Marin Treselj, A. Seifahrt, K. Hodapp, A. Bedalov, M. Mugrauer
{"title":"A search for wide brown dwarf companions to stars within 10 pc","authors":"Marin Treselj, A. Seifahrt, K. Hodapp, A. Bedalov, M. Mugrauer","doi":"10.1063/1.3099175","DOIUrl":"https://doi.org/10.1063/1.3099175","url":null,"abstract":"We present the first results of a large imaging survey to identify wide brown dwarf companions to stars within 10 pc. We have performed a deep (H‐band limit ∼19.0 mag), wide field (up to 16×16 arcmin) astrometric imaging campaign in two epochs around more than 230 nearby stars.Preliminary results show that the wide low‐mass companion fraction is far lower than expected, indicating that interactions with the galactic disk may have removed the weakly bound wide companions around old stars.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"27 1","pages":"565-567"},"PeriodicalIF":0.0,"publicationDate":"2008-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82485898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Seifahrt, C. Helling, A. Burgasser, K. Allers, K. Cruz, M. Cushing, U. Heiter, D. Looper, S. Witte
{"title":"Observation and modelling of dusty, low gravity L, and M dwarfs","authors":"A. Seifahrt, C. Helling, A. Burgasser, K. Allers, K. Cruz, M. Cushing, U. Heiter, D. Looper, S. Witte","doi":"10.1063/1.3099103","DOIUrl":"https://doi.org/10.1063/1.3099103","url":null,"abstract":"Observational facilities allow now the detection of optical and IR spectra of young M‐ and L‐dwarfs. This enables empirical comparisons with old M‐ and L‐ dwarfs, and detailed studies in comparison with synthetic spectra. While classical stellar atmosphere physics seems perfectly appropriate for old M‐dwarfs, more physical and chemical processes, cloud formation in particular, needs to be modelled in the substellar regime to allow a detailed spectral interpretation. \u0000 \u0000Not much is known so far about the details of the inset of cloud formation at the spectral transition region between M and L dwarfs. Furthermore there is observational evidence for diversity in the dust properties of objects having the same spectral type. Do we understand these differences? The question is also how young M‐ and L‐dwarfs need to be classified, which stellar parameter do they have and whether degenerations in the stellar parameter space due to the changing atmosphere physics are present, like in the L‐T transition region. \u0000 \u0000The Splinter was driven by these questions which we will use to encourage interactions between observation and theory. Given the recent advances, both in observations and spectral modelling, an intensive discussion between observers and theoreticians will create new synergies in our field.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"9 1","pages":"283-290"},"PeriodicalIF":0.0,"publicationDate":"2008-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91238258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Activity and rotation of low mass stars in young open clusters","authors":"A. Seifahrt, A. Reiners, A. Scholz, G. Basri","doi":"10.1063/1.3099123","DOIUrl":"https://doi.org/10.1063/1.3099123","url":null,"abstract":"We present first results from a multi‐object spectroscopy campaign in IC2602, the Hyades, the Pleiades, and the Coma cluster using VLT/FLAMES. We analysed the data for radial velocity, rotational velocity (v sin i), and Hα‐activity. Here, we highlight three aspects of this study in the context of rotational braking and the rotation‐activity relationship among low mass stars. Finally we discuss the cluster membership of sources in IC2602.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"21 1","pages":"373-376"},"PeriodicalIF":0.0,"publicationDate":"2008-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72919313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Integral-Field Spectroscopy of SLACS Lenses","authors":"O. Czoske, M. Barnabè, L. Koopmans","doi":"10.1063/1.3141531","DOIUrl":"https://doi.org/10.1063/1.3141531","url":null,"abstract":"The combination of two‐dimensional kinematics and gravitational lens modelling permits detailed reconstruction of the phase‐space structure of early‐type galaxies and sets constraints on the dark‐matter distribution in their inner regions. We describe a project which combines integral‐field spectroscopy from an ESO Large Programme using VIMOS on the VLT with deep HST ACS and NICMOS images to study a sample of 17 early‐type lens galaxies at z≈0.1–0.3, drawn from the Sloan Lens ACS survey (SLACS).","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"56 1","pages":"137-140"},"PeriodicalIF":0.0,"publicationDate":"2008-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88008430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Six Hot Topics in Planetary Astronomy","authors":"D. Jewitt","doi":"10.1007/978-3-540-76935-4_9","DOIUrl":"https://doi.org/10.1007/978-3-540-76935-4_9","url":null,"abstract":"","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"2014 1","pages":"1-37"},"PeriodicalIF":0.0,"publicationDate":"2008-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88226541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Transonic Properties of Accretion Disk Around Compact Objects","authors":"B. Mukhopadhyay","doi":"10.1007/978-1-4020-8868-1_17","DOIUrl":"https://doi.org/10.1007/978-1-4020-8868-1_17","url":null,"abstract":"","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"30 1","pages":"261-272"},"PeriodicalIF":0.0,"publicationDate":"2008-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80681415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Modeling Gamma‐Ray Attenuation in High Redshift GeV Spectra","authors":"R. Gilmore, P. Madau, J. Primack, R. Somerville","doi":"10.1063/1.3076738","DOIUrl":"https://doi.org/10.1063/1.3076738","url":null,"abstract":"We present two models for the cosmological UV background light, and calculate the opacity of GeV gamma—rays out to redshift 9. The contributors to the background include 2 possible quasar emissivities, and output from star—forming galaxies as determined by recent a semi—analytic model (SAM) of structure formation. The SAM used in this work is based upon a hierarchical build‐up of structure in a ΛCDM universe and is highly successful in reproducing a variety of observational parameters. Above 1 Rydberg energy, ionizing radiation is subject to reprocessing by the IGM, which we treat using our radiative transfer code, CUBA. The two models for quasar emissivity differing above z = 2.3 are chosen to match the ionization rates observed using flux decrement analysis and the higher values of the line‐of‐sight proximity effect. We also investigate the possibility of aflat star formation rate density at z>5. We conclude that observations of gamma—rays from 10 to 100 GeV by Fermi (GLAST) and the next generation of g...","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"41 1","pages":"577-580"},"PeriodicalIF":0.0,"publicationDate":"2008-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77952652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Bussmann, A. Dey, J. Lotz, L. Armus, K. Brand, Michael J. I. Brown, V. Desai, P. Eisenhardt, J. Higdon, S. Higdon, B. Jannuzi, E. Floc’h, J. Melbourne, B. Soifer, D. Weedman
{"title":"HST Morphologies of z~2 Dust Obscured Galaxies I: Power-law Sources","authors":"R. Bussmann, A. Dey, J. Lotz, L. Armus, K. Brand, Michael J. I. Brown, V. Desai, P. Eisenhardt, J. Higdon, S. Higdon, B. Jannuzi, E. Floc’h, J. Melbourne, B. Soifer, D. Weedman","doi":"10.1088/0004-637X/693/1/750","DOIUrl":"https://doi.org/10.1088/0004-637X/693/1/750","url":null,"abstract":"We present high spatial resolution optical and near-infrared imaging obtained using the ACS, WFPC2 and NICMOS cameras aboard the Hubble Space Telescope of 31 24um--bright z~2 Dust Obscured Galaxies (DOGs) identified in the Bootes Field of the NOAO Deep Wide-Field Survey. Although this subset of DOGs have mid-IR spectral energy distributions dominated by a power-law component suggestive of an AGN, all but one of the galaxies are spatially extended and not dominated by an unresolved component at rest-frame UV or optical wavelengths. The observed V-H and I-H colors of the extended components are 0.2-3 magnitudes redder than normal star-forming galaxies. All but 1 have axial ratios >0.3, making it unlikely that DOGs are composed of an edge-on star-forming disk. We model the spatially extended component of the surface brightness distributions of the DOGs with a Sersic profile and find effective radii of 1-6 kpc. This sample of DOGs is smaller than most sub-millimeter galaxies (SMGs), but larger than quiescent high-redshift galaxies. Non-parametric measures (Gini and M20) of DOG morphologies suggest that these galaxies are more dynamically relaxed than local ULIRGs. We estimate lower limits to the stellar masses of DOGs based on the rest-frame optical photometry and find that these range from ~10^(9-11) M_sun. If major mergers are the progenitors of DOGs, then these observations suggest that DOGs may represent a post-merger evolutionary stage.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2008-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82280489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The accretion regime of LS 5039: 3-D SPH simulations","authors":"A. Okazaki, G. Romero, S. Owocki","doi":"10.22323/1.067.0074","DOIUrl":"https://doi.org/10.22323/1.067.0074","url":null,"abstract":"LS 5039 is a TeV gamma-ray binary with extended radio emission. It consists of a compact object in the mildly eccentric (e=0.35), 3.9-day orbit around a massive O star. The nature of the compact object is not yet established. In this paper, assuming that the compact object is a black hole, we study the accretion of O-star wind by the black hole, by performing three-dimensional Smoothed Particle Hydrodynamics (SPH) simulations. In order to roughly emulate the effect of the stellar radiation effectively canceling the stellar gravity, we assume that the O star's gravity does not exert on the wind. The wind particles are ejected with half the observed terminal velocity in a narrow range of azimuthal and vertical angles toward the black hole, in order to emulate the wind significantly slower than the terminal speed, and optimize the resolution and computational efficiency of simulations. We find that the mass-accretion rate closely follows the classical Bondi-Hoyle-Littleton accretion rate, which is of the order of 10^{16}g/s around periastron. The accretion rate at this level would provide jets enough power to produce the gamma-rays detected by HESS. Since the accretion peak occurs near the periastron passage, we need a strong gamma-ray absorption around periastron in order for the microquasar scenario to be consistent with the observed orbital modulation of the TeV gamma-ray flux.","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2008-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86210184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Self‐Organizing Maps in application to the OGLE data and Gaia Science Alerts","authors":"L. Wyrzykowski, V. Belokurov","doi":"10.1063/1.3059046","DOIUrl":"https://doi.org/10.1063/1.3059046","url":null,"abstract":"The Optical Gravitational Lensing Experiment is long‐term observing project aiming at detection of microlensing events in crowded stellar fields. As a natural by‐product it collects photometric time‐series of millions of variable stars towards the Galactic Centre and in Magellanic Clouds. In November 2008 third phase of the OGLE will conclude its continuous run since 2001. Huge data set gathered with superb quality is one of very few of such kind currently available. Nearly a billion objects towards the Galactic bulge and Magellanic Clouds need to be now investigated and classified into variability classes. Self‐Organizing Map (SOM) is a promising tool for exploring large multi‐dimensional datasets. It is quick and convenient to train in an unsupervised process and as an outcome it produces naturally clustered patterns. Application of SOM to the new OGLE‐III data set will be presented along with the first preliminary results. SOM technique, tested on OGLE data, will be also implemented within Gaia mission...","PeriodicalId":8453,"journal":{"name":"arXiv: Astrophysics","volume":"88 14 1","pages":"201-206"},"PeriodicalIF":0.0,"publicationDate":"2008-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84064227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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