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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"

37058 results found.

  1. GRB 250818B: SAO RAS optical observations
  2. Swift GRB 250818A: Global MASTER-Net observations report
  3. GRB 250818B: NOT optical observations
  4. GRB 250818A: Swift-XRT refined Analysis
  5. GRB 250818B: EP-FXT counterpart detection
  6. GRB 250818A: Swift-BAT refined analysis
  7. Fermi Gamma-ray Burst Monitor trigger 777251788/250818970 is not a GRB
  8. GRB 250818C: Fermi GBM Final Real-time Localization
  9. GRB 250818B: Keck redshift of the optical afterglow
  10. GRB 250818B: KAIT optical observations
  11. GRB 250818A: Swift/UVOT Upper Limits
  12. GRB 250818A: Enhanced Swift-XRT position
  13. GRB 250813B: SVOM/ECLAIRs refined analysis
  14. GRB 250818A: Fermi GBM Observation
  15. GRB 250818B: SVOM/VT optical observation
  16. GRB 250814A: Further GRAWITA TNG NIR observations
  17. GRB 250818B: Swift-XRT afterglow detection
  18. GRB 250818B: GOTO optical counterpart candidate
  19. GRB 250818B: SVOM detection of a short burst
  20. GRB 250818A: Swift detection of a burst
  21. GRB 250818A: Fermi GBM Final Real-time Localization
  22. sb25081602: Swift-XRT observations
  23. GRB 250816A: SVOM/GRM observation of a short burst
  24. Fermi GRB 250814B: Global MASTER-Net observations report
  25. GRB 250816A: Fermi GBM Final Real-time Localization
  26. GRB 250814A: Swift-BAT refined analysis
  27. GRB 250815A: Fermi GBM Final Localization
  28. GRB 250813B: Liverpool Telescope optical upper limits
  29. GRB 250814A: Further COLIBRÍ optical upper limit
  30. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  31. GRB 250814A: GRAWITA TNG NIR observations
  32. GRB 250812A: SVOM/VT optical continued observation
  33. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  34. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  35. GRB250814A: TRT optical upper limits
  36. GRB 250814B: SVOM/GRM observation
  37. GRB 250814C: SVOM/GRM observation of a short burst
  38. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  39. GRB 250813B: SVOM/GRM observation
  40. GRB 250814A: P200/WIRC observations of the afterglow candidate
  41. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  42. GRB 250814A: KAIT optical upper limit
  43. GRB 250814A: Swift-XRT refined Analysis
  44. GRB 240814A: Fermi GBM Observation
  45. GRB 250814A: Possible afterglow candidate from P200/WIRC
  46. GRB 250813B: Fermi GBM Observation
  47. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  48. Swift GRB250814.32: Global MASTER-Net observations report
  49. GRB 250814A: J-band upper limit from WINTER
  50. GRB 250813B: NOT observations of the optical afterglow
  51. GRB 250813B: SVOM/VT optical observations
  52. Subject GRB 250813B: SVOM/MXT refined analysis
  53. GRB 250814A: COLIBRÍ optical upper limit
  54. GRB 250814B: Fermi GBM Final Real-time Localization
  55. GRB 250813A: AstroSat CZTI detection
  56. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  57. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  58. GRB 250814A: DDOTI Optical Upper Limit
  59. GRB 250813B: EP-FXT counterpart detection
  60. GRB 250813B: Swift-XRT afterglow detection
  61. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  62. GRB 250814A: Fermi GBM Final Real-time Localization
  63. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  64. GRB 250813B: Ondrejov D50 fast decay
  65. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  66. GRB 250813B: Ondrejov D50 optical afterglow detection
  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. EP250812a: NOT, NTT, and GS observations
  72. GRB 250812A: Swift/UVOT Detection
  73. GRB 250813A: Fermi GBM Final Localization
  74. EP250812a: SVOM/VT optical counterpart
  75. GRB 250812A: EP-FXT counterpart detection
  76. GRB 250812A: Swift ToO observations
  77. GRB 250807B: Swift-BAT refined analysis
  78. EP 250812a: GOTO optical upper limit
  79. GRB 250812A: Kilonova-Catcher optical afterglow detection
  80. EP250812a: Swift-XRT counterpart detection
  81. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  82. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  83. GRB 250812A: SVOM/VT optical afterglow confirmation
  84. GRB 250812A: Swift-XRT afterglow detection
  85. GRB 250812A: TRT likely optical counterpart detection
  86. GRB 250812A: SVOM detection of a faint long burst
  87. GRB 250809A: Swift-BAT refined analysis
  88. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  89. GRB 250807A: Swift-BAT refined analysis
  90. GRB 250809A: Swift/UVOT Detection
  91. Corrected Swift-XRT Refined Analysis of GRB 250809A
  92. GRB 250809A: Swift-XRT refined Analysis
  93. GRB 250807B: SVOM/VT optical observation
  94. GRB 250809A: LCOGT Optical Upper Limits
  95. GRB 250702B: Chandra X-ray Detection
  96. Fermi GRB 250808A: Global MASTER-Net observations report
  97. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  98. GRB 250808A: VLT X-shooter candidate counterpart
  99. GRB 250809A: Prompt enhanced Swift-XRT position
  100. GRB 250809A: Swift detection of a gamma ray burst

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