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Neuhauser R.,Astrophysikalisches Institute und Universitats Sternwarte | Ehrig-Eggert C.,Astrophysikalisches Institute und Universitats Sternwarte | Kunitzsch P.,Astrophysikalisches Institute und Universitats Sternwarte
Astronomische Nachrichten | Year: 2017

We present here an Arabic report about supernova 1006 (SN 1006) written by the famous Persian scholar Ibn Sīnā (Lat. Avicenna, AD 980–1037), which has not been discussed in astronomical literature before. The short observational report about a new star is part of Ibn Sīnā's book called al-Shifā', a work on philosophy including physics, astronomy, and meteorology. We present the Arabic text and our English translation. After a detailed discussion of the dating of the observation, we show that the text specifies that the transient celestial object was stationary and/or tail-less (a star among the stars), that it remained for close to 3 months getting fainter and fainter until it disappeared, that it threw out sparks, that is, it was scintillating and very bright, and that the colour changed with time. The information content is consistent with the other Arabic and non-Arabic reports about SN 1006. Hence, it is quite clear that Ibn Sīnā refers to SN 1006 in his report, given as an example for transient celestial objects in a discussion of Aristotle's Meteorology. Given the wording and the description, for example, for the colour evolution, this report is independent of other reports known so far. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Olofsson J.,Max Planck Institute for Astronomy | Juhasz A.,Leiden University | Henning T.,Max Planck Institute for Astronomy | Mutschke H.,Astrophysikalisches Institute und Universitats Sternwarte | And 3 more authors.
Astronomy and Astrophysics | Year: 2012

Context. Debris disks trace remnant reservoirs of leftover planetesimals in planetary systems. In the past years, a handful of "warm" debris disks have been discovered in which emission in excess starts in the mid-infrared. An interesting subset of these warm debris disks shows emission features in mid-infrared spectra, which points towards the presence of μm-sized dust grains, with temperatures above hundreds K. Given the ages of the host stars, the presence of these small grains is puzzling, and raises questions about their origin and survival in time. Aims. This study focuses on determining the mineralogy of the dust around seven debris disks with evidence for warm dust, based on Spitzer/IRS spectroscopic data, to provide new insights into the origin of the dust grains. Methods. We developed and present a new radiative transfer code (Debra) dedicated to spectral energy distribution (SED) modeling of optically thin disks. The Debra code is designed such that it can simultaneously determine dust composition and disk properties. We used this code on the SEDs of seven warm debris disks, in combination with recent laboratory experiments on dust optical properties. Results. We find that most, if not all, debris disks in our sample are experiencing a transient phase, suggesting a production of small dust grains on relatively short timescales. Dust replenishment should be efficient on timescales of months for at least three sources. From a mineralogical point of view, we find that crystalline pyroxene grains (enstatite) have low abundances compared to crystalline olivine grains. The main result of our study is that we find evidence for Fe-rich crystalline olivine grains (Fe/[Mg + Fe] ∼ 0.2) for several debris disks. This finding contrasts with studies of gas-rich protoplanetary disks, where Fe-bearing crystalline grains are usually not observed. Conclusions. These Fe-rich olivine grains, and the overall differences between the mineralogy of dust in Classâ ‰ II disks compared to debris disks suggests that the transient crystalline dust in warm debris disk is of a new generation. We discuss possible crystallization routes to explain our results, and also comment on the mechanisms that may be responsible for the production of small dust grains. © 2012 ESO.

Neuhauser R.,Astrophysikalisches Institute und Universitats Sternwarte | Neuhauser D.L.,Schillbachstrasse 42
Astronomische Nachrichten | Year: 2015

A large variation in 14C around AD 775 has been considered to be caused by one or more solar super-flares within one year. We critically review all known aurora reports from Europe as well as the Near, Middle, and Far East from AD 731 to 825 and find 39 likely true aurorae plus four more potential aurorae and 24 other reports about halos, meteors, thunderstorms etc., which were previously misinterpreted as aurorae or misdated; we assign probabilities for all events according to five aurora criteria. We find very likely true aurorae in AD 743, 745, 762, 765, 772, 773, 793, 796, 807, and 817. There were two aurorae in the early 770s observed near Amida (now Diyarbaki{dotless}r in Turkey near the Turkish-Syrian border), which were not only red, but also green-yellow - being at a relatively low geomagnetic latitude, they indicate a relatively strong solar storm. However, it cannot be argued that those aurorae (geomagnetic latitude 43 to 50°, considering five different reconstructions of the geomagnetic pole) could be connected to one or more solar super-flares causing the 14C increase around AD 775: There are several reports about low- to mid-latitude aurorae at 32 to 44° geomagnetic latitude in China and Iraq; some of them were likely observed (quasi-)simultaneously in two of three areas (Europe, Byzantium/Arabia, East Asia), one lasted several nights, and some indicate a particularly strong geomagnetic storm (red colour and dynamics), namely in AD 745, 762, 793, 807, and 817 - always without 14C peaks. We use 39 likely true aurorae as well as historic reports about sunspots together with the radiocarbon content from tree rings to reconstruct the solar activity: From AD ∼733 to ∼823, we see at least nine Schwabe cycles; instead of one of those cycles, there could be two short, weak cycles - reflecting the rapid increase to a high 14C level since AD 775, which lies at the end of a strong cycle. In order to show the end of the dearth of naked-eye sunspots, we discuss two more Schwabe cycles until AD ∼844. The 14C record (from both Intcal and Miyake et al. 2013a) is anti-correlated to auroral and sunspot activity, as expected from solar wind modulation of cosmic rays which produce the radiocarbon. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Neuhauser R.,Astrophysikalisches Institute und Universitats Sternwarte | Neuhauser D.L.,Schillbachstrasse 42
Astronomische Nachrichten | Year: 2016

Hoyt & Schatten (1998) claim that Simon Marius would have observed the sun from 1617 Jun 7 to 1618 Dec 31 (Gregorian calendar) all days, except three short gaps in 1618, but would never have detected a sunspot – based on a quotation from Marius in Wolf (1857), but mis-interpreted by Hoyt & Schatten. Marius himself specified in early 1619 that for one and a half year.. rather few or more often no spots could be detected.. which was never observed before (Marius 1619). The generic statement by Marius can be interpreted such that the active day fraction was below 0.5 (but not zero) from fall 1617 to spring 1619 and that it was 1 before fall 1617 (since August 1611). Hoyt & Schatten cite Zinner (1952), who referred to Zinner (1942), where observing dates by Marius since 1611 are given but which were not used by Hoyt & Schatten. We present all relevant texts from Marius where he clearly stated that he observed many spots in different form on and since 1611 Aug 3 (Julian) = Aug 13 (Greg.) (on the first day together with Ahasverus Schmidnerus); 14 spots on 1612 May 30 (Julian) = Jun 9 (Greg.), which is consistent with drawings by Galilei and Jungius for that day, the latter is shown here for the first time; at least one spot on 1611 Oct 3 and/or 11 (Julian), i.e. Oct 13 and/or 21 (Greg.), when he changed his sunspot observing technique; he also mentioned that he has drawn sunspots for 1611 Nov 17 (Julian) = Nov 27 (Greg.); in addition to those clearly datable detections, there is evidence in the texts for regular observations. For all the information that can be compared to other observers, the data from Marius could be confirmed, so that his texts are highly credible. We also correct several shortcomings or apparent errors in the database by Hoyt & Schatten (1998) regarding 1612 (Harriot), 1615 (Saxonius, Tard´e), 1616 (Tard´e), 1617–1619 (Marius, Riccioli/Argoli), and Malapert (for 1618, 1620, and 1621). Furthermore, Schmidnerus, Cysat, David & Johann Fabricius, Tanner, Perovius, Argoli, and Wely are not mentioned as observers for 1611, 1612, 1618, 1620, and 1621 in Hoyt & Schatten. Marius and Schmidnerus are among the earliest datable telescopic sunspot observers (1611 Aug 3, Julian), namely after Harriot, the two Fabricius (father and son), Scheiner, and Cysat. Sunspots records by Malapert from 1618 to 1621 show that the last low-latitude spot was seen in Dec 1620, while the first high-latitude spots were noticed in June and Oct 1620, so that the Schwabe cycle turnover (minimum) took place around that time, which is also consistent with the sunspot trend mentioned by Marius and with naked-eye spots and likely true aurorae. We consider discrepancies in the Hoyt & Schatten (1998) systematics, we compile the active day fractions for the 1610s, and we critically discuss very recent publications on Marius which include the following Maunder Minimum. Our work should be seen as a call to go back to the historical sources. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim). Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Maciejewski G.,Astrophysikalisches Institute und Universitats Sternwarte | Maciejewski G.,Nicolaus Copernicus University | Seeliger M.,Astrophysikalisches Institute und Universitats Sternwarte | Adam Ch.,Astrophysikalisches Institute und Universitats Sternwarte | And 2 more authors.
Acta Astronomica | Year: 2011

Studies of transiting extrasolar planets provide unique opportunity to get to know the internal structure of those worlds. The transiting exoplanet XO-5 b was found to have an anomalously high Safronov number and surface gravity. Our aim was to refine parameters of this intriguing system and search for signs of transit timing variations. We gathered high-precision light curves for two transits of XO-5 b. Assuming three different limb darkening laws, we found the best-fitting model and redetermined parameters of the system, including planet-to-star radius ratio, impact parameter and central time of transits. Error estimates were derived by the prayer bead method and Monte Carlo simulations. Although system's parameters obtained by us were found to agree with previous studies within one sigma, the planet was found to be notable smaller with the radius of 1.03-0.05 +0.06 Jupiter radii. Our results confirm the high Safronov number and surface gravity of the planet. With two new mid-transit times, the ephemeris was refined to BJDTDB = (2454485.66842 ± 0.00028) + (4.1877537 ± 0.000017)E. No significant transit timing variation was detected.

Neuhauser D.L.,Schillbachstrasse 42 | Neuhauser R.,Astrophysikalisches Institute und Universitats Sternwarte
Astronomische Nachrichten | Year: 2015

The interpretation of the strong 14C variation around AD 775 as one (or several) solar super-flare(s) by, e.g., Usoskin et al. (2013) is based on alleged aurora sightings in the mid AD 770s in Europe: A red cross /crucifix in AD 773/4/6 from the Anglo-Saxon Chronicle, inflamed shields in AD 776 (both listed in the aurora catalogue of Link 1962), and riders on white horses in AD 773 (newly proposed as aurora in Usoskin et al. 2013), the two latter from the Royal Frankish Annals. We discuss the reports about these three sightings in detail here. We can show that all three can be interpreted convincingly as halo displays: The red cross or crucifix is formed by the horizontal arc and a vertical pillar of light (either with the Sun during sunset or with the moon after sunset); the inflamed shields and the riders on white horses were both two mock suns, especially the latter narrated in form of a Christian adaptation of the antique dioscuri motive. While the latter event took place early in AD 774 (dated AD 773 in Usoskin et al. 2013), the two other sightings have tobe dated AD 776, i.e. anyway too late for being in connection with a 14C rise that started before AD 775. We also sketch the ideological background of those sightings and there were many similar reports throughout that time. In addition, we present a small drawing of a lunar halo display with horizontal arc and vertical pillar forming a cross for shortly later, namely AD 806 June 4, the night of full moon, also from the Anglo-Saxon Chronicle we also show historic observations of halo phenomena (mock suns and crosses) from G. Kirch and Hevelius - and a modern photograph. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Neuhauser R.,Astrophysikalisches Institute und Universitats Sternwarte | Neuhauser D.L.,Schillbachstrasse 42
Astronomische Nachrichten | Year: 2015

The motivation for our study is the disputed cause for the strong variation of 14C around AD 775. Our method is to compare the 14C variation around AD 775 with other periods of strong variability. Our results are: (a) We see three periods, where 14C varied over 200 yr in a special way showing a certain pattern of strong secular variation: after a Grand Minimum with strongly increasing 14C, there is a series of strong short-term drop(s), rise(s), and again drop(s) within 60 yr, ending up to 200 yr after the start of the Grand Minimum. These three periods include the strong rises around BC 671, AD 775, and AD 1795. (b) We show with several solar activity proxies (radioisotopes, sunspots, and aurorae) for the AD 770s and 1790s that such intense rapid 14C increases can be explained by strong rapid decreases in solar activity and, hence, wind, so that the decrease in solar modulation potential leads to an increase in radioisotope production. (c) The strong rises around AD 775 and 1795 are due to three effects, (i) very strong activity in the previous cycles (i.e. very low 14C level), (ii) the declining phase of a very strong Schwabe cycle, and (iii) a phase of very weak activity after the strong 14C rise - very short and/or weak cycle(s) like the suddenly starting Dalton minimum. (d) Furthermore, we can show that the strong change at AD 1795 happened after a pair of two packages of four Schwabe cycles with certain hemispheric leadership (each package consists of two Gnevyshev-Ohl pairs, respectively two Hale-Babcock pairs). We show with several additional arguments that the rise around AD 775 was not that special. We conclude that such large, short-term rises in 14C (around BC 671, AD 775, and 1795) do not need to be explained by highly unlikely solar super-flares nor other rare events, but by extra-solar cosmic rays modulated due to solar activity variations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Maciejewski G.,Astrophysikalisches Institute und Universitats Sternwarte | Maciejewski G.,Nicolaus Copernicus University | Dimitrov D.,Bulgarian Academy of Science | Neuhauser R.,Astrophysikalisches Institute und Universitats Sternwarte | And 7 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2010

Photometric follow-ups of transiting exoplanetsmay lead to discoveries of additional, lessmassive bodies in extrasolar systems. This is possible by detecting and then analysing variations in transit timing of transiting exoplanets. We present photometric observations gathered in 2009 and 2010 for exoplanetWASP-3b during the dedicated transit-timing-variation campaign. The observed transit timing cannot be explained by a constant period but by a periodic variation in the observations minus calculations diagram. Simplified models assuming the existence of a perturbing planet in the system and reproducing the observed variations of timing residuals were identified by three-body simulations.We found that the configuration with the hypothetical second planet of mass ~15M⊕, located close to the outer 2:1 mean-motion resonance, is the most likely scenario reproducing observed transit timing. We emphasize, however, that more observations are required to constrain better the parameters of the hypothetical second planet in the WASP-3 system. For final interpretation not only transit timing but also photometric observations of the transit of the predicted second planet and high-precision radial velocity data are needed. © 2010 The Authors. Journal compilation. © 2010 RAS.

Rada W.,University of Babylon | Neuhauser R.,Astrophysikalisches Institute und Universitats Sternwarte
Astronomische Nachrichten | Year: 2015

We present two Arabic texts of historic observations of supernova SN 1006 from Yemen as reported by al-Yamānī and Ibn al-Daybac (14th to 16th century AD). An English translation of the report by the latter was given before (Stephenson & Green 2002), but the original Arabic text was not yet published. In addition, we present for the first time the earlier report, also from Yemen, namely by al-Yamānī in its original Arabic and with our English translation. It is quite obvious that the report by Ibn al-Daybac is based on the report by al-Yamānī(or a common source), but the earlier report by al-Yamānī is more detailed and in better (Arabic) language. We discuss in detail the dating of these observations. The most striking difference to other reports about SN 1006 is the apparent early discovery in Yemen in the evening of 15th of Rajab of the year 396h (i.e. AD 1006 April 17±2 on the Julian calendar), as reported by both al-Yamānī and Ibn al-Daybac, i.e. ∼1.5 weeks earlier than the otherwise earliest known reports. We also briefly discuss other information from the Yemeni reports on brightness, light curve, duration of visibility, location, stationarity, and color. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adam C.,Astrophysikalisches Institute und Universitats Sternwarte | Neuhauser R.,Astrophysikalisches Institute und Universitats Sternwarte | Mugrauer M.,Astrophysikalisches Institute und Universitats Sternwarte | Schmidt J.G.,Astrophysikalisches Institute und Universitats Sternwarte | Schmidt T.O.B.,Astrophysikalisches Institute und Universitats Sternwarte
Monthly Notices of the Royal Astronomical Society | Year: 2013

We report the discovery of a very low mass companion to HIP 45314 (HR 3672) located about 2.7 arcsec north-west of HR 3672 A. With four years of epoch difference between the two observations obtained with the Very Large Telescope we can reject by more than 4σ that B would be a non-moving background object unrelated to A. HR 3672 A is a B 7-8 main-sequence star with an age of 140 ± 80 Myr and from the magnitude difference between HR 3672 A and B and the Two Micron All Sky Survey magnitudes, we can estimate the magnitude of HR 3672 B (Ks = 12.42 ± 0.28 mag) and then, for age and distance of the primary star, using models, its luminosity and mass (0.2-0.5M·). We present a reanalysis of the probable membership of HR 3672 A to the Platais 9 cluster, and introduce a new method for astrometric calibration of data without dedicated calibration images. In the deepest available image (co-add of all epochs) no additional companion candidates within 13 arcsec were detected down to 0.03M·. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

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