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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').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

28066 results found.

  1. GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
  2. GRB 260915A: 10.4m GTC deep optical limits
  3. GRB 260915A: SVOM/VT optical upper limits from VHF data
  4. Fermi GBM Sub-Threshold Detection of GRB 260915A
  5. GRB 260915A: SVOM detection of a burst
  6. Fermi GBM Sub-Threshold Detection of GRB 260914A
  7. GRB 260914A: SVOM/VT optical observation from VHF data
  8. GRB 260914A: SVOM detection of a burst
  9. GRB 260818A: Continued ATCA observations
  10. GRB 260913A: SVOM detection of a faint burst
  11. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  12. GRB 260910B: GOTO tentative optical counterpart candidates
  13. GRB 260909A: Swift ToO observations
  14. GRB 260910B: Fermi GBM Final Real-time Localization
  15. GRB 260903A: Swift-XRT observations
  16. EP260806a: VLA+ALMA radio detections
  17. GRB 260909A: OHP/T193 z-band upper limit
  18. GRB 260910A: Fermi GBM Final Real-time Localization
  19. EP260806a: NOEMA detection
  20. EP260623a: NOEMA detections
  21. GRB 260909A: Mondy optical observations and afterglow candidate
  22. GRB 260909A: SVOM detection of a burst
  23. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  24. GRB 260907A: Glowbug gamma-ray detection of a likely short burst
  25. GRB 260903A: Swift ToO observations
  26. GRB 260907B: Fermi GBM Final Real-time Localization
  27. GRB 260907A: Fermi GBM Final Real-time Localization
  28. EP260903a: EP-FXT follow-up observation
  29. GRB 260830A: GECAM-B detection of a burst
  30. EP260903a: EP-WXT detection of a fast X-ray transient
  31. GRB 260830A: Insight-HXMT/HE detection
  32. GRB 260903A: OHP/T193 optical afterglow detection
  33. GRB 260903A: NOT optical observations and afterglow fading
  34. NuSTAR Transient 260828: SOAR Optical Upper Limits
  35. GRB 260903A: Retraction of optical counterpart of GCN 45501
  36. GRB 260903A: LCO optical counterpart detection
  37. GRB 260827A: Insight-HXMT/HE detection
  38. GRB 260903A: SVOM detection of a soft faint burst
  39. EP260901a: EP-FXT follow-up observation
  40. Konus-Wind detection of GRB 260829A
  41. GRB 260818A: ATCA detection of a candidate radio counterpart
  42. EP260830a: EP-FXT follow-up observation
  43. NuSTAR Transient 260828: LCO Optical Upper Limits
  44. EP260901a: EP-WXT detection of a fast X-ray transient
  45. GRB 260829A: AstroSat CZTI detection
  46. GRB 260830A: NuSTAR detection of prompt emission
  47. EP260830a: EP-WXT detection of a fast X-ray transient
  48. NuSTAR 260828: a 1100s hard X-ray transient
  49. GRB 260831B: SVOM detection of a possible burst
  50. IPN triangulation of GRB 260829A
  51. GRB 260827A: Glowbug gamma-ray detection
  52. EP260727a: ATCA 10 GHz detection
  53. GRB 260831A: Fermi GBM Final Real-time Localization
  54. GRB 260829A: Fermi GBM Detection
  55. GRB 260825A: AstroSat CZTI detection
  56. GRB 260829A: Fermi GBM Final Real-time Localization
  57. GRB 260818B: VLT optical and nIR observations
  58. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  59. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  60. GRB 260827A: Fermi GBM Final Real-time Localization
  61. GRB 260818B: 6 GHz VLA observations
  62. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  63. GRB 260807A: EP-FXT follow-up observations
  64. GRB 260822A: SVOM/VT optical upper limits
  65. GRB 260825A: Fermi GBM Final Real-time Localization
  66. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  67. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  68. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  69. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  70. EP260822a: EP-FXT non-detection and upper limit
  71. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  72. GRB 260822A: GOTO optical counterpart detection
  73. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  74. EP260822a: Einstein Probe detection of a fast X-ray transient
  75. The EP-WXT trigger 01709287395 is likely a flaring star
  76. GRB260822B: Fermi GBM Final Localization
  77. GRB 260822A: SVOM detection of a short burst
  78. GRB 260818B: SVOM/C-GFT optical upper limit
  79. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  80. GRB 260820A: Insight-HXMT/HE detection
  81. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  82. EP detected a brightening of LMXB 1ES 1735-26.9
  83. GRB260820A: Fermi GBM Final Real-Time Localization
  84. GRB 260818B: Insight-HXMT detection
  85. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  86. GRB 260818B: SVOM detection of a short burst
  87. GRB 260810A: Insight-HXMT/HE detection
  88. GRB 260818A: SVOM possible detection of a long and faint GRB
  89. EP260806a: SVOM/ECLAIRs detection through targeted search
  90. EP260806a: WFST optical observations
  91. EP260812b: Optical upper limit with Kinder
  92. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  93. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  94. GRB 260813A: Fermi GBM Final Real-time Localization
  95. EP260812b: Liverpool Telescope observations
  96. EP260812b: GOTO detection of the optical counterpart
  97. EP260812b: Einstein Probe detection of an X-ray transient
  98. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  99. Fermi GBM Sub-Threshold Detection of GRB 260809A
  100. GRB 260810A: Glowbug gamma-ray detection

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