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31.
Kulkarni SR Ofek EO Rau A Cenko SB Soderberg AM Fox DB Gal-Yam A Capak PL Moon DS Li W Filippenko AV Egami E Kartaltepe J Sanders DB 《Nature》2007,447(7143):458-460
Historically, variable and transient sources have both surprised astronomers and provided new views of the heavens. Here we report the discovery of an optical transient in the outskirts of the lenticular galaxy Messier 85 in the Virgo cluster. With a peak absolute R magnitude of -12, this event is distinctly brighter than novae, but fainter than type Ia supernovae (which are expected in a population of old stars in lenticular galaxies). Archival images of the field do not show a luminous star at that position with an upper limit in the g filter of about -4.1 mag, so it is unlikely to be a giant eruption from a luminous blue variable star. Over a two-month period, the transient source emitted radiation energy of almost 10(47) erg and subsequently faded in the optical sky. It is similar to, but six times more luminous at peak than, an enigmatic transient in the galaxy M31 (ref. 1). A possible origin of M85 OT2006-1 is a stellar merger. If so, searches for similar events in nearby galaxies will not only allow study of the physics of hyper-Eddington sources, but also probe an important phase in the evolution of stellar binary systems. 相似文献
32.
Shara MM Martin CD Seibert M Rich RM Salim S Reitzel D Schiminovich D Deliyannis CP Sarrazine AR Kulkarni SR Ofek EO Brosch N Lépine S Zurek D De Marco O Jacoby G 《Nature》2007,446(7132):159-162
Cataclysmic variables (classical novae and dwarf novae) are binary star systems in which a red dwarf transfers hydrogen-rich matter, by way of an accretion disk, to its white dwarf companion. In dwarf novae, an instability is believed to episodically dump much of the accretion disk onto the white dwarf. The liberation of gravitational potential energy then brightens these systems by up to 100-fold every few weeks or months. Thermonuclear-powered eruptions thousands of times more luminous occur in classical novae, accompanied by significant mass ejection and formation of clearly visible shells from the ejected material. Theory predicts that the white dwarfs in all dwarf novae must eventually accrete enough mass to undergo classical nova eruptions. Here we report a shell, an order of magnitude more extended than those detected around many classical novae, surrounding the prototypical dwarf nova Z Camelopardalis. The derived shell mass matches that of classical novae, and is inconsistent with the mass expected from a dwarf nova wind or a planetary nebula. The shell observationally links the prototypical dwarf nova Z Camelopardalis with an ancient nova eruption and the classical nova process. 相似文献
33.
INTRODUCTION
The Indian Pulp & Paper Industry is more than a
century old industry . The first paper mill was
established in the year 1832 and today the number
has grown to more than 400 in the organised sector
which are located through out the country . In
addition there are another 500 pulp & paper mills in
the unorganized sector. The Indian pulp & paper
industry can be categorised into large, medium and
small depending on the scale of operation as
indicated in Table -I
Most of the large mills established initially were
based on woody raw materials. 相似文献
34.
Berger E Price PA Cenko SB Gal-Yam A Soderberg AM Kasliwal M Leonard DC Cameron PB Frail DA Kulkarni SR Murphy DC Krzeminski W Piran T Lee BL Roth KC Moon DS Fox DB Harrison FA Persson SE Schmidt BP Penprase BE Rich J Peterson BA Cowie LL 《Nature》2005,438(7070):988-990
Despite a rich phenomenology, gamma-ray bursts (GRBs) are divided into two classes based on their duration and spectral hardness--the long-soft and the short-hard bursts. The discovery of afterglow emission from long GRBs was a watershed event, pinpointing their origin to star-forming galaxies, and hence the death of massive stars, and indicating an energy release of about 10(51) erg. While theoretical arguments suggest that short GRBs are produced in the coalescence of binary compact objects (neutron stars or black holes), the progenitors, energetics and environments of these events remain elusive despite recent localizations. Here we report the discovery of the first radio afterglow from the short burst GRB 050724, which unambiguously associates it with an elliptical galaxy at a redshift z = 0.257. We show that the burst is powered by the same relativistic fireball mechanism as long GRBs, with the ejecta possibly collimated in jets, but that the total energy release is 10-1,000 times smaller. More importantly, the nature of the host galaxy demonstrates that short GRBs arise from an old (> 1 Gyr) stellar population, strengthening earlier suggestions and providing support for coalescing compact object binaries as the progenitors. 相似文献
35.
36.
Cepheids are a class of variable (pulsating) stars whose absolute luminosities are related in a simple manner to their pulsational periods. By measuring the period and using the 'period-luminosity' relationship, astronomers can use the observed visual brightness to determine the distance to the star. Because these stars are very luminous, they can be observed in other galaxies, and therefore can be used to help determine the expansion rate of the Universe (the Hubble constant). Calibration of the period-luminosity relation is a necessary first step, but the small number of sufficiently nearby Cepheids has forced the use of a number of indirect means, with associated systematic uncertainties. Here we present a distance to the Cepheid zeta Geminorum, determined using a direct measurement (by an optical interferometer) of its changes in diameter as it pulsates. Within our uncertainty of 15 per cent, our distance is in agreement with previous indirect determinations. Planned improvements to the instrument will allow us to calibrate directly the period-luminosity relation to better than a few per cent. 相似文献
37.
Soderberg AM Berger E Page KL Schady P Parrent J Pooley D Wang XY Ofek EO Cucchiara A Rau A Waxman E Simon JD Bock DC Milne PA Page MJ Barentine JC Barthelmy SD Beardmore AP Bietenholz MF Brown P Burrows A Burrows DN Bryngelson G Byrngelson G Cenko SB Chandra P Cummings JR Fox DB Gal-Yam A Gehrels N Immler S Kasliwal M Kong AK Krimm HA Kulkarni SR Maccarone TJ Mészáros P Nakar E O'Brien PT Overzier RA de Pasquale M Racusin J Rea N York DG 《Nature》2008,453(7194):469-474
Massive stars end their short lives in spectacular explosions--supernovae--that synthesize new elements and drive galaxy evolution. Historically, supernovae were discovered mainly through their 'delayed' optical light (some days after the burst of neutrinos that marks the actual event), preventing observations in the first moments following the explosion. As a result, the progenitors of some supernovae and the events leading up to their violent demise remain intensely debated. Here we report the serendipitous discovery of a supernova at the time of the explosion, marked by an extremely luminous X-ray outburst. We attribute the outburst to the 'break-out' of the supernova shock wave from the progenitor star, and show that the inferred rate of such events agrees with that of all core-collapse supernovae. We predict that future wide-field X-ray surveys will catch each year hundreds of supernovae in the act of exploding. 相似文献
38.
Briggs TA Rice GI Daly S Urquhart J Gornall H Bader-Meunier B Baskar K Baskar S Baudouin V Beresford MW Black GC Dearman RJ de Zegher F Foster ES Francès C Hayman AR Hilton E Job-Deslandre C Kulkarni ML Le Merrer M Linglart A Lovell SC Maurer K Musset L Navarro V Picard C Puel A Rieux-Laucat F Roifman CM Scholl-Bürgi S Smith N Szynkiewicz M Wiedeman A Wouters C Zeef LA Casanova JL Elkon KB Janckila A Lebon P Crow YJ 《Nature genetics》2011,43(2):127-131
We studied ten individuals from eight families showing features consistent with the immuno-osseous dysplasia spondyloenchondrodysplasia. Of particular note was the diverse spectrum of autoimmune phenotypes observed in these individuals (cases), including systemic lupus erythematosus, Sj?gren's syndrome, hemolytic anemia, thrombocytopenia, hypothyroidism, inflammatory myositis, Raynaud's disease and vitiligo. Haplotype data indicated the disease gene to be on chromosome 19p13, and linkage analysis yielded a combined multipoint log(10) odds (LOD) score of 3.6. Sequencing of ACP5, encoding tartrate-resistant acid phosphatase, identified biallelic mutations in each of the cases studied, and in vivo testing confirmed a loss of expressed protein. All eight cases assayed showed elevated serum interferon alpha activity, and gene expression profiling in whole blood defined a type I interferon signature. Our findings reveal a previously unrecognized link between tartrate-resistant acid phosphatase activity and interferon metabolism and highlight the importance of type I interferon in the genesis of autoimmunity. 相似文献
39.
40.
Ding L Ley TJ Larson DE Miller CA Koboldt DC Welch JS Ritchey JK Young MA Lamprecht T McLellan MD McMichael JF Wallis JW Lu C Shen D Harris CC Dooling DJ Fulton RS Fulton LL Chen K Schmidt H Kalicki-Veizer J Magrini VJ Cook L McGrath SD Vickery TL Wendl MC Heath S Watson MA Link DC Tomasson MH Shannon WD Payton JE Kulkarni S Westervelt P Walter MJ Graubert TA Mardis ER Wilson RK DiPersio JF 《Nature》2012,481(7382):506-510
Most patients with acute myeloid leukaemia (AML) die from progressive disease after relapse, which is associated with clonal evolution at the cytogenetic level. To determine the mutational spectrum associated with relapse, we sequenced the primary tumour and relapse genomes from eight AML patients, and validated hundreds of somatic mutations using deep sequencing; this allowed us to define clonality and clonal evolution patterns precisely at relapse. In addition to discovering novel, recurrently mutated genes (for example, WAC, SMC3, DIS3, DDX41 and DAXX) in AML, we also found two major clonal evolution patterns during AML relapse: (1) the founding clone in the primary tumour gained mutations and evolved into the relapse clone, or (2) a subclone of the founding clone survived initial therapy, gained additional mutations and expanded at relapse. In all cases, chemotherapy failed to eradicate the founding clone. The comparison of relapse-specific versus primary tumour mutations in all eight cases revealed an increase in transversions, probably due to DNA damage caused by cytotoxic chemotherapy. These data demonstrate that AML relapse is associated with the addition of new mutations and clonal evolution, which is shaped, in part, by the chemotherapy that the patients receive to establish and maintain remissions. 相似文献