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To: stefano@bicar.it
From: atel@astronomerstelegram.org
Subject: ATel  17578, 17579, 17580
Message-Id: <20260107071732.1A51728806A7@server.astronomerstelegram.org>
Date: Wed,  7 Jan 2026 02:17:32 -0500 (EST)

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Posted: Within the last 24 hours
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ATEL #17578							     ATEL #17578

Title:	EP J075040.5+662346: Einstein Probe detection of an X-ray transient
		associated with the CV ZTF18abujfcu
Author:	D. Y. Li (NAO, CAS), Z. C. Zou (NJU), H. Zhou (PMO, CAS),
		Y. Liu, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP)
		team
Queries:	ep_ta@bao.ac.cn
Posted:	6 Jan 2026; 09:34 UT
Subjects:X-ray, Cataclysmic Variable

We report the detection of an X-ray transient, designated EP J075040.5+662346,
with the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP)
mission. The source was identified through stacking of WXT data, and remained
at a relatively constant flux level from October 2025 to January 2026.
The WXT position of the source is R.A. = 117.650 deg, Dec. = 66.393 (J2000)
with an uncertainty of 2.1 arcmin in radius (90% C.L. statistical and systematic).
The estimated 0.5-4 keV flux derived from the WXT spectrum is ~5 x 10^(-12)
erg/s/cm^2. Due to solar constraints, it was not visible to WXT between
April and September 2025. Stacking of the pre-April WXT data shows no significant
emission.

A target-of-opportunity follow-up observation was performed with the Follow-up
X-ray Telescope (FXT) starting at 2026-01-05 09:43:12 (UTC). Within the
WXT error circle, an uncatalogued X-ray source was detected at R.A. = 117.6688
deg, DEC = 66.3960 deg (J2000), with an uncertainty of 10 arcsec in radius
(90% C.L. statistical and systematic). The FXT position lies around 2.5
arcsec away from the known cataclysmic variable ZTF18abujfcu. The FXT light
curve exhibits significant short-term variability. The average 0.5-10 keV
spectrum can be fitted with a power law model with a photon index of 1.34
(-0.08/+0.08). No significant absorption was required. The derived average
0.5-10 keV flux is 1.10 (-0.09/+0.10) x 10^(-11) erg/s/cm^2. The quoted
errors are at 90% confidence level.

Launched on January 9, 2024, EP is a space X-ray observatory to monitor
the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook
of X-ray and Gamma-ray Astrophysics).

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Password Certification: Yuan Liu (liuyuan@bao.ac.cn)
https://www.astronomerstelegram.org/?read=17578
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ATEL #17579							     ATEL #17579

Title:	Spectroscopic classification of PNV J12312434-5907133 as a
		2025 Galactic nova
Author:	J Strader, B Molina, P Craig, L Chomiuk (Michigan State)
Queries:	strader@pa.msu.edu
Posted:	6 Jan 2026; 22:14 UT
Subjects:Optical, Nova

PNV J12312434-5907133 was discovered on UT 2025 Nov 29.7 by J. Seach (<a
href=http://www.cbat.eps.harvard.edu/unconf/followups/J12312434-5907133.html>CBAT</a>);
it is possible the peak was missed due to solar conjunction. We obtained
a spectrum of the source with the Goodman Spectrograph on the SOAR telescope
on 2026 Jan 7.32. The spectrum shows broad (FWHM ~ 3300-5000 km/s) multi-component
H and He emission lines and a red continuum, suggesting a classification
as a Galactic classical nova.

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Password Certification: Jay Strader (strader@pa.msu.edu)
https://www.astronomerstelegram.org/?read=17579
==============================================================================
ATEL #17580							     ATEL #17580

Title:	Detection of FRB 20251018 by the PuMA Collaboration at the
		Argentine Institute of Radio Astronomy
Author:	H. Prajapati (RIT), S. B. Araujo Furlan (IATE, FAMAF), E.
		Zubieta (IAR, UNLP), C. O. Lousto (RIT), G. Gancio (IAR), F. Garcia
		(IAR, UNLP), S. del Palacio (Chalmers, IAR), on behalf of the PuMA
		Collaboration
Queries:	ezubieta@iar.unlp.edu.ar
Posted:	7 Jan 2026; 00:25 UT
Subjects:Radio, Fast Radio Burst

The PuMA Collaboration reports the detection of a new Fast Radio Burst
(FRB), designated FRB 20251018, using the 30-m radio telescope (Antenna
A2) at the Argentine Institute of Radio Astronomy (IAR). This detection
is part of an ongoing high-cadence FRB search program conducted from the
Southern Hemisphere [1].

Observations were performed at a central frequency of 1400 MHz with 400
MHz of bandwidth, two circular polarizations, using ROACH1-based digital
backends [2,3] with a sampling time of 81.92 microseconds. The burst was
detected in an observation starting on MJD 60966.207662 (2025-10-18, 04:59:02
UTC). The pulse arrived approximately 905.754 seconds after the start of
the observation. The event has a width of ~ 2.4 +/- 0.8 ms and a Dispersion
Measure (DM) of 242 +/- 1 pc cm^-3. This excess DM corresponds to an estimated
redshift of z ~ 0.18 and a luminosity distance of approximately 870 Mpc
(assuming standard cosmology).

The pointing center for the detection is (J2000):

R.A. = 01h 07.7m

Dec. = -46d 33' (-46.55 deg)

(Galactic coordinates: l = 294.61 deg, b = -70.31 deg)

This location is in the general direction of the Sculptor supercluster
of galaxies and is centered on the cluster A2870. The localization uncertainty
is limited by the primary beam width of the antenna (FWHM ~ 31'). The candidate
was identified using the PRESTO software package with a signal-to-noise
ratio (SNR) of 8.2 and validated by the FETCH machine learning classifier
with a probability of p>0.999. Based on the radiometer equation and observed
parameters, we estimate a peak flux density of approximately 3.9 +/-0.9
Jy. RFI mitigation was performed using RFIClean and rfifind in tandem.
To confirm the astrophysical nature of the signal, we performed a hierarchical
channel-zapping test: we successively masked frequency channels in five
stages, removing up to leaving the cleanest 170 MHz of the central band.
The signal remained robust against these cuts, confirming its broadband
nature and ruling out narrowband RFI.

This is the first FRB detected by the IAR program after analyzing approximately
95 hours of data at this location of the sky during the second half of
2025.

A plot of the pulse profile and dynamic spectrum is available at:

https://ccrgpages.rit.edu/~lousto/cand_tstart_60966.207662037035_tcand_905.7474970_dm_243_snr_8.20.png

References:

[1] https://puma.iar.unlp.edu.ar/

[2] Gancio, G. et al., 2020, A&A, 633, A84

[3] Lousto, C. O. et al., 2024, RMxAC, 56, 134

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