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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"

35946 results found.

  1. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  2. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  3. GRB 250821A: Enhanced Swift-XRT position
  4. GRB 250821A: Swift/UVOT Upper Limits
  5. GRB 250821A: LCOGT Optical Upper Limits
  6. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  7. GRB 250821A: Prompt enhanced Swift-XRT position
  8. GRB 250821A: Swift detection of a burst
  9. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  10. GRB 250819A: Insight-HXMT detection
  11. GRB 250818B: 10 GHz VLA detection
  12. GRB 250814A: Swift/UVOT Upper Limits
  13. GRB 250813B: Swift/UVOT Upper Limit
  14. IPN triangulation of GRB 250816A (short)
  15. IPN triangulation of GRB 250814C (short)
  16. IPN triangulation of GRB 250804B (short)
  17. GRB 250818B: FTW optical and NIR observations show reddening of the counterpart
  18. GRB 250818B: Kilonova-Catcher optical afterglow detection
  19. GRB 250818B: Liverpool Telescope optical detections
  20. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  21. GRB 250818A: AstroSat CZTI detection
  22. GRB 250818B: Swift/UVOT Detection
  23. Fermi Gamma-ray Burst Monitor trigger 777342746/250820022 is not a GRB
  24. GRB 250820A: Fermi GBM Final Real-time Localization
  25. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  26. GRB 250818B: TRT Optical Observation
  27. Fermi GRB 250816A: Global MASTER-Net observations report
  28. GRB 250818B: SAO RAS optical observations
  29. Swift GRB 250818A: Global MASTER-Net observations report
  30. GRB 250818B: NOT optical observations
  31. GRB 250818A: Swift-XRT refined Analysis
  32. GRB 250818B: EP-FXT counterpart detection
  33. GRB 250818A: Swift-BAT refined analysis
  34. Fermi Gamma-ray Burst Monitor trigger 777251788/250818970 is not a GRB
  35. GRB 250818C: Fermi GBM Final Real-time Localization
  36. GRB 250818B: Keck redshift of the optical afterglow
  37. GRB 250818B: KAIT optical observations
  38. GRB 250818A: Swift/UVOT Upper Limits
  39. GRB 250818A: Enhanced Swift-XRT position
  40. GRB 250813B: SVOM/ECLAIRs refined analysis
  41. GRB 250818A: Fermi GBM Observation
  42. GRB 250818B: SVOM/VT optical observation
  43. GRB 250814A: Further GRAWITA TNG NIR observations
  44. GRB 250818B: Swift-XRT afterglow detection
  45. GRB 250818B: GOTO optical counterpart candidate
  46. GRB 250818B: SVOM detection of a short burst
  47. GRB 250818A: Swift detection of a burst
  48. GRB 250818A: Fermi GBM Final Real-time Localization
  49. GRB 250816A: SVOM/GRM observation of a short burst
  50. Fermi GRB 250814B: Global MASTER-Net observations report
  51. GRB 250816A: Fermi GBM Final Real-time Localization
  52. GRB 250814A: Swift-BAT refined analysis
  53. GRB 250815A: Fermi GBM Final Localization
  54. GRB 250813B: Liverpool Telescope optical upper limits
  55. GRB 250814A: Further COLIBRÍ optical upper limit
  56. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  57. GRB 250814A: GRAWITA TNG NIR observations
  58. GRB 250812A: SVOM/VT optical continued observation
  59. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  60. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  61. GRB250814A: TRT optical upper limits
  62. GRB 250814B: SVOM/GRM observation
  63. GRB 250814C: SVOM/GRM observation of a short burst
  64. GRB 250813B: SVOM/GRM observation
  65. GRB 250814A: P200/WIRC observations of the afterglow candidate
  66. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  67. GRB 250814A: KAIT optical upper limit
  68. GRB 250814A: Swift-XRT refined Analysis
  69. GRB 240814A: Fermi GBM Observation
  70. GRB 250814A: Possible afterglow candidate from P200/WIRC
  71. GRB 250813B: Fermi GBM Observation
  72. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  73. GRB 250814A: J-band upper limit from WINTER
  74. GRB 250813B: NOT observations of the optical afterglow
  75. GRB 250813B: SVOM/VT optical observations
  76. Subject GRB 250813B: SVOM/MXT refined analysis
  77. GRB 250814A: COLIBRÍ optical upper limit
  78. GRB 250814B: Fermi GBM Final Real-time Localization
  79. GRB 250813A: AstroSat CZTI detection
  80. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  81. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  82. GRB 250814A: DDOTI Optical Upper Limit
  83. GRB 250813B: EP-FXT counterpart detection
  84. GRB 250813B: Swift-XRT afterglow detection
  85. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  86. GRB 250814A: Fermi GBM Final Real-time Localization
  87. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  88. GRB 250813B: Ondrejov D50 fast decay
  89. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  90. GRB 250813B: Ondrejov D50 optical afterglow detection
  91. GRB 250813B: SVOM detection of a bright long burst
  92. EP250812a: Nickel optical upper limit
  93. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  94. GRB 250812A: NTT spectroscopic redshift z = 2.57
  95. GRB 250812A: Swift/UVOT Detection
  96. GRB 250813A: Fermi GBM Final Localization
  97. GRB 250812A: EP-FXT counterpart detection
  98. GRB 250812A: Swift ToO observations
  99. GRB 250807B: Swift-BAT refined analysis
  100. GRB 250812A: Kilonova-Catcher optical afterglow detection

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