Swift, Loiano, and pt5m observations of Gaia16avf

ATel #9290; K. Sokolovsky (IAASARS NOA/SAI MSU/ASC Lebedev), L. Wyrzykowski (Warsaw University Astronomical Observatory), G. Altavilla, R. Gualandi (INAF-Osservatorio Astronomico di Bologna), L. Hardy, S. Littlefair, L. Rhodes (University of Sheffield)
on 31 Jul 2016; 18:47 UT
Credential Certification: Kirill Sokolovsky (kirx@scan.sai.msu.ru)

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Gaia16avf was detected on 2016-07-17 as a blue transient at the position (12:37:31.3 +57:31:56.5, J2000) consistent with the nucleus of the non-active galaxy SDSS J123731.27+573156.6 (z=0.15013). Swift observed Gaia16avf on 2016-07-27 for 1.3ks. No X-ray source was detected by Swift/XRT at the transient's position down to the level of 0.002 cts/s. Simultaneous Swift/UVOT observations reveal a red optical source detected only in V and B bands. Gaia16avf was also observed with pt5m telescope at the Roque de los Muchachos observatory on La Palma (Hardy et al. 2015, MNRAS, 454, 4316), through clouds on the night of 2016-07-21 and on 2016-07-25 and 27 with BFOSC@1.5m G.D. Cassini Telescope, Loiano, Italy. The photometric measurements are summarized in the table:

 
   JD(UTC)    band   mag  err  telescope  
2457591.408    R    17.43 0.11 pt5m  
2457595.35775  r    17.39 0.07 Loiano  
2457595.36205  r    17.34 0.07 Loiano 
2457595.36701  g    18.53 0.07 Loiano 
2457596.71504 UVW1 >19.59 n/a  Swift/UVOT 
2457596.71707  U   >19.51 n/a  Swift/UVOT  
2457596.71846  B    19.24 0.23 Swift/UVOT  
2457596.72185 UVW2 >20.43 n/a  Swift/UVOT  
2457596.72522  V    18.12 0.20 Swift/UVOT 
2457596.72784 UVM2 >19.86 n/a  Swift/UVOT  
2457597.34628  r    17.38 0.05 Loiano  
2457597.35016  g    18.60 0.05 Loiano  

The lack of blue continuum indicates that Gaia16avf is unlikely to be a tidal disruption event. It may be a heavily reddened supernova close to the nucleus of the galaxy. Alternatively, the transient might have faded completely so the Swift observations are dominated by the host galaxy. The lack of X-ray detection is consistent with the host galaxy showing no signs of active nucleus.

We thank Neil Gehrels and the Swift team for scheduling this ToO observation. The photometric calibrations for the ground-based observations were obtained using the Cambridge Photometric Calibration Server (CPCS), designed and maintained by Sergey Koposov and Lukasz Wyrzykowski. We acknowledge ESA Gaia, DPAC and the Photometric Science Alerts Team.

Gaia16avf at the Gaia Alerts page