100,419 research outputs found
Detection of the irradiated donor in the LMXBs 4U 1636-536 (=V801 Ara) and 4U 1735-444 (=V926 Sco)
No full textPhase-resolved VLT spectroscopy of the bursting low-mass X-ray binaries 4U 1636-536/V801 Ara and 4U 1735-444/V926 Sco is presented. Doppler images of the N iiiλ4640 Bowen transition reveal compact spots which we attribute to fluorescent emission from the donor star and enable us to define a new set of spectroscopic ephemerides. We measure Kem= 277 ± 22 and 226 ± 22 km s−1 from the N iii spots in V801 Ara and V926 Sco, respectively, which represent strict lower limits to the radial velocity semi-amplitude of the donor stars. Our new ephemerides provide confirmation that light-curve maxima in V801 Ara and likely V926 Sco occur at superior conjunction of the donor star and hence photometric modulation is caused by the visibility of the X-ray heated donor. The velocities of He iiλ4686 and the broad Bowen blend are strongly modulated with the orbital period, with phasing supporting emission dominated by the disc bulge. In addition, a reanalysis of burst oscillations in V801 Ara, using our spectroscopic T0, leads to K1= 90–113 km s−1. We also estimate the K-corrections for all possible disc flaring angles and present the first dynamical constraints on the masses of these X-ray bursters. These are K2= 360 ± 74 km s−1, f(M) = 0.76 ± 0.47 M⊙ and q= 0.21–0.34 for V801 Ara and K2= 298 ± 83 km s−1, f(M) = 0.53 ± 0.44 M⊙ and q= 0.05–0.41 for V926 Sco. Disc flaring angles α≥ 12° and q≃ 0.26–0.34 are favoured for V801 Ara whereas the lack of K1 constraint for V926 Sco prevents tight constraints on this system. Although both binaries seem to have intermediate inclinations, the larger equivalent width of the narrow N iii line in V801 Ara at phase 0.5 relative to phase 0 suggests that it has the higher inclination of the two
The spectroscopic evolution of the recurrent nova T Pyxidis during its 2011 outburst. I. The optically thick phase and the origin of moving lines in novae
No full textAims: We aim to derive the physical properties of the recurrent nova T Pyx and the structure of the ejecta during the early stages of expansion of the 2011 outburst.
Methods: The nova was observed with high resolution spectroscopy (R ≈ 65 000), from one day after discovery of the outburst and until the last visibility of the star at the end of May 2011. The interstellar absorption lines of Na I, Ca II, CH, CH+, and archival H I 21 cm emission line observations were used to determine a kinematical distance. Interstellar diffuse absorption features have been used to determine the extinction independent of previous assumptions. Sample Fe-peak line profiles show the optical depth and radial velocity evolution of the discrete components.
Results: We propose a distance to T Pyx ≥ 4.5 kpc, with a strict lower limit of 3.5 kpc (the previously accepted distance). We derive an extinction, E(B - V) ≈ 0.5 ± 0.1, that is higher than previous estimates. The first observation, Apr. 15, displayed He I, He II, C III, and N III emission lines and a maximum velocity derived from the P Cyg profiles of the Balmer and He I lines of ≈2500 km s-1 that is characteristic of the fireball stage. These ions were undetectable in the second spectrum, Apr. 23, and we use the recombination time to estimate the mass of the ejecta, 10-5f Msun for a filling factor f. Numerous absorption-line systems were detected in the Balmer, Fe-peak, Ca II, and Na I lines, mirrored in broader emission-line components, that showed an "accelerated" displacement in velocity. We also show that the time sequence of these absorptions, which are common to all lines and arise only in the ejecta, can be described by a recombination front moving outward in the expanding gas without either a stellar wind or circumstellar collisions. By the end of May, the ejecta were showing signs of turning optically thin in the ultraviolet
Phase-resolved spectroscopy of the low-mass X-ray binaries 1636-536/V801 Arae and 1735-444/V926 Scorpii
No full textPhase-resolved spectroscopy of the low-mass X-ray binaries 1636-536/V801 Arae and 1735-444/V926 Scorpii Augusteijn, T.; van der Hooft, F.; de Jong, J.A.; van Kerkwijk, M.H.; van Paradijs, J.A. Published in: Astronomy & Astrophysics Link to publication Citation for published version (APA): Augusteijn, T., van der Hooft, F., de Jong, J. A., van Kerkwijk, M. H., & van Paradijs, J. A. (1998). Phaseresolved spectroscopy of the low-mass X-ray binaries 1636-536/V801 Arae and 1735-444/V926 Scorpii. Astronomy & Astrophysics, 332, 561-568. General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract. We present phase-resolved spectroscopy of the optical counterparts V 801 Ara and V 926 Sco of the low-mass X-ray binaries 1636-536 and 1735-444. To assist in the interpretation of the spectroscopic observations we derive new ephemerides for the photometric variations of both sources. Superior conjunction of the line emission region occurs at photometric phase ∼0.7 in both sources, which indicates that these variations are dominated by a component originating from the point where the mass stream from the donor star intersects the outer disk. We find that the properties of 1636-536/V 801 Ara and 1735-444/V 926 Sco are very similar
Perigrinatie ofte veertichiarige reyse der kinderen Israels uyt Egipten, door de Roodezee : mitsgaders de woestyne tot in 't beloofde landt Canaan : met groote vlijt uyt verscheyden auctoren by een gestelt, uyt de H.Schrift gecorigeert, ende in 't licht g
No full textGenummerd rechtsonder: 3 | Beschreven in: Poortman en Augusteijn, Kaarten in bijbels p. 247 |
The spectroscopic evolution of the recurrent nova T Pyxidis during its 2011 outburst. II. The optically thin phase and the structure of the ejecta in recurrent novae
No full textAims. We continue our study of the physical properties of the recurrent nova T Pyx, focussing on the structure of the ejecta in the nebular stage of expansion during the 2011 outburst.
Methods. The nova was observed contemporaneously with the Nordic Optical Telescope (NOT), at high resolution spectroscopic resolution (R ≈ 65 000) on 2011 Oct. 11 and 2012 Apr. 8 (without absolute flux calibration), and with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST), at high resolution (R ≈ 30 000) on 2011 Oct. 10 and 2012 Mar. 28 (absolute fluxes). The NOT spectra cover 3800–7300 Å, the HST spectra from 2011 Oct. cover 1150–5700 Å while the 2012 Mar. spectrum covers 1150–1700 Å. We use standard plasma diagnostics (e.g. [O III] and [N II] line ratios and the Hβ line fluxes) to constrain electron densities and temperatures. Using Monte Carlo modeling of the ejecta, we derive the structure and filling factor from comparisons to the optical and ultraviolet line profiles.
Results. The ejecta can be modeled using an axisymmetric conical – bipolar – geometry with a low inclination of the axis to the line of sight, i = 15 ± 5 degrees, compatible with published results from high angular resolution optical spectro-interferometry. The structure is similar to that observed in the other short orbital period recurrent novae (e.g. CI Aql, U Sco) and RNe candidate KT Eri during their nebular stages. We show that the electron density scales as t-3 as expected from a ballistically ejected constant mass shell; there is no need to invoke a continuing mass outflow following the eruption. The derived mass for the ejecta with filling factor f ≈ 3%, Mej ≈ 2 × 10-6 M⊙ is similar to that obtained for other recurrent nova ejecta but inconsistent with the previously reported extended optically thick epoch of the explosion. We suggest that the system underwent a common envelope phase following the explosion that produced the recombination event. Implications for the dynamics of the recurrent novae are discussed.
Conclusions. The compact recurrent novae can be understood within a single phenomenological model with bipolar, although not jet-like, low mass ejecta
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
De gelegentheyt van 't Paradys ende 't landt Canaan : mitsgaders d' eerst bewoonde landen der patriarchen
No full textGenummerd rechtsonder : 5 | Beschreven in: Poortman en Augusteijn, Kaarten in bijbels p. 206 |
De gelegentheyt van 't Paradys ende 't landt Canaan : mitsgaders de eerst bewoonde landen der patriarchen
No full textGenummerd rechtsonder : 2 | Beschreven in: Poortman en Augusteijn, Kaarten in bijbels p. 246 |
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
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