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S. Kimeswenger

Publications and source records attributed to S. Kimeswenger.

At least 55 records · Page 3Linked to original sources
arXiv2004

Metal Enrichment of the Intra-Cluster Medium: Ram-Pressure Stripping of Cluster Galaxies

We present numerical simulations of the dynamical and chemical evolution of galaxy clusters. X-ray spectra show that the intra-cluster medium contains a significant amount of metals. As heavy elements are produced in the stars of galaxies material from the galaxies must have been expelled to enrich the ambient medium. We have performed hydrodynamic simulations investigating various processes. In this presentation we show the feedback from gas which is stripped from galaxies by ram-pressure stripping. The efficiency, resulting spatial distribution of the metals and the time dependency of this enrichment process on galaxy cluster scale is shown.

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arXiv2004

Spectroscopic investigation of unstudied southern PNe

We present a spectroscopic investigation of two hitherto unstudied galactic planetary nebulae (MeWe 1-10 and MeWe 1-11) and one candidate object (MeWe 2-5). The candidate object clearly has been identified as a bipolar hourglass shaped PN. The galactic foreground extinction was derived and using photoionization models with CLOUDY the two round objects were classified as highly evolved nebulae.

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arXiv2003

A new strongly X-ray flaring M9 dwarf in the solar neighborhood

We report on the discovery of a very low mass (VLM) star in the solar neighborhood, originally identified as an optical counterpart of a flaring X-ray source detected in the ROSAT All-Sky survey. Optical spectroscopy and infrared photometry consistently reveal a spectral type of M9 \pm 0.5 and a distance of ~11 pm 2pc. The optical counterpart of 1RXS J115928.5-524717 shows a large proper motion of 1.08\pm0.06 "/year. 1RXS~J115928.5-524717 is the fourth object among the VLM stars displaying a huge X-ray flare, reaching the unprecedent value of L_X/L_{bol}~0.1.

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arXiv2003

The early stages of NOVA Oph 2003 (V2573 Oph)

Intermediate resolution spectroscopy of NOVA Oph 2003 (V2573 Oph), which was first detected March 21th 2003 but reported July 19th} 2003, obtained 19th to 23rd of July is presented here. The photometry during the early phases of the object is shortly discussed. We also retrieved very accurate astrometry of the target in this crowded field. This is needed to be able to do further observations of the post-nova during the next years. The inspection of the sky survey plates gives a possible progenitor candidate and allows to derive a lower limit for the outburst magnitude of about 10.0 mag. The spectrum shows an overall expansion of 2200 km/s and has clearly complex outflow substructures. The spectroscopy identifies this object as classical nova, "Fe II" subclass.

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arXiv2003

Optical Spectroscopy of IRAS 02091+6333

We present a detailed spectroscopic investigation, spanning four winters, of the asymptotic giant branch (AGB) star IRAS 02091+6333. Zijlstra & Weinberger (2002) found a giant wall of dust around this star and modelled this unique phenomenon. However their work suffered from the quality of the optical investigations of the central object. Our spectroscopic investigation allowed us to define the spectral type and the interstellar foreground extinction more precisely. Accurate multi band photometry was carried out. This provides us with the possibility to derive the physical parameters of the system. The measurements presented here suggest a weak irregular photometric variability of the target, while there is no evidence of a spectroscopic variability over the last four years.

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arXiv2002

Modelling the Recurrent Nova CI Aql in Quiescence

We present detailed photometric investigations of the recurrent nova CI Aql. New data obtained after the 2000 outburst are used to derive a 3D geometrical model of the system. The resulting light curves clearly indicate the existence of an asymmetric spray around the accretion disk, as claimed in the past e.g. for the super-soft X-ray source CAL87 in the LMC. The simulated light curves give us the mass transfer rates varying from \dot M ~ 2.5 x 10^{-8} M_\odot / yr in 1991-1996 to 5.5 x 10^{-8} < \dot M < 1.5 x 10^{-7}M_\odot / yr in 2001/2002. The distance and the interstellar foreground extinction resulting from the model are 1.55 kpc and E(B-V) = 0.98 respectively. During fast photometry sequences in 2002 short timescale variations (t ~ 13 minutes) of the mass loss are found. Moreover a change in the orbital period of the system is detectable and results in a mass loss of 2.2 x 10^{-6} < ΔM < 5.7 x 10^{-6} M_\odot during the nova explosion.

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arXiv2002

ate helium flash in V605 Aql: PNe evolution and shell formation in quick motion

The "born-again" PNe V605 Aql (A58) and V4344 Sgr (Sakurai) give us the rare chance to follow shell formation and building of the winds in "real-time". The high carbon abundance, and thus the high dust formation rate, enhances the mechanisms. Thus the timescales are shortened. My data presented here gives a quick look on the results of new observations of V605 Aql and its old planetary nebula (PN) A58 obtained at the ESO NTT (August 2002).

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arXiv2002

The peculiar variable V838 Mon

V838 Mon underwent, after a first nova-like outburst in January and a usual decline, a second outburst after one month, and a third weak one again a month later. Moreover a very small increase of the temperature at the beginning of April gives us a hint on a physical process with a period of one month. We obtained a BVRIc time sequence and modelled the photometric behaviour of the object. This leads us to the conclusion that the interstellar foreground extinction has to be 0.6 < E(B-V) < 0.8 and that the quasi-photosphere had persistently unusually low temperatures for nova-like systems. The photometry was used to follow the dramatic changes of the expansion. While the appearing 10 micron excess can be well described by the heating of material ejected during this event, the IRAS emission near the location of the progenitor, originates most likely from dust, which were formed during the previous evolution of the object. Assuming that the light echoes are coming from circumstellar material, the distance is 640 to 680 pc - smaller than the 790 pc given in Munari et al. (2002). In our opinion V838 Mon and V4332 Sgr are manifestations of a new class of eruptive variables. We do not count M31 RV to this class.

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arXiv2002

Symbiotic Miras vs. Planetary Nebulae in the Near Infrared

While symbiotic Miras and planetary nebulae are hard to distinguish by optical spectroscopy, their near infrared colors differ. We propose the near infrared two-color diagram to be an excellent tool to easily distinguish these two classes of objects.

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arXiv2002

DENIS Survey Data Probing Different Types of PNe

We present near-infrared photometry of a large sample of planetary nebulae (PNe) and show that the IJK colours are a good tool to distinguish different classes of PNe, like nebulae around symbiotic Miras or IR-[WC] PNe from genuine PNe.

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arXiv2001

Nova Sco 2001 (V1178 Sco)

We present intermediate resolution spectroscopy and near infrared photometry of NOVA Sco 2001 (V1178 Sco), which was first detected May 13th 2001 and reported June 21th 2001, and obtained by us the same day. We also retrieved very accurate astrometry of the target in this very crowded field. This is needed to be able to do follow up observations of the postnova during the next years. The spectrum shows an overall expansion of 2100 km/s and has clearly complex, and most likely nonsymmetric, outflow substructures. We clearly identify this object as classical nova, "Fe II" subclass.

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arXiv2001

Planetary nebula or symbiotic Mira? Near infrared colours mark the difference

Nebulae around symbiotic Miras look very much like genuine planetary nebulae, although they are formed in a slightly different way. We present near infrared photometry of known and suspected symbiotic nebulae obtained with the Deep Near Infrared Southern Sky Survey (DENIS). We demonstrate that the near infrared colours are an excellent tool to distinguish symbiotic from genuine planetary nebulae. In particular we find that the bipolar planetary nebulae M 2-9 and Mz 3 are in fact symbiotic Miras. Further observations on prototype symbiotic Miras prove that the proposed classification scheme works generally.

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arXiv2001

Effects of CSPN Models on PNe Shell Modeling

Modeling planetary nebulae (PNe) shells using different ionizing spectra for a hot central star (CSPN) of evolved PNe, we found that especially a blackbody model leads to wrong nebular diagnostics and abundances.

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arXiv2001

V4334 Sgr (Sakurai's Nova): The Distance Problem

The central star V4334 Sgr (Sakurai's Nova) of the planetary nebula PN G010.4+04.4 underwent in 1995-1996 the rare event of a very late helium flash. It represents only one out of two such events during the era of modern astronomy (the second event was V605 Aql = Nova Aql 1919). All the other prominent objects of that type originate from events occurring several thousands of years ago (e.g. A30, A78). Thus it is of special interest for stellar evolution theory to model the detailed observations obtained during the last four years. Those models depend essentially on basic stellar parameters like effective temperature, surface gravity and stellar radius. Most of them depend strongly on the assumed distance to the object. Some models may give some constraints on this parameter, but most of them depend on the assumption as input parameter. Hence to determine a relyable distance is of considerable significance.This should be obtained through models that give us lower and upper boundaries, or through means which are independent of models. The detailed review, by using every kind of determination available up to now, leads to a galactic foreground extinction of E(B-V) = 0.75+/-0.05 and a distance of D =2.0 (-0.6;+1.0) kpc.

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arXiv2001

Modeling the Dust Shell of V4334 Sgr

The central star V4334 Sgr (Sakurai's Nova) of the planetary nebula PN G010.4+04.4 underwent in 1995-1996 the rare event of a very late helium flash. It is only one of two such events during the era of modern astronomy (the second event was V605 Aql = Nova Aql 1919). All other prominent objects of that type originate from events several thousands of years ago (e.g. A30, A78). Hence, only snapshots can be modeled for those objects. V4334 Sgr allows for the first time a dynamic consideration of the formation of the dust shell from the beginning. We present here a model which is able to describe the complete photometric behavior of the object, including the fine structure dips of the optical light curve during the first two years of the mass loss and the dust formation.

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arXiv2001

Optical Coordinates of Southern Planetary Nebulae

A homogeneous set of new measurements of nearly all (995 out of 1007) objects from the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae or in the first supplement of this catalogue in the area covered by the DENIS survey (delta < +2) is given here. 24 new and 27 wrong crossidentifications with sources in the IRAS PSC catalogue and some confusion in the literature is listed as well.

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arXiv2000

The DENIS Point Source Catalogue towards the Magellanic Clouds

We have compiled the near infrared Point Source Catalogue (PSC) towards the Magellanic Clouds (MCs) extracted from the data obtained with the Deep Near Infrared Survey of the Southern Sky - DENIS (Epchtein et al. 1997). The catalogue covers an area of of 19.87* 16 square degrees centered on (RA, DEC)=(5h27m20s, -69o00'00'') for the Large Magellanic Cloud (LMC) and 14.7* 10 square degrees centered on (RA, DEC)=(h02m40s, -73o00'00'' for the Small Magellanic Cloud (SMC) at the epoch J2000. It contains about 1300000 sources towards the LMC and 300000 sources towards the SMC each detected in at least 2 of the 3 photometric bands involved in the survey (I, J, Ks). 70% of the detected sources are true members of the Magellanic Clouds, respectively and consist mainly of red giants, asymptotic giant branch stars and super-giants. The observations have all been made with the same instrument and the data have been calibrated and reduced uniformly. The catalogue provides a homogeneous set of photometric data.

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