AstroNote 2024-129

We detected a previously unknown variability (~0.3 magnitudes fading) of GSC2.3 N81Z000565 in the KATS database. It was with its normal magnitude (CV magnitude about 15.7) during 2021-11-10 (around HJD 2459529) and 2022-01-26 (around HJD 2459606) and was found fading from CV=15.8 to CV=16.0 during 2022-10-21 (around HJD 2459874) and 2024-04-04 (around HJD 2460405).

We checked public data from ZTF and ATLAS and obtained more details about this event. The more continuous data shows that the fading happened around HJD 2459658 and reached a minimum around HJD 2460150, ongoing for at least 2.0 years and has not ended. It has an amplitude of 0.32 magnitudes in r band and ATLAS c band, 0.37 magnitudes in g band, and 0.29 magnitudes in ATLAS o band.

Light curve from the KATS database, ZTF and ATLAS data is posted at http://xjltp.china-vo.org/vsspj063224-80100109-3.html. Selected KATS magnitudes are listed below.

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Time(HJD) | magnitude(CV) | error | Dome
2459529.393 | 15.70 | 0.026880 | N86
2459547.434 | 15.69 | 0.062473 | N86
2459576.394 | 15.70 | 0.081134 | N86
2459606.241 | 15.68 | 0.032259 | N86
2459874.429 | 15.96 | 0.027213 | N86
2459913.391 | 15.98 | 0.062090 | N86
2459971.193 | 16.01 | 0.054938 | N86
2460026.132 | 16.02 | 0.056673 | N86
2460240.423 | 16.02 | 0.026362 | N86
2460314.367 | 16.01 | 0.046763 | N86
2460376.160 | 16.00 | 0.045463 | N86
2460405.138 | 16.00 | 0.026106 | N86
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The star has the coordinates 06 32 24.80 +10 01 09.3 and magnitudes V=15.66 derived from Gaia DR3 catalogue, and J=13.89, H=13.52, K=13.38 in 2MASS. J-K=0.5; Bp-Rp=1.1, and WISE data suggest some infrared excess but insufficient for a T Tauri type variable. The spectral class given by Gaia DR3 through ESP-ELS is F, which makes it not likely to be an R CrB variable, though the object's behaviour is similar to that type. The regular light curve seems to show a symmetric form, indicating that it may be an eclipsing event.

We encourage the spectroscopic and photometric observations of VSSP J063224.80+100109.3. Archival searches for historical fadings are also requested.

KATS: Kilodegree Asteroid Tracking Survey (KATS) held by Xingming Observatory with Gao Yu Telescope Array, an array of 6 Celestron 28 cm f/2.2 Rowe-Ackermann Schmidt Astrograph + QHY-600M, located at N86.