ALBERT

Description: Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable gamma-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce pi(0) decay gamma-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fermi-LAT Collaboration -- Abdo, A A -- Ackermann, M -- Ajello, M -- Atwood, W B -- Baldini, L -- Ballet, J -- Barbiellini, G -- Bastieri, D -- Bechtol, K -- Bellazzini, R -- Berenji, B -- Blandford, R D -- Bloom, E D -- Bonamente, E -- Borgland, A W -- Bouvier, A -- Brandt, T J -- Bregeon, J -- Brez, A -- Brigida, M -- Bruel, P -- Buehler, R -- Burnett, T H -- Buson, S -- Caliandro, G A -- Cameron, R A -- Caraveo, P A -- Carrigan, S -- Casandjian, J M -- Cecchi, C -- Celik, O -- Charles, E -- Chaty, S -- Chekhtman, A -- Cheung, C C -- Chiang, J -- Ciprini, S -- Claus, R -- Cohen-Tanugi, J -- Conrad, J -- Corbel, S -- Corbet, R -- DeCesar, M E -- den Hartog, P R -- Dermer, C D -- de Palma, F -- Digel, S W -- Donato, D -- do Couto e Silva, E -- Drell, P S -- Dubois, R -- Dubus, G -- Dumora, D -- Favuzzi, C -- Fegan, S J -- Ferrara, E C -- Fortin, P -- Frailis, M -- Fuhrmann, L -- Fukazawa, Y -- Funk, S -- Fusco, P -- Gargano, F -- Gasparrini, D -- Gehrels, N -- Germani, S -- Giglietto, N -- Giordano, F -- Giroletti, M -- Glanzman, T -- Godfrey, G -- Grenier, I A -- Grondin, M-H -- Grove, J E -- Guiriec, S -- Hadasch, D -- Harding, A K -- Hayashida, M -- Hays, E -- Healey, S E -- Hill, A B -- Horan, D -- Hughes, R E -- Itoh, R -- Jean, P -- Johannesson, G -- Johnson, A S -- Johnson, R P -- Johnson, T J -- Johnson, W N -- Kamae, T -- Katagiri, H -- Kataoka, J -- Kerr, M -- Knodlseder, J -- Koerding, E -- Kuss, M -- Lande, J -- Latronico, L -- Lee, S-H -- Lemoine-Goumard, M -- Garde, M Llena -- Longo, F -- Loparco, F -- Lott, B -- Lovellette, M N -- Lubrano, P -- Makeev, A -- Mazziotta, M N -- McConville, W -- McEnery, J E -- Mehault, J -- Michelson, P F -- Mizuno, T -- Moiseev, A A -- Monte, C -- Monzani, M E -- Morselli, A -- Moskalenko, I V -- Murgia, S -- Nakamori, T -- Naumann-Godo, M -- Nestoras, I -- Nolan, P L -- Norris, J P -- Nuss, E -- Ohno, M -- Ohsugi, T -- Okumura, A -- Omodei, N -- Orlando, E -- Ormes, J F -- Ozaki, M -- Paneque, D -- Panetta, J H -- Parent, D -- Pelassa, V -- Pepe, M -- Pesce-Rollins, M -- Piron, F -- Porter, T A -- Raino, S -- Rando, R -- Ray, P S -- Razzano, M -- Razzaque, S -- Rea, N -- Reimer, A -- Reimer, O -- Reposeur, T -- Ripken, J -- Ritz, S -- Romani, R W -- Roth, M -- Sadrozinski, H F-W -- Sander, A -- Parkinson, P M Saz -- Scargle, J D -- Schinzel, F K -- Sgro, C -- Shaw, M S -- Siskind, E J -- Smith, D A -- Smith, P D -- Sokolovsky, K V -- Spandre, G -- Spinelli, P -- Stawarz, L -- Strickman, M S -- Suson, D J -- Takahashi, H -- Takahashi, T -- Tanaka, T -- Tanaka, Y -- Thayer, J B -- Thayer, J G -- Thompson, D J -- Tibaldo, L -- Torres, D F -- Tosti, G -- Tramacere, A -- Uchiyama, Y -- Usher, T L -- Vandenbroucke, J -- Vasileiou, V -- Vilchez, N -- Vitale, V -- Waite, A P -- Wallace, E -- Wang, P -- Winer, B L -- Wolff, M T -- Wood, K S -- Yang, Z -- Ylinen, T -- Ziegler, M -- Maehara, H -- Nishiyama, K -- Kabashima, F -- Bach, U -- Bower, G C -- Falcone, A -- Forster, J R -- Henden, A -- Kawabata, K S -- Koubsky, P -- Mukai, K -- Nelson, T -- Oates, S R -- Sakimoto, K -- Sasada, M -- Shenavrin, V I -- Shore, S N -- Skinner, G K -- Sokoloski, J -- Stroh, M -- Tatarnikov, A M -- Uemura, M -- Wahlgren, G M -- Yamanaka, M -- New York, N.Y. -- Science. 2010 Aug 13;329(5993):817-21. doi: 10.1126/science.1192537.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Space Science Division, Naval Research Laboratory, Washington, DC 20375, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20705855" target="_blank"〉PubMed〈/a〉

Description: The relationship between protein three-dimensional structure and function is essential for mechanism determination. Unfortunately, most techniques do not provide a direct measurement of this relationship. Structural data are typically limited to static pictures, and function must be inferred. Conversely, functional assays usually provide little information on structural conformation. We developed a single-molecule technique combining optical tweezers and fluorescence microscopy that allows for both measurements simultaneously. Here we present measurements of UvrD, a DNA repair helicase, that directly and unambiguously reveal the connection between its structure and function. Our data reveal that UvrD exhibits two distinct types of unwinding activity regulated by its stoichiometry. Furthermore, two UvrD conformational states, termed "closed" and "open," correlate with movement toward or away from the DNA fork.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4424897/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4424897/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Comstock, Matthew J -- Whitley, Kevin D -- Jia, Haifeng -- Sokoloski, Joshua -- Lohman, Timothy M -- Ha, Taekjip -- Chemla, Yann R -- R01 GM045948/GM/NIGMS NIH HHS/ -- R01 GM065367/GM/NIGMS NIH HHS/ -- R21 RR025341/RR/NCRR NIH HHS/ -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2015 Apr 17;348(6232):352-4. doi: 10.1126/science.aaa0130. Epub 2015 Apr 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, Center for the Physics of Living Cells, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. ; Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA. ; Department of Physics, Center for the Physics of Living Cells, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. Howard Hughes Medical Institute, Urbana, IL 61801, USA. Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. ; Department of Physics, Center for the Physics of Living Cells, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. ychemla@illinois.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25883359" target="_blank"〉PubMed〈/a〉

Description: Symbiotic stars often contain white dwarfs with quasi-steady shell burning on their surfaces. However, in most symbiotics, the origin of this burning is unclear. In symbiotic slow novae, however, it is linked to a past thermonuclear runaway. In 2015 June, the symbiotic slow nova AG Peg was seen in only its second optical outburst since 1850. This recent outburst was of much shorter duration and lower amplitude than the earlier eruption, and it contained multiple peaks – like outbursts in classical symbiotic stars such as Z And. We report Swift X-ray and UV observations of AG Peg made between 2015 June and 2016 January. The X-ray flux was markedly variable on a time-scale of days, particularly during four days near optical maximum, when the X-rays became bright and soft. This strong X-ray variability continued for another month, after which the X-rays hardened as the optical flux declined. The UV flux was high throughout the outburst, consistent with quasi-steady shell burning on the white dwarf. Given that accretion discs around white dwarfs with shell burning do not generally produce detectable X-rays (due to Compton-cooling of the boundary layer), the X-rays probably originated via shocks in the ejecta. As the X-ray photoelectric absorption did not vary significantly, the X-ray variability may directly link to the properties of the shocked material. AG Peg's transition from a slow symbiotic nova (which drove the 1850 outburst) to a classical symbiotic star suggests that shell burning in at least some symbiotic stars is residual burning from prior novae.

Description: Symbiotic star surveys have traditionally relied almost exclusively on low resolution optical spectroscopy. However, we can obtain a more reliable estimate of their total Galactic population by using all available signatures of the symbiotic phenomenon. Here we report the discovery of a hard X-ray source, 4PBC J0642.9+5528, in the Swift hard X-ray all-sky survey, and identify it with a poorly studied red giant, SU Lyn, using pointed Swift observations and ground-based optical spectroscopy. The X-ray spectrum, the optical to UV spectrum, and the rapid UV variability of SU Lyn are all consistent with our interpretation that it is a symbiotic star containing an accreting white dwarf. The symbiotic nature of SU Lyn went unnoticed until now, because it does not exhibit emission lines strong enough to be obvious in low resolution spectra. We argue that symbiotic stars without shell-burning have weak emission lines, and that the current lists of symbiotic stars are biased in favour of shell-burning systems. We conclude that the true population of symbiotic stars has been underestimated, potentially by a large factor.

Description: Single-stranded (ss)DNA binding (SSB) proteins bind with high affinity to ssDNA generated during DNA replication, recombination, and repair; however, these SSBs must eventually be displaced from or reorganized along the ssDNA. One potential mechanism for reorganization is for an ssDNA translocase (ATP-dependent motor) to push the SSB along ssDNA. Here...

Description: Since the Fermi discovery of -rays from novae, one of the biggest questions in the field has been how novae generate such high-energy emission. Shocks must be a fundamental ingredient. Six months of radio observations of the 2012 Nova V5589 Sgr with the VLA and 15 weeks of X-ray observations with Swift /XRT show that the radio emission consisted of: (1) a shock-powered, non-thermal flare; and (2) weak thermal emission from 10 –5 M of freely expanding, photoionized ejecta. Absorption features in the optical spectrum and the peak optical brightness suggest that V5589 Sgr lies 4 kpc away (3.2–4.6 kpc). The shock-powered flare dominated the radio light curve at low frequencies before day 100. The spectral evolution of the radio flare, its high radio brightness temperature, the presence of unusually hard ( kT x 〉 33 keV) X-rays, and the ratio of radio to X-ray flux near radio maximum all support the conclusions that the flare was shock-powered and non-thermal. Unlike most other novae with strong shock-powered radio emission, V5589 Sgr is not embedded in the wind of a red-giant companion. Based on the similar inclinations and optical line profiles of V5589 Sgr and V959 Mon, we propose that shocks in V5589 Sgr formed from collisions between a slow flow with an equatorial density enhancement and a subsequent faster flow. We speculate that the relatively high speed and low mass of the ejecta led to the unusual radio emission from V5589 Sgr, and perhaps also to the non-detection of -rays.

Description: We report observations of the flickering variability of the symbiotic recurrent nova RS Oph at quiescence in five bands ( UBVRI ). We find evidence of a correlation between the peak-to-peak flickering amplitude ( F ) and the average flux of the hot component ( F av ). The correlation is highly significant, with a correlation coefficient of 0.85 and a p -value of ~10 –20 . Combining the data from all wavebands, we find a dependence of the type $\Delta F \propto F_{{\rm av}}^k$ , with power-law index k  = 1.02 ± 0.04 for the UBVRI flickering of RS Oph. Thus, the relationship between the amplitude of variability and the average flux of the hot component is consistent with linearity. The rms amplitude of flickering is on average 8 per cent (±2 per cent) of F av . The detected correlation is similar to that found in accreting black holes/neutron stars and cataclysmic variables. The possible reasons are briefly discussed. The data are available upon request from the authors.