1. Gamma-Ray Bursts: Death of a Star and the Birth of a Black Hole
AGN with Extreme X-ray amplitude variations,
or how they might fool you!
Gamma-Ray Bursts: Death of a Star and the Birth of a Black Hole
Dirk Grupe
Swift Mission Operating Center Department of Astrophysics and Astronomy Pennsylvania State University

2. The way the discover typically TDEs is by a few X-ray observations that indicate a rapidly decaying source
IC 3599 by
Grupe et al. (1995)
Brandt et al. (1995)
But IC 3599 is a
Seyfert 2 galaxy
It is however an example where we have more than 2 data points
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3. The typical TDE candidate has two observations, one in an extremely high state and one in a low state – often discovered archival data
RX J :
RASS: 0.54 counts s-1
pointed: gone 15 month later!
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XMM J
(Lin et al. 2011, ApJ 738, 52;
see also Dacheng Lin's talk)
Optical spectrum of RX J
(Grupe et al. 1999, A&A 350)

4. What can also happen in a survey is that we see an AGN as a bright source and then in a later observation as an extremely faint X-ray emitter.
Log CR ROSAT pointed
RX J
IC 3599
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RX J
WPVS 007
Log CR RASS
ROSAT RASS vs pointed obs.
(Grupe et al. 2001, A&A367, 470)
Swift observations of two epochs
(Grupe et al. 2010, ApJS 187, 64

5. WPVS 007 is a normal Narrow-Line Seyfert 1 galaxy which has shown extreme X-ray bahavior.
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Grupe et al. 2007, AJ, 133, 1988

6. Making things worse the decay slope of the long term light curve is close to 5/3
ROSAT PSPC Count rate
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Time [years]

7. WPVS 007's high state X-ray spectrum is also extremely soft, exactly what is expected from a TDE
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Grupe et al. 1995, A&A 300

8. So, is WPVS 007 a TDE? No, because we detect it in X-rays again with Swift
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Grupe et al. 2007, AJ 133; 2008, AJ 136; 2012 in prep

9. The low-state X-ray spectrum of WPVS 007 can be modeled by a partial covering absorber  Absorption not a flare or TDE
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Grupe et al. 1995, A&A 300
Grupe et al. 2008, AJ, 136
partial covering absorber
 WPVS 007 is not a TDE, but an highly absorbed AGN!

10. The real answer, however, came from UV observations: WPVS 007 shows extremely deep UV absorption troughs, just like a BAL QSO!
WPVS 007
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BAL QSO
Leighly et al. 2009, ApJ, 701, 176
FUSE observation in November 2003

11. RX J2217.9-5941: Narrow-Line Seyfert 1 galaxy with strong X-ray decay
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Factor of ~30 between RASS and HRI
Typical spectrum of an AGN with
A partial covering absorber
Grupe et al., 2001, A&A 369
Grupe et al., 2004, AJ, 128
Chandra data from 2003
Shown is the lower flux spectrum
from August 2003
Recent Swift observations how it still
in a low state

12. The next example is Mkn 335 – a typically X-ray Bright Narrow-Line Seyfert 1 galaxy
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Swift XRT
X-ray low state a factor of 35 fainter than compared with XMM a year earlier
Grupe et al. 2007, ApJ, 668, L111
Again partial covering absorber
Grupe et al. 2008, ApJ, 681, 982

13. Mkn 335 becomes even more dramatic when looking at the spectral energy distribution
XMM 2000
Swift 2007
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Grupe et al. 2007, ApJ, 668, L111

14. Mkn 335 has show bright and extreme low states several times in the last 5 years!
Swift monitoring since
May 2007
X-ray as well as UV
Mkn 335 shows variability
by factors of more than 30
in X-rays
and by about 1 mag in the UV
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Grupe et al. 2012, ApJS, 199, 28

15. Mkn 335 switches back and forth between high and low states during the last few years.
Swift monitoring in 2010 to
2012
XRT count rate and
Hardness ratio
And UVOT in W2
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16. The UV however does not help you here either
The UV however does not help you here either. Mkn 355 and WPVS 007 vary strongly in the UV as well
WPVS 007 Swift UVOT
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17. The UV however does not help you here either. Some Seyfert 1
The UV however does not help you here either. Some Seyfert 1.5s show even variability by 1.5 mag in the UV within less than a year
Swift UVOT W2 mag epoch 2
Swift UVOT W2 mag difference
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Swift UVW2 mag epoch 1
Swift XRT CR ratio
Grupe et al. 2010, ApJS, 187, 64

18. XMM program to observe AGN in deep minimum states: PG 0844+349 and 1H 0707-495
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Gallo et al., 2011, MNRAS 412, 161
Fabian et al., 2012, MNRAS 419, 116

19. How can we distinguish between a TDE in an AGN and e. g
How can we distinguish between a TDE in an AGN and e.g. accretion disk instability or just absorption?
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Method 1: Look at the X-ray spectrum!

20. Besides X-rays the answer may come from Optical spectra as well, again the example here is IC 3599
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Brandt et al., 1995, MNRAS
Grupe et al., 1995, A&A 299
Strong H and He lines  material of a main sequence star!
See also Drew Clausen's talk (Monday), Komossa & Bade (1999)

21. Some AGN may fool you and look like TDEs
Some AGN vary by factors of several 100 in X-rays
And by > 1 mag in the UV
Best example is WPVS 007
Variability NOT caused by tidal disruption
Caused by absorption
All these source have one thing in common: They are Narrow Line Seyfert 1s
TDEs can occur in Seyferts (e.g. IC 3599)
If discovered on time, keep monitoring
Look at the X-ray spectrum
and get optical spectra and look for strong
H and He line
Be Aware, These sources (NLS1s) can fool you!
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