181 under the assumption that neither acceleration nor deceleration occurred. Previously, only reports from China and Japan were known, pointing to an event near the northern circumpolar region. Any further reports from other cultures can therefore be highly relevant. We present here an Arabic poem in praise of Saladin by the contemporaneous author Ibn Sanā' al-Mulk (Cairo, Egypt). We re-date its composition to between Dec 1181 and May 1182. It contains a new bright star, which can be identified as SN 1181. The poem also provides new and independent information on the object type (called `najm' for `star'), location on sky (in or near the Arabic constellation al-Kaff al-Khabīb, lit. the henna-dyed hand (five bright stars in Cassiopeia), and brightness (brighter than alpha Cas, 2.25 mag). In addition, we present another Arabic text on SN 1006, also from Cairo, by the historian al-Maqrīzī, probably based on the contemporaneous al-Musabbihī

astro-ph.SR↗

arXiv2024

The Mira discovery problem -- Observations by David Fabricius in 1596 and 1609 (and by others before?): Positional accuracy, brightness, color index, and period

The pulsating variable star Mira (omikron Ceti) was observed by David Fabricius (Frisia) in 1596 and 1609. We review suggested previous detections (e.g. China, Hipparchos). We analyze all Mira records from Fabricius in their historical context. Fabricius measured the separation of Mira to other stars to \pm 1.6-1.7'. From his texts, we derive a brightness (slightly brighter than Hamal) of ca. 1.9 \pm 0.1 mag and a color index B-V \simeq 1.3-1.4 mag (`like Mars') for 1596 Aug 3 (jul.). Mira started to fainten 19 days later and was observed until mid/late Oct. We show why such a red star cannot be followed by the naked eye until ca. 6 mag: For Mira's color at disappearance and altitude from Frisia, the limit is reduced by ca. 1.0 mag. Since Fabricius connected the Mira brightening with the close-by prograde Jupiter, he re-detected it only 12 years later, probably shortly before a relatively bright maximum - discoveries are strongly affected by biases. A Mira period of 330.2 days is consistent with both the oldest data (from Fabricius 1596 to Hevelius 1660) and the most current data (VSX 2004-2023), so that we see no evidence for secular period or phase shifts. (We also present Fabricius' observations of P Cygni in 1602.)

astro-ph.SR↗

arXiv2022

YETI follow-up observations of the T Tauri star CVSO30 with transit-like dips

The T Tauri star CVSO30, also known as PTFO8-8695, was studied intensively with ground based telescopes as well as with satellites over the last decade. It showed a variable light curve with additional repeating planetary transit-like dips every ~0.8h. However, these dimming events changed in depth and duration since their discovery and from autumn 2018 on, they were not even present or near the predicted observing times. As reason for the detected dips and their changes within the complex light curve, e.g. a disintegrating planet, a circumstellar dust clump, stellar spots, possible multiplicity and orbiting clouds at a Keplerian co-rotating radius were discussed and are still under debate. In this paper, we present additional optical monitoring of CVSO30 with the meter class telescopes of the Young Exoplanet Transit Initiative in Asia and Europe over the last seven years and characterize CVSO30 with the new Early Data Release 3 of the ESA Gaia Mission. As a result, we describe the evolution of the dimming events in the optical wavelength range since 2014 and present explanatory approaches for the observed variabilities. We conclude that orbiting clouds of gas at a Keplerian co-rotating radius are the most promising scenario to explain most changes in CVSO30's light curve.

astro-ph.EP↗

arXiv2022

The origin of the high-mass X-ray binary 4U 2206+54/BD +53 2790

Based on the Gaia EDR3 astrometric parameters and our new systemic radial velocity of the high-mass X-ray binary 4U 2206+54/BD+53 2790, we studied the trace back motion of the system and propose that it originated in the subgroup of the Cepheus OB1 association (Age~4-10 Myr) with its brightest star BD+53 2820 (B0V; L~$10^{4.7}$L$_\odot$). The kinematic age of 4U 2206+54 is about 2.8$\pm$0.4 Myr, it is at a distance of 3.1-3.3 kpc and has a space velocity of 75-100 km/s with respect to this member star (BD+53 2820) of the Cep OB1 association. This runaway velocity indicates that the progenitor of the neutron star hosted by 4U 2206+54 lost about 4-9 $M_{\odot}$ during the supernova explosion and the latter one received a kick velocity of at least 200-350 km/s. Since the high-mass X-ray binary 4U 2206+54/BD+53 2790 was born as a member of a subgroup of Cep OB1, the initially most massive star in the system terminated its evolution within ~7-9 Myr, corresponding to an initial mass >= 32$M_{\odot}$.

astro-ph.SR↗

arXiv2021

Identification of additional young nearby runaway stars based on Gaia data release 2 observations and the lithium test

Runaway stars are characterised by their remarkably high space velocities, and the study of their formation mechanisms has attracted considerable interest. Young, nearby runaway stars are the most favorable for identifying their place of origin, and for searching for possible associated objects such as neutron stars. Usually the research field of runaway stars focuses on O- and B-type stars, because these objects are better detectable at larger distances than late-type stars. Early-type runaway stars have the advantage, that they evolve faster and can therefore better be confirmed to be young. In contrast to this, the catalogue of young runaway stars within 3 kpc by Tetzlaff, Neuhäuser, & Hohle (2011) contains also stars of spectral type A and later. The objects in this catalogue were originally classified as young ($\le 50$ Myr) runaway stars by using Hipparcos data to estimate the ages from their location in the Hertzsprung-Russell diagram and evolutionary models. In this article, we redetermine and/or constrain their ages not only by using the more precise second data release of the Gaia mission, but also by measuring the equivalent width of the lithium (6708 $\unicode{xC5}$) line, which is a youth indicator. Therefore, we searched for lithium absorption in the spectra of 51 target stars, taken at the University Observatory Jena between March and September 2020 with the Échelle spectrograph FLECHAS, and within additional TRES-spectra from the Fred L. Whipple Observatory. The main part of this campaign with its 308 reduced spectra, accessible at VizieR, was already published. In this work, which is the continuation and completion of the in 2015 initiated observing campaign, we found three additional young runaway star candidates.

astro-ph.SR↗

arXiv2021

Critical comments on publications by S. Hoffmann and N. Vogt on historical novae/supernovae and their candidates

We critically discuss recent articles by S. Hoffmann and N. Vogt on historical novae and supernovae (SNe) as well as their list of `24 most promising events' `with rather high probability to be a nova' (Hoffmann et al. 2020). Their alleged positional accuracy of previously suggested historical nova/SN records is based on inhomogeneous datasets (Vogt et al. 2019), but then used for the nova search in Hoffmann et al. (2020). Their claim that previously only `point coordinates' for nova/SN candidates were published, is fabricated. Their estimate of expected nova detection rates is off by a factor of 10 due to miscalculation. They accept counterparts down to 4 to 7 mag at peak, which is against the consensus for the typical limit of naked-eye discovery. When they discuss previously suggested identifications of historical novae, which they all doubt, they do not present new facts (Hoffmann 2019). Their catalog of `24 most promising events' for novae (Hoffmann et al. 2020) neglects important recent literature (e.g. Pankenier et al. 2008 and Stephenson and Green 2009), the claimed methods are not followed, etc. At least half of their short-list candidates were and are to be considered comets. For many of the others, duration of more than one night and/or a precise position is missing and/or the sources were treated mistakenly. Two highlights, a fabricated SN AD 667/668 and a presumable recurrent nova in AD 891, are already rejected in detail in Neuhaeuser et al. (2021); in both cases, all evidence speaks in favor of comets. There remains only one reliable case, where close to one (possible) historically reported position, a nova shell was already found (AD 1437, Shara et al. 2017). Follow-up observations cannot be recommended.

astro-ph.SR↗

arXiv2021

Orbit determination just from historical observations? Test case: The comet of AD 760 is identified as 1P/Halley

Recent advances in techniques of critical close reading of historical texts can now be applied to records of pre-telescopic celestial observations - allowing significant progress for analyzing and solving orbits of past comets: we exemplify our method by solving the orbit of the comet in AD 760 only with historical observations and then identify it with 1P/Halley. A detailed eyewitness record with drawing of a comet in AD 760 in the Syriac Chronicle of Zuqnin (finished AD 775/6) was not yet included in the study of its orbit - the Chinese reports alone do not yield a sufficient number of dated positions. We analyze the Syriac and Chinese sources with critical methods for quantitative astronomical usage, we also consider a few further records from the Mediterranean and West Asian area. With our conservatively derived dated positions we can determine the best fitting Keplerian orbital solution by least squares fitting yielding the orbital elements; the parameter ranges for non-periodic solutions and highly eccentric periodic solutions are consistent with each other. The allowed parameter ranges for perihelion distance and inclination are sufficiently small to identify the comet with 1P/Halley. Although 1P/Halley is the only comet, where the telescopic orbit is credibly linked to pre-telescopic returns, e.g. to AD 760, our identification confirms claims from extrapolating telescopic observations backward in time - here independently based on historical data. In particular, we obtained a precise perihelion time (760 May 19.1 \pm 1.7). The inferior conjunction between comet and Sun as on the previously published orbit (760 May 31.9) is shifted by about one day compared to our new orbit (June 1.8), only the new one is consistent with the last observation (June 1.0) before conjunction as reported in the Chronicle of Zuqnin. We also study the comet's brightness evolution ...

astro-ph.EP↗

arXiv2021

A search for runaway stars in twelve Galactic supernova remnants

Runaway stars can result from core-collapse supernovae in multiple stellar systems. If the supernova disrupts the system, the companion gets ejected with its former orbital velocity. A clear identification of a runaway star can yield the time and place of the explosion as well as orbital parameters of the pre-supernova binary system. Previous searches have mostly considered O- and B-type stars as runaway stars because they are always young in absolute terms (not much older than the lifetime of the progenitor) and can be detected up to larger distances. We present here a search for runaway stars of all spectral types. For late-type stars, a young age can be inferred from the lithium test. We used Gaia data to identify and characterise runaway star candidates in nearby supernova remnants, obtained spectra of 39 stars with UVES at the VLT and HDS at the Subaru telescope and found a significant amount of lithium in the spectra of six dwarf stars. We present the spectral analysis, including measurements of radial velocities, atmospheric parameters and lithium abundances. Then we estimate the ages of our targets from the Hertzsprung-Russell diagram and with the lithium test, present a selection of promising runaway star candidates and draw constraints on the number of ejected runaway stars compared to model expectations.

astro-ph.SR↗

arXiv2020

Identification of young nearby runaway stars based on Gaia data and the lithium test

Young nearby runaway stars are suitable to search for their place of origin and possibly associated objects, for example neutron stars. Tetzlaff, Neuhäuser & Hohle (2011) selected young ($\le 50$ Myr) runaway star candidates from Hipparcos, for which they had estimated the ages from the location in the Hertzsprung-Russell diagram and evolutionary models. Here, we redetermine or constrain their young ages more precisely not only by using the new Gaia DR2 data, but also by measuring lithium, which is a youth indicator. For 308 stars, we took spectra to search for the strong resonance doublet of the lithium-7 isotope at 6708 $\unicode{xC5}$. The spectra were taken with the Échelle spectrograph FLECHAS at the University Observatory Jena between February 2015 and June 2018 and with TRES between April 2011 and June 2017 at the Fred L. Whipple Observatory. We found 208 stars with significant occurrence of lithium in their spectra, and five possess a possible age younger or about 50 Myr. Three of these targets are even closer than GJ 182, the nearest known runaway star at about 24 pc. Theses stars are young runaway stars suitable for further investigation of their origin from either a dynamical or supernova ejection.

astro-ph.SR↗

arXiv2019

Spectroscopic characterization of nine binary star systems as well as HIP107136 and HIP107533

We present the results of our 2nd radial velocity monitoring campaign, carried out with the Échelle spectrograph FLECHAS at the University Observatory Jena in the course of the Großschwabhausen binary survey between December 2016 and June 2018. The aim of this project is to obtain precise radial velocity measurements for spectroscopic binary stars in order to redetermine, verify, improve and constrain their Keplerian orbital solutions. In this paper we describe the observations, data reduction and analysis and present the results of this project. In total, we have taken 721 RV measurements of 11 stars and derived well determined orbital solutions for 9 systems (7 single-, and 2 double-lined spectroscopic binaries) with periods in the range between 2 and 70 days. In addition, we could rule out the orbital solutions for the previously classified spectroscopic binary systems HIP107136 and HIP107533, whose radial velocities are found to be constant on the km/s-level over a span of time of more than 500 days. In the case of HIP2225 a significant change of its systematic velocity is detected between our individual observing epochs, indicating the presence of an additional companion, which is located on a wider orbit in this system.

astro-ph.SR↗

arXiv2019

Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei

UX Orionis stars (UXors) are Herbig Ae/Be or T Tauri stars exhibiting sporadic occultation of stellar light by circumstellar dust. GM\,Cephei is such a UXor in the young ($\sim4$~Myr) open cluster Trumpler\,37, showing prominent infrared excess, emission-line spectra, and flare activity. Our photometric monitoring (2008--2018) detects (1)~an $\sim$3.43~day period, likely arising from rotational modulation by surface starspots, (2)~sporadic brightening on time scales of days due to accretion, (3)~irregular minor flux drops due to circumstellar dust extinction, and (4)~major flux drops, each lasting for a couple of months with a recurrence time, though not exactly periodic, of about two years. The star experiences normal reddening by large grains, i.e., redder when dimmer, but exhibits an unusual "blueing" phenomenon in that the star turns blue near brightness minima. The maximum extinction during relatively short (lasting $\leq 50$~days) events, is proportional to the duration, a consequence of varying clump sizes. For longer events, the extinction is independent of duration, suggestive of a transverse string distribution of clumps. Polarization monitoring indicates an optical polarization varying $\sim3\%$--8$\%$, with the level anticorrelated with the slow brightness change. Temporal variation of the unpolarized and polarized light sets constraints on the size and orbital distance of the circumstellar clumps in the interplay with the young star and scattering envelope. These transiting clumps are edge-on manifestations of the ring- or spiral-like structures found recently in young stars with imaging in infrared of scattered light, or in submillimeter of thermalized dust emission.

astro-ph.SR↗

arXiv2018

Search for young transiting exoplanets within YETI project

The Young Exoplanet Transit Initiative (YETI) is a project focused on the photometric monitoring of stellar open clusters in order to find new young transiting exoplanets, eclipsing binaries and study other variability phenomena. Here, we present the status of the initiative and plans for future photometric campaigns of three open clusters younger than 50 Myr: NGC 869, NGC 884 and IC 4665, by using the world-wide one meter-class telescope network. Based on the experience gained by several astronomical observatories included in this network, dedicated numerical algorithms and recent results obtained during the first observing campaigns, we expect to confirm several young transiting objects: low-mass stars, brown dwarfs and exoplanets. The photometric precision given for a typical telescope used in this project, allows for transit detection of Jupiter-size planets at close-in orbits with periods up to ~30 days and also hundreds of new various variable stars.

astro-ph.EP↗

arXiv2018

Reconstructed sunspot positions in the Maunder Minimum based on the correspondence of Gottfried Kirch

We present reconstructed sunspot positions based on observations reported in letters between Gottfried Kirch and other contemporary astronomers from AD 1680 to 1709, i.e. in the last decades of the Maunder Minimum. The letters were compiled and edited by Herbst (2006). The letters (and observations) from Kirch are mostly by Gottfried Kirch, but some also by his 2nd wife Maria M. Kirch (married 1692) and their son Christfried Kirch (born 1694). Using excerpts from the letters, some with drawings, we found some 35 sunspot groups (often for several days in a row or with interruptions) by Kirch and/or his letter partners (in three cases, only the month is given: 1704 Jan, Feb, 1707 Mar, otherwise always the exact dates) - usually one group at a time. We also found 17 explicit spotless days, several of them new (previously without any known observations). We could constrain the heliographic latitude by Bayesian inference for 19 sunspot groups - five of them completely new (one group 1680 May 20-22 from Kirch and Ihle, one to two groups 1680 Jun 15-23 for Kirch, one group 1684 May 6 from Ihle, and one group 1688 Dec 14-15 from Kirch), while the others mostly agree (within 2sigma) with previously published values for those dates by others. With these data, we then amend the butterfly diagram for the Maunder Minimum. By comparison of our data with the sunspot group catalog in Hoyt & Schatten (1998), we noticed a number of discrepancies, e.g. that dates for British observers in the Maunder Minimum (Flamsteed, Caswell, Derham, Stannyan, Gray, and Sharp) as listed in Hoyt & Schatten (1998) are their original Julian dates, not converted to the Gregorian calendar (10-11 day offset in Hoyt & Schatten). Most of these modifications also apply to the modified sunspot group catalog in Vaquero et al. (2016). We also present two aurorae observed by the Kirchs in 1707 and 1716.

physics.hist-ph↗

arXiv2018

The Radial and Rotational Velocity of $ζ$ Ophiuchi

We present the results of our spectroscopic monitoring campaign of $ζ$ Oph, carried out at the University observatory Jena with the spectrograph FLECHAS between July 2015 and September 2016. The main aim of the project is to determine the radial velocity of the star precisely, as a wide range of radial velocity measurements of $ζ$ Oph are given in the literature. Beside the proper motion and parallax, the radial velocity is an important input parameter for the calculation of the space motion of the star. $ζ$ Oph is considered to be a runaway star and potential former companion of the progenitor star of the pulsar PSRJ1932+1059, which both may have been located in a binary system and were then released during a supernova explosion about 1 Myr ago in the Upper Scorpius OB association. For the calculation that the pulsar and $ζ$ Oph could have been at the same place, a radial velocity of $-$9.0 km/s for $ζ$ Oph was used in the literature. By analysing the hydrogen and helium lines in 48 FLECHAS spectra, we determined the radial velocity of $ζ$ Oph to be 12.2$\pm$3.3 km/s and the projected rotational velocity to 432$\pm$16 km/s with no indication for variability.

astro-ph.SR↗

arXiv2017

Radial velocity measurements and orbit determination of eight single-lined spectroscopic binary systems

Since early 2015 a new radial velocity monitoring campaign is going on at the University Observatory Jena. The aim of this project is to obtain current radial velocity measurements of selected single-lined spectroscopic binary systems, to redetermine and/or constrain their orbital solutions. In this paper we characterize the properties of the target sample of the project, describe the spectroscopic observations, the data-reduction and analysis and present the first results of the project, taken with the fiber-linked astronomical spectrograph FLECHAS. We present 391 radial velocity measurements of eight spectroscopic binaries, which were taken within an epoch difference of 1.6 years. These radial velocities were used to determine the spectroscopic orbital elements of the observed binary systems, which exhibit orbital periods in the range between nearly one up to several dozens of days. We could constrain the orbital solutions of seven of these binary systems, and redetermine the orbital solution of phi Dra, whose orbit exhibits >4 times longer orbital period and is more eccentric than given in the 9th Catalogue of Spectroscopic Binary Orbits.

astro-ph.SR↗