EP241101a
GCN Circular 38039
Subject
EP241101a: EP-WXT detection of a fast X-ray transient
Date
2024-11-02T08:11:40Z (7 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. F. Liang (PMO, CAS), Q. C. Liu (THU), Q. Y. Wu, D. H. Zhao, H. N. Yang, W. M. Yuan (NAO, CAS) report on behalf of the Einstein Probe team:
We report on the detection of a fast X-ray transient designated EP241101a, which was detected by EP-WXT at 2024-11-01T23:52:49 (UTC) and triggered the on-board processing unit at 2024-11-01T23:54:17 (trigger ID: 01709114858). The WXT position of EP241101a is R.A.= 37.763 deg, DEC = 22.731 deg (J2000) with an uncertainty of 2.8 arcmin (radius, 90% C.L. statistical and systematic). The light curve of the transient observed by the WXT lasts more than 100 seconds. The average 0.5-4 keV spectrum can be fitted with an absorbed power-law with a photon index of 0.9 (+0.6/-0.6) (with the column density fixed at the Galactic value of 1.5x10^21 cm^-2). The unabsorbed average flux in 0.5-4 keV is 1.2 (+0.5/-0.4) x 10^(-9) erg/s/cm^2.
An autonomous observation was performed by the Follow-up X-ray Telescope (FXT) about 45 minutes later, the exposure time is about 1.6 ks. The delay of the FXT observation was due to the Earth obscuration. No significant source was detected by the FXT during its autonomous observation within the WXT error circle, thus we obtained a flux upper limit of 7.1 x 10^(-14) erg/s/cm^2 in the 0.5-10 keV. The quoted uncertainties are at the 90% confidence level for the above parameters.
No previously known bright X-ray sources are found within the error circle around the source position. Further follow-up observations are encouraged to identify the nature of this X-ray transient.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
GCN Circular 38047
Subject
EP241101a: BOOTES-7 optical upper limit
Date
2024-11-02T18:46:16Z (7 months ago)
From
ipg@iaa.es
Via
Web form
I. Perez-Garcia, S.-Y. Wu, E. Fernandez-Garcia, M. D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Perez del Pulgar, A. Castellon, A. Reina (Univ. de Malaga), Y.-D. Hu (INAF-OAB, Brera), L. Hernandez-Garcia (Univ. de Valparaiso), M. Gritsevich (Univ. of Helsinki), D. R. Xiong (Yunnan Observatories of CAS), B.-B. Zhang (Nanjing Univ.) and A. Maury (Space, San Pedro de Atacama), on behalf of a larger collaboration, report:
Following the detection of the fast X-ray transient EP241101a by the Einstein Probe (Liang et al. GCNC 38039), the 0.6m BOOTES-7 robotic telescope at San Pedro de Atacama (Chile) observed the fast X-ray transient location starting on Nov 02, 04:55 UT (5 hours after trigger and 4 minutes after notification) in different optical bands. No new optical source is detected on the co-added images (clear-filter) within the EP/WXT 2.8 arcmin radius error box down to 20.1 mag.
We thank the staff at San Pedro de Atacama Celestial Explorations observatory for their excellent support.
GCN Circular 38049
Subject
EP241101a: Global MASTER-Net observations report
Date
2024-11-02T22:18:31Z (7 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
legacy email
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),
D. Buckley
(South African Astronomical Observatory),
O.A. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich
(Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the EP241101a ( EP Team et al., GCN 38039) errorbox 48605 sec after notice time and 78664 sec after trigger time at 2024-11-02 21:43:53 UT, with upper limit up to 16.6 mag. The observations began at zenith distance = 55 deg. The sun altitude is -42.1 deg.
The galactic latitude b = -34 deg., longitude l = 152 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2656731
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
78695 | 2024-11-02 21:43:53 | MASTER-SAAO | (02h 29m 45.53s , +22d 22m 29.4s) | C | 60 | 16.1 |
79911 | 2024-11-02 22:04:09 | MASTER-SAAO | (02h 29m 58.67s , +22d 24m 38.5s) | C | 60 | 16.6 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 38060
Subject
EP241101a: OHP/T193 optical observations
Date
2024-11-03T13:58:27Z (7 months ago)
From
Christophe Adami at LAM <christophe.adami@lam.fr>
Via
Web form
C. Adami (LAM), report on behalf of a larger collaboration:
We observed the field of EP241101a (Liang et al., GCN 38039; Perez-Garcia et al.,
GCN 38047; Lipunov et al., GCN 38049) using the T193cm telescope at Observatoire de
Haute-Provence (France) equipped with the MISTRAL spectro-imager. 7 exposures were
obtained in the r-band (7x600s) from 2024 02 November 19:38 UT to 2024 02 November
20:56 UT (~+20.5h after detection).
The combined frame has a magnitude histogram peaked at r-band=22.1 (AB). The photometric
calibration was performed using nearby objects from the PanSTARRS catalog and the magnitude
is not corrected for Galactic extinction.
There is no clear additionnal objects in the MISTRAL image as compared with the PanStarrs
i-band image (the deepest in PanStarrs). The most appealing candidate present in the MISTRAL
image and not visible in any of the PanStarrs images is below the MISTRAL magnitude histogram
peak and is located at RA=02:30:53.09, DEC=22:43:48.11 with a preliminar estimated magnitude
of r-band=22.8+/-0.5. Following MISTRAL observations of this source will be reported.
We acknowledge the excellent support from Observatoire de Haute-Provence, in particular
Stephane Favard.
GCN Circular 38061
Subject
EP241101a: Optical upper limits with Kinder observations
Date
2024-11-03T15:29:37Z (7 months ago)
From
Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941@gmail.com>
Via
Web form
A. Aryan, T.-W. Chen, W.-J. Hou (all NCU), A. K. H. Kong (NTHU), J. Gillanders (Oxford), S. J. Smartt (Oxford/QUB), Y. J. Yang, A. Sankar. K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, H.-C. Lin, C.-H. Lai, H.-Y. Hsiao, C.-S. Lin, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report:
We observed the field of the fast X-ray transient EP241101a (Liang et al., GCN 38039; Perez-Garcia et al., GCN 38047; Lipunov et al., GCN 38049; Adami et al., GCN 38060) using the 1m LOT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2024arXiv240609270C). The first LOT epoch of observations started at 16:59 UTC on the 2nd of November 2024 (MJD = 60616.707), 0.71d after the EP WXT trigger.
We utilized the astroalign (Beroiz et al. 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al. 2022, ApJ, 935, 167) packages to align and stack the individual frames. We do not find any evidence of a new and uncataloged source in the stacked images within the 2.8 arcminute error circle of EP-WXT localization.
Moreover, we utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform the PSF photometry on our stacked frames. The details of the observations and measured 3-sigma upper limits (in the AB system) are as follows:
Telescope | Filter | MJD (start) | t-t0 (d) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass
LOT | r | 60616.707 | 0.71 | 300 * 6 | >22.9| 1".47 | 1.08
LOT | g | 60616.730 | 0.73 | 300 * 6 | >23.0| 1".39 | 1.16
We notice that the probable optical counterpart candidate identified in the MISTRAL images (Adami et al., GCN 38060) is already present in the SDSS DR12 (SDSS J023053.10+224348.0) images, as well as in the DESI Legacy Survey images.
The presented magnitudes are calibrated using the field stars from the SDSS catalog and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E(B-V) = 0.17 mag in the direction of the transient (Schlafly & Finkbeiner 2011).
GCN Circular 38064
Subject
EP241101a: Possible detection of an optical counterpart with FTW
Date
2024-11-03T17:56:13Z (7 months ago)
From
Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann@physik.lmu.de>
Via
Web form
Malte Busmann (LMU), Daniel Gruen (LMU), Brendan O’Connor (Carnegie Mellon U.) and Antonella Palmese (Carnegie Mellon U.) report:
We observed the 90% localization area of EP241101a (Liang et al., GCN 38039) with the Three Channel Imager (3KK) at the Fraunhofer Telescope Wendelstein (FTW) for 40 x 180 s in the r, i and J band simultaneously. Observations started at 2024-11-03T01:36:19 UT (1.07 days after the EP-WXT trigger). Our observations are calibrated against the PS1 catalog and reach 24.5 AB mag in the r band and 24.0 AB mag in the i band at the 3σ limit.
We performed difference imaging in the r band with images from the DESI Legacy Survey DR10. In the difference image, we detect a source at
RA, DEC (J2000) = 02:31:10.85, +22:44:54.75
corresponding to PSO J037.7952+22.7485 in the PS1 catalog, which is labeled as a variable source and a possible AGN/QSO. Compared to the mean magnitude in PS1 the source is brighter by ~0.5 mag in r-band and ~0.4 mag in i-band. This detection is consistent with the upper limits from Perez-Garcia et al., GCN 38047; Lipunov et al., GCN 38049 and Aryan et al., GCN 38061.
While it is difficult to explain the short duration flare of EP241101a in the context of an AGN/QSO, we do not uncover any other variable sources to depth r>24.5 AB mag and i>24.0 AB mag over the entire 90% WXT localization.
Further observations are encouraged to determine the nature of the source.
We thank the staff of the Wendelstein Observatory for obtaining these observations.
GCN Circular 38073
Subject
EP241101a: EP-FXT observations update
Date
2024-11-04T16:27:13Z (7 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Q. Y. Wu (NAO, CAS), S. M. Jia, Y. Chen (IHEP, CAS), Y. F. Liang (PMO, CAS), Q. C. Liu (THU), D. H. Zhao, H. N. Yang, W. Yuan (NAO, CAS) report on behalf of the Einstein Probe team:
Following the on-board detection of the fast X-ray transient EP241101a by EP-WXT, an autonomous follow-up observation was conducted by EP-FXT approximately 45 minutes later, with no counterpart detected (Liang at al., GCN 38039). We further analyzed the data during the FXT's slew to the target before the observation commenced, an uncatalogued X-ray source was found at R.A. = 37.7526 deg, DEC = 22.7175 deg (J2000) with an uncertainty of about 10 arcsecs (radius, 90% C.L. statistical and systematic). The slew observation began from 2024-11-01T23:54:21 (UTC), and observed the source from 2024-11-01T23:57:02 to 2024-11-01T23:58:02, which is from T0+253s to T0+313s (T0 = 2024-11-01T23:52:49). The spectrum of the source can be fitted by an absorbed power law with a photon index of 2.4(+/-0.4) (with a column density fixed at the Galactic one of 1.46 x 10^21 cm^-2), giving an average unabsorbed flux of 4.4(+0.7/-0.6) x 10^-11 erg/s/cm^2 in the 0.5-10 keV band. The FXT source is about 3 arcmin away from the optical candidate reported by Busmann et al. (GCN 38064), indicating that the optical source may not be associated with EP241101a.
We have conducted another FXT observation of EP241101a from T0+31.7ks to T0+43.7 ks with an exposure time of 6.5 ks. No significant source was detected within the WXT error circle, putting a flux upper limit of 1.5 x 10^(-14) erg/s/cm^2 in the 0.5-10 keV.
Given the rapid X-ray decay and the absence of an optical counterpart down to ~24.5 magnitude (Perez-Garcia et al., GCN 38047; Lipunov et al., GCN 38049; Adami et al., GCN 38060; Aryan et al., GCN 38061; Busmann et al., GCN 38064), we encourage further observations to determine the nature of the source.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with on-board X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is an international collaborative mission led by the Chinese Academy of Sciences (CAS) and participated by the European Space Agency (ESA), the Max-Planck Institute for Extraterrestrial Physics (MPE) in Germany and the Centre National d’Etudes Spatiales (CNES) in France.
GCN Circular 38079
Subject
EP241101a NUTTelA-TAO / BSTI Measurements 2024-11-02
Date
2024-11-05T11:30:41Z (7 months ago)
Edited On
2024-11-05T14:01:36Z (7 months ago)
From
Toktarkhan Komesh at Nazarbayev University <toktarkhan.komesh@nu.edu.kz>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Toktarkhan Komesh at Nazarbayev University <toktarkhan.komesh@nu.edu.kz>
Via
Web form
B. Grossan (UCB, NU) , Z. Maksut (NU), M. Krugov (FAI), Ernazar Abdikamalov (NU), T. Komesh (NU), Zh. Abdullayev (NU), and G. F. Smoot (UCB, NU, IAS, DIPC), report on behalf of the Energetic Cosmos Laboratory:
We used the Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) and the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32,14) to image the field of EP241101a, centered on the position reported by Liang et al. 2024 (GCN 38039), during variable cloudy conditions. Each image was calibrated with 3 bright PS1 stars on our images for our standard SDSS filters. We report the following 5 sigma upper limits (UL) in 750 s exposures on UT 2024-11-02:
t_start(UT) UL g' UL r'
---------------- ------ ------
14:50:29 18.2 17.4
15:02:59 18.6 17.9
15:15:29 19.0 18.4
We detected nothing at the position of the rapidly fading X-ray source of Wu et al. 2024 (GCN 38073). All of our detected sources matched those in the PS1 images or catalog in both filters. We do not detect the source given by Busmann et al. 2024 (GCN 38064), consistent with our sensitivity limits. Given the optical non-detections more than covering the 90% localization of Liang et al. (X-ray detection, UT 2024-11-01T23:54), Perez-Garcia et al. (GCN 38047; UT 2024-11-02T04:55), the NUTTelA observations described above (UT 2024-11-02 14:50), Aryan et al. (GCN 38061; UT 24-11-02 16:59), Adami et al. (GCN 38060; UT24-11-02 19:38) , Lipunov et al. (GCN38049; UT 2024-11-02 21:43), and Busmann et al. (UT 2024-11-03T01:36), the measurements suggest that, assuming a power-law decay, no bright optical emission occurred between 11-02T04:55 and 11-03T01:36.
----------------------------------
UCB = University of California, Berkeley, USA
NU = Nazarbayev University, Astana, Kazakhstan
FAI = Fesenkov Astrophysical Institute, Kazakhstan
IAS = Institute for Advanced Study, Hong Kong University of Science and Technology
DIPC = Basque Country UPV/EHU, E-48080 San Sebastian, Spain
The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan. This research has been supported, in part, by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP14870504).
GCN Circular 38109
Subject
EP241101a: CrAO ZTSH optical observations
Date
2024-11-07T03:48:50Z (7 months ago)
From
Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>
Via
legacy email
N. Pankov (HSE, IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO) report on
behalf of GRB-IKI-FuN collaboration:
We observed the EP241101a detected by EP-WXT (Liang et al., GCN 38039) with
the 2.6-meter ZTSh telescope of CrAO in the R-filter. The observations
were carried out on 02.11.2024 and 03.11.2024. We found several OT
candidates entire the EP-WXT localization area. In particular the source
(PS1 catalog PSO J037.7952+22.7485) reported by Busmann et al., GCN 38064
and the source reported by Adami et al., GCN 38060 were also marked as
candidates in our preliminary analysis. And we do not find any sources
within the enhanced localization area of EP-FXT (Wu et al., GCN 38073).
Preliminary photometry of the sources and upper limits are the following:
Date UT start TO+ Exp. Filter GCN#38064 GCN#38064 UL(3)
(mid, days) (s) OT OT
2024-11-02 23:59:22 1.03548 46x120 R 19.98+-0.05 n/d 21.0
2024-11-03 21:18:54 1.91711 36x120 R 20.47+-0.02 21.88+-0.04 22.0
Photometry is calibrated using nearby USNO-B1.0 stars (R2 magnitude).
Based on our observations and previously reported candidates, we cannot
suggest an obvious candidate for OT EP341101a.