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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"

26206 results found.

  1. GRB 250820A: Fermi GBM Final Real-time Localization
  2. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  3. Fermi GRB 250816A: Global MASTER-Net observations report
  4. Swift GRB 250818A: Global MASTER-Net observations report
  5. GRB 250818B: NOT optical observations
  6. GRB 250818A: Swift-XRT refined Analysis
  7. GRB 250818B: EP-FXT counterpart detection
  8. GRB 250818A: Swift-BAT refined analysis
  9. Fermi Gamma-ray Burst Monitor trigger 777251788/250818970 is not a GRB
  10. GRB 250818C: Fermi GBM Final Real-time Localization
  11. Fermi trigger No 776849714: Global MASTER-Net observations report
  12. GRB 250818B: KAIT optical observations
  13. GRB 250818A: Swift/UVOT Upper Limits
  14. LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
  15. GRB 250813B: SVOM/ECLAIRs refined analysis
  16. GRB 250818A: Fermi GBM Observation
  17. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  18. GRB 250818B: SVOM/VT optical observation
  19. GRB 250814A: Further GRAWITA TNG NIR observations
  20. GRB 250818B: GOTO optical counterpart candidate
  21. GRB 250818B: SVOM detection of a short burst
  22. GRB 250818A: Swift detection of a burst
  23. GRB 250818A: Fermi GBM Final Real-time Localization
  24. sb25081602: Swift-XRT observations
  25. GRB 250816A: SVOM/GRM observation of a short burst
  26. SVOM/sb25081602: detection of a likely X-ray transient
  27. Fermi GRB 250814B: Global MASTER-Net observations report
  28. GRB 250816A: Fermi GBM Final Real-time Localization
  29. GRB 250814A: Swift-BAT refined analysis
  30. GRB 250815A: Fermi GBM Final Localization
  31. GRB 250813B: Liverpool Telescope optical upper limits
  32. GRB 250814A: Further COLIBRÍ optical upper limit
  33. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  34. GRB 250814A: GRAWITA TNG NIR observations
  35. GRB 250812A: SVOM/VT optical continued observation
  36. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  37. GRB250814A: TRT optical upper limits
  38. GRB 250814B: SVOM/GRM observation
  39. GRB 250814C: SVOM/GRM observation of a short burst
  40. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  41. GRB 250813B: SVOM/GRM observation
  42. GRB 250814A: P200/WIRC observations of the afterglow candidate
  43. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  44. GRB 250814A: Swift-XRT refined Analysis
  45. GRB 240814A: Fermi GBM Observation
  46. GRB 250814A: Possible afterglow candidate from P200/WIRC
  47. GRB 250813B: Fermi GBM Observation
  48. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  49. Fermi trigger No 776818276: Global MASTER-Net observations report
  50. Swift GRB250814.32: Global MASTER-Net observations report
  51. GRB 250814A: J-band upper limit from WINTER
  52. GRB 250813B: NOT observations of the optical afterglow
  53. GRB 250813B: SVOM/VT optical observations
  54. Subject GRB 250813B: SVOM/MXT refined analysis
  55. GRB 250814A: COLIBRÍ optical upper limit
  56. GRB 250814B: Fermi GBM Final Real-time Localization
  57. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  58. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  59. GRB 250814A: DDOTI Optical Upper Limit
  60. GRB 250813B: EP-FXT counterpart detection
  61. GRB 250813B: Swift-XRT afterglow detection
  62. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  63. GRB 250814A: Fermi GBM Final Real-time Localization
  64. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  65. GRB 250813B: Ondrejov D50 fast decay
  66. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  67. GRB 250813B: SVOM detection of a bright long burst
  68. EP250812a: Nickel optical upper limit
  69. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  70. GRB 250812A: NTT spectroscopic redshift z = 2.57
  71. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  72. EP250812a: NOT, NTT, and GS observations
  73. GRB 250812A: Swift/UVOT Detection
  74. GRB 250813A: Fermi GBM Final Localization
  75. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  76. EP250812a: Liverpool Telescope upper limits
  77. EP250812a: SVOM/VT optical counterpart
  78. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  79. IceCube Alert 250813.14: Global MASTER-Net observations report
  80. GRB 250812A: EP-FXT counterpart detection
  81. GRB 250807B: Swift-BAT refined analysis
  82. EP 250812a: GOTO optical upper limit
  83. GRB 250812A: Kilonova-Catcher optical afterglow detection
  84. EP250812a: Swift-XRT counterpart detection
  85. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  86. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  87. EP250812a: Einstein Probe detection of an X-ray transient
  88. GRB 250812A: SVOM/VT optical afterglow confirmation
  89. GRB 250812A: TRT likely optical counterpart detection
  90. GRB 250812A: SVOM detection of a faint long burst
  91. GRB 250809A: Swift-BAT refined analysis
  92. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  93. GRB 250807A: Swift-BAT refined analysis
  94. GRB 250809A: Swift/UVOT Detection
  95. Corrected Swift-XRT Refined Analysis of GRB 250809A
  96. GRB 250809A: Swift-XRT refined Analysis
  97. GRB 250807B: SVOM/VT optical observation
  98. EP250807a: EP-FXT follow-up observation upper limit
  99. GRB 250809A: LCOGT Optical Upper Limits
  100. GRB 250702B: Chandra X-ray Detection

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