Search

Your search keyword '"Harman, D.J."' showing total 8 results
Start Over Author "Harman, D.J."
8 results on '"Harman, D.J."'

1. A recurrent nova super-remnant in the Andromeda galaxy

Author

Darnley, M.J., Hounsell, R., O’Brien, T.J., Henze, M., Rodríguez-Gil, P., Shafter, A.W., Shara, M.M., Vaytet, N.M.H., Bode, M.F., Ciardullo, R., Davis, B.D., Galera-Rosillo, R., Harman, D.J., Harvey, E.J., Healy, M.W., Ness, J.-U., Ribeiro, V.A.R.M., Williams, S.C., Darnley, M.J., Hounsell, R., O’Brien, T.J., Henze, M., Rodríguez-Gil, P., Shafter, A.W., Shara, M.M., Vaytet, N.M.H., Bode, M.F., Ciardullo, R., Davis, B.D., Galera-Rosillo, R., Harman, D.J., Harvey, E.J., Healy, M.W., Ness, J.-U., Ribeiro, V.A.R.M., and Williams, S.C.

Abstract

The accretion of hydrogen onto a white dwarf star ignites a classical nova eruption(1,2)-a thermonuclear runaway in the accumulated envelope of gas, leading to luminosities up to a million times that of the Sun and a high-velocity mass ejection that produces a remnant shell (mainly consisting of insterstellar medium). Close to the upper mass limit of a white dwarf(3) (1.4 solar masses), rapid accretion of hydrogen (about 10(-7) solar masses per year) from a stellar companion leads to frequent eruptions on timescales of years(4,5) to decades(6). Such binary systems are known as recurrent novae. The ejecta of recurrent novae, initially moving at velocities of up to 10,000 kilometres per second(7), must 'sweep up' the surrounding interstellar medium, creating cavities in space around the nova binary. No remnant larger than one parsec across from any single classical or recurrent nova eruption is known(8-10), but thousands of successive recurrent nova eruptions should be capable of generating shells hundreds of parsecs across. Here we report that the most frequently recurring nova, M31N 2008-12a in the Andromeda galaxy (Messier 31 or NGC 224), which erupts annually(11), is indeed surrounded by such a super-remnant with a projected size of at least 134 by 90 parsecs. Larger than almost all known remnants of even supernova explosions(12), the existence of this shell demonstrates that the nova M31N 2008-12a has erupted with high frequency for millions of years.

Published
2019

2. M31N 2008-12a - The Remarkable Recurrent Nova in M31: Panchromatic Observations of the 2015 Eruption

Author

Darnley, M.J., Henze, M., Bode, M.F., Hachisu, I., Hernanz, M., Hornoch, K., Hounsell, R., Kato, M., Ness, J.-U., Osborne, J.P., Page, K.L., Ribeiro, V.A.R.M., Rodríguez-Gil, P., Shafter, A.W., Shara, M.M., Steele, I.A., Williams, S.C., Arai, A., Arcavi, I., Barsukova, E.A., Boumis, P., Chen, T., Fabrika, S., Figueira, J., Gao, X., Gehrels, N., Godon, P., Goranskij, V.P., Harman, D.J., Hartmann, D.H., Hosseinzadeh, G., Horst, J.C., Itagaki, K., José, J., Kabashima, F., Kaur, A., Kawai, N., Kennea, J.A., Kiyota, S., Kučáková, H., Lau, K.M., Maehara, H., Naito, H., Nakajima, K., Nishiyama, K, O'Brien, T.J., Quimby, R., Sala, G., Sano, Y., Sion, E.M., Valeev, A.F., Watanabe, F., Watanabe, M., Williams, B.F., Xu, Z., Darnley, M.J., Henze, M., Bode, M.F., Hachisu, I., Hernanz, M., Hornoch, K., Hounsell, R., Kato, M., Ness, J.-U., Osborne, J.P., Page, K.L., Ribeiro, V.A.R.M., Rodríguez-Gil, P., Shafter, A.W., Shara, M.M., Steele, I.A., Williams, S.C., Arai, A., Arcavi, I., Barsukova, E.A., Boumis, P., Chen, T., Fabrika, S., Figueira, J., Gao, X., Gehrels, N., Godon, P., Goranskij, V.P., Harman, D.J., Hartmann, D.H., Hosseinzadeh, G., Horst, J.C., Itagaki, K., José, J., Kabashima, F., Kaur, A., Kawai, N., Kennea, J.A., Kiyota, S., Kučáková, H., Lau, K.M., Maehara, H., Naito, H., Nakajima, K., Nishiyama, K, O'Brien, T.J., Quimby, R., Sala, G., Sano, Y., Sion, E.M., Valeev, A.F., Watanabe, F., Watanabe, M., Williams, B.F., and Xu, Z.

Abstract

Contains fulltext : 164095.pdf (preprint version ) (Open Access)

Published
2016

5. J320 (PN G190.3−17.7) as a poly-polar planetary nebula surrounded by point-symmetric knots.

Author

Harman, D.J., Bryce, M., López, J.A., Meaburn, J., and Holloway, A.J.

Subjects
*PLANETARY nebulae, *SPECTROMETERS, *INTERSTELLAR medium, *KINEMATICS, *DYNAMICS, *ASTROPHYSICS
Abstract

Spatially resolved, long-slit spectra obtained with the Manchester echelle spectrometer of the planetary nebula J320 have been compared with Hubble Space Telescope and ground-based images. The morphology and kinematics of the nebular core have been convincingly modelled using the Xshape code. Two and possibly three bipolar lobes, expanding at but with different axial orientations, have been found to constitute the bright central nebula. These are found to be surrounded by two sets of point-symmetric, high-speed knots reminiscent of those that could be generated by a bipolar, rotating, episodic jet. Another isolated knot exists but without a counterpart. The sequence and nature of the periodic ejections that have given rise to this complex structure are considered in view of the most recent theories of the shaping and evolution of planetary nebulae. [ABSTRACT FROM AUTHOR]

Published
2004
Full Text
View/download PDF

6. Hubble Space Telescope imaging and ground-based spectroscopy of old nova shells – II. The bipolar shell of the slow nova HR Del.

Author

Harman, D.J. and O'Brien, T.J.

Subjects
*SUPERNOVA remnants, *CIRCUMSTELLAR matter, *INTERSTELLAR medium, *SPECTRUM analysis
Abstract

Presents Hubble Space Telescope WFPC2 imaging of slow nova HR Del in filters centered on the lines of Hα, [N II] and [O III], with corresponding William Herschel Telescope ISIS slit spectroscopy for the lines of Hα, Hβ, [N II] and [O III]. Data showing the ejected shell of HR Del is composed of many small bright knots; Distribution of the knots in a bipolar structure with an equatorial ring, and polar rings or caps; Evidence for a fast wind from the central binary system.

Published
2003
Full Text
View/download PDF

8. Validation of a model for identification of patients with compensated cirrhosis at high risk of decompensation

Author

Rebecca Harris, Audrey Dillon, Imad Waked, Philip J. Johnson, David J. Harman, Stephen Stewart, Alessandro Cucchetti, Sarah Berhane, Guruprasad P. Aithal, Omar Elshaarawy, Lisa Coffey, Indra Neil Guha, Martin W. James, Guha I.N., Harris R., Berhane S., Dillon A., Coffey L., James M.W., Cucchetti A., Harman D.J., Aithal G.P., Elshaarawy O., Waked I., Stewart S., and Johnson P.J.

Subjects
Liver Cirrhosis, Alcohol-Associated Liver Disease Outcome, Male, medicine.medical_specialty, Cirrhosis, Prognosi, Liver Cirrhosi, liver failure, prognostic factor, alcohol-associated liver disease outcome, NAFLD prediction, Predictive Value of Test, Risk Assessment, Severity of Illness Index, Follow-Up Studie, 03 medical and health sciences, Liver disease, 0302 clinical medicine, Model for End-Stage Liver Disease, Predictive Value of Tests, Risk Factors, Internal medicine, medicine, Humans, Decompensation, Prospective Studies, NAFLD Prediction, Aged, Framingham Risk Score, Hepatology, business.industry, Prognostic Factor, Risk Factor, Hazard ratio, Gastroenterology, Middle Aged, Prognosis, medicine.disease, Prospective Studie, Liver, 030220 oncology & carcinogenesis, Cohort, Disease Progression, Egypt, Female, 030211 gastroenterology & hepatology, Liver function, business, Ireland, Liver Failure, Follow-Up Studies, Human
Abstract

Background & Aims It is important to rapidly identify patients with advanced liver disease. Routine tests to assess liver function and fibrosis provide data that can be used to determine patients’ prognoses. We tested the validated the ability of combined data from the ALBI and FIB-4 scoring systems to identify patients with compensated cirrhosis at highest risk for decompensation. Methods We collected data from 145 patients with compensated cirrhosis (91% Child A cirrhosis and median MELD scores below 8) from a cohort in Nottingham, United Kingdom, followed for a median 4.59 years (development cohort). We collected baseline clinical features and recorded decompensation events. We used these data to develop a model based on liver function (assessed by the ALBI score) and extent of fibrosis (assessed by the FIB-4 index) to determine risk of decompensation. We validated the model in 2 independent external cohorts (1 in Dublin, Ireland and 1 in Menoufia, Egypt) comprising 234 patients. Results In the development cohort, 19.3% of the patients developed decompensated cirrhosis. Using a combination of ALBI and FIB-4 scores, we developed a model that identified patients at low vs high risk of decompensation (hazard ratio [HR] for decompensation in patients with high risk score was 7.10). When we tested the scoring system in the validation cohorts, the HR for decompensation in patients with a high-risk score was 12.54 in the Ireland cohort and 5.10 in the Egypt cohort. Conclusion We developed scoring system, based on a combination of ALBI and FIB-4 scores, that identifies patients at risk for liver decompensation. We validated the scoring system in 2 independent international cohorts (Europe and the Middle East), so it appears to apply to diverse populations.

Published
2019

Catalog

Books, media, physical & digital resources
See catalog results