2005ApJ...626..396P

Query : 2005ApJ...626..396P

2005ApJ...626..396P - Astrophys. J., 626, 396-410 (2005/June-2)

X-ray observations of the boundary layer in dwarf novae at low accretion rates.

PANDEL D., CORDOVA F.A., MASON K.O. and PRIEDHORSKY W.C.

Abstract (from CDS):

We present a spectral analysis of XMM-Newton data of 10 dwarf novae, 9 of which were observed during a quiescent state. The X-ray spectra indicate the presence of a hot, optically thin plasma with a temperature distribution consistent with a simple, isobaric cooling flow. The likely origin of the X-ray emission is cooling plasma in the boundary layer settling onto the white dwarf. Using a cooling flow model, we derive the temperatures, accretion rates, rotational velocities, and elemental abundances of the X-ray-emitting gas. We discuss the implications of our findings for the structure of the boundary layer. A comparison of X-ray and ultraviolet luminosities finds no evidence of underluminous boundary layers in any of the quiescent dwarf novae. The X-ray spectrum of EI UMa differs significantly from those of the other objects, showing a strong fluorescent Fe Kα line and a strong O VII line triplet. Based on the observational evidence, we argue that EI UMa is most likely an intermediate polar and not, as previously thought, a dwarf nova.

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Journal keyword(s): Accretion, Accretion Disks - Stars: Binaries: Close - Stars: Novae, Cataclysmic Variables - Stars: Dwarf Novae - Stars: Individual: Constellation Name: OY Carinae - Stars: Individual: Constellation Name: WW Ceti - Stars: Individual: Constellation Name: AB Draconis - Stars: Individual: Constellation Name: U Geminorum - Stars: Individual: Constellation Name: VW Hydri - Stars: Individual: Constellation Name: WX Hydri - Stars: Individual: Constellation Name: T Leonis - Stars: Individual: Constellation Name: TY Piscis Austrini - Stars: Individual: Constellation Name: EI Ursae Majoris - Stars: Individual: Constellation Name: SU Ursae Majoris - X-Rays: Binaries

Simbad objects: 10

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Number of rows : 10

N	Identifier	Otype	ICRS (J2000) RA	ICRS (J2000) DEC	Mag B	Mag V	Mag R	Mag I	Sp type	#ref 1850 - 2026	#notes
1	V* WW Cet	CV*	00 11 24.7726635744	-11 28 43.204518696					~	185	0
2	V* WX Hyi	CV*	02 09 50.8241651856	-63 18 39.831098040	10.70			13.038	~	206	0
3	V* VW Hyi	CV*	04 09 11.3967378648	-71 17 41.554528260	12.786	12.543	14.160		DQ	661	0
4	V* U Gem	CV*	07 55 05.2324414746	+22 00 05.044127985	15.3	14.54			DA	1135	0
5	V* SU UMa	CV*	08 12 28.2695986944	+62 36 22.427676396					B2	516	0
6	V* EI UMa	CV*	08 38 21.9952217352	+48 38 02.163728328	14.9	14.78			~	97	1
7	V* OY Car	CV*	10 06 22.0793274312	-70 14 04.584660540					~	586	0
8	V* QZ Vir	CV*	11 38 26.8241432424	+03 22 07.110298596		15.81			~	269	1
9	V* AB Dra	CV*	19 49 06.5315089272	+77 44 23.339250276	15.209	14.928	14.097		~	124	0
10	V* TY PsA	CV*	22 49 39.9054462120	-27 06 53.126335980	15.61	15.67	16.19		DA	105	0

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