EP240908a
GCN Circular 37458
Subject
EP240908a: Optical afterglow confirmation
Date
2024-09-11T18:49:47Z (a year ago)
From
Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>
Via
Web form
J. Quirola-Vasquez (Radboud Univ.), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. J. Levan (Radboud Univ. & Warwick Univ.), P. G. Jonker (Radboud Univ), F. E. Bauer (PUC), J. van Dalen (Radboud Univ.), M. E. Ravasio (Radboud Univ.), D. Mata Sanchez (IAC), M. A. P. Torres (IAC), A. Martin-Carrillo (UCD), report on behalf of a larger collaboration:
We performed additional observations of the X-ray counterpart of EP 240908a (Mao et al., GCN 37432) using the Gemini-North telescope equipped with the GMOS-N imager. A total of 4 exposures by 180 s each were secured, with mid time 2024 Sep 10.417 UT (2.19 days after the revised EP detection time; Mao et al., GCN 37443).
The source reported by Quirola-Vasquez et al. (GCN 37438) is well detected in the new images and is still point-like (with a seeing of 0.6"). With respect to our previous observation, we measure a decay by ~0.5 mag, which confirms this object as the optical counterpart of EP 240908a
We acknowledge rapid and expert support of the observing staff at the Gemini telescope.
GCN Circular 37444
Subject
EP240908a: Mondy and AbAO follow-up observations
Date
2024-09-10T09:16:50Z (a year ago)
From
Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>
Via
legacy email
N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya.
Inasaridze (AbAO), S. Belkin (HSE, IKI) report on behalf of GRB-IKI-FuN:
We observed the field of fast X-Ray transient EP240908a (Mao et al., GCN
37432) with AZT-33IK 1.5-m telescope of Mondy observatory, and AS-32 0.7-m
telescope of Abastumani observatory (AbAO). The observations were started
on 2024-09-08 at 19:05 UT at Mondy (~ 1 day since EP trigger).
The series of images in the R-filter were taken. Preliminary upper limits
are given below:
Date UTStart JD Filter Exp. OT err UL(3sigma) Telescope
(mid, days) (s)
2024-09-09 19:05:56 60562.82703 R 45x120 n/d n/d 23.5 AZT-33IK
2024-09-09 19:37:24 60562.84333 R 74x60 n/d n/d 19.7 AS-32
The magnitudes were calibrated with nearby USNO-B1.0 stars (R2 magnitudes).
We do not resolve the optical source proposed by Quirola-Vasquez et al.
(GCN 37438). In a stacke Mondy image we clearly detect a nearby LS DR10
elliptical source at RA=00:56:00.5 DEC=+08:04:33.2 which is apart of 3.6
arcsec from the proposed OT. This elliptical source might be a host galaxy
of the EP240908a.
GCN Circular 37443
Subject
EP240908a: Updates on the WXT detection result around the trigger time
Date
2024-09-10T09:09:30Z (a year ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
X. Mao, J. W. Hu (NAOC, CAS), J. Q. Peng (IHEP, CAS), S. K. Yang, H. He (WHU), W. Yuan (NAOC, CAS) on behalf of the Einstein Probe team
We have reported the detection of the fast X-ray transient EP240908a by the Einstein Probe (EP) mission (EP Team et al. GCN 37432). Based on the newly received EP-WXT telemetry data of this source, the transient event started at 2024-09-08T17:28:27 (UTC). The WXT position of the source is R.A. = 13.992 deg, DEC = 8.089 deg (J2000) with an uncertainty of 2.7 arcmin in radius (90% C.L. statistical and systematic), which is 1.1 arcmin away from the FXT position (EP Team et al. GCN 37432). The lightcurve of the transient observed by the WXT lasted around 950 seconds and has a peak flux of ~1 x 10^-9 erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 1.6(-0.5, +0.4) (with the column density fixed at the Galactic one of 7 x 10^20 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 7.4(-1.9, +2.4) x 10^(-10) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.
An optical counterpart candidate was detected within the FXT error circle with an AB magnitude r ~ 24 (Quirola-Vasquez et al. GCN 37438). Further follow-up observations are encouraged to identify the nature of this X-ray transient.
GCN Circular 37438
Subject
EP240908a: optical afterglow candidate
Date
2024-09-09T19:09:59Z (a year ago)
From
Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>
Via
Web form
J. Quirola-Vasquez (Radboud Univ.), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. J. Levan (Radboud Univ. & Warwick Univ.), P. G. Jonker (Radboud Univ), F. E. Bauer (PUC), J. van Dalen (Radboud Univ.), M. E. Ravasio (Radboud Univ.), D. Mata Sanchez (IAC), M. A. P. Torres (IAC), A. Martin-Carrillo (UCD), report on behalf of a larger collaboration:
We observed the position of the X-ray counterpart of EP 240908a (Mao et al., GCN 37432) using the Gemini-North telescope equipped with the GMOS-N imager. A total of 4 exposures by 180 s each were secured, with mid time 2024 Sep 9.561 UT (0.777 days after the EP detection time).
Within the FXT error circle (Mao et al., GCN 37432), we detect a source not readily visible in the Legacy survey images. We measure its position (J2000):
RA = 00:56:00.88
Dec = +08:04:31.9
The source is pointlike (in a seeing of 0.6") and well detected in our data with an AB magnitude r ~ 24. Sources of comparable brightness are visible in the Legacy survey, which has a detection limit of r ~ 24.5 in this area of the sky. We thus propose this as a candidate afterglow of EP 240908a, though further observations are planned in order to confirm variability.
We acknowledge rapid and expert support of the observing staff at the Gemini telescope.
GCN Circular 37437
Subject
EP EP240908a: Global MASTER-Net observations report
Date
2024-09-09T17:45:30Z (a year 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-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 EP EP240908a ( EP Team et al., GCN 37432) errorbox 17611 sec after notice time and 74056 sec after trigger time at 2024-09-09 15:23:21 UT, with upper limit up to 16.7 mag. The observations began at zenith distance = 60 deg. The sun altitude is -29.9 deg.
MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP EP240908a errorbox 25003 sec after notice time and 81447 sec after trigger time at 2024-09-09 17:26:32 UT, with upper limit up to 16.5 mag. The observations began at zenith distance = 78 deg. The sun altitude is -20.7 deg.
The galactic latitude b = -54 deg., longitude l = 126 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2595501
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
74086 | 2024-09-09 15:23:21 | MASTER-Tunka | (00h 56m 24.44s , +07d 52m 19.7s) | C | 60 | 16.7 | Coadd
81478 | 2024-09-09 17:26:32 | MASTER-Kislovodsk | (00h 54m 07.82s , +08d 09m 35.1s) | C | 60 | 15.3 |
81800 | 2024-09-09 17:31:55 | MASTER-Kislovodsk | (00h 54m 11.89s , +08d 11m 57.0s) | C | 60 | 16.1 |
82122 | 2024-09-09 17:37:17 | MASTER-Kislovodsk | (00h 54m 05.94s , +08d 10m 11.3s) | C | 60 | 16.5 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 37434
Subject
EP240908a: TRT optical upper limit
Date
2024-09-09T11:34:12Z (a year ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
S.Y. Fu, S.Q. Jiang (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), X. Liu, J. An, Z.P. Zhu, S.Y. Gao, D. Xu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang (NAOC) report on behalf of a large collaboration:
We observed the field of EP240908a (Mao et al., GCN 37432) using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Sierra Remote Observatories, USA. Observations started at 07:27:05.3 UTC on 2024-09-09, and 6 x 300 s frames in R-band were obtained.
No new optical source is detected in the stacked image within or beside the ~ 10-arcsec EP/FXT error circle (Mao et al., GCN 37432), down to a 5-sigma limiting magnitude of R ~ 21.6, calibrated with PanSTARRS sources in the field and not corrected for Galactic extinction.
GCN Circular 37432
Subject
EP240908a: EP detection of a fast X-ray transient
Date
2024-09-09T09:04:51Z (a year ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
X. Mao (NAOC, CAS), J. Q. Peng (IHEP, CAS), S. K. Yang, H. He (WHU), J. W. Hu, W. M. Yuan, C. C. Jin, Y. Liu, Z. X. Ling, C. Zhang, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, W. W. Cui, D. W. Han, C. K. Li, L. M. Song, X. F. Zhao, J. Zhang, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team
We report on the detection of a fast X-ray transient designated EP240908a by the Einstein Probe (EP) mission. The transient event triggered the Wide-field X-ray Telescope (WXT) on-board processing unit and also an automated observation by the on-board Follow-up X-ray Telescope (FXT). The amount of information available around the trigger time is still limited due to delayed data transmission. The exact time of the trigger by WXT is unknown, due to the unsuccessful receipt of the alert message and the delayed data telemetry, but is estimated to occur between 2024-09-08 15:55 and 18:49 UTC.
Based on the FXT data currently transmitted, the FXT observation began at 2024-09-08T18:49:05 UTC with an exposure time of about 3 ks. An uncataloged X-ray source was detected at R.A. = 14.0031, DEC = 8.0735 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). No significant variation in the light curve was observed during the FXT observation. The spectrum can be fitted by an absorbed power-law with NH = 1.5(-1.5/+1.7) x 10^21 cm^-2 and a photon index of 2.1(-0.6/+0.7). The derived unabsorbed 0.5 - 10.0 keV flux is 7.4(-2.0/+1.3) x 10^-13 erg/s/cm^2. A ToO observation with FXT has been planned. No previously known bright X-ray sources have been found within the error circle of the source position. Further information on this source will be updated when more data is available, particularly the WXT data from which the source was first detected. 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 X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).