COLIBRI optical observation of GRS 1915+105 during the unprecedented low luminosity state

ATel #17882; Jean-Gregoire Ducoin (CPPM), Francesco Magnani (CPPM), Damien Dornic (CPPM), Stephane Basa (UAR Pytheas), William H. Lee (UNAM), Camila Angulo (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Francis Fortin (IRAP), Leonardo Garcia-Garcia (UNAM), Ramandeep Gill (UNAM), Noemie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego Lopez-Camara (UNAM), Enrique Moreno Mendez (UNAM), Margarita Pereyra (UNAM), Fredd Sanchez Alvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM)
on 9 Jul 2026; 15:53 UT
Credential Certification: Jean-Gregoire Ducoin (ducoin@cppm.in2p3.fr)

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We imaged the field of the black hole X-ray binary GRS 1915+105, that has recently undergone an unusual fading in radio emission and reached its lowest level ever recorded (Motta et al., 2026; Atel #17865), as well as a low luminosity state in X-ray (Marino et al., 2026; ATel #17869).

We used the DDRAGO two-channel wide-field imager on the COLIBRI telescope. We observed for two days and obtained 32 minutes of simultaneous exposure in the i and zy (similar to Sloan z) filters each day.

The data were reduced, coadded with the COLIBRI pipeline and analysed with STDWeb (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.

In the stacked image, we do not detect any source at the GRS 1915+105 position down to the following 3-sigma limit:

From 2026-07-05T05:10:15 to 2026-07-05T05:49:40 UTC

i > 22.77
zy > 21.96

From 2026-07-06T04:48:05 to 2026-07-06T05:31:51 UTC

i > 23.12
zy > 22.30

Further observations are planned.

We thank the staff of the Observatorio Astronomico Nacional at Sierra de San Pedro Martir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM.

COLIBRI 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 Astronomico Nacional on the Sierra de San Pedro Martir, Baja California, Mexico.