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To: stefano@bicar.it
From: atel@astronomerstelegram.org
Subject: ATel  17504, 17505
Message-Id: <20251122071207.68E7F288081E@server.astronomerstelegram.org>
Date: Sat, 22 Nov 2025 02:12:07 -0500 (EST)

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ATEL #17504							     ATEL #17504

Title:	Fermi-LAT detection of renewed gamma-ray activity from the
		FSRQ OQ 334
Author:	C. Bartolini (University of Trento &amp; INFN Bari), on behalf
		of the Fermi Large Area Telescope Collaboration
Queries:	chiara.bartolini-1@unitn.it
Posted:	21 Nov 2025; 15:14 UT
Subjects:Gamma Ray, >GeV, Request for Observations, AGN, Blazar, Quasar

The Large Area Telescope (LAT), one of the two instruments on the Fermi
Gamma-ray Space Telescope, has observed gamma-ray renewed activity from
a source positionally consistent with the flat spectrum radio quasar (FSRQ)
OQ 334, also known as B2 1420+32, GB2 1420+326 and 4FGL J1422.5+3223 (Abdollahi
et al. 2022, ApJS, 260, 53), with radio coordinates R.A: 215.62657 deg,
Dec.: 32.38623 deg; (J2000; Petrov & Taylor 2011, AJ, 142, 89), and a redshift
z=0.6819 (Hewett & Wild 2010, MNRAS, 405, 2302).

Preliminary analysis indicates that this source was in an elevated gamma-ray
emission state on November 20, 2025, with a daily averaged gamma-ray flux
(E>100MeV) of (1.2 +/- 0.1) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty
only). This corresponds to a flux increase of a factor of 20 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 2.0+/-0.1, indicating a harder spectrum than the 4FGL-DR4
value of 2.24+/-0.01. The Fermi-LAT collaboration has previously reported
gamma-ray flaring activity positionally consistent with this source in
ATels #12277, #12942, #13382, and #16680.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray
monitoring of this source will continue. A preliminary light curve for
OQ 334 can be accessed via the <a href="https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J1422.3+3223">Fermi-LAT
Light-Curve Repository</a>.  We encourage multifrequency observations of
this source. For this source, the Fermi-LAT contact person is Stefano Ciprini
(stefano.ciprini[at]roma2.infn.it) and C. C Cheung (Teddy.Cheung@nrl.navy.mil).

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: Chiara Bartolini (chiara.bartolini-1@unitn.it)
https://www.astronomerstelegram.org/?read=17504
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ATEL #17505							     ATEL #17505

Title:	Comet C/2025 R2 (SWAN) displays an anti-tail
Author:	Federico Manzini (Stazione Astronomica di Sozzago), Virginio
		Oldani (Stazione Astronomica di Sozzago), Paolo Ochner (UniPD, INAF-OAPd),
		Andrea Reguitti (INAF-OAPd), Luigi R. Bedin (INAF-OAPd), Claudio Balcon
		(Stazione Astronomica di Belluno)
Queries:	manzini.ff@aruba.it
Posted:	21 Nov 2025; 16:51 UT
Subjects:Optical, Comet

The long-period comet C/2025 R2 (SWAN) has already been the subject of
two Astronomer's 
Telegrams (ATel #17462 and #17469). It recently showed a significant increase
in brightness 
followed by signs of fragmentation. Orbital elements indicate a period
of about 784 years (see JPL 
Horizons system at https://ssd.jpl.nasa.gov/horizons/). 
The geometric configuration between Earth, the comet, and the Sun determines
the visibility of 
particular structures in the coma and tail. Near the comet's orbital plane,
the dimensions of the tail 
can be observed in its perpendicular plane, where the dust is only minimally
affected by the orbital 
velocity vector. At particular elongation angles, when the Earth crosses
or approaches the comet's 
orbital plane and the line of sight is close to it, comets can also display
the rare phenomenon of an 
anti-tail. This feature is formed by larger dust particles, which are less
affected by solar radiation 
pressure and tend to remain confined near the orbital plane and project
as a sunward-pointing 
feature. 
The Earth-Sun-comet geometry for C/2025 R2 has been favorable for the appearance
of an anti- 
tail since mid-November. Earth crossed the orbital plane of C/2025 R2 on
September 10, 2025, 
and will remain close to it (PlAng between -5° and -4°) until December
5, 2025. 
Our monitoring began in early November, but no hints of anti-tail were
detected in our observations 
of November 3 and 9 (67/92-cm Schmidt telescope - Asiago Astrophysical
Observatory, INAF- 
OAPd, Italy), and November 4 (0.4-m telescope, Stazione Astronomica di
Belluno). The first signs 
of a presence of an anti-tail were visible in r-band images taken with
the 1.82-m Copernico 
Telescope (Asiago Astrophysical Observatory, INAF-OAPd, Italy) on November
10, 2025, when 
Earth was at PlAng=-7.8°. A confirmation of the anti-tail was obtained
on 18 November 2025,  
using r-band images (14x180s) from the 0.4-m telescope at the Stazione
Astronomica di Sozzago (Italy),  
with Earth at PlAng=-6.2°. 
Brightness measurements at distances of approximately 84,000 and 124,000
km from the nucleus 
(performed on polar-projection processed images centered on the comet optocenter)
showed two 
intensity peaks at PA=75°±1° and PA=234°±1.5°, corresponding to the
normal dust tail and the  
anti-tail, respectively. 
At the observation date, these angles are consistent with the Horizons
ephemeris values: 
PsAng=71.0°, the position angle of the Sun-comet vector, which approximates
the gas tail direction 
(anti-sunward); PsAMV=244°, which indicates the expected orientation of
the dust tail (opposite to 
the comet's heliocentric velocity vector), phase angle (STO) 36°. 
The anti-tail of C/2025 R2 is expected to become more condensed in the
near future, as the 
viewing angle with respect to the orbital plane continues to decrease.
However, the comet is also 
moving rapidly away from Earth, and the feature may gradually fade.

Figures and captions are available at:: https://web.oapd.inaf.it/bedin/files/PAPERs_eMATERIALs/ATel/C2025R2/
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