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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"

36154 results found.

  1. GRB 250818C: Fermi GBM Final Real-time Localization
  2. GRB 250818B: Keck redshift of the optical afterglow
  3. GRB 250818B: KAIT optical observations
  4. GRB 250818A: Swift/UVOT Upper Limits
  5. GRB 250818A: Enhanced Swift-XRT position
  6. GRB 250813B: SVOM/ECLAIRs refined analysis
  7. GRB 250818A: Fermi GBM Observation
  8. GRB 250818B: SVOM/VT optical observation
  9. GRB 250814A: Further GRAWITA TNG NIR observations
  10. GRB 250818B: Swift-XRT afterglow detection
  11. GRB 250818B: GOTO optical counterpart candidate
  12. GRB 250818B: SVOM detection of a short burst
  13. GRB 250818A: Swift detection of a burst
  14. GRB 250818A: Fermi GBM Final Real-time Localization
  15. GRB 250816A: SVOM/GRM observation of a short burst
  16. Fermi GRB 250814B: Global MASTER-Net observations report
  17. GRB 250816A: Fermi GBM Final Real-time Localization
  18. GRB 250814A: Swift-BAT refined analysis
  19. GRB 250815A: Fermi GBM Final Localization
  20. GRB 250813B: Liverpool Telescope optical upper limits
  21. GRB 250814A: Further COLIBRÍ optical upper limit
  22. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  23. GRB 250814A: GRAWITA TNG NIR observations
  24. GRB 250812A: SVOM/VT optical continued observation
  25. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  26. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  27. GRB250814A: TRT optical upper limits
  28. GRB 250814B: SVOM/GRM observation
  29. GRB 250814C: SVOM/GRM observation of a short burst
  30. GRB 250813B: SVOM/GRM observation
  31. GRB 250814A: P200/WIRC observations of the afterglow candidate
  32. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  33. GRB 250814A: KAIT optical upper limit
  34. GRB 250814A: Swift-XRT refined Analysis
  35. GRB 240814A: Fermi GBM Observation
  36. GRB 250814A: Possible afterglow candidate from P200/WIRC
  37. GRB 250813B: Fermi GBM Observation
  38. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  39. GRB 250814A: J-band upper limit from WINTER
  40. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 250813B: NOT observations of the optical afterglow
  42. GRB 250813B: SVOM/VT optical observations
  43. Subject GRB 250813B: SVOM/MXT refined analysis
  44. GRB 250814A: COLIBRÍ optical upper limit
  45. GRB 250814B: Fermi GBM Final Real-time Localization
  46. GRB 250813A: AstroSat CZTI detection
  47. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  48. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  49. GRB 250814A: DDOTI Optical Upper Limit
  50. GRB 250813B: EP-FXT counterpart detection
  51. GRB 250813B: Swift-XRT afterglow detection
  52. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  53. GRB 250814A: Fermi GBM Final Real-time Localization
  54. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  55. GRB 250813B: Ondrejov D50 fast decay
  56. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  57. GRB 250813B: Ondrejov D50 optical afterglow detection
  58. GRB 250813B: SVOM detection of a bright long burst
  59. EP250812a: Nickel optical upper limit
  60. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  61. GRB 250812A: NTT spectroscopic redshift z = 2.57
  62. GRB 250812A: Swift/UVOT Detection
  63. GRB 250813A: Fermi GBM Final Localization
  64. GRB 250812A: EP-FXT counterpart detection
  65. GRB 250812A: Swift ToO observations
  66. GRB 250807B: Swift-BAT refined analysis
  67. GRB 250812A: Kilonova-Catcher optical afterglow detection
  68. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  69. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  70. GRB 250812A: SVOM/VT optical afterglow confirmation
  71. GRB 250812A: Swift-XRT afterglow detection
  72. GRB 250812A: TRT likely optical counterpart detection
  73. GRB 250812A: SVOM detection of a faint long burst
  74. GRB 250809A: Swift-BAT refined analysis
  75. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  76. GRB 250807A: Swift-BAT refined analysis
  77. GRB 250809A: Swift/UVOT Detection
  78. Corrected Swift-XRT Refined Analysis of GRB 250809A
  79. GRB 250809A: Swift-XRT refined Analysis
  80. GRB 250807B: SVOM/VT optical observation
  81. GRB 250809A: LCOGT Optical Upper Limits
  82. GRB 250702B: Chandra X-ray Detection
  83. Fermi GRB 250808A: Global MASTER-Net observations report
  84. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  85. GRB 250808A: VLT X-shooter candidate counterpart
  86. GRB 250809A: Prompt enhanced Swift-XRT position
  87. GRB 250809A: Swift detection of a gamma ray burst
  88. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  89. GRB 250808A: Fermi GBM Observation
  90. GRB 250808A: Swift-XRT candidate counterpart detection
  91. GRB 250807A: SVOM/VT optical continued observation
  92. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  93. GRB 250808A: SVOM detection of a long burst
  94. GRB 250808A: Fermi GBM Final Real-time Localization
  95. Konus-Wind detection of GRB 250807A
  96. GRB 250807B: Swift/UVOT Detection
  97. GRB 250807B: Kilonova-Catcher optical afterglow detection
  98. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  99. GRB 250807A: Swift/UVOT Detection
  100. GRB 250807A: Swift-XRT refined Analysis

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