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To: stefano@bicar.it
From: atel@astronomerstelegram.org
Subject: ATel  17881, 17882
Message-Id: <20260710070555.F190728804FC@server.astronomerstelegram.org>
Date: Fri, 10 Jul 2026 03:05:55 -0400 (EDT)

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Posted: Within the last 24 hours
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ATEL #17881							     ATEL #17881

Title:	Fermi-LAT detection of renewed gamma-ray activity from the
		FSRQ 3C 273
Author:	P. Monti-Guarnieri (University of Trieste and INFN Trieste),
		F. Casaburo (INAF OAR, INFN Roma Tor Vergata and Sapienza University
		of Roma), on behalf of the Fermi Large Area Telescope Collaboration
Queries:	pietro.monti-guarnieri@phd.units.it
Posted:	9 Jul 2026; 07:45 UT
Subjects:Gamma Ray, >GeV, AGN, Blazar, Quasar

The Large Area Telescope (LAT), one of the two instruments on the Fermi
Gamma-ray Space Telescope, has observed renewed gamma-ray activity from
a source positionally consistent with the flat-spectrum radio quasar 3C
273, also known as 4FGL J1229.0+0202 (Abdollahi et al. 2022, ApJS, 260,
53), with coordinates R.A. = 187.27791 deg, Dec. = +2.05239 deg (J2000;
Johnston et al. 1995, AJ, 110, 880), and redshift z=0.158 (Strauss et al.
1992, ApJS, 83, 29).

Preliminary analysis indicates that this source was in an elevated gamma-ray
emission state on July 7, 2026, with a daily averaged gamma-ray flux (E>100MeV)
of (3.4+/-0.4) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only).
This corresponds to a flux increase of a factor of more than 10 relative
to the average flux reported in the fourth data release of the fourth Fermi-LAT
catalog (4FGL-DR4, Ballet et al. 2023, arXiv:2307.12546). The corresponding
photon index is 2.7+/-0.1 and is consistent with the 4FGL-DR4 value of
2.69+/-0.01 within the uncertainties. The Fermi LAT Collaboration has previously
reported gamma-ray flaring activity from 3C 273 in ATel #1707, #2168, #2200
and #16698.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray
monitoring of this source will continue. This source belongs to the "LAT
Monitored Sources" and, consequently, a preliminary estimation of the daily
gamma-ray flux observed by Fermi-LAT is publicly available at <a href="https://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/3C_273">3C
273</a>. A preliminary light curve for 3C 273 can also be accessed via
the Fermi-LAT Light-Curve Repository at <a href="https://fermi.gsfc.nasa.gov/ssc/data/access/lat/lcr/source.html?source_name=4FGL_J1229.0+0202">4FGL
J1229.0+0202</a>. We encourage multifrequency observations of this source.
For this source, the Fermi-LAT contact persons are Werner Collmar (wec@mpe.mpg.de)
and Gino Tosti (tosti@pg.infn.it)

The Fermi-LAT is a pair conversion telescope designed to cover the energy
band from 20 MeV to greater than 300 GeV. It is the product of an international
collaboration between NASA and DOE in the U.S. and many scientific institutions
across France, Italy, Japan and Sweden.

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Password Certification: Giovanni La Mura (giovanni.lamura@inaf.it)
https://www.astronomerstelegram.org/?read=17881
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ATEL #17882							     ATEL #17882

Title:	COLIBRI optical observation of GRS 1915+105 during the unprecedented
		low luminosity state
Author:	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)
Queries:	ducoin@cppm.in2p3.fr
Posted:	9 Jul 2026; 15:53 UT
Subjects:Optical, Binary, Black Hole, Transient

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.

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Password Certification: Jean-Gregoire Ducoin (ducoin@cppm.in2p3.fr)
https://www.astronomerstelegram.org/?read=17882
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