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Title: THE DWARF NOVA OUTBURSTS OF NOVA HER 1960 (=V446 HER)

Abstract

V446 Her is the best example of an old nova which has developed dwarf nova (DN) eruptions in the post-nova state. We report on observed properties of the long-term light curve of V446 Her, using photometry over 19 years. Yearly averages of the outburst (OB) magnitudes show a decline of {approx}0.013 mag yr{sup -1}, consistent with the decline of other post-novae that do not have DN OBs. Previous suggestions of bimodal distributions of the amplitudes and widths of the OBs are confirmed. The OBs occur at a mean spacing of 18 days but the range of spacings is large (13-30 days). From simulations of DN OBs, it has been predicted that the OB spacing in V446 Her will increase as M-dot from the red dwarf companion slowly falls following the nova; however, the large intrinsic scatter in the spacings serves to hide any evidence of this effect. We do find a systematic change in the OB pattern in which the brighter, wider type of OBs disappeared after late 2003, and this phenomenon is suggested to be due to falling M-dot following the nova.

Authors:
 [1];  [2];  [3]
  1. Astronomy Department, Indiana University, Swain Hall West, Bloomington, IN 47405 (United States)
  2. Department of Physical Sciences, Arkansas Tech University, 1701 N. Boulder Ave., Russellville, AR 72801-2222 (United States)
  3. Department of Terrestrial Magnetism, Carnegie Institute of Washington, 5241 Broad Branch Road NW, Washington, DC 2001 (United States)
Publication Date:
OSTI Identifier:
21583175
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 141; Journal Issue: 4; Other Information: DOI: 10.1088/0004-6256/141/4/121
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ERUPTION; NOVAE; PHOTOMETRY; SIMULATION; VISIBLE RADIATION; BINARY STARS; ELECTROMAGNETIC RADIATION; ERUPTIVE VARIABLE STARS; RADIATIONS; STARS; VARIABLE STARS

Citation Formats

Honeycutt, R. K., Robertson, J. W., and Kafka, S., E-mail: honey@astro.indiana.edu, E-mail: jrobertson@atu.edu, E-mail: skafka@dtm.ciw.edu. THE DWARF NOVA OUTBURSTS OF NOVA HER 1960 (=V446 HER). United States: N. p., 2011. Web. doi:10.1088/0004-6256/141/4/121.
Honeycutt, R. K., Robertson, J. W., & Kafka, S., E-mail: honey@astro.indiana.edu, E-mail: jrobertson@atu.edu, E-mail: skafka@dtm.ciw.edu. THE DWARF NOVA OUTBURSTS OF NOVA HER 1960 (=V446 HER). United States. doi:10.1088/0004-6256/141/4/121.
Honeycutt, R. K., Robertson, J. W., and Kafka, S., E-mail: honey@astro.indiana.edu, E-mail: jrobertson@atu.edu, E-mail: skafka@dtm.ciw.edu. 2011. "THE DWARF NOVA OUTBURSTS OF NOVA HER 1960 (=V446 HER)". United States. doi:10.1088/0004-6256/141/4/121.
@article{osti_21583175,
title = {THE DWARF NOVA OUTBURSTS OF NOVA HER 1960 (=V446 HER)},
author = {Honeycutt, R. K. and Robertson, J. W. and Kafka, S., E-mail: honey@astro.indiana.edu, E-mail: jrobertson@atu.edu, E-mail: skafka@dtm.ciw.edu},
abstractNote = {V446 Her is the best example of an old nova which has developed dwarf nova (DN) eruptions in the post-nova state. We report on observed properties of the long-term light curve of V446 Her, using photometry over 19 years. Yearly averages of the outburst (OB) magnitudes show a decline of {approx}0.013 mag yr{sup -1}, consistent with the decline of other post-novae that do not have DN OBs. Previous suggestions of bimodal distributions of the amplitudes and widths of the OBs are confirmed. The OBs occur at a mean spacing of 18 days but the range of spacings is large (13-30 days). From simulations of DN OBs, it has been predicted that the OB spacing in V446 Her will increase as M-dot from the red dwarf companion slowly falls following the nova; however, the large intrinsic scatter in the spacings serves to hide any evidence of this effect. We do find a systematic change in the OB pattern in which the brighter, wider type of OBs disappeared after late 2003, and this phenomenon is suggested to be due to falling M-dot following the nova.},
doi = {10.1088/0004-6256/141/4/121},
journal = {Astronomical Journal (New York, N.Y. Online)},
number = 4,
volume = 141,
place = {United States},
year = 2011,
month = 4
}
  • We have constructed vertically integrated, steady state convective models of accretion disks to explore the mechanism of instability in dwarf novae. The models and observations of dwarf novae suggest a picture in which transferred matter piles up in an optically thin torus. The torus eventually becomes optically thick and the resulting convective structure is thermally unstable. Matter then flows inward, and the sudden conversion of gravitational potential energy to radiation is identified as the dwarf nova outburst. At sufficiently high mass accretion rates, the inflow is continuous.
  • The disk instability model for dwarf nova eruptions is investigated by computing the spectral development of the accretion disk through a complete limit cycle. Observed stellar spectra are used to model the radiation emitted by optically thick annuli within the disc. The general findings agree with those of Smak (1984) and Pringle et al. (1986). It is suggested that the dwarf nova oscillations might be a source of information concerning the evolution of the inner disk and that detailed observations of this phenomenon can be used to test various outburst mechanisms. 74 references.
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