Chandra LETG X-ray Grating Observations of AT2019pev/ZTF19abvgxrq
ATel #13213; S. Mathur (Ohio State), K. Auchettl (DARK/UCSC), C. S. Kochanek (Ohio State), T. Holoien (Carnegie), K. Z. Stanek (Ohio State), D. Grupe (Moorehead State)
on 22 Oct 2019; 15:41 UT
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)
Subjects: X-ray, Transient
Referred to by ATel #: 13238
We obtained a 91~ks Chandra LETG X-ray spectrum of the TDE candidate AT2019pev/ZTF19abvgxrq (ATel #13127, ATel #13135, ATel #13163, ATel #13170) on 14/15 October 2019. The spectrum is reasonably well-fit by a kT=0.24 keV disk black body model or a power-law with a photon index of Gamma=3.3, consistent with models for the earlier Chandra observations on 1 October 2019 (ATel #13163). We note that such a steep photon index is not seen in normal AGN. We do find a somewhat better fit combining a kT=0.23 keV disk black body model with a relatively flat temperature profile (T~r^(-1/2) instead of r^(-3/4)) with a power-law having a photon index of Gamma=1.8.
The source flux of 7.7e-12 erg/cm^2/s (0.3-2.5 keV) was lower than the flux of 1.3e-11 erg/cm^2/s (0.3-2.5 keV) in the earlier observation. However, Swift observations between the two Chandra observations show that the flux dropped to ~4e-12 erg/cm^2/s (0.3-2.5 keV) after the first Chandra observation but was again rising by the time of the second. Swift observations taken after the second Chandra observation indicate that the X-ray flux has dropped again to a flux of ~5e-12 erg/cm^2/s (0.3-2.5 keV).
No absorption beyond Galactic is required by the data. If we add an absorption component, we find lower column densities (N(H)~5e20 instead of 2.8e21/cm^2 in ATel #13163) with log(xi)=2.44 (instead of 2.95) and a systemic blue shift of v=0.009c (instead of 0.01c).
We thank the Chandra team for rapidly scheduling and executing these observations.
