Transient Bright Object AT2019abn in M51

On 22 or 25 January 2019 a new bright object, almost dead-center in the animation above, was detected in the western arm of M51 by the Zwicky Transient Facility at Mt. Palomar. A brightening first appears in my data on January 26, becomes a bit more defined on January 27 (which is unfortunately only 8 minutes per channel, due to poor weather) and is quite obvious as a reddish star by January 31. The object has been variously categorized as a luminous blue variable, intermediate-luminosity red transient, or supernova impostor. Later images and spectra support the ILRT designation. It appears to have been a F-type supergiant surrounded by a dense dust shroud, which was probably destroyed in the event.

The frames for this animation were prepared in Pixinsight as follows:

1. Calibrate with Batch Preprocessing
2. Register with StarAlign
3. Stack with ImageIntegration
4. Dynamic Background Extraction
5. Photometric Color Calibration (for RGB data)
6. Stretch with Screen Transfer Function, applied to Histogram Transformation

No other stretching, noise reduction or sharpening were applied. The animation was assembled in Photoshop CS2. The final image of M51 is here.