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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
  1. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  2. EP250302a: Mondy Observations and Optical Light Curve
  3. EP250302a: VLT/MUSE optical redshift z = 1.131
  4. INTEGRAL: end of scientific operations
  5. EP250302A: VLT near-infrared observations
  6. EP250302A: VLT/X-shooter tentative redshift
  7. EP250302a: OHP/T193 optical and spectroscopic observations
  8. EP250302a: Global MASTER-Net observations report
  9. EP250302a: Xinglong F60B optical observation
  10. EP250302a: Swift-XRT observations of a fading X-ray source
  11. EP250302a: Einstein Probe detection of an X-ray transient
  12. EP250302a: SVOM/C-GFT optical observations
  13. GRB 250226A: GRANDMA Optical Observations
  14. EP250302a: Montarrenti Observatory optical detection
  15. Fermi GRB 250302A: Global MASTER-Net observations report
  16. EP250302a: FTW optical and NIR detection
  17. EP250302a: Nanshan/HMT optical counterpart detection
  18. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  19. GRB 250302A: Fermi GBM Final Real-time Localization
  20. GRB 250228A: Fermi GBM Final Localization
  21. The EP-WXT trigger 01709132140 is likely a flaring star
  22. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  23. GRB 250225B: VLT near-infrared afterglow confirmation
  24. EP250228a: Optical observations with Kinder and Swift/UVOT
  25. Konus-Wind detection of GRB 250226A
  26. GRB 250225B: EIRSAT-1 GMOD Detection
  27. GRB 250226A: KAO Optical Upper Limit
  28. GRB 250226A: AbAO AS-32 Optical Upper Limit
  29. EP250227a: Global MASTER-Net observations report
  30. EP250223A: Upper limits from Fermi-GBM Observations
  31. EP250227a: TRT optical upper limit
  32. GRB 250225B: VLT/HAWKI near-infrared observations
  33. EP250227a: Optical upper limits with Kinder observations
  34. EP250227a: NOT optical observations
  35. EP250227a: Einstein Probe detected of a fast X-ray transient
  36. EP250228a: updates on the EP observations
  37. GRB 250226A: Fermi GBM Observation
  38. EP250225a: EP-FXT follow-up observation
  39. EP250223a: J band upper limit by SYSU 80cm telescope
  40. EP250228a: Swift/XRT localisation
  41. EP250228a: Global MASTER-Net observations report
  42. EP250228a: Einstein Probe detection of an X-ray transient
  43. GRB 250226A / EP250226a: LCO detection of the afterglow
  44. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  45. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  46. GRB 250225B: VLT/Xshooter imaging
  47. GRB 250205A / EP250205A: further radio observations with the VLA
  48. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  49. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  50. GRB 250225B: INTEGRAL SPI-ACS detection
  51. EP250225a: NOT optical candidate counterpart
  52. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  53. EP250226a / GRB 250226A: SVOM/VT optical observations
  54. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  55. EP250225a: TRT optical upper limits
  56. EP250226a/GRB 250226A: 1.6m Mephisto observations
  57. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  58. EP250226a/GRB 250226A: Kinder optical follow-up observations
  59. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  60. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  62. Fermi GRB 250226B: Global MASTER-Net observations report
  63. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  64. GRB 250226B: Fermi GBM Final Real-time Localization
  65. GRB 250225B: Fermi GBM Observation
  66. GRB 250221A: ATCA Detections and Upper Limits
  67. GRB 250225B: REM NIR upper limits
  68. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  69. Konus-Wind detection of GRB 250225B
  70. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  71. EP250223a: CrAO ZTSH optical observation
  72. GRB 250225B: VLT optical and near-infrared candidate counterpart
  73. GRB 250225B: VLT/FORS2 candidate optical afterglow
  74. GRB 250225B: SVOM/GRM observation of a long burst
  75. GRB 250226A: GECAM-B detection
  76. GRB 250221A: EP-FXT detection of the X-ray afterglow
  77. GRB 250214A: SVOM/GRM observation
  78. EP250226a/GRB 250226A: GSP detects optical counterpart
  79. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  80. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  81. EP250226a / GRB 250226A: TRT optical counterpart observation
  82. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  83. EP250226a: Global MASTER-Net observations report
  84. Swift GRB 250225B: Global MASTER-Net observations report
  85. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  86. Fermi GRB 250226A: Global MASTER-Net observations report
  87. Fermi trigger No 762205158: Global MASTER-Net observations report
  88. GRB 250226A: Fermi GBM Final Real-time Localization
  89. EP250225a: Global MASTER-Net observations report
  90. EP250225a: GSP optical upper limit
  91. EP250223a: GMG Optical Observation
  92. EP250225a: Einstein Probe detected of a fast X-ray transient
  93. Fermi GRB 250225A: Global MASTER-Net observations report
  94. GRB 250225B: Swift detection of a burst
  95. EP250223a: GROWTH-India Telescope optical observations
  96. GRB 250221A: Swift-BAT refined analysis
  97. GRB 250223C: SVOM/GRM observation of a long burst
  98. EP250215A: J band upper limit by SYSU 80cm telescope
  99. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  100. GRB 250225A: Fermi GBM Final Real-time Localization

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