Alert Notice 810: ASASSN-18dg and SDSS-J080449.49+161624.8 to be observed with HST

February 3, 2023

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Further to AAVSO Alert Notice 796, Dr. Anna Francesca Pala (European Space Agency, ESAC, Spain) informs us that observations of the cataclysmic variable ASASSN-18dg have been scheduled with the Hubble Space Telescope for:

2023 10 February 21:27:18  - 11 February 04:39:43 UT

Observers are reminded that a positive V observation no more than 24 hours before the HST observation start-time is required for the HST team to make a decision about allowing the observations to take place. Your observations from tonight through February 10/11 are critical, and please continue nightly V snapshots through February 25. This target is faint at minimum; recent observations of ASASSN-18dg in the AAVSO International Database show it ranging 18.4-20.2 V and most recently showed it at magnitude 18.9745 V +/- 0.1442 on 2023 Jan. 19.008322 UT (A. Popowicz, Pyskowice, Poland) and <18.8 CV +/- 0.3 on Jan. 28.14598 UT (S. Dvorak, Clermont, FL).

The other target for February is SDSS-J080449.49+161624.8. HST is scheduled to observe it on February 16. Please carry out nightly V snapshots beginning now, particularly February 11-17, and continuing through March 3. When the exact time is known, it will be posted in the forum threads above. This target appears to have had an outburst at the beginning of January. It is also faint at minimum; recent observations of SDSS-J080449.49+161624.8 in the AAVSO International Database show it ranging 18.3-19.7 V (Popowicz) and most recently showed it at magnitude 18.429 CV +/- 0.128 on 2023 Feb. 01.19066 UT (Dvorak).

Please see Alert Notice 796 for additional details and instructions.

Coordinates (J2000): 

ASASSN-18dg:  R.A. 04 07 49.30   Dec. -00 07 16.7  (Eri)  (from VSX entry for ASASSN-18dg)

SDSS-J080449.49+161624.8:  R.A. 08 04 49.49   Dec. +16 16 24.9  (Cnc)  (from VSX entry for SDSS-J080449.49+161624.8)

Charts with comparison stars for ASASSN-18dg or SDSS-J080449.49+161624.8 may be created using the AAVSO Variable Star Plotter (VSP).

Please report observations to the AAVSO International Database using the name ASASSN-18dg or SDSS-J080449.49+161624.8, respectively. Reduce and submit observations as soon as possible after making them.

This Alert Notice was compiled by Elizabeth O. Waagen using information provided by Dr. Pala.


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