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The relationship between X-ray luminosity and duty cycle for dwarf novae and their specific frequency in the inner Galaxy

The relationship between X-ray luminosity and duty cycle for dwarf novae and their specific frequency in the inner Galaxy
The relationship between X-ray luminosity and duty cycle for dwarf novae and their specific frequency in the inner Galaxy
We measure the duty cycles for an existing sample of well-observed, nearby dwarf novae (DNe) using data from American Association of Variable Star Observers, and present a quantitative empirical relation between the duty cycle of DNe outbursts and the X-ray luminosity of the system in quiescence. We have found that log DC = 0.63(±0.21) × (log LX(erg s-1) - 31.3) - 0.95(±0.1), where DC stands for duty cycle. We note that there is intrinsic scatter in this relation greater than what is expected from purely statistical errors. Using the DN X-ray luminosity functions from Pretorius & Knigge and Byckling et al., we compare this relation to the number of DNe in the Galactic Bulge Survey which were identified through optical outbursts during an 8-d-long monitoring campaign. We find a specific frequency of X-ray-bright (LX ≳ 1031 erg s- 1) cataclysmic variables (CVs) undergoing DNe outbursts in the direction of the Galactic bulge of 6.6± 4.7{×} 10^{-5} M_{{*sun;}}^{-1}. Such a specific frequency would give a solar neighbourhood space density of long-period CVs of ρ = 5.6 ± 3.9 × 10-6 pc-3. We advocate the use of specific frequency in future work, given that projects like Large Synoptic Survey Telescope will detect DNe well outside the distance range over which ρ ≈ const.
accretion, accretion discs, stars: dwarf novae, novae, cataclysmic variables
0035-8711
3455-3462
Britt, C.T.
91612ea1-45fc-4047-a119-8d89662a4b3b
Maccarone, T.
c2f1d87b-e2ef-4e33-b09f-a2861d917ea8
Pretorius, M.L.
ce6e49d6-c48e-495f-94bf-96bb8388bd07
Hynes, R.I.
f6158bd7-6589-436a-86e0-c43a779cdd0b
Jonker, P.G.
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Torres, M.A.P.
e7b42f8b-33a2-47bb-94b5-cad7d50a1177
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Johnson, C.B.
5e6e72b5-f070-44d5-a2c3-9942bce624c8
Heinke, C.O.
50442ec4-8a45-4aa5-b425-28d0c896dc08
Steeghs, D.
ab1118c0-944a-427a-bfbf-6b82e1320280
Greiss, S.
5959cc28-5b1d-4e97-b3f1-7f057fcf415c
Nelemans, G.
d8405945-6a36-4e77-9253-167c3dc52e6e
Britt, C.T.
91612ea1-45fc-4047-a119-8d89662a4b3b
Maccarone, T.
c2f1d87b-e2ef-4e33-b09f-a2861d917ea8
Pretorius, M.L.
ce6e49d6-c48e-495f-94bf-96bb8388bd07
Hynes, R.I.
f6158bd7-6589-436a-86e0-c43a779cdd0b
Jonker, P.G.
1c657281-c0dd-4db9-9fd1-899a6c8a34bd
Torres, M.A.P.
e7b42f8b-33a2-47bb-94b5-cad7d50a1177
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Johnson, C.B.
5e6e72b5-f070-44d5-a2c3-9942bce624c8
Heinke, C.O.
50442ec4-8a45-4aa5-b425-28d0c896dc08
Steeghs, D.
ab1118c0-944a-427a-bfbf-6b82e1320280
Greiss, S.
5959cc28-5b1d-4e97-b3f1-7f057fcf415c
Nelemans, G.
d8405945-6a36-4e77-9253-167c3dc52e6e

Britt, C.T., Maccarone, T., Pretorius, M.L., Hynes, R.I., Jonker, P.G., Torres, M.A.P., Knigge, C., Johnson, C.B., Heinke, C.O., Steeghs, D., Greiss, S. and Nelemans, G. (2015) The relationship between X-ray luminosity and duty cycle for dwarf novae and their specific frequency in the inner Galaxy. Monthly Notices of the Royal Astronomical Society, 448 (4), 3455-3462. (doi:10.1093/mnras/stv256).

Record type: Article

Abstract

We measure the duty cycles for an existing sample of well-observed, nearby dwarf novae (DNe) using data from American Association of Variable Star Observers, and present a quantitative empirical relation between the duty cycle of DNe outbursts and the X-ray luminosity of the system in quiescence. We have found that log DC = 0.63(±0.21) × (log LX(erg s-1) - 31.3) - 0.95(±0.1), where DC stands for duty cycle. We note that there is intrinsic scatter in this relation greater than what is expected from purely statistical errors. Using the DN X-ray luminosity functions from Pretorius & Knigge and Byckling et al., we compare this relation to the number of DNe in the Galactic Bulge Survey which were identified through optical outbursts during an 8-d-long monitoring campaign. We find a specific frequency of X-ray-bright (LX ≳ 1031 erg s- 1) cataclysmic variables (CVs) undergoing DNe outbursts in the direction of the Galactic bulge of 6.6± 4.7{×} 10^{-5} M_{{*sun;}}^{-1}. Such a specific frequency would give a solar neighbourhood space density of long-period CVs of ρ = 5.6 ± 3.9 × 10-6 pc-3. We advocate the use of specific frequency in future work, given that projects like Large Synoptic Survey Telescope will detect DNe well outside the distance range over which ρ ≈ const.

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More information

Published date: 1 April 2015
Keywords: accretion, accretion discs, stars: dwarf novae, novae, cataclysmic variables

Identifiers

Local EPrints ID: 430097
URI: https://eprints.soton.ac.uk/id/eprint/430097
ISSN: 0035-8711
PURE UUID: 1104860a-3137-44b0-8d76-d88799965ead

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Date deposited: 11 Apr 2019 16:30
Last modified: 11 Apr 2019 16:30

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