Abstract
Abstract Tidal disruption events (TDEs) occur when a star passes close enough to a galaxy’s supermassive black hole to be disrupted by tidal forces. We discuss new observations of IGRJ12580+0134, a TDE observed in NGC 4845 (d = 17 Mpc) in 2010 November, with the Karl G. Jansky Very Large Array (VLA 9 9 The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. ). We also discuss a reanalysis of 2010–2011 Swift and XMM-Newton observations, as well as new, late-time Swift observations. Our JVLA observations show a decay of the nuclear radio flux until 2015, when a plateau was seen, and then a significant (factor ∼3) radio flare during 2016. The 2016 radio flare was also accompanied by radio spectral changes, but was not seen in the X-rays. We model the flare as resulting from the interaction of the nuclear jet with a cloud in the interstellar medium. This is distinct from late-time X-ray flares in a few other TDEs where changes in the accretion state and/or a fallback event were suggested, neither of which appears possible in this case. Our reanalysis of the Swift and XMM-Newton data from 2011 shows significant evidence for thermal emission from a disk, as well as a very soft power law. This, in addition to the extreme X-ray flux increase seen in 2010 (a factor of >100) bolsters the identification of IGRJ12580+0134 as a TDE, not an unusual active galactic nucleus variability event.
Highlights
Tidal disruption events (TDEs) are expected to occur every 103–105 yr for a typical galaxy (Magorrian & Tremaine 1999; Wang & Merritt 2004; Van Velzen & Farrar 2014; Holoien et al 2016)
Sw J1644+57 (z = 0.3534; Bloom et al 2011; Burrows et al 2011; Levan et al 2011; Zauderer et al 2011, 2013) and Sw J2058+05 (z = 1.1853; Cenko et al 2012) are examples of TDEs that have associated jets, exhibiting super-Eddington X-ray emission and a long-lasting radio emission expected to arise from the jet-circum-nuclear medium (CNM) interaction
By day 1604, the flux in the C, S, and L bands had increased by a factor of 2.5–3. This defines the epoch of our new “flare.” there is almost no information on the radio variability of the nuclear source of NGC 4845 previous to the TDE, we note that the two L-band fluxes in 1995 and 1998 are consistent with one another at the 2σ level
Summary
Tidal disruption events (TDEs) are expected to occur every 103–105 yr for a typical galaxy (Magorrian & Tremaine 1999; Wang & Merritt 2004; Van Velzen & Farrar 2014; Holoien et al 2016). Sw J1644+57 (z = 0.3534; Bloom et al 2011; Burrows et al 2011; Levan et al 2011; Zauderer et al 2011, 2013) and Sw J2058+05 (z = 1.1853; Cenko et al 2012) are examples of TDEs that have associated jets, exhibiting super-Eddington X-ray emission and a long-lasting radio emission expected to arise from the jet-CNM interaction. Detailed modeling of both Sw J1644+57 and Sw J2058+05 suggests that the jets were strongly relativistically beamed.
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