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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"

38918 results found.

  1. Konus-Wind detection of GRB 250107C
  2. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  3. GRB 250101A: CMO RC-500 optical observations
  4. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  5. GRB 250109A: Fermi GBM Observation
  6. EP250108a: NOT optical observations
  7. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  8. GRB 250109a: GMG Optical Upper Limit
  9. Konus-Wind detection of GRB 250107D (short/hard)
  10. IPN triangulation of GRB 250107D (short/hard)
  11. IPN triangulation of GRB 250107C
  12. EP250108a: Liverpool Telescope likely optical counterpart
  13. GRB 250108B: Gemini-North likely redshift z = 2.197
  14. GRB 250108B: Swift-BAT refined analysis
  15. GRB 250108B: 1.3m DFOT upper limit
  16. GRB 250108B: REM optical/NIR upper limits
  17. GRB 250109A /EP250109a: Fermi GBM Final Localization
  18. EP250109a: SVOM/VT optical candidate
  19. EP250109a: Global MASTER-Net observations report
  20. GRB 250107C: SVOM/GRM observation
  21. GRB 250101A: Terskol K-800 optical observations
  22. EP250109a: Swift/XRT non-detection
  23. GRB 250108A: Swift/UVOT Upper Limits
  24. EP250108a: Global MASTER-Net observations report
  25. GRB 250108A: NOT optical upper limit
  26. GRB 250108B: Swift-XRT refined Analysis
  27. Swift GRB 250108B: Global MASTER-Net observations report
  28. Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
  29. LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
  30. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  31. GRB 250103A: 1.6m Mephisto optical observations
  32. GRB 250108A: Swift-XRT afterglow detection
  33. GRB 250108A:SVOM/VT optical candidate
  34. GRB 250108B: Swift/UVOT Upper Limits
  35. GRB 250103A: Swift-XRT afterglow detection
  36. GRB 250108B: Enhanced Swift-XRT position
  37. GRB 250108B: Swift detection of a burst
  38. GRB 250108A: Swift ToO observations
  39. GRB 250108A: SVOM detection of a soft long burst
  40. GRB 250107A: Fermi GBM Observation
  41. GRB 241228B: Fermi-LAT detection
  42. Fermi GRB 250107B: Global MASTER-Net observations report
  43. GRB 250107A: Swift ToO observations
  44. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  45. GRB 250107B: Fermi GBM Final Real-time Localization
  46. GRB 250106A: SVOM/VT 2nd optical deep observation
  47. GRB 250101A: J band upper limit by SYSU 80cm telescope
  48. GRB 250107A: Fermi GBM Final Real-time Localization
  49. GRB 250106A: NOT optical observations
  50. GRB 250103B: REM optical/NIR upper limits
  51. GRB 250101A: REM optical/NIR counterpart detection
  52. GRB 250106A: Swift-XRT observations
  53. GRB 250106A: SVOM/VT optical candidate
  54. GRB 250106A: Swift ToO observations
  55. GRB 250106A: SVOM detection of a long burst
  56. Fermi trigger No 757753930: Global MASTER-Net observations report
  57. GRB 241229A: SVOM/VT optical upperlimit
  58. GRB 250103B: Swift-XRT refined Analysis
  59. GRB 250103B: LCO/1m optical afterglow candidate detection
  60. GRB 250103A: Bassano Bresciano Observatory upper limit
  61. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  62. GRB 250103A: Swift-XRT observations
  63. GRB 250101A: 1.3m DFOT optical afterglow detection
  64. GRB 241229A: 1.3m DFOT upper limit
  65. GRB 241228B: 1.3m DFOT Optical observations
  66. GRB 241228A: 1.3m DFOT upper limit
  67. GRB 250103A: NOT spectroscopic redshift
  68. GRB 250103B：SVOM/VT optical counterpart
  69. GRB 250103A: Montarrenti Observatory optical detection
  70. GRB 250101A: further LCOGT optical afterglow observations
  71. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  72. GRB 250103A: NOT optical observations
  73. GRB 250103A: TSHAO optical upper limit
  74. GRB 250103A: Fermi GBM Observation
  75. GRB 250103B: LCOGT Optical Upper Limit
  76. Swift GRB 250103B: Global MASTER-Net observations report
  77. GRB 250103A: SVOM/VT optical counterpart confirmation
  78. GRB 250103A: Swift ToO observations
  79. GRB 250101a: Liverpool Telescope optical follow-up
  80. GRB 250103B: SVOM detection of a long burst
  81. GRB 250103B: Swift detection of a burst
  82. GRB 250103A: Xinglong 2.16m Optical Candidate
  83. Fermi GRB 250102A: Global MASTER-Net observations report
  84. GRB 250101B: SVOM/GRM observation
  85. GRB 250103A: GOTO optical upper limit
  86. GRB 250103A: SVOM/C-GFT optical upper limit
  87. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  88. IceCube Alert 250102.58: Global MASTER-Net observations report
  89. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  90. GRB 250103A: SVOM detection of a long burst
  91. GRB 250102A: Fermi GBM Final Real-time Localization
  92. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  93. GRB 250101A: Swift-BAT refined analysis
  94. GRB 250101A: further SAO RAS optical observations
  95. GRB 250101A: LCO optical counterpart detection
  96. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  97. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  98. GRB 250101A: Swift/UVOT Detection
  99. GRB 250101A: 1.6m Mephisto multi-band optical followup
  100. GRB 250101A: Swift-XRT refined Analysis

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