Detection Of The 1st Observed Outburst Of DW Cancri

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Detection Of The 1st Observed Outburst Of DW
Cancri
Submitted To The JAAVSO
Tim Crawford (Presenter) Arch Cape Observatory,
79916 W. Beach Road, Arch Cape, OR 97102,
USA David Boyd 5 Silver Lane, West Challow,
Wantage, OX12 9TX, UK Carlo Gualdoni Como,
Italy Tomas Gomez Lira 8, 6-A, 28007 Madrid.
Spain Walter MacDonald II PO Box142, Winchester,
ON K0C 2K0 Canada Arto Oksanen Verkkoniementie
30, FI-40950 Muurame, Finland
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Detection Of The 1st Observed Outburst Of DW
Cancri
January 25th, 2007 (UT 070740)
138
123
DW Cnc 11.36
127
Walter MacDonald
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DW Cancri Is Not Just Another Variable Star
DW Cnc Is An Intermediate Polar
So Far Less Than 30 Intermediate Polars Have
Been Identified No More Than 1/3 Have
Probably Been Observed In Outburst
Background NGC6397
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Intermediate Polars Contain aNon-Synchronously
Rotating Magnetized White Dwarf With A Cool
Companion (near the main sequence)
These High Mass Transfer Systems Have An
Accretion Disk Near the White Dwarf Whose
Accretion Activity Is Disrupted By The
Magnetic Field Of the White Dwarf As It Flows
Towards The Magnetic Poles From The Accretion
Disk
M.A. Garlick
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Long Term Light Curve DW Cnc
Visual CCD Observations Early Dates Are
Mostly Visual Therefore Obs Tend To Be Less
Than 15 Mag. Note No Obs Under 14.1 Mag
1/13/96 - 1/21/07
Peranso Software
From AAVSO Data Base
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January 25th, 2007 (UT 070740) DW Cnc OutBurst
Detected
The V Filter Observations Shown On This LC
Chart Were Gathered By Six Amateur Astronomers
From Six Different Nations
12/24/06 02/04/07
Italy
Spain
Canada
GB
AAVSO Data Base
USA
Finland
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Equipment Used
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Large Amplitude Flickering Was Observed As
Detected By Previous Studies of DW Cnc
25 Minutes 1/26/07 During OB
Crawford
3.6 Hours 1/29/07 Post OB
Crawford
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According to Sterken Jascheck,1996, The
Brightness VariationsAre Caused By A Combination
OfEclipsing And By The RotationallyModulated
Accretion Effects
Visualization by Andy Beardmore
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Post Outburst Light Curve
21.5 Hours Of Obs By Boyd from 1/27, 2/3,
2/4,2/52/6 2007Plus 3.6 Hours Of Obs By
Crawford From 1/29
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Primary Period Display Of The White Dwarf Portion
Of DW Cnc System
Post Outburst Light Curve Data
CLEANest Method - Peranso
Rotational Period 38.6 Minutes (Pspin)
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Prewhitened To Remove Primary Period.
Shows Cluster Around 72 minutes With Strongest
Signal At 73.7 Minutes. Plus A Strong One Day
Alias At 70.07 Minutes.
CLEANest Method
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Spin Orbital Beat Period
1/Pbeat 1/Pspin - 1/Porb
Due To Rotation The Accretion Flows
Preferentially On To One Pole Then The Other At
The Beat Period. Our Strong One Day Alias At 70.3
Min Closely Agrees With Patterson et al. 2004
Study Of Pbeat 69.9 Min (Patterson Calculated
Porb 86.1 Min).
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What Caused The Outburst
Disk Instabilities Or Mass Transfer Event?
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Like Dwarf Novae Some IPs
Outbursts Appear To Be The Result of Disk
Instabilities(GK Per, XY Ari YY Dra, For
Example). These Systems Typically Brighten 3-5
Mag For A Duration of 5-50 Days. While Other
IPs Eruptions Are Thought To Be The Result Of A
Mass Transfer Event (TV Col V1223 Sgr, For
Example). These Systems Typically Have Pspin gt
5 of Porb With lt1-2 Mag Change For A Duration
of .5day.
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DW Cnc Had A Magnitude
Change (4 Mag) Similar To Those Systems Whose
Outbursts Are Due To Disk Instabilities But
Possibly A Shorter Duration. With A Pspin 55
Of Porb, DW Cnc Shares This Characteristic
(Pspin gt 5 of Porb) With Those Systems Whose
Outbursts Are Due To A Mass Transfer
Event. Therefore, We Could Reach No Conclusion
As To Which Mechanism Was Responsible For This
First Detected Outburst.
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In Order to Resolve The QuestionOf What Caused
The OutburstOf DW CNC
We Need To Have Observations In Different
Spectrums, Especially X-Ray If Any One Knows How
We Can Trigger Such Observations With IP
Outbursts Please Let Me Know!
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References
AAVSO, 49 Bay State Road, Cambridge, MA
02138 Patterson, Joseph et al. 2004, PASP, 116,
516-526. (Rapid Oscillations in Cataclysmic
Variables XVI. DW Cnc) Sterken, C. Jaschek,
C., 1996, Light Curves of Variable Stars,
Cambridge University Press.
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