1. TDE in the XMM-Newton slew survey
Richard Saxton
S. Komossa, A. Read,
P. Lira, K. Alexander, P. Esquej,
P. Rodriguez, M. Wieringa, I. Steele

2. Contents
Characteristics of soft-X-ray selected TDE focussing on the ones found in the XMM slew
Where do X-rays in TDE come from?
Galaxy types
Latest results

3. ROSAT – the first TDE detector
Theory had it that disrupted material would circularise and be accreted causing an EUV / soft X-ray flare (Rees 88 etc.) in galactic nuclei. Debris would fall back at a rate of t-5/3 and luminosity would follow the mass.
Launched in 1990
Sky survey found 100,000 objects

4. ROSAT high variability galaxies – Tidal Disruptions (TD)
RXJ
Komossa &
Greiner 1999
RXJ
Greiner+ 2000
Komossa 2012
RXJ
Grupe, Thomas &
Leighly 1999
Rosat discovered several quiescent galaxies with soft X-ray flux variations > 100. Light curve decay roughly compatible with t-5/3 . Dropping by factors of 1000s in some cases.
NGC 5905
Bade, Komossa &
Dahlem 1996;
Gezari+ 2003

5. Summary of ROSAT results
Decays with t-5/3
Decays by factors of 1000s
X-ray spectrum is soft as expected
Shown to be TDE (candidates) rather than AGN, SNR, ULX, Blazars etc.
Number counts low because nothing deep to compare against. Four new ones were found by comparing RASS with XMM pointed obs – 2% of sky hence will be hundreds found when compared with eRosita final cat. (Maksym 2014, Khabibullin & Sazonov 2014)

6. XMM-Newton slew survey
Has covered ~85% of sky in the 0.2-2, 2-12 and keV bands as of Jan 2015
and found >30,000 sources
Compare with ROSAT >10x limit of 3x10-13 ergs/s/cm2 - Nearby X-ray TDE.

7. List of TDE in XMM slew SRC Z Lbol (Log) Soft Hard Radio NGC 3599
0.002 42 Y N ?
SDSS 1323
0.07 44
SDSS 1201
0.15 45
2MAS 0619
2MAS 0740
0.02
1 mJy
XMM
New One
0.029 43
Mainetti, Campana and Colpi 2016

8. Slew – temporal characteristics
Overall index -5/3
SDSS
SDSS J
XMM
Not biased because of 20 yr baseline
2MASS
NGC 3599
2MASS

9. Slew – UV temporal characteristics
2MASS
2MASS

10. Slew – temporal characteristics
Soft X-ray
Supernova hump making the UV / optical bump ?
t-1.2
t-5/3
uvw2 (2246Å) – GALEX NUV

11. Slew – dips Strong dips, due to what ? SDSS 1201+30 0740-85 Swift 1644
Curtis Saxton et al. 2012

12. Slew – dips : 0740-85 Dips are not caused by neutral absorption.
Could be ionised absorption or intrinsic emission drop

13. Slew – slow rise Slow rise sometimes ? 0619-65 NGC 3599
18 months
5 months
NGC 3599
Tidal stripping of red giant: MacLeod, Guillochon & Ramirez-Ruiz 2012
Delayed TDE : Guillochon & Ramirez-Ruiz 2015

14. Slew – spectral characteristics
Brem=0.3 keV
Bbod = 66 eV
Disk_bbod = 59 eV
SDSS
SDSS J
Γ=2, Bbod=86 eV
Bbod = 95 eV
Γ=2, Bbod=114 eV
NGC 3599
2MASS

15. Slew – spectral characteristics
Modelling X-ray spec with multi-coloured disk black-body underpredicts the UV.
Power-law + Disk black-body

16. Slew – spectral characteristics
Fit UV, soft and hard X-rays
Optxagn – Done et al. 2011
Thermal for UV
Comptonised thermal – soft
Power-law for hard
With strongly-ionised absorber
cf ASSASN 14li (Miller et al. 2016)

17. Where do X-rays in TDE come from ?
Kara et al – Swift 1644 reflection from accreting matter
- M_BH a few x 10^6
- 400s doubling = <70 Rg
soft X-ray light curve
0740 – variability , hence from within 70 Rg

18. Galaxy Types
Arcavi et al. 2014; French et al E+A galaxies disproportionately
represented in optical TDE samples
starburst ~2 Gyr ago
H_delta (ew) ~3 Ang, H_alpha (ew) < 1 Ang
– also resides in a post-starburst host galaxy

19. New source
z=0.029
15x brighter than ROSAT upper limit

20. Summary Soft X-ray TDE rate about 10-4 /gal/year.
7 events found in slew survey, 3 are well monitored
Mix of soft and soft+hard – don’t know how many just hard
Index=5/3 over long-term curve but highly variable in detail.
Unsure if variability intrinsic or ionised absorption or both.
At least one found in E+A galaxy
Hard emission most likely from Compton rather than a jet
Open question why hard component sometimes not present.
Radio usually not present but weak emission in