The broad-lined Type Ic supernova 2003jd Valenti, S.; Benetti, S.; Cappellaro, E. ...
Monthly notices of the Royal Astronomical Society,
February 2008, Letnik:
383, Številka:
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The results of a worldwide coordinated observational campaign on the broad-lined Type Ic supernova (SN Ic) 2003jd are presented. In total, 74 photometric data points and 26 spectra were collected ...using 11 different telescopes. SN 2003jd is one of the most luminous SN Ic ever observed. A comparison with other Type Ic supernovae (SNe Ic) confirms that SN 2003jd represents an intermediate case between broad-line events (2002ap, 2006aj) and highly energetic SNe (1997ef, 1998bw, 2003dh, 2003lw), with an ejected mass of Mej= 3.0 ± 1 M⊙ and a kinetic energy of Ek(tot) = 7+3−2× 1051erg. SN 2003jd is similar to SN 1998bw in terms of overall luminosity, but it is closer to SNe 2006aj and 2002ap in terms of light-curve shape and spectral evolution. The comparison with other SNe Ic suggests that the V-band light curves of SNe Ic can be partially homogenized by introducing a time-stretch factor. Finally, because of the similarity of SN 2003jd to the SN 2006aj/XRF 060218 event, we discuss the possible connection of SN 2003jd with a gamma-ray burst (GRB).
We present new spectroscopic and photometric data of the Type Ibn supernovae 2006jc, 2000er and 2002ao. We discuss the general properties of this recently proposed supernova family, which also ...includes SN 1999cq. The early-time monitoring of SN 2000er traces the evolution of this class of objects during the first few days after the shock breakout. An overall similarity in the photometric and spectroscopic evolution is found among the members of this group, which would be unexpected if the energy in these core-collapse events was dominated by the interaction between supernova ejecta and circumstellar medium. Type Ibn supernovae appear to be rather normal Type Ib/c supernova explosions which occur within a He-rich circumstellar environment. SNe Ibn are therefore likely produced by the explosion of Wolf–Rayet progenitors still embedded in the He-rich material lost by the star in recent mass-loss episodes, which resemble known luminous blue variable eruptions. The evolved Wolf–Rayet star could either result from the evolution of a very massive star or be the more evolved member of a massive binary system. We also suggest that there are a number of arguments in favour of a Type Ibn classification for the historical SN 1885A (S-Andromedae), previously considered as an anomalous Type Ia event with some resemblance to SN 1991bg.
We analyze OGLE-2003-BLG-262, a relatively short (t sub(E) = 12.5 plus or minus 0.1 day) microlensing event generated by a point-mass lens transiting the face of a K giant source in the Galactic ...bulge. We use the resulting finite-source effects to measure the angular Einstein radius, theta sub(E) = 195 plus or minus 17 mu as, and so constrain the lens mass to the FWHM interval 0.08 < M/M sub(o) < 0.54. The lens-source relative proper motion is mu sub(rel) = 27 plus or minus 2 km s super(-1) kpc super(-1). Both values are typical of what is expected for lenses detected toward the bulge. Despite the short duration of the event, we detect marginal evidence for a "parallax asymmetry" but argue that this is more likely to be induced by acceleration of the source, a binary lens, or possibly by statistical fluctuations. Although OGLE-2003-BLG-262 is only the second published event to date in which the lens transits the source, such events will become more common with the new OGLE-III survey in place. We therefore give a detailed account of the analysis of this event to facilitate the study of future events of this type.
We present densely sampled BVRI light curves of the optical transient associated with the gamma-ray burst (GRB) 030329, the result of a coordinated observing campaign conducted at five observatories. ...Augmented with published observations of this GRB, the compiled optical data set contains 2687 photometric measurements, obtained between 78 minutes and 79 days after the burst. This data set allows us to follow the photometric evolution of the transient with unprecedented detail. We use the data to constrain the light curve of the underlying supernova (SN) 2003dh and show that it evolved faster than and was probably somewhat fainter than the Type Ic SN 1998bw, associated with GRB 980425. We find that our data can be described by a broken power-law decay perturbed by a complex variable component. The early- and late-time decay slopes are determined to be alpha sub(1) similar to 1.1 and alpha sub(2) similar to 2. Assuming this single-break power-law model, we constrain the break to lie between approx3 and approx8 days after the burst. This simple, singly broken power-law model, derived only from the analysis of our optical observations, may also account for available multiband data, provided that the break happened approx8 days after the burst. The more complex double-jet model of Berger et al. provides a comparable fit to the optical, X-ray, millimeter, and radio observations of this event. The unique early coverage available for this event allows us to trace the color evolution of the afterglow during the first hours after the burst. We detect a significant change in optical colors during the first day. Our color analysis is consistent with a cooling-break frequency sweeping through the optical band during the first day. The light curves of GRB 030329 reveal a rich array of variations, superposed over the mean power-law decay. We find that the early variations ( similar to 8 days after the burst) are asymmetric, with a steep rise followed by a relatively slower (by a factor of about 2) decline. The variations maintain a similar timescale during the first 4 days and then get significantly longer. The structure of these variations is similar to those previously detected in the afterglows of several GRBs.
Photometric observations of V4633 Sgr (Nova Sagittarii 1998) during 1998–2005 reveal the presence of a stable photometric periodicity at P1= 180.8 min which is probably the orbital period of the ...underlying binary system. A second period was present in the light curve of the object for 6 yr. Shortly after the nova eruption it was measured as P2= 185.6 min. It has decreased monotonically in the following few years reaching the value P2= 183.9 min in 2003. In 2004 it was no longer detectable. We suggest that the second periodicity is the spin of the magnetic white dwarf of this system that rotates nearly synchronously with the orbital revolution. According to our interpretation, the post-eruption evolution of Nova V4633 Sgr follows a track similar to the one taken by V1500 Cyg (Nova Cygni 1975) after that nova eruption, on a somewhat longer time-scale. The asynchronism is probably the result of the nova outburst that led to a considerable expansion of the white dwarf's photosphere. The increase in the moment of inertia of the star was associated with a corresponding decrease in its spin rate. Our observations have followed the spinning-up of the white dwarf resulting from the contraction of its outer envelope as the star is slowly returning to its pre-outburst state. It is thus the second known asynchronous polar classical nova.
Aims. We present a detailed analysis of OGLE 2004-BLG-482, a relatively high-magnification single-lens microlensing event that exhibits clear extended-source effects. These events are relatively ...rare, but they potentially contain unique information on the stellar atmosphere properties of their source star, as shown in this study. Methods. Our dense photometric coverage of the overall light curve and a proper microlensing modelling allow us to derive measurements of the OGLE 2004-BLG-482source star’s linear limb-darkening coefficients in three bands, including standard Johnson-Cousins I and R, as well as in a broad clear filter. In particular, we discuss in detail the problems of multi-band and multi-site modelling on the expected precision of our results. We also obtained high-resolution UVES spectra as part of a ToO programme at ESO VLT, from which we derive the source star’s precise fundamental parameters. Results. From the high-resolution UVES spectra, we find that OGLE 2004-BLG-482’s source star is a red giant of MK type a bit later than M3, with Teff = 3667 ± 150 K, log g = 2.1 ± 1.0 and an assumed solar metallicity. This is confirmed by an OGLE calibrated colour − magnitude diagram. We then obtain from a detailed microlensing modelling of the light curve linear limb-darkening coefficients that we compare to model-atmosphere predictions available in the literature, and find a very good agreement for the I and R bands. In addition, we perform a similar analysis using an alternative description of limb darkening based on a principal component analysis of ATLAS limb-darkening profiles, and also find a very good agreement between measurements and model predictions.
KPD1930+2752 is a short-period pulsating subdwarf B (sdB) star. It is also an ellipsoidal variable with a known binary period of 2.3 h. The companion is most likely a white dwarf and the total mass ...of the system is close to the Chandresekhar limit. In this paper, we report the results of Whole Earth Telescope (WET) photometric observations during 2003 and a smaller multisite campaign of 2002. From 355h of WET data, we detect 68 pulsation frequencies and suggest an additional 13 frequencies within a crowded and complex temporal spectrum between 3065 and 6343 mu Hz (periods between 326 and 157s). We examine pulsation properties including phase and amplitude stability in an attempt to understand the nature of the pulsation mechanism. We examine a stochastic mechanism by comparing amplitude variations with simulated stochastic data. We also use the binary nature of KPD1930+2752 for identifying pulsation modes via multiplet structure and a tidally induced pulsation geometry. Our results indicate a complicated pulsation structure that includes short-period ( approximately 16h) amplitude variability, rotationally split modes, tidally induced modes and some pulsations which are geometrically limited on the sdB star.
Observations of the long-lived emission-or 'afterglow'-of long-duration γ-ray bursts place them at cosmological distances, but the origin of these energetic explosions remains a mystery. Observations ...of optical emission contemporaneous with the burst of γ-rays should provide insight into the details of the explosion, as well as into the structure of the surrounding environment. One bright optical flash was detected during a burst, but other efforts have produced negative results. Here we report the discovery of the optical counterpart of GRB021004 only 193 seconds after the event. The initial decline is unexpectedly slow and requires varying energy content in the γ-ray burst blastwave over the course of the first hour. Further analysis of the X-ray and optical afterglow suggests additional energy variations over the first few days.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
KPD 1930+2752 is a short-period pulsating subdwarf B (sdB) star. It is also an ellipsoidal variable with a known binary period of 2.3 h. The companion is most likely a white dwarf and the total mass ...of the system is close to the Chandresekhar limit. In this paper, we report the results of Whole Earth Telescope (WET) photometric observations during 2003 and a smaller multisite campaign of 2002. From 355 h of WET data, we detect 68 pulsation frequencies and suggest an additional 13 frequencies within a crowded and complex temporal spectrum between 3065 and 6343 μHz (periods between 326 and 157 s). We examine pulsation properties including phase and amplitude stability in an attempt to understand the nature of the pulsation mechanism. We examine a stochastic mechanism by comparing amplitude variations with simulated stochastic data. We also use the binary nature of KPD 1930+2752 for identifying pulsation modes via multiplet structure and a tidally induced pulsation geometry. Our results indicate a complicated pulsation structure that includes short-period (≈16 h) amplitude variability, rotationally split modes, tidally induced modes and some pulsations which are geometrically limited on the sdB star.
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