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From: atel@astronomerstelegram.org
Subject: ATel 17367, 17368
Message-Id: <20250902070902.ED400288085D@server.astronomerstelegram.org>
Date: Tue, 2 Sep 2025 03:09:02 -0400 (EDT)

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Posted: Within the last 24 hours
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ATEL #17367							     ATEL #17367

Title:	The detection of the X-ray emission from V572 Vel (Nova Vel
		2025) with Swift XRT. 
Author:	G. J. M. Luna (UNAHUR/CONICET),  K. L. Page (U. Leicester),
		N. P. M. Kuin (MSSL),M. Orio (Univ. of Wisconsin and INAF-Padova),
		I. J. Lima (UNESP)
Queries:	juan.luna@unahur.edu.ar
Posted:	1 Sep 2025; 20:29 UT
Subjects:Ultra-Violet, X-ray, Nova

V572 Vel entered into an outburst on June 25.44 (CBET #5574), reaching
U=5.6 magnitudes on June 25.57. The optical light curve available at the
AAVSO database reports visual magnitudes of about V=4.8 on June 27 and
5.8 on July 1st. FERMI LAT reports a detection just a few hours after the
optical discovery (Jean et al. Atel #17252). Lima et al. (RNAAS, in press)
found no evidence of intrinsic optical linear polarization on observations
obtained 1 day and 1 month after the outburst.

Swift has observed V572 Vel on average every two days, starting on June
26th for about 1.5 ks each time in WT mode, and no X-rays were detected.
By the end of August, the optical emission had faded sufficiently such
that the XRT could be switched to the more sensitive Photon Counting mode.
The first of these observations, taken on August 31, revealed a clear,
but faint, X-ray source, with a count rate of 0.030 +0.005/-0.004 count
s^-1 (0.3-10 keV, single pixel events only). The spectrum (comprising only
27 photons) can be approximated by an absorbed single-temperature optically-thin
plasma with kT > 2.0 keV and NH = (2.1 +4.8/-1.2) x 1022cm-2.
The observed (unabsorbed) flux over 0.3-10 keV is 4.2 (5.8) x 10-12
erg cm-2 s-1.

Comparing the spectrum taken on Aug 31st to that taken Aug 17th we see
largely the same spectral features at a reduced brightness. The HI Balmer
series is present as well as the HeII lines.  The following other lines
are deemed present: N III] 1750, Al III ? 1840, C III] 1909, N II]/[N IV]
2147/2151, O II/S iII 2330, O II 2476 blend with He II 2511, Mg II 2800,
O III 3134, C III/N III 4630, as well as second order lines of N III] 1750(2)
at 2966 and C III] 1909(2) at 3273. All numbers are in angstroms.   The
line at 2000A is unknown. Some weak zeroth orders are close to the spectrum
but no obvious signs have been seen. We took the latest spectrum with the
nominal grism setting, unlike the first spectrum, which was done to avoid
strong contaminating background sources. The Mg II line is now much narrower
and shows a small dip at -40A, corresponding to a velocity of -4200km/s
if that is due to an absorbing outflow.

Further Swift observations are planned, and we thank the Swift PI, Brad
Cenko, and his deputies for approving the time, as well as the Swift planning
and operations teams for their continuing support.

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Password Certification: Gerardo Juan Manuel Luna (juan.luna@unahur.edu.ar)
https://www.astronomerstelegram.org/?read=17367
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ATEL #17368							     ATEL #17368

Title:	EP250828a: Early near-infrared follow-up with MIRAGE on the
		MDM 1.3m telescope
Author:	K. De (Columbia/CCA), S. Ibrahim (Columbia), T. Suen (Columbia),
		M. Sitaram (Columbia), D. Schiminovich (Columbia), G. Mo (Caltech/Carnegie),
		K. Shin (Caltech)
Queries:	kd3038@columbia.edu
Posted:	2 Sep 2025; 04:43 UT
Subjects:Infra-Red, Optical, X-ray, Transient

We observed the field of the X-ray transient EP250828a (Liu et al., GCN
41574; Aryan et al., GCN 41579; Taguchi et al., GCN 41582; Yao et al.,
GCN 41583; Fu et al., GCN 41584; Zheng et al., GCN 41586; Lipunov et al.,
GCN 41588; Bochenek et al., GCN 41590; Aryan et al., GCN 41591; Ni et al.,
GCN 41592) during commissioning operations of the MDM InfraRed Astronomy
inGaas Explorer (MIRAGE) instrument on the MDM 1.3m telescope.  Observations
were carried out starting at UTC 2025-08-28 10:59:08, starting ~ 3.4 hours
after the time of the X-ray detection.

We obtained a series of dithered exposures in Y-band amounting to a total
exposure time of 850 s. Images were aligned, stacked and calibrated to
the PS1 catalog. Performing forced photometry at the position of the X-ray
and optical counterpart reported in GCN 41582, 41583, 41591, 41592, we
do not detect a point source to a 5 sigma limiting magnitude of > 19.1
AB mag. Analysis will be improved as further commissioning data is processed.

MIRAGE is a new YJH-band near-infrared imager for the MDM 1.3m telescope.
We thank the MDM Observatory staff for supporting the commissioning observations.

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Password Certification: Kishalay De (kde1@mit.edu)
https://www.astronomerstelegram.org/?read=17368
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