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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"

35431 results found.

  1. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  2. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  3. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  4. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  5. GRB 250117A: GECAM observation of a short burst
  6. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  7. GRB 250119B: Fermi GBM Final Real-time Localization
  8. GRB 250119A: Fermi GBM Final Real-time Localization
  9. GRB 250118A: Fermi GBM Final Real-time Localization
  10. EP250108a / AT2025kg: VLA radio upper limit
  11. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  12. Konus-Wind detection of GRB 250116A
  13. GRB 250116A: GECAM-B detection of a long burst
  14. GRB 241217A / EP241217B: radio detection with the VLA
  15. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  16. Swift Trigger 1282245 is not a GRB
  17. GRB 250116A: Fermi-LAT detection
  18. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  19. GRB 250114B: Swift-XRT afterglow detection
  20. GRB 250114B: SVOM/VT upper limit
  21. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  22. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  23. Konus-Wind detection of GRB 250113A
  24. IPN triangulation of GRB 250113A
  25. GRB 250114B: Liverpool Telescope optical upper limit
  26. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  27. GRB 250114B: Swift-XRT observations
  28. GRB 250114A: LCO optical counterpart detection.
  29. GRB 250114B: OHP/T193 optical upper limit
  30. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  31. GRB 250114A: Swift-XRT refined Analysis
  32. GRB 250114A: LCOGT optical afterglow i-band detection
  33. GRB 250114B : GIT optical upper limit
  34. GRB 250114B: Swift ToO observations
  35. EP250111a: SAO RAS optical upper limit
  36. GRB 250114B: a short GRB detected with INTEGRAL
  37. GRB 250114A: Enhanced Swift-XRT position
  38. GRB 250113A: INTEGRAL/SPI-ACS detection
  39. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  40. GRB 250114A: REM detection of the optical and NIR counterpart
  41. GRB 250114A: LCO optical observations
  42. GRB 250114A: TRT optical observations
  43. Swift GRB 250114A: Global MASTER-Net observations report
  44. GRB 250114A: Swift detection of a burst with an optical counterpart
  45. GRB 250101A: Terskol Zeiss-2000 optical observations
  46. EP250108a / AT 2025kg: SAO RAS optical observations
  47. GRB 250113A: SVOM/GRM observation of a long burst
  48. GRB 250107A: VZLUSAT-2 detection
  49. GRB 250109A / EP250109a: GRBAlpha detection
  50. GRB 250107D: GRBAlpha detection
  51. GRB 250106A: Swift-XRT afterglow detection
  52. EP250111a: KAIT optical observations
  53. GRB 250109A / EP250109a: Mephisto optical upper limits
  54. EP250111a: Mondy optical observation
  55. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  56. GRB 250101B: Fermi GBM Observation
  57. EP250108a: further NOT optical observations
  58. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  59. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  60. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  61. GRB 250108A: Swift/XRT afterglow fading
  62. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  63. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  64. Konus-Wind detection of GRB 250107C
  65. GRB 250101A: CMO RC-500 optical observations
  66. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  67. GRB 250109A: Fermi GBM Observation
  68. EP250108a: NOT optical observations
  69. GRB 250109a: GMG Optical Upper Limit
  70. Konus-Wind detection of GRB 250107D (short/hard)
  71. IPN triangulation of GRB 250107D (short/hard)
  72. IPN triangulation of GRB 250107C
  73. GRB 250108B: Gemini-North likely redshift z = 2.197
  74. GRB 250108B: Swift-BAT refined analysis
  75. GRB 250108B: 1.3m DFOT upper limit
  76. GRB 250108B: REM optical/NIR upper limits
  77. GRB 250109A /EP250109a: Fermi GBM Final Localization
  78. GRB 250107C: SVOM/GRM observation
  79. GRB 250101A: Terskol K-800 optical observations
  80. EP250109a: Swift/XRT non-detection
  81. GRB 250108A: Swift/UVOT Upper Limits
  82. GRB 250108A: NOT optical upper limit
  83. GRB 250108B: Swift-XRT refined Analysis
  84. Swift GRB 250108B: Global MASTER-Net observations report
  85. Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
  86. LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
  87. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  88. GRB 250103A: 1.6m Mephisto optical observations
  89. GRB 250108A: Swift-XRT afterglow detection
  90. GRB 250108A:SVOM/VT optical candidate
  91. GRB 250108B: Swift/UVOT Upper Limits
  92. GRB 250103A: Swift-XRT afterglow detection
  93. GRB 250108B: Enhanced Swift-XRT position
  94. GRB 250108B: Swift detection of a burst
  95. GRB 250108A: Swift ToO observations
  96. GRB 250108A: SVOM detection of a soft long burst
  97. GRB 250107A: Fermi GBM Observation
  98. GRB 241228B: Fermi-LAT detection
  99. Fermi GRB 250107B: Global MASTER-Net observations report
  100. GRB 250107A: Swift ToO observations

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