X-RAY AND OPTICAL OBSERVATIONS OF THE UNIQUE BINARY SYSTEM HD 49798/RX J0648.0-4418

Mereghetti, S; La Palombara, N; Tiengo, A; Pizzolato, F; Esposito, P; Woudt, P A; Israel, G L; Stella, L

doi:10.1088/0004-637X/737/2/51

Title: X-RAY AND OPTICAL OBSERVATIONS OF THE UNIQUE BINARY SYSTEM HD 49798/RX J0648.0-4418

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Abstract

We report the results of XMM-Newton observations of HD 49798/RX J0648.0-4418, the only known X-ray binary consisting of a hot sub-dwarf and a white dwarf. The white dwarf rotates very rapidly (P = 13.2 s) and has a dynamically measured mass of 1.28 {+-} 0.05 M{sub sun}. Its X-ray emission consists of a strongly pulsed, soft component, well fit by a blackbody with kT{sub BB} {approx} 40 eV, accounting for most of the luminosity, and a fainter hard power-law component (photon index {approx}1.6). A luminosity of {approx}10{sup 32} erg s{sup -1} is produced by accretion onto the white dwarf of the helium-rich matter from the wind of the companion, which is one of the few hot sub-dwarfs showing evidence of mass loss. A search for optical pulsations at the South African Astronomical Observatory 1.9 m telescope gave negative results. X-rays were also detected during the white dwarf eclipse. This emission, with luminosity 2 x 10{sup 30} erg s{sup -1}, can be attributed to HD 49798 and represents the first detection of a hot sub-dwarf star in the X-ray band. HD 49798/RX J0648.0-4418 is a post-common-envelope binary which most likely originated from a pair of stars with masses {approx}8-10 M{sub sun}.more »« less

Authors:

Mereghetti, S; La Palombara, N; Tiengo, A; Pizzolato, F ^[1]; Esposito, P ^[2]; Woudt, P A ^[3]; Israel, G L; Stella, L ^[4]

INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, I-20133 Milano (Italy)
INAF-Osservatorio Astronomico di Cagliari, localita Poggio dei Pini, strada 54, I-09012 Capoterra (Italy)
Astronomy Department, and Astrophysics, Cosmology and Gravity Centre, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa)
INAF-Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone (Italy)

Publication Date:: Sat Aug 20 00:00:00 EDT 2011

OSTI Identifier:: 21579974

Resource Type:: Journal Article

Journal Name:: Astrophysical Journal

Additional Journal Information:: Journal Volume: 737; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/737/2/51; Journal ID: ISSN 0004-637X

Country of Publication:: United States

Language:: English

Subject:: 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EMISSION; LUMINOSITY; PULSARS; SPIN; WHITE DWARF STARS; X RADIATION; ANGULAR MOMENTUM; COSMIC RADIO SOURCES; DWARF STARS; ELECTROMAGNETIC RADIATION; IONIZING RADIATIONS; OPTICAL PROPERTIES; PARTICLE PROPERTIES; PHYSICAL PROPERTIES; RADIATIONS; STARS

Citation Formats


                    Mereghetti, S, La Palombara, N, Tiengo, A, Pizzolato, F, Esposito, P, Woudt, P A, Israel, G L, and Stella, L. X-RAY AND OPTICAL OBSERVATIONS OF THE UNIQUE BINARY SYSTEM HD 49798/RX J0648.0-4418.  United States: N. p., 2011. 
        Web.  doi:10.1088/0004-637X/737/2/51.

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                    Mereghetti, S, La Palombara, N, Tiengo, A, Pizzolato, F, Esposito, P, Woudt, P A, Israel, G L, & Stella, L. X-RAY AND OPTICAL OBSERVATIONS OF THE UNIQUE BINARY SYSTEM HD 49798/RX J0648.0-4418.  United States.  https://doi.org/10.1088/0004-637X/737/2/51

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                    Mereghetti, S, La Palombara, N, Tiengo, A, Pizzolato, F, Esposito, P, Woudt, P A, Israel, G L, and Stella, L. 2011.  
        "X-RAY AND OPTICAL OBSERVATIONS OF THE UNIQUE BINARY SYSTEM HD 49798/RX J0648.0-4418".  United States.  https://doi.org/10.1088/0004-637X/737/2/51.

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@article{osti_21579974,

  title        = {X-RAY AND OPTICAL OBSERVATIONS OF THE UNIQUE BINARY SYSTEM HD 49798/RX J0648.0-4418},

  author       = {Mereghetti, S and La Palombara, N and Tiengo, A and Pizzolato, F and Esposito, P and Woudt, P A and Israel, G L and Stella, L},

  abstractNote = {We report the results of XMM-Newton observations of HD 49798/RX J0648.0-4418, the only known X-ray binary consisting of a hot sub-dwarf and a white dwarf. The white dwarf rotates very rapidly (P = 13.2 s) and has a dynamically measured mass of 1.28 {+-} 0.05 M{sub sun}. Its X-ray emission consists of a strongly pulsed, soft component, well fit by a blackbody with kT{sub BB} {approx} 40 eV, accounting for most of the luminosity, and a fainter hard power-law component (photon index {approx}1.6). A luminosity of {approx}10{sup 32} erg s{sup -1} is produced by accretion onto the white dwarf of the helium-rich matter from the wind of the companion, which is one of the few hot sub-dwarfs showing evidence of mass loss. A search for optical pulsations at the South African Astronomical Observatory 1.9 m telescope gave negative results. X-rays were also detected during the white dwarf eclipse. This emission, with luminosity 2 x 10{sup 30} erg s{sup -1}, can be attributed to HD 49798 and represents the first detection of a hot sub-dwarf star in the X-ray band. HD 49798/RX J0648.0-4418 is a post-common-envelope binary which most likely originated from a pair of stars with masses {approx}8-10 M{sub sun}. After the current He-burning phase, HD 49798 will expand and reach the Roche lobe, causing a higher accretion rate onto the white dwarf which can reach the Chandrasekhar limit. Considering the fast spin of the white dwarf, this could lead to the formation of a millisecond pulsar. Alternatively, this system could be a Type Ia supernova progenitor with the appealing characteristic of a short time delay, being the descendent of relatively massive stars.},

  doi          = {10.1088/0004-637X/737/2/51},

  url          = {https://www.osti.gov/biblio/21579974},
  journal      = {Astrophysical Journal},

  issn         = {0004-637X},

  number       = 2,

  volume       = 737,

  place        = {United States},

  year         = {Sat Aug 20 00:00:00 EDT 2011},

  month        = {Sat Aug 20 00:00:00 EDT 2011}

}

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