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We present new Adaptive Optics (AO) imaging and spectroscopic measurements ofGalactic Center source G1 from W. M. Keck Observatory. Our goal is tounderstand its nature and relationship to G2, which is the first example of aspatially-resolved object interacting with the supermassive black hole (SMBH).Both objects have been monitored with AO for the past decade (2003 - 2014) andare comparatively close to the black hole ($a_{\rm{min}} \sim$200-300 AU) onvery eccentric orbits ($e_{\rm{G1}}\sim$0.99; $e_{\rm{G2}}\sim$0.96). While G2has been tracked before and during periapse passage ($T_{0} \sim$ 2014.2), G1has been followed since soon after emerging from periapse ($T_{0} \sim$2001.3). Our observations of G1 double the previously reported observationaltime baseline, which improves its orbital parameter determinations. G1'sorbital trajectory appears to be in the same plane as that of G2, but with asignificantly different argument of periapse ($\Delta\omega$ = 21$\pm$4degrees). This suggests that G1 is an independent object and not part of a gasstream containing G2 as has been proposed. Furthermore, we show for the firsttime that: (1) G1 is extended in the epochs closest to periapse along thedirection of orbital motion and (2) G1 becomes significantly smaller over time,(450 AU in 2004 to less than 170 AU in 2009). Based on these observations, G1appears to be the second example of an object tidally interacting with a SMBH.G1's existence 14 years after periapse, along with its compactness in epochsfurther from the time of periapse, suggest that this source is stellar innature.

The Post-Periapse Evolution of Galactic Center Source G1: The second case of a resolved tidal interaction with a supermassive black hole