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To: stefano@bicar.it
From: atel@astronomerstelegram.org
Subject: ATel  17152, 17153
Message-Id: <20250419071137.1BED128807C7@server.astronomerstelegram.org>
Date: Sat, 19 Apr 2025 03:11:37 -0400 (EDT)

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Posted: Within the last 24 hours
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ATEL #17152							     ATEL #17152

Title:	X-ray outburst of IGR J06074+2205 faint again
Author:	Roberto Nesci (INAF/IAPS), Mariateresa Fiocchi (INAF/IAPS),
		Antonio Vagnozzi (MPC589)
Queries:	roberto.nesci@inaf.it
Posted:	18 Apr 2025; 15:31 UT
Subjects:X-ray, Binary, Pulsar

The HMXB IGR J06074+2205 in the last years had recurrent X-ray flares,
during a few days, with a recurrence period of 80 +-2 days (Mihara et al.
2023 ATel #16351). These outbursts are believed to be produced by the crossing
of the circumstellar disc of the Be star by the companion pulsar. The optical
indicator of the disc is a strong H-alpha emission, with historic maximum
Equivalent Width of 12 Angstrom. Indeed a large outburst (1.9 c/s) happened
on March 2024-03-14 (Nesci et al. ATel #16525) when the E.W. was 10 Angstrom.

Our spectroscopic monitoring with the 50 cm telescope of the S. Lucia di
Stroncone Observatory (MPC 589) showed that the E.W. was just 5.0 Angstrom
at the beginning of November 2024, so that the expected X-ray outburst
around November 10 should be very small or undetectable: actually our Swift/XRT
observations showed a peak count rate of 0.21 c/s (ATel #16899). 
Our H-alpha monitoring of the source showed a fast increase of the H-alpha
emission since February 2025, reaching 10 Angstrom E. W. in April, so that
a large flare was expected at the next periastron passage around April
15. Our Swift XRT daily monitoring started on April 11: the source was
at the quiescent level (0.065 c/s) until April 17, when a clear flux increase
(0.21 c/s) was detected, but the flux decreased down to 0.12 c/s already
on April 18. Our Swift/XRT monitoring is scheduled until April 21 but,
if the orbital period is correct, the periastron passage of the pulsar
should already be over and no further flux increases should happen. 
The modest X-ray flux occurred in this periastron passage, similar to that
of November when the H-alpha emission was low, poses some doubts about
the simple model of the X-ray outburst described above: a possible way
out could be that the structure of the circumstellar disk of the Be star
is rather patchy. 
We thank the Swift Time Allocation Committee for the approval of our ToO
request.

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Password Certification: Roberto Nesci (roberto.nesci@inaf.it)
https://www.astronomerstelegram.org/?read=17152
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ATEL #17153							     ATEL #17153

Title:	Fermi-LAT detection of enhanced gamma-ray activity from the
		BL Lac PMN J0334-3725
Author:	Omer Faruk Coban (Institute of Space Sciences, ICE-CSIC),
		on behalf of the Fermi Large Area Telescope Collaboration
Queries:	coban@ice.csic.es
Posted:	18 Apr 2025; 16:17 UT
Subjects:Gamma Ray, AGN, Blazar

The Large Area Telescope (LAT), one of the two instruments on the Fermi
Gamma-ray Space Telescope, has observed enhanced gamma-ray activity from
a source positionally consistent with the BL Lac object PMN J0334-3725,
also known as 4FGL J0334.2-3725 (The Fermi-LAT collaboration 2020, ApJS,
247, 33), with coordinates R.A. = 53.56427 deg, Dec. = -37.42863 deg (J2000;
Hunt et al. 2021, AJ, 162, 18), and redshift z = 0.230 (Narendra et al.
2022, ApJS, 259, 16).

Preliminary analysis indicates that this source was in an elevated gamma-ray
emission state on April 17, 2025, with a daily averaged gamma-ray flux
(E>100MeV) of (0.4 +/- 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 Fermi-LAT catalog (4FGL). This
is the highest LAT daily flux ever observed for this source. The corresponding
photon index is 2.1+/-0.2, and is consistent with the 4FGL value of 2.02+/-0.02
within the uncertainties.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray
monitoring of this source will continue. A preliminary light curve for
PMN J0334-3725 can be accessed via <a href="https://fermi.gsfc.nasa.gov/ssc/data/access/lat/LightCurveRepository/source.html?source_name=4FGL_J0334.2-3725">the
Fermi-LAT Light-Curve Repository</a>. We encourage multifrequency observations
of this source. For this source, the Fermi-LAT contact person is Omer Faruk
Coban (coban@ice.csic.es).

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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