EP241201a
GCN Circular 38446
Subject
EP241201a: 1.6m Mephisto Optical Upper Limits
Date
2024-12-06T02:27:12Z (a year ago)
From
Brajesh Kumar at SWIFAR, YNU <brajesh@ynu.edu.cn>
Via
Web form
Guowang Du, Jinghua Zhang, Shiyan Zhong, Yiheng Xie, Yanan Cao, Yu Pan, Xingzhu Zou, Xinlei Chen, Brajesh Kumar, Yuanpei Yang, Yuan Fang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team:
The field of EP241201a (Chen et al., GCN 38415) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory starting from 11:21:59 UT 2024-12-04 (~2.5 days after the trigger). Several frames with exposures of 300s and 294s in the uvgr and iz bands were taken. In the stacked images, no credible candidate was detected within the EP-WXT error circle (Chen et al., GCN 38415) and at the location of possible source (Lee et al., GCN 38418). This is consistent with the reports by Liu et al. (GCN 38425), and Perez-Garcia et al. (GCN 38427). The 3-sigma upper limits are listed below.
Start_Time(UT) Band Exp(s) Lim-mag(AB)
2024-12-04T11:22:00 u 300*3 >21.93
2024-12-04T11:38:30 v 300*3 >22.34
2024-12-04T11:21:59 g 300*3 >22.29
2024-12-04T11:38:30 r 300*3 >22.59
2024-12-04T11:22:00 i 294*3 >21.23
2024-12-04T11:38:31 z 294*2 >20.18
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Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21.
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GCN Circular 38430
Subject
EP241201a: EP-FXT follow-up observations
Date
2024-12-03T15:57:18Z (a year ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
W. Chen (NAO, CAS), G. Y. Zhao (SYSU), C. Zhou (HUST), T. Zhao (NAO, CAS), W. D. Zhang (NAO, CAS) report on behalf of the Einstein Probe team:
Following the detection of the fast X-ray transient EP241201a (Chen et al., GCN 38415), we performed an observation with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe mission. The observation started at 2024-12-02T09:23:55 (UTC), about 12 hours after the EP-WXT detection, with an exposure time of 2.9 ks. Within the WXT error circle, an uncatalogued X-ray source is detected at R.A. = 282.4865 deg, DEC = 66.0693 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The average FXT spectrum in 0.5-10 keV can be fitted by an absorbed power law with a photon index of 4.8(-1.5,+1.7) and a column density of 1.2(-0.5,+0.6) x 10^22 cm^-2, giving an average unabsorbed flux of 2.9(-2.0, +14.4) x 10^-12 erg/s/cm^2 in the 0.5-10 keV band. Compared to the WXT detection, its flux has droped by about three orders of magnitude. The X-ray spectrum in 0.5-10 keV can also be fittted by an absorbed black body with a temperature of 0.27(-0.06, +0.08) keV and a column density of 4.9(-3.2, +4.0) x 10^21 cm^-2, giving an average unabsorbed flux of 3.9(-1.5, +3.7) x 10^-13 erg/s/cm^2.
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).
GCN Circular 38427
Subject
EP241201a: BOOTES-5 optical upper limit
Date
2024-12-03T10:36:32Z (a year ago)
From
ipg@iaa.es
Via
Web form
I. Perez-Garcia, S.-Y. Wu, E. Fernandez-Garcia, M. D. Caballero-Garcia, G. Garcia-Segura, R. Sanchez-Ramirez, S. Guziy and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Perez del Pulgar, A. Castellon (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), S. Jeong (ADD, Daejeon) and D. Hiriart and W. H. Lee (UNAM), on behalf of a larger collaboration, report:
Following the detection of the fast X-ray transient EP241201a by the Einstein Probe (Chen et al. GCNC 38415), the 0.6m BOOTES-5 robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) observed the fast X-ray transient location starting on Dec 02, 05:32 UT (8.5 hours after trigger and 1 minute after notification) in different optical bands. No new optical source is detected on the co-added images (20*60 sec clear-filter) within the EP/WXT 3 arcmin radius error box down to 20.3 mag. Additionally, the source reported 4.8 hr later by Kinder (Lee et al, GCNC 38418) is neither detected in our observation nor in the NOT one at a later epoch (Liu et al., GCNC 38425).
We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for their excellent support.
GCN Circular 38425
Subject
EP241201a: NOT optical observations
Date
2024-12-03T06:06:27Z (a year ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
X. Liu, S.Q. Jiang, S.Y. Fu, Z.P. Zhu, J. An, D. Xu (NAOC), J.P.U. Fynbo (DAWN/NBI), A.H. de la Fuente, A.G. Theil (NOT) report:
We observed the field of EP241201a detected by EP-WXT (Chen et al, GCN 38415) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 2024-12-02T19:53:15, i.e., ~ 22.9 hrs after the EP-WXT trigger, and 5x200 s Sloan r-filter images were obtained.
No reliable optical transient is found within the EP-WXT 2.34 arcmin error circle (Chen et al, GCN 38415) after performing image differencing using the DESI Legacy Survey as template, down to a 5-sigma upper limit of r > 22.5, calibrated with nearby Pan-STARRS stars and not corrected for Galactic extinction.
In addition, the plausible optical transient candidate reported by Kinder (Lee et al, GCN 38418) is not present in our stacked image.
GCN Circular 38418
Subject
EP241201a: Kinder optical counterpart candidate
Date
2024-12-02T15:45:07Z (a year ago)
From
Janet Chen at National Central University <janetstars@gmail.com>
Via
Web form
M.-H. Lee (NCU), S. Yang (HNAS), A. Aryan, T.-W. Chen, Y. J. Yang, W.-J. Hou (all NCU), S. J. Smartt (Oxford/QUB), A. K. H. Kong (NTHU), J. Gillanders (Oxford), C.-C. Ngeow, A. Sankar.K, Y.-H. Li, H.-Y. Miao, Y.-C. Pan, C.-H. Lai, H.-C. Lin, H.-Y. Hsiao, C.-S. Lin, J.-K. Guo (all NCU), 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 EP241201a (Chen et al., GCN 38415) using the 1m LOT at the Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2024 arXiv:2406.09270). The first LOT epoch of observations started at 10:25 UTC on 2nd December 2024 (MJD 60646.434), 13.40 hr after the EP-WXT trigger.
We utilized the Kinder pipeline (Yang et al. A&A 646, A22) to stack the images and subtract them from the DESI Legacy Survey (Dey et al. 2019) DR10 template images. Although no definitive candidates were detected in the difference images, we conducted a manual inspection of both the target and difference images. During this process, we identified a plausible optical transient candidate at RA=18:50:38.079, Dec=+66:03:11.36, located approximately 2.28 arcminutes from the reported coordinates of EP241201a. Despite the low signal-to-noise ratio (SNR) of this candidate, we believe it to be real due to its well-defined Gaussian profile.
The details of the observations and measured PSF magnitude with template subtraction (in the AB system) of the possible counterpart of EP241201a are as follows:
--------------------------------------------------------------------------------------------------Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass
LOT | r | 60646.434 | 13.40 | 300 * 6 | 22.69 +/- 0.41 | 1".43 | 2.06
The presented magnitude was calibrated using the field stars from the Pan-STARRS1 catalog (Chambers et al., 2016 arXiv:1612.05560) and was not corrected for the expected Galactic foreground extinction corresponding to a reddening of A_r = 0.13 mag in the direction of the transient (Schlafly & Finkbeiner 2011).
We note an extended source in the Legacy Survey image 5".8 west and 3".8 south from the plausible optical transient candidate, at RA=18:50:37.128, Dec=+66:03:07.56, is possibly its host galaxy, with r-band magnitude as 20.47 mag and photo-z = 0.313 +/- 0.056, the distance module is then 40.91. Assuming the r-band can be roughly K-corrected to the g-band, with the Milky Way extinction correction, the optical counterpart candidate has the rest-frame M_g = -18.35 mag.
Further follow-up observations are encouraged to confirm this candidate, as it is beyond our 3-sigma detection limit of r > 21.6 mag.
GCN Circular 38416
Subject
EP241201a: Global MASTER-Net observations report
Date
2024-12-02T10:27:31Z (a year ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
legacy email
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko,
A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin,
V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP241201a ( EP Team et al., GCN 38415) errorbox 10284 sec after notice time and 48020 sec after trigger time at 2024-12-02 10:21:42 UT, with upper limit up to 19.5 mag. Observations started at twilight. The observations began at zenith distance = 28 deg. The sun altitude is -11.8 deg.
The galactic latitude b = 25 deg., longitude l = 96 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2692013
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
48028 | 2024-12-02 10:21:42 | MASTER-Tunka | (18h 51m 35.06s , +66d 13m 05.0s) | C | 15 | 19.0 |
48056 | 2024-12-02 10:22:09 | MASTER-Tunka | (18h 51m 34.90s , +66d 14m 05.6s) | C | 15 | 19.0 |
48091 | 2024-12-02 10:22:38 | MASTER-Tunka | (18h 51m 40.39s , +66d 13m 06.2s) | C | 30 | 19.5 |
48133 | 2024-12-02 10:23:20 | MASTER-Tunka | (18h 51m 35.74s , +66d 12m 06.9s) | C | 30 | 19.5 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 38415
Subject
EP241201a: EP detection of a fast X-ray transient
Date
2024-12-02T07:27:17Z (a year ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
W. Chen, T. Zhao(NAO,CAS), C. Zhou(HUST), G. Y. Zhao(SYSU), W. D. Zhang(NAO,CAS) report on behalf of the Einstein Probe team:
We report the detection of an X-ray transient EP241201a by EP-WXT, which triggered the on-board processing unit at 2024-12-01T21:01:22 (UTC) (trigger ID: 01709126276). We analysed the telemetry data of WXT, and found in the lightcurve a fast X-ray flare that started at 2024-12-01T20:59:16 (UTC) and lasted for about 230 seconds. The position is R.A. = 282.596 deg, DEC = 66.081 deg (J2000) with an uncertainty of about 2.343 arcmin (radius, 90% C.L. statistical and systematic). The average 0.5-4 keV spectrum that was extracted from the time interval of the flare can be fitted with an absorbed power law with a photon index of 3.9(-1.4,+1.6) and a column density of 1.5(-0.6,+0.8)e22 cm^-2. The unabsorbed flux in 0.5-4 keV is 7.1(-4.9,+32.7)e-9 erg/s/cm^2.
We plan to perform a target of opportunity observation with the Follow-up X-ray Telescope (FXT) on board EP. Further follow-up observations are encouraged to explore the orgin of EP241201a.
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).