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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"

28072 results found.

  1. GRB 260909A: Swift-XRT observations
  2. GRB 260916A: MAXI/GSC detection
  3. GRB 260915A: Swift ToO observations
  4. GRB 260915A: J-band upper limit by SYSU 80cm infrared telescope
  5. GRB 260915A: SVOM/C-GFT optical upper limits
  6. GRB 260914A: VLT/X-shooter observations and redshift confirmation
  7. GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
  8. GRB 260915A: 10.4m GTC deep optical limits
  9. GRB 260915A: SVOM/VT optical upper limits from VHF data
  10. Fermi GBM Sub-Threshold Detection of GRB 260915A
  11. GRB 260915A: SVOM detection of a burst
  12. Fermi GBM Sub-Threshold Detection of GRB 260914A
  13. GRB 260914A: SVOM/VT optical observation from VHF data
  14. GRB 260914A: SVOM detection of a burst
  15. GRB 260818A: Continued ATCA observations
  16. GRB 260913A: SVOM detection of a faint burst
  17. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  18. GRB 260910B: GOTO tentative optical counterpart candidates
  19. GRB 260909A: Swift ToO observations
  20. GRB 260910B: Fermi GBM Final Real-time Localization
  21. GRB 260903A: Swift-XRT observations
  22. EP260806a: VLA+ALMA radio detections
  23. GRB 260909A: OHP/T193 z-band upper limit
  24. GRB 260910A: Fermi GBM Final Real-time Localization
  25. EP260806a: NOEMA detection
  26. EP260623a: NOEMA detections
  27. GRB 260909A: Mondy optical observations and afterglow candidate
  28. GRB 260909A: SVOM detection of a burst
  29. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  30. GRB 260907A: Glowbug gamma-ray detection of a likely short burst
  31. GRB 260903A: Swift ToO observations
  32. GRB 260907B: Fermi GBM Final Real-time Localization
  33. GRB 260907A: Fermi GBM Final Real-time Localization
  34. EP260903a: EP-FXT follow-up observation
  35. GRB 260830A: GECAM-B detection of a burst
  36. EP260903a: EP-WXT detection of a fast X-ray transient
  37. GRB 260830A: Insight-HXMT/HE detection
  38. GRB 260903A: OHP/T193 optical afterglow detection
  39. GRB 260903A: NOT optical observations and afterglow fading
  40. NuSTAR Transient 260828: SOAR Optical Upper Limits
  41. GRB 260903A: Retraction of optical counterpart of GCN 45501
  42. GRB 260903A: LCO optical counterpart detection
  43. GRB 260827A: Insight-HXMT/HE detection
  44. GRB 260903A: SVOM detection of a soft faint burst
  45. EP260901a: EP-FXT follow-up observation
  46. Konus-Wind detection of GRB 260829A
  47. GRB 260818A: ATCA detection of a candidate radio counterpart
  48. EP260830a: EP-FXT follow-up observation
  49. NuSTAR Transient 260828: LCO Optical Upper Limits
  50. EP260901a: EP-WXT detection of a fast X-ray transient
  51. GRB 260829A: AstroSat CZTI detection
  52. GRB 260830A: NuSTAR detection of prompt emission
  53. EP260830a: EP-WXT detection of a fast X-ray transient
  54. NuSTAR 260828: a 1100s hard X-ray transient
  55. GRB 260831B: SVOM detection of a possible burst
  56. IPN triangulation of GRB 260829A
  57. GRB 260827A: Glowbug gamma-ray detection
  58. EP260727a: ATCA 10 GHz detection
  59. GRB 260831A: Fermi GBM Final Real-time Localization
  60. GRB 260829A: Fermi GBM Detection
  61. GRB 260825A: AstroSat CZTI detection
  62. GRB 260829A: Fermi GBM Final Real-time Localization
  63. GRB 260818B: VLT optical and nIR observations
  64. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  65. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  66. GRB 260827A: Fermi GBM Final Real-time Localization
  67. GRB 260818B: 6 GHz VLA observations
  68. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  69. GRB 260807A: EP-FXT follow-up observations
  70. GRB 260822A: SVOM/VT optical upper limits
  71. GRB 260825A: Fermi GBM Final Real-time Localization
  72. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  73. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  74. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  75. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  76. EP260822a: EP-FXT non-detection and upper limit
  77. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  78. GRB 260822A: GOTO optical counterpart detection
  79. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  80. EP260822a: Einstein Probe detection of a fast X-ray transient
  81. The EP-WXT trigger 01709287395 is likely a flaring star
  82. GRB260822B: Fermi GBM Final Localization
  83. GRB 260822A: SVOM detection of a short burst
  84. GRB 260818B: SVOM/C-GFT optical upper limit
  85. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  86. GRB 260820A: Insight-HXMT/HE detection
  87. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  88. EP detected a brightening of LMXB 1ES 1735-26.9
  89. GRB260820A: Fermi GBM Final Real-Time Localization
  90. GRB 260818B: Insight-HXMT detection
  91. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  92. GRB 260818B: SVOM detection of a short burst
  93. GRB 260810A: Insight-HXMT/HE detection
  94. GRB 260818A: SVOM possible detection of a long and faint GRB
  95. EP260806a: SVOM/ECLAIRs detection through targeted search
  96. EP260806a: WFST optical observations
  97. EP260812b: Optical upper limit with Kinder
  98. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  99. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  100. GRB 260813A: Fermi GBM Final Real-time Localization

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