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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"

36155 results found.

  1. GRB 250717B: Swift-XRT observations
  2. GRB 250718B: Fermi GBM Final Localization Correction
  3. GRB 250718B: Fermi GBM Final Real-time Localization
  4. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  5. Swift Trigger 1334535: a possible GRB 250718A
  6. GRB 250717B: Swift ToO observations
  7. GRB 270713A: Kitab and AbAO Optical Observations
  8. GRB 250717B: Fermi GBM Observation
  9. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  10. Konus-Wind detection of GRB 250716A
  11. GRB 250716A: Swift-XRT afterglow detection
  12. GRB 250717B: Fermi GBM Final Real-time Localization
  13. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  14. GRB 250717A: Fermi GBM Final Real-time Localization
  15. GRB 250716A: Swift ToO observations
  16. GRB 250716A: GOTO tentative optical counterpart candidate
  17. GRB 250716A: Fermi GBM Observation
  18. GRB 250714A: SVOM/GRM observation
  19. Fermi GRB 250716A: Global MASTER-Net observations report
  20. GRB 250716A: Fermi GBM Final Real-time Localization
  21. Fermi GRB 250715A: Global MASTER-Net observations report
  22. GRB 250715A: Fermi GBM Final Real-time Localization
  23. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  24. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  25. GRB 250713A: Mephisto optical upper limits
  26. Fermi GRB 250714A: Global MASTER-Net observations report
  27. GRB 250713A: SVOM/VT optical upper limit
  28. GRB 250713A: NOT optical upper limits
  29. GRB 250713A: OHP/T193 upper limit
  30. GRB 250713A: SVOM/C-GFT upper limit
  31. GRB 250714A: Fermi GBM Final Real-time Localization
  32. GRB 250706B/C: 7DT Follow-up Observations
  33. GRB 250713A: Swift-XRT observations
  34. GRB 250713A: EP-FXT counterpart detection
  35. GRB 250706A: Swift-BAT refined analysis
  36. GRB 250702F: Swift-BAT refined analysis
  37. GRB 250628A: Swift-BAT refined analysis
  38. GRB 250713A: JinShan optical upper limits
  39. GRB 250713A: SVOM detection of a long burst
  40. GRB 250711A: DDOTI Optical Upper Limit
  41. GRB 250711A: SVOM/GRM observation
  42. Fermi GRB 250711A: Global MASTER-Net observations report
  43. GRB 250704A: GRANDMA observations
  44. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  45. GRB 250711A: Fermi GBM Final Real-time Localization
  46. GRB 250704A: SVOM/ECLAIRs refined analysis
  47. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  48. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  49. GRB 250702B,D,E / EP250702a: ALMA detection
  50. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  51. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  52. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  53. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  54. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 250709A: Fermi GBM Final Localization
  56. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  57. GRB 250706B/C: Insight-HXMT detection
  58. EP250704a/GRB 250704B: 10 GHz VLA detection
  59. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  60. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  61. GRB 250704B / EP250704a: VLA radio detection
  62. Fermi GRB 250708A: Global MASTER-Net observations report
  63. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  64. EP250704a/GRB250704B : HCT optical and NIR upper limits
  65. GRB 250708A: Fermi GBM Final Real-time Localization
  66. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  67. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  68. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  69. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  70. GRB 250702F: radio detection with the VLA
  71. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  72. GRB 250706B/C: Fermi-LAT detection
  73. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  74. GRB 250706B: Swift/UVOT Detection
  75. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  76. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  77. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  78. GRB 250702F: GRANDMA observations
  79. GRB 250706A: Swift-XRT refined Analysis
  80. GRB 250706B: refined SVOM/MXT data analysis
  81. GRB 250706A: Swift/UVOT Upper Limits
  82. GRB 250706B: REM optical observations
  83. GRB 250706A: REM optical/NIR observations
  84. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  85. Swift GRB 250706A: Global MASTER-Net observations report
  86. GRB 250706A: JinShan optical upper limits
  87. GRB 250706A: SAO RAS optical observations
  88. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  89. GRB250706B: Swift-XRT counterpart detection
  90. GRB 250706B: iTelescope optical observations
  91. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  92. GRB 250706B: SVOM/VT optical observation
  93. GRB 250706B: TRT bright optical counterpart detection
  94. GRB 250706A: GROWTH-India Telescope optical upper limit
  95. GRB 250706B: SVOM detection of a long burst
  96. GRB 250706A: Swift detection of a burst
  97. GRB 250704B: Swift-XRT refined Analysis
  98. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  99. GRB 250703A: EIRSAT-1 GMOD Detection
  100. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST

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