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Pires A.M.,Leibniz Institute for Astrophysics Potsdam | Haberl F.,Max Planck Institute for Extraterrestrial Physics | Zavlin V.E.,NASA | Motch C.,University of Strasbourg | And 2 more authors.
Astronomy and Astrophysics | Year: 2014

Context. The group of seven thermally emitting isolated neutron stars (INSs) discovered by ROSAT and known as the "Magnificent Seven" (M7) is unique among the various neutron star populations. Crustal heating by means of magnetic field decay and an evolutionary link with magnetars may explain why these objects rotate more slowly and have higher thermal luminosities and magnetic field intensities than standard rotation-powered pulsars of similar age. Aims. The third brightest INS, RX J1605.3+3249, is the only object amidst the seven still lacking a detected periodicity. The source spectrum, while purely thermal with no significant magnetospheric emission, is complex and displays both narrow and broad absorption features that can potentially be used to constrain the surface component of the magnetic field, as well as the mass-to-radius ratio of the neutron star. Methods. We observed the source with the XMM-Newton Observatory for 60 ks aiming at unveiling the neutron star rotation rate and investigating its spectrum in detail. We confront our results with previous observations of the source and discuss its properties in the context of the M7 as a group and of the known population of Galactic INSs. Results. A periodic signal at P = 3.387864(16) s, most likely the neutron star spin period, is detected at the 4σ confidence level. The amplitude of the modulation was found to be energy dependent and is more significantly detected when the timing search is restricted to photons with energy higher than ~0.5 keV. The coherent combination of the new data with a past XMM-Newton EPIC-pn observation of the source constrains the pulsar spin-down rate at the 2σ confidence level, \hbox{$\dot{\nu}\sim-1.39\times10^{-13}$} Hz s-1, implying a dipolar magnetic field of Bdip ~ 7.4 × 1013 G. If confirmed, RX J1605.3+3249 would be the neutron star with the highest dipolar field amongst the M7. The spectrum of the source shows evidence of a cool blackbody component, as well as for the presence of two broad absorption features. Furthermore, high-resolution spectroscopy with the RGS cameras confirms the presence of a narrow absorption feature at energy ~0.57 keV in the co-added spectrum of the source, also seen in other thermally emitting isolated neutron stars. Conclusions. Phase-resolved spectroscopy, as well as a dedicated observing campaign aimed at determining a timing solution, will give invaluable constraints on the neutron star geometry and will allow one to confirm the high value of spin down, which would place the source closer to a magnetar than any other M7 INS. © 2014 ESO.


Ginski C.,Sterrewacht Leiden | Schmidt T.O.B.,Hamburger Sternwarte | Schmidt T.O.B.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Mugrauer M.,Astrophysikalisches Institute und Universitats Sternwarte Jena | And 5 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2014

The formation of massive planetary or brown dwarf companions at large projected separations from their host star is not yet well understood. In order to put constraints on formation scenarios, we search for signatures in the orbit dynamics of the systems. We are specifically interested in the eccentricities and inclinations since those parameters might tell us about the dynamic history of the systems and where to look for additional low-mass sub-stellar companions. For this purpose, we utilized VLT/NACO to take several well-calibrated high-resolution images of six target systems and analyse them together with available literature data points of those systems as well as Hubble Space Telescope archival data. We used a statistical least-squares Monte Carlo approach to constrain the orbit elements of all systems that showed significant differential motion of the primary star and companion. We show for the first time that the GQ Lup system shows significant change in both separation and position angle. Our analysis yields best-fitting orbits for this system, which are eccentric (e between 0.21 and 0.69), but cannot rule out circular orbits at high inclinations. Given our astrometry, we discuss formation scenarios of the GQ Lup system. In addition, we detected an even fainter new companion candidate to GQ Lup, which is most likely a background object. We also updated the orbit constraints of the PZ Tel system, confirming that the companion is on a highly eccentric orbit with e > 0.62. Finally, we show with a high significance, that there is no orbital motion observed in the cases of the DH Tau, HD 203030 and 1RXS J160929.1-210524 systems, and give the most precise relative astrometric measurement of the UScoCTIO 108 system to date. © 2014 The Authors.


Ginski C.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Mugrauer M.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Seeliger M.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Eisenbeiss T.,Astrophysikalisches Institute und Universitats Sternwarte Jena
Monthly Notices of the Royal Astronomical Society | Year: 2012

To understand the influence of additional wide stellar companions on planet formation, it is necessary to determine the fraction of multiple stellar systems amongst the known extrasolar planet population. We target recently discovered radial velocity exoplanetary systems observable from the Northern hemisphere and with sufficiently high proper motion to detect stellar companions via direct imaging. We utilize the Calar Alto 2.2-m telescope in combination with its lucky imaging camera AstraLux. 71 planet host stars have been observed so far, yielding one new low-mass (0.239±0.022M ⊙) stellar companion, 4.5arcsec (227au of projected separation) north-east of the planet host star HD185269, detected via astrometry with AstraLux. We also present follow-up astrometry on three previously discovered stellar companions, showing for the first time common proper motion of the 0.5-arcsec companion to HD126614. Additionally, we determined the achieved detection limits for all targets, which allow us to characterize the detection space of possible further companions of these stars. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.


Mugrauer M.,Astrophysikalisches Institute und Universitats Sternwarte Jena
Astronomische Nachrichten | Year: 2016

The Cassegrain-Teleskop-Kamera (CTK-II) and the Refraktor-Teleskop-Kamera (RTK) are two CCD-imagers which are operated at the 25 cm Cassegrain and 20cm refractor auxiliary telescopes of the University Observatory Jena. This article describes the main characteristics of these instruments. The properties of the CCD-detectors, the astrometry, the image quality, and the detection limits of both CCD-cameras, as well as some results of ongoing observing projects, carried out with these instruments, are presented. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Mugrauer M.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Dincel B.,Astrophysikalisches Institute und Universitats Sternwarte Jena
Astronomische Nachrichten | Year: 2016

We report on our follow-up spectroscopy of HD 1071478 B, a recently detected faint co-moving companion of the exoplanet host star HD 107148 A. The companion is separated from its primary star by about 35″ (or 1790 AU of projected separation) and its optical and near infrared photometry is consistent with a white dwarf, located at the distance of HD 107148 A. In order to confirm the white dwarf nature of the co-moving companion, we obtained follow-up spectroscopic observations of HD 107148 B with CAFOS at the CAHA 2.2 m telescope. According to our CAFOS spectroscopy HD 107148 B is a DA white dwarf with an effective temperature in the range between 5900 and 6400K. The properties of HD 107148 B can further be constrained with the derived effective temperature and the known visual and infrared photometry of the companion, using evolutionary models of DA white dwarfs. We obtain for HD 107148 B a mass of 0.56 ± 0.05 M⊙, a luminosity of (2.0 ± 0.2) × 10–4 L⊙, log g [cm s–2]) = 7.95 ± 0.09, and a cooling age of 2100 ± 270 Myr. With its white dwarf companion the exoplanet host star HD 107148 A forms an evolved stellar system, which hosts at least one exoplanet. So far, only few of these evolved systems are known, which represent only about 5 % of all known exoplanet host multiple stellar systems. HD 107148 B is the second confirmed white dwarf companion of an exoplanet host star with a projected separation to its primary star of more than 1000 AU. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim). Copyright © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


Tetzlaff N.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Eisenbeiss T.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Neuhauser R.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Hohle M.M.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Hohle M.M.,Max Planck Institute for Extraterrestrial Physics
Monthly Notices of the Royal Astronomical Society | Year: 2011

RXJ1856.5-3754 and RXJ0720.4-3125 are the only young isolated radio-quiet neutron stars (NSs) for which trigonometric parallaxes were measured. Due to detection of their thermal emission in X-rays, they are important to study NS cooling and to probe theoretical cooling models. Hence, a precise determination of their age is essential. Recently, new parallax measurements of RXJ1856.5-3754 and RXJ0720.4-3125 were obtained. Considering that NSs may originate from binary systems that got disrupted due to an asymmetric supernova, we attempt to identify runaway stars which may have been former companions to the NS progenitors. Such an identification would strongly support a particular birth scenario with time and place. We trace back each NS, runaway star and the centres of possible birth associations (assuming that most NSs are ejected directly from their parent association) to find close encounters. The kinematic age is then given by the time since the encounter. We use Monte Carlo simulations to account for observational uncertainties and evaluate the outcome statistically. Using the most recent parallax measurement of 8.16 ± 0.80mas for RXJ1856.5-3754 by Walter et al., we find that it originated in the Upper Scorpius association 0.46 ± 0.05Myr ago. This kinematic age is slightly larger than the value we reported earlier (0.3Myr) using the old parallax value of 5.6 ± 0.6mas by Kaplan. Our result is strongly supported by its current radial velocity which we predict to be 6+19 - 20kms-1. This implies an inclination angle to the line of sight of 88°± 6° consistent with estimates by van Kerkwijk & Kulkarni from the bow shock. No suitable runaway star was found to be a potential former companion of RXJ1856.5-3754. Making use of a recent parallax measurement for RXJ0720.4-3125 of 3.6 ± 1.6mas by Eisenbeiss, we find that this NS was possibly born in Trumpler 10 0.85 ± 0.15Myr ago. This kinematic age is somewhat larger than the one obtained using the old parallax value of 2.77 ± 1.29mas by Kaplan et al. (0.5Myr). We suggest the B0 runaway supergiant HIP 43158 as a candidate for a former companion of the progenitor star. Then, the current distance of RXJ0720.4-3125 to the Sun should be 286+27 - 23pc, in agreement with recent measurements. We then expect the radial velocity of RXJ0720.4-3125 to be -76+34 - 17kms-1. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.


Mugrauer M.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Ginski C.,Astrophysikalisches Institute und Universitats Sternwarte Jena
Monthly Notices of the Royal Astronomical Society | Year: 2015

We present the results of our high-contrast imaging survey of close stellar and substellar companions of exoplanet host stars, carried out with the adaptive optics imager NACO at the ESO Paranal observatory, in Chile. In total, 33 exoplanet host stars were observed with NACO in the Ks-band. New comoving companions could be identified close to the stars HD 9578, HD 96167, and HD 142245. The newly detected companions exhibit masses between 0.21 and 0.56 M⊙ and are located at projected separations from their primaries between about 190 and 510 au. In the case of HD 142245, we found evidence that the detected companion is actually a close binary itself with a projected separation of only about 4 au, i.e. HD 142245 might be a hierarchical triple stellar system, which hosts an exoplanet, a new member in the short list of such systems, presently known. In our imaging campaign, a limiting magnitude of Ks = 18.5 mag is reached in average in the background noise limited region around our targets at projected separations beyond about 100 au, which allows the detection of substellar companions with masses down to about 60MJup. With our NACO observations we can rule out additional stellar companions at projected separations between about 30 and 370 au around the observed exoplanet host stars. © 2015 The Authors.


Tetzlaff N.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Neuhauser R.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Hohle M.M.,Max Planck Institute for Extraterrestrial Physics | Maciejewski G.,Astrophysikalisches Institute und Universitats Sternwarte Jena
Monthly Notices of the Royal Astronomical Society | Year: 2010

Young isolated radio-quiet neutron stars are still hot enough to be detectable at X-ray and optical wavelengths due to their thermal emission and can hence probe cooling curves. An identification of their birth sites can constrain their age.For that reason, we try to identify the parent associations for four of the so-called Magnificent Seven neutron stars for which proper motion and distance estimates are available. We are tracing back in time each neutron star and possible birth association centre to find close encounters. The associated time of the encounter expresses the kinematic age of the neutron star which can be compared to its characteristic spin-down age. Owing to observational uncertainties in the input data, we use Monte Carlo simulations and evaluate the outcome of our calculations statistically.RX J. 1856.5-3754 most probably originated from the Upper Scorpius association about 0.3 Myr ago. RX J. 0720.4-3125 was either born in the young local association TW Hydrae about 0.4 Myr ago or in Trumpler 10 0.5 Myr in the past. Also RX J1605.3 + 3249 and RBS 1223 seem to come from a nearby young association such as the Scorpius-Centraurus complex or the extended Corona-Australis association. For RBS 1223 also a birth in Scutum OB2 is possible.We also give constraints on the observables as well as on the radial velocity of the neutron star. Given the birth association, its age and the flight time of the neutron star, we estimate the mass of the progenitor star.Some of the potential supernovae were located very nearby (<100 pc) and thus should have contributed to the 10Be and 60Fe material found in the Earth's crust.In addition, we reinvestigate the previously suggested neutron star/runaway pair PSR B1929+10/ζ Ophiuchi and conclude that it is very likely that both objects were ejected during the same supernova event. © 2010 The Authors. Journal compilation © 2010 RAS.


Mugrauer M.,Astrophysikalisches Institute und Universitats Sternwarte Jena | Berthold T.,Sternwarte Sonneberg 4pi Systeme GmbH
Astronomische Nachrichten | Year: 2010

The Schmidt-Teleskop-Kamera (STK) is a new CCD-imager, which is operated since begin of 2009 at the University Observatory Jena. This article describes the main characteristics of the new camera. The properties of the STK detector, the astrometry and image quality of the STK, as well as its detection limits at the 0.9 m telescope of the University Observatory Jena are presented. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


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

Evolutionary models and mass estimates for brown dwarfs remain uncertain, hence determining the masses of brown dwarfs by model-independent methods is important to test and constrain such theories. Following the orbital motion of brown dwarf companions around their primaries gives us the opportunity to dynamically calculate the masses of these systems. In addition, detecting curvature (acceleration or deceleration) in the orbit would confirm that the companion is physically associated with its primary, thus eliminating the possibility of a by-chance alignment of the primary's and the companion's proper motions and positions. Furthermore, the orbit parameters can be important indicators for the formation process of such wide, massive substellar companions. The binary brown dwarf companions to HD 130948 were discovered by Potter et al. We present various observations of this triple system over the course of 7 yr. With these data points we can show that HD 130948 BC are indeed comoving with HD 130948 A with higher significance than before (̃32.4σ), and also for the first time that the BC pair shows differential motion relative to A (̃2.2σ).We introduce an orbit fitting approach and constrain the orbit parameters for the orbit of the BC binary around their host star. ©2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

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