2018A&A...616A..53L


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.04CEST01:31:36

2018A&A...616A..53L - Astronomy and Astrophysics, volume 616A, 53-53 (2018/8-1)

X-ray, UV, and optical observations of the accretion disk and boundary layer in the symbiotic star RT Crucis.

LUNA G.J.M., MUKAI K., SOKOLOSKI J.L., LUCY A.B., CUSUMANO G., SEGRETO A., ARANCIBIA M.J., NUNEZ N.E., PUEBLA R.E., NELSON T. and WALTER F.

Abstract (from CDS):

Compared to mass transfer in cataclysmic variables, the nature of accretion in symbiotic binaries in which red giants transfer material to white dwarfs (WDs) has been difficult to uncover. The accretion flows in a symbiotic binary are most clearly observable, however, when there is no quasi-steady shell burning on the WD to hide them. RT Cru is the prototype of such non-burning symbiotics, with its hard (δ-type) X-ray emission providing a view of its innermost accretion structures. In the past 20yr, RT Cru has experienced two similar optical brightening events, separated by ∼4000-days and with amplitudes of ΔV∼1.5mag. After Swift became operative, the Burst Alert Telescope (BAT) detector revealed a hard X-ray brightening event almost in coincidence with the second optical peak. Spectral and timing analyses of multi-wavelength observations that we describe here, from NuSTAR, Suzaku, Swift/X-Ray Telescope (XRT) + BAT + UltraViolet Optical Telescope (UVOT) (photometry) and optical photometry and spectroscopy, indicate that accretion proceeds through a disk that reaches down to the WD surface. The scenario in which a massive, magnetic WD accretes from a magnetically truncated accretion disk is not supported. For example, none of our data show the minute-time-scale periodic modulations (with tight upper limits from X-ray data) expected from a spinning, magnetic WD. Moreover, the similarity of the UV and X-ray fluxes, as well as the approximate constancy of the hardness ratio within the BAT band, indicate that the boundary layer of the accretion disk remained optically thin to its own radiation throughout the brightening event, during which the rate of accretion onto the WD increased to 6.7x10–9M/yr(d/2kpc)2. For the first time from a WD symbiotic, the NuSTAR spectrum showed a Compton reflection hump at E>10keV, due to hard X-rays from the boundary layer reflecting off of the surface of the WD; the reflection amplitude was 0.77±0.21. The best fit spectral model, including reflection, gave a maximum post-shock temperature of kT=53±4keV, which implies a WD mass of 1.25±0.02M. Although the long-term optical variability in RT Cru is reminiscent of dwarf-novae-type outbursts, the hard X-ray behavior does not correspond to that observed in well-known dwarf nova. An alternative explanation for the brightening events could be that they are due to an enhancement of the accretion rate as the WD travels through the red giant wind in a wide orbit, with a period of about ∼4000-days. In either case, the constancy of the hard X-ray spectrum while the accretion rate rose suggests that the accretion-rate threshold between a mostly optically thin and thick boundary layer, in this object, may be higher than previously thought.

Abstract Copyright: © ESO 2018

Journal keyword(s): binaries: symbiotic - accretion, accretion disks - X-rays: binaries

Simbad objects: 18

goto Full paper

goto View the reference in ADS

Number of rows : 18

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 V* V592 Cas No* 00 20 52.2230642582 +55 42 16.233043666 12.07 12.86 12.79     OB 91 0
2 * omi Cet Mi* 02 19 20.79210 -02 58 39.4956   7.63 6.53 5.03   M5-9IIIe+DA 1434 0
3 V* GK Per No* 03 31 12.0096626899 +43 54 15.467450081   10.2 14.0     K1IV 866 0
4 EGB 4 NL* 06 29 33.9598585876 +71 04 36.392469723   13.29 13.27 13.04   ~ 131 0
5 EM* MWC 560 Sy* 07 25 51.2841922233 -07 44 08.078237799   10.01 9.70 10.60   M4ep+Beq 182 0
6 CD-57 3057 Sy* 10 11 02.9422954740 -57 48 13.944256831   11.26 9.99     M4IIIe 59 0
7 V* RT Cru Sy* 12 34 53.7358537036 -64 33 56.097590683   12.20 11.35 12.09   ~ 78 0
8 V* EX Hya DN* 12 52 24.2220533405 -29 14 56.001981146   13.51 13.49 13.55   M5-6V 647 0
9 V* T CrB Sy* 15 59 30.1619486506 +25 55 12.607985109   11.516 10.247 9.70   M3IIIe_sh 648 0
10 V* V2116 Oph Sy* 17 32 02.1544831482 -24 44 44.125962969   20.78 18.4     M6IIIe 645 1
11 V* RS Oph No* 17 50 13.1592776879 -06 42 28.481553668   12.29 4.30     OB+M2ep 922 0
12 V* MV Lyr No* 19 07 16.2886975947 +44 01 07.867270712   12.18 12.843   12.578 M5Ve 249 0
13 V* CH Cyg Sy* 19 24 33.0697620341 +50 14 29.057625755 8.14 8.77 7.08   5.345 M7IIIab+Be 737 0
14 V* EF Aql Mi* 19 51 51.7199771970 -05 48 16.713394736           ~ 10 0
15 EM* AS 453 Sy* 21 02 09.8173494732 +45 46 32.736335364   16.04 14.68 11.38   Mep 235 0
16 V* SS Cyg DN* 21 42 42.8034554117 +43 35 09.863763484 11.07 8.2 7.70     K5V 1211 1
17 V* Z And Sy* 23 33 39.9551345052 +48 49 05.973842875 8.86 9.35 8.00     M2III+B1eq 501 0
18 V* R Aqr Sy* 23 43 49.4629939776 -15 17 04.184232557   8.823 7.683 9.37   M6.5-8.5e 736 0

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2018A&A...616A..53L and select 'bookmark this link' or equivalent in the popup menu


2020.07.04-01:31:36

© Université de Strasbourg/CNRS

    • Contact