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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"
  1. GRB 250816A: SVOM/GRM observation of a short burst
  2. SVOM/sb25081602: detection of a likely X-ray transient
  3. Fermi GRB 250814B: Global MASTER-Net observations report
  4. GRB 250816A: Fermi GBM Final Real-time Localization
  5. GRB 250814A: Swift-BAT refined analysis
  6. GRB 250815A: Fermi GBM Final Localization
  7. GRB 250813B: Liverpool Telescope optical upper limits
  8. GRB 250814A: Further COLIBRÍ optical upper limit
  9. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  10. GRB 250814A: GRAWITA TNG NIR observations
  11. GRB 250812A: SVOM/VT optical continued observation
  12. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  13. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  14. GRB250814A: TRT optical upper limits
  15. GRB 250814B: SVOM/GRM observation
  16. GRB 250814C: SVOM/GRM observation of a short burst
  17. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  18. GRB 250813B: SVOM/GRM observation
  19. GRB 250814A: P200/WIRC observations of the afterglow candidate
  20. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  21. GRB 250814A: KAIT optical upper limit
  22. GRB 250814A: Swift-XRT refined Analysis
  23. GRB 240814A: Fermi GBM Observation
  24. GRB 250814A: Possible afterglow candidate from P200/WIRC
  25. GRB 250813B: Fermi GBM Observation
  26. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  27. Fermi trigger No 776818276: Global MASTER-Net observations report
  28. Swift GRB250814.32: Global MASTER-Net observations report
  29. GRB 250814A: J-band upper limit from WINTER
  30. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 250813B: NOT observations of the optical afterglow
  32. GRB 250813B: SVOM/VT optical observations
  33. Subject GRB 250813B: SVOM/MXT refined analysis
  34. GRB 250814A: COLIBRÍ optical upper limit
  35. GRB 250814B: Fermi GBM Final Real-time Localization
  36. GRB 250813A: AstroSat CZTI detection
  37. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  38. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  39. GRB 250814A: DDOTI Optical Upper Limit
  40. GRB 250813B: EP-FXT counterpart detection
  41. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  42. GRB 250813B: Swift-XRT afterglow detection
  43. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  44. GRB 250814A: Fermi GBM Final Real-time Localization
  45. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  46. GRB 250813B: Ondrejov D50 fast decay
  47. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  48. GRB 250813B: Ondrejov D50 optical afterglow detection
  49. GRB 250813B: SVOM detection of a bright long burst
  50. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  51. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  52. EP250812a: Nickel optical upper limit
  53. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  54. GRB 250812A: NTT spectroscopic redshift z = 2.57
  55. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  56. EP250812a: NOT, NTT, and GS observations
  57. GRB 250812A: Swift/UVOT Detection
  58. GRB 250813A: Fermi GBM Final Localization
  59. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  60. EP250812a: Liverpool Telescope upper limits
  61. EP250812a: SVOM/VT optical counterpart
  62. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  63. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  64. IceCube Alert 250813.14: Global MASTER-Net observations report
  65. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  66. GRB 250812A: EP-FXT counterpart detection
  67. GRB 250812A: Swift ToO observations
  68. GRB 250807B: Swift-BAT refined analysis
  69. EP 250812a: GOTO optical upper limit
  70. GRB 250812A: Kilonova-Catcher optical afterglow detection
  71. EP250812a: Swift-XRT counterpart detection
  72. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  73. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  74. EP250812a: Einstein Probe detection of an X-ray transient
  75. GRB 250812A: SVOM/VT optical afterglow confirmation
  76. GRB 250812A: Swift-XRT afterglow detection
  77. GRB 250812A: TRT likely optical counterpart detection
  78. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB 250812A: SVOM detection of a faint long burst
  80. GRB 250809A: Swift-BAT refined analysis
  81. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  82. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  83. GRB 250807A: Swift-BAT refined analysis
  84. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  85. GRB 250809A: Swift/UVOT Detection
  86. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  87. Corrected Swift-XRT Refined Analysis of GRB 250809A
  88. GRB 250809A: Swift-XRT refined Analysis
  89. GRB 250807B: SVOM/VT optical observation
  90. EP250807a: EP-FXT follow-up observation upper limit
  91. GRB 250809A: LCOGT Optical Upper Limits
  92. GRB 250702B: Chandra X-ray Detection
  93. EP250807a: Global MASTER-Net observations report
  94. Fermi GRB 250808A: Global MASTER-Net observations report
  95. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  96. GRB 250808A: VLT X-shooter candidate counterpart
  97. GRB 250809A: Prompt enhanced Swift-XRT position
  98. GRB 250809A: Swift detection of a gamma ray burst
  99. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. GRB 250808A: Fermi GBM Observation

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