TNS Astronomical Transient Report No. 286037 [ 2026TNSTR..65....1W ]
Date Received (UTC): 2026-01-08 21:56:15
Date made public:
Sender: Noémie Globus
Reporting Group: None Discovery Data Source: None
Alan M. Watson (UNAM), Diego López-Cámara (UNAM), Ny Avo Rakotondrainibe (LAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report/s the discovery of a new astronomical transient.
IAU Designation: SN 2025alij
Discoverer internal name: mystery source
Coordinates (J2000): RA = 06:57:45.530 (104.439708) DEC = +23:22:18.20 (23.371722)
Discovery date: 2025-12-22 03:04:00.000 (JD=2461031.6277778)
Remarks: We report the discovery of a new optical transient at RA = 06:57:45.53, Dec = +23:22:18.2 (J2000; uncertainty ~0.2"). This source was discovered during the follow-up of the Einstein Probe alert EP251221a, but is located well outside the WXT error box, so we consider them unrelated. Due to its brightness well beyond the archival images and its fading, we classify the object as an astronomical transient. We encourage follow-up at all wavelengths. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
Photometry
Discovery (first detection):
Discovery date: 2025-12-22 03:04:00.000
Flux: 21.38 ABMag
Filter: r-Sloan
Instrument: DDRAGO
Telescope: COLIBRÍ 1.3-meter telescope
Remarks: We initially observed from 2025-12-22 03:04 to 13:21 UTC and obtained 170 minutes of exposure in the r. The source was discovered at a preliminary magnitude of r = 21.38 +/- 0.01, using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. The limiting magnitude of the image was r = 23.71 (10 sigma). The data were reduced and coadded with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
Last non-detection:
Archival info: Other
Remarks: At the position of the source, we note the presence of an underlying faint object in the public archive database of CFHT, which we identify as a potential host galaxy. No known minor planet is consistent with the position.
Details of the new object can be viewed here: https://www.wis-tns.org/object/2025alij
Date Received (UTC): 2026-01-08 21:56:15
Date made public:
Sender: Noémie Globus
Reporting Group: None Discovery Data Source: None
Alan M. Watson (UNAM), Diego López-Cámara (UNAM), Ny Avo Rakotondrainibe (LAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report/s the discovery of a new astronomical transient.
IAU Designation: SN 2025alij
Discoverer internal name: mystery source
Coordinates (J2000): RA = 06:57:45.530 (104.439708) DEC = +23:22:18.20 (23.371722)
Discovery date: 2025-12-22 03:04:00.000 (JD=2461031.6277778)
Remarks: We report the discovery of a new optical transient at RA = 06:57:45.53, Dec = +23:22:18.2 (J2000; uncertainty ~0.2"). This source was discovered during the follow-up of the Einstein Probe alert EP251221a, but is located well outside the WXT error box, so we consider them unrelated. Due to its brightness well beyond the archival images and its fading, we classify the object as an astronomical transient. We encourage follow-up at all wavelengths. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
Photometry
Discovery (first detection):
Discovery date: 2025-12-22 03:04:00.000
Flux: 21.38 ABMag
Filter: r-Sloan
Instrument: DDRAGO
Telescope: COLIBRÍ 1.3-meter telescope
Remarks: We initially observed from 2025-12-22 03:04 to 13:21 UTC and obtained 170 minutes of exposure in the r. The source was discovered at a preliminary magnitude of r = 21.38 +/- 0.01, using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. The limiting magnitude of the image was r = 23.71 (10 sigma). The data were reduced and coadded with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
Last non-detection:
Archival info: Other
Remarks: At the position of the source, we note the presence of an underlying faint object in the public archive database of CFHT, which we identify as a potential host galaxy. No known minor planet is consistent with the position.
Details of the new object can be viewed here: https://www.wis-tns.org/object/2025alij