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D. E. Calvelo S. D. Vrtilek D. Steeghs M. A. P. Torres J. Neilsen A. V. Filippenko J. I. González Hernández † 《Monthly notices of the Royal Astronomical Society》2009,399(2):539-549
We present Doppler and modulation tomography of the X-ray nova XTE J1118+480 with data obtained during quiescence using the 10-m Keck II telescope. The hotspot where the gas stream hits the accretion disc is seen in Hα, Hβ, He i λ5876 and Ca ii λ8662, thus verifying the presence of continued mass transfer within the system. The disc is clearly seen in Hα and Ca ii λ8662. We image the mass-donor star in narrow absorption lines of Na i λλ5890, 5896, 8183, 8195 and Ca ii λ8662, implying an origin from the secondary itself rather than the interstellar medium. We also detect deviations in the centroid of the double peak of Hα akin to those found by Zurita et al. suggesting disc eccentricity. 相似文献
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Subsurface video footage can be used as a successful identification tool for various marine organisms; however, processing of such information has proven challenging. This study tests the use of automated software to assist with photo-identification of the great white shark Carcharodon carcharias in the region of Gansbaai, on the south coast of South Africa. A subsurface photo catalogue was created from underwater video footage. Single individuals were identified by using pigmentation patterns. From this catalogue, two images of the head for each individual were inserted into automated contour-recognition software (Interactive Individual Identification System Beta Contour 3.0). One image was used to search the database, the other served as a reference image. Identification was made by means of a contour, assigned using the software to the irregular border of grey and white on the shark's head. In total, 90 different contours were processed. The output provided ranks, where the first match would be a direct identification of the individual. The method proved to be accurate, in particular for high-quality images where 88.24% and 94.12%, respectively, were identified by two independent analysts as first match, and with all individuals identified within the top 10 matches. The inclusion of metadata improved accuracy and precision, allowing identification of even low-quality images. 相似文献
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M. T. Rushton T. R. Geballe A. V. Filippenko R. Chornock W. Li D. C. Leonard † R. J. Foley A. Evans B. Smalley J. Th. van Loon S. P. S. Eyres 《Monthly notices of the Royal Astronomical Society》2005,360(4):1281-1289
We report optical and near-infrared spectroscopy, and optical spectropolarimetry, of the peculiar variable V838 Mon during the multiple outburst phase in early 2002. The spectral evolution is exceptional. Our earliest spectra (2002 January) are noteworthy for their strong absorption lines of barium and strontium in the optical, and bands of CO and circumstellar H2 O in the near-infrared. All but the CO weaken or are absent in later spectra. The behaviour of the CO band during this phase is extraordinary: initially in absorption, it was observed two months later in optically thick emission. The excitation of the CO is probably the result of the propagation of a shock wave at the third maximum. The two spectropolarimetric epochs were taken 6 and 27 d after the second outburst on 2002 February 8. The polarization at both times was measured to be pV ≈ 2.7 per cent. Nearly all of the measured polarization is believed to be due to interstellar dust, a conclusion that is consistent with previous studies. At both epochs, however, a weak and variable intrinsic component is thought to be present. Between January and March of 2002 the luminosity of V838 Mon increased by a factor of 15 and the apparent diameter increased fourfold. 相似文献
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A. Pastorello P. A. Mazzali G. Pignata S. Benetti E. Cappellaro A. V. Filippenko W. Li W. P. S. Meikle A. A. Arkharov G. Blanc F. Bufano A. Derekas M. Dolci N. Elias-Rosa R. J. Foley M. Ganeshalingam A. Harutyunyan L. L. Kiss R. Kotak V. M. Larionov J. R. Lucey N. Napoleone H. Navasardyan F. Patat J. Rich S. D. Ryder M. Salvo B. P. Schmidt V. Stanishev P. Székely S. Taubenberger S. Temporin M. Turatto W. Hillebrandt 《Monthly notices of the Royal Astronomical Society》2007,377(4):1531-1552
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N. Elias-Rosa S. Benetti M. Turatto E. Cappellaro S. Valenti A. A. Arkharov J. E. Beckman A. Di Paola M. Dolci A. V. Filippenko R. J. Foley K. Krisciunas V. M. Larionov W. Li W. P. S. Meikle A. Pastorello G. Valentini W. Hillebrandt 《Monthly notices of the Royal Astronomical Society》2008,384(1):107-122
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A. Pastorello M. Turatto S. Benetti E. Cappellaro I. J. Danziger P. A. Mazzali F. Patat A. V. Filippenko D. J. Schlegel † T. Matheson ‡ 《Monthly notices of the Royal Astronomical Society》2002,333(1):27-38
We present the photometric and spectroscopic evolution of the type IIn SN 1995G in NGC 1643, on the basis of 4 years of optical and infrared observations. This supernova shows very flat optical light curves similar to SN 1988Z, with a slow decline rate at all times. The spectra are characterized by strong Balmer lines with multiple components in emission and with a P Cygni absorption component blueshifted by only 700 km s−1 . This feature indicates the presence of a slowly expanding shell above the SN ejecta as in the case of SNe 1994aj and 1996L. As in other SNe IIn, the slow luminosity decline cannot be explained only with a radioactive energy input, and an additional source of energy is required, most likely that produced by the interaction between supernova ejecta and a pre-existent circumstellar medium (CSM). It was estimated that the shell material has a density n H ≫108 cm-3 , consistent with the absence of forbidden lines in the spectra. About 2 years after the burst the low-velocity shell is largely overtaken by the SN ejecta and the luminosity drops at a faster rate. 相似文献
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A. Melandri C. Guidorzi S. Kobayashi D. Bersier C. G. Mundell P. Milne A. Pozanenko W. Li A. V. Filippenko Y. Urata M. Ibrahimov I. A. Steele A. Gomboc R. J. Smith N. R. Tanvir E. Rol K. Huang 《Monthly notices of the Royal Astronomical Society》2009,395(4):1941-1949
We present a comprehensive multiwavelength temporal and spectral analysis of the 'fast rise exponential decay' GRB 070419A. The early-time emission in the γ-ray and X-ray bands can be explained by a central engine active for at least 250 s, while at late times the X-ray light curve displays a simple power-law decay. In contrast, the observed behaviour in the optical band is complex (from 102 up to 106 s). We investigate the light-curve behaviour in the context of the standard forward/reverse shock model; associating the peak in the optical light curve at ∼450 s with the fireball deceleration time results in a Lorenz factor Γ≈ 350 at this time. In contrast, the shallow optical decay between 450 and 1500 s remains problematic, requiring a reverse shock component whose typical frequency is above the optical band at the optical peak time for it to be explained within the standard model. This predicts an increasing flux density for the forward shock component until t ∼ 4 × 106 s , inconsistent with the observed decay of the optical emission from t ∼ 104 s . A highly magnetized fireball is also ruled out due to unrealistic microphysic parameters and predicted light-curve behaviour that is not observed. We conclude that a long-lived central engine with a finely tuned energy injection rate and a sudden cessation of the injection is required to create the observed light curves, consistent with the same conditions that are invoked to explain the plateau phase of canonical X-ray light curves of γ-ray bursts. 相似文献
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Shields JC Rix HW McIntosh DH Ho LC Rudnick G Filippenko AV Sargent WL Sarzi M 《The Astrophysical journal》2000,536(1):L27-L30
We examine the supernova remnant SNR 0540-697 in the Large Magellanic Cloud (LMC) using data from the Chandra Advanced CCD Imaging Spectrometer. The X-ray emission from this supernova remnant (SNR) had previously been hidden in the bright emission of the nearby X-ray binary LMC X-1; however, new observations with Chandra can finally reveal the SNR's structure and spectrum. We find the SNR to be a thick-shelled structure about 19 pc in diameter, with a brightened northeast region. Spectral results suggest a temperature of 0.31 keV and an X-ray luminosity (0.3-3.0 keV) of 8.4x1033 ergs s(-1). We estimate an age of 12,000-20,000 yr for this SNR, but note that this estimate does not take into account the possibility of cavity expansion or other environmental effects. 相似文献