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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"

36144 results found.

  1. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  2. GRB 250717A: Fermi GBM Final Real-time Localization
  3. GRB 250716A: Swift ToO observations
  4. GRB 250716A: GOTO tentative optical counterpart candidate
  5. GRB 250716A: Fermi GBM Observation
  6. GRB 250714A: SVOM/GRM observation
  7. Fermi GRB 250716A: Global MASTER-Net observations report
  8. GRB 250716A: Fermi GBM Final Real-time Localization
  9. Fermi GRB 250715A: Global MASTER-Net observations report
  10. GRB 250715A: Fermi GBM Final Real-time Localization
  11. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  12. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  13. GRB 250713A: Mephisto optical upper limits
  14. Fermi GRB 250714A: Global MASTER-Net observations report
  15. GRB 250713A: SVOM/VT optical upper limit
  16. GRB 250713A: NOT optical upper limits
  17. GRB 250713A: OHP/T193 upper limit
  18. GRB 250713A: SVOM/C-GFT upper limit
  19. GRB 250714A: Fermi GBM Final Real-time Localization
  20. GRB 250706B/C: 7DT Follow-up Observations
  21. GRB 250713A: Swift-XRT observations
  22. GRB 250713A: EP-FXT counterpart detection
  23. GRB 250706A: Swift-BAT refined analysis
  24. GRB 250702F: Swift-BAT refined analysis
  25. GRB 250628A: Swift-BAT refined analysis
  26. GRB 250713A: JinShan optical upper limits
  27. GRB 250713A: SVOM detection of a long burst
  28. GRB 250711A: DDOTI Optical Upper Limit
  29. GRB 250711A: SVOM/GRM observation
  30. Fermi GRB 250711A: Global MASTER-Net observations report
  31. GRB 250704A: GRANDMA observations
  32. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  33. GRB 250711A: Fermi GBM Final Real-time Localization
  34. GRB 250704A: SVOM/ECLAIRs refined analysis
  35. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  36. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  37. GRB 250702B,D,E / EP250702a: ALMA detection
  38. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  39. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  40. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  41. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  42. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  43. GRB 250709A: Fermi GBM Final Localization
  44. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  45. GRB 250706B/C: Insight-HXMT detection
  46. EP250704a/GRB 250704B: 10 GHz VLA detection
  47. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  48. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  49. GRB 250704B / EP250704a: VLA radio detection
  50. Fermi GRB 250708A: Global MASTER-Net observations report
  51. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  52. EP250704a/GRB250704B : HCT optical and NIR upper limits
  53. GRB 250708A: Fermi GBM Final Real-time Localization
  54. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  55. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  56. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  57. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  58. GRB 250702F: radio detection with the VLA
  59. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  60. GRB 250706B/C: Fermi-LAT detection
  61. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  62. GRB 250706B: Swift/UVOT Detection
  63. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  64. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  65. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  66. GRB 250702F: GRANDMA observations
  67. GRB 250706A: Swift-XRT refined Analysis
  68. GRB 250706B: refined SVOM/MXT data analysis
  69. GRB 250706A: Swift/UVOT Upper Limits
  70. GRB 250706B: REM optical observations
  71. GRB 250706A: REM optical/NIR observations
  72. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  73. Swift GRB 250706A: Global MASTER-Net observations report
  74. GRB 250706A: JinShan optical upper limits
  75. GRB 250706A: SAO RAS optical observations
  76. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  77. GRB250706B: Swift-XRT counterpart detection
  78. GRB 250706B: iTelescope optical observations
  79. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  80. GRB 250706B: SVOM/VT optical observation
  81. GRB 250706B: TRT bright optical counterpart detection
  82. GRB 250706A: GROWTH-India Telescope optical upper limit
  83. GRB 250706B: SVOM detection of a long burst
  84. GRB 250706A: Swift detection of a burst
  85. GRB 250704B: Swift-XRT refined Analysis
  86. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  87. GRB 250703A: EIRSAT-1 GMOD Detection
  88. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  89. GRB 250704B: Swift/UVOT Upper Limits
  90. GRB 250704A: Swift/UVOT Detection
  91. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  92. GRB 250704B: Insight-HXMT detection
  93. Konus-Wind detection of GRB 250703A
  94. IPN triangulation of GRB 250703A
  95. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  96. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  97. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  98. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  99. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  100. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection

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