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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"

36189 results found.

  1. Konus-Wind detection of GRB 250725A
  2. GRB 250725A: SVOM/GRM observation
  3. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  4. GRB 250725A: Swift/UVOT Upper Limits
  5. GRB 250725A: Fermi-LAT detection
  6. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  7. GRB 250725A: BOOTES-7 early optical detection
  8. GRB 250725A: SVOM/VT optical candidate
  9. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  10. GRB 250725A: Enhanced Swift-XRT position
  11. GRB 250725A: Swift detection of a burst
  12. Swift GRB 250725A: Global MASTER-Net OT detection
  13. GRB 250725A: Fermi GBM Final Real-time Localization
  14. Fermi GRB 250725A: Global MASTER-Net observations report
  15. Swift GRB 250725A: Global MASTER-Net observations report
  16. GRB 250723B: Fermi GBM Final Real-time Localization
  17. GRB 250721A: Fermi GBM Observation
  18. GRB 250723A: Fermi GBM Final Real-time Localization
  19. Swift-BAT trigger 1334535 is not a GRB
  20. GRB 250721A: Swift-XRT observations
  21. GRB 250722A: Fermi GBM Final Real-time Localization
  22. GRB 250713A : SVOM/ECLAIRs refined analysis
  23. GRB 250717B: SVOM/GRM observation
  24. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  25. GRB 250721A: Tiled Swift observations
  26. GRB 250721A: MAXI/GSC detection
  27. GRB 250721A: Fermi GBM Final Localization
  28. GRB 250720B: Fermi GBM Final Localization Correction
  29. GRB 250720A: Fermi GBM Final Localization
  30. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  31. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  32. GRB 250717B: COLIBRÍ optical upper limit
  33. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  34. GRB 250717B: Swift-XRT observations
  35. GRB 250718B: Fermi GBM Final Localization Correction
  36. GRB 250718B: Fermi GBM Final Real-time Localization
  37. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  38. Swift Trigger 1334535: a possible GRB 250718A
  39. GRB 250717B: Swift ToO observations
  40. GRB 270713A: Kitab and AbAO Optical Observations
  41. GRB 250717B: Fermi GBM Observation
  42. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  43. Konus-Wind detection of GRB 250716A
  44. GRB 250716A: Swift-XRT afterglow detection
  45. GRB 250717B: Fermi GBM Final Real-time Localization
  46. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  47. GRB 250717A: Fermi GBM Final Real-time Localization
  48. GRB 250716A: Swift ToO observations
  49. GRB 250716A: GOTO tentative optical counterpart candidate
  50. GRB 250716A: Fermi GBM Observation
  51. GRB 250714A: SVOM/GRM observation
  52. Fermi GRB 250716A: Global MASTER-Net observations report
  53. GRB 250716A: Fermi GBM Final Real-time Localization
  54. Fermi GRB 250715A: Global MASTER-Net observations report
  55. GRB 250715A: Fermi GBM Final Real-time Localization
  56. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  57. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  58. GRB 250713A: Mephisto optical upper limits
  59. Fermi GRB 250714A: Global MASTER-Net observations report
  60. GRB 250713A: SVOM/VT optical upper limit
  61. GRB 250713A: NOT optical upper limits
  62. GRB 250713A: OHP/T193 upper limit
  63. GRB 250713A: SVOM/C-GFT upper limit
  64. GRB 250714A: Fermi GBM Final Real-time Localization
  65. GRB 250706B/C: 7DT Follow-up Observations
  66. GRB 250713A: Swift-XRT observations
  67. GRB 250713A: EP-FXT counterpart detection
  68. GRB 250706A: Swift-BAT refined analysis
  69. GRB 250702F: Swift-BAT refined analysis
  70. GRB 250628A: Swift-BAT refined analysis
  71. GRB 250713A: JinShan optical upper limits
  72. GRB 250713A: SVOM detection of a long burst
  73. GRB 250711A: DDOTI Optical Upper Limit
  74. GRB 250711A: SVOM/GRM observation
  75. Fermi GRB 250711A: Global MASTER-Net observations report
  76. GRB 250704A: GRANDMA observations
  77. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  78. GRB 250711A: Fermi GBM Final Real-time Localization
  79. GRB 250704A: SVOM/ECLAIRs refined analysis
  80. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  81. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  82. GRB 250702B,D,E / EP250702a: ALMA detection
  83. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  84. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  85. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  86. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  87. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 250709A: Fermi GBM Final Localization
  89. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  90. GRB 250706B/C: Insight-HXMT detection
  91. EP250704a/GRB 250704B: 10 GHz VLA detection
  92. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  93. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  94. GRB 250704B / EP250704a: VLA radio detection
  95. Fermi GRB 250708A: Global MASTER-Net observations report
  96. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  97. EP250704a/GRB250704B : HCT optical and NIR upper limits
  98. GRB 250708A: Fermi GBM Final Real-time Localization
  99. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  100. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C

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