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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"
  1. EP250109b: optical upper limits with the Liverpool Telescope
  2. GRB 250109A / EP250109a: GRBAlpha detection
  3. GRB 250107D: GRBAlpha detection
  4. GRB 250106A: Swift-XRT afterglow detection
  5. Fermi trigger No 758442826: Global MASTER-Net observations report
  6. EP250111a: KAIT optical observations
  7. GRB 250109A / EP250109a: Mephisto optical upper limits
  8. EP250108a: Mephisto detection
  9. EP250111a: Mondy optical observation
  10. EP250108a / AT 2025kg: LCO optical observations
  11. EP250111a: Global MASTER-Net observations report
  12. EP250111a: Swift/XRT detection and fading
  13. EP250108a / AT 2025kg: Swift UVOT detections
  14. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  15. EP250108a: optical follow-up observations with the Liverpool Telescope
  16. EP250111a: NOT likely optical counterpart
  17. EP250111a: a new X-ray transient detected by Einstein Probe
  18. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  19. GRB 250101B: Fermi GBM Observation
  20. EP250108a: further NOT optical observations
  21. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  22. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  23. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  24. GRB 250108A: Swift/XRT afterglow fading
  25. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  26. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  27. Konus-Wind detection of GRB 250107C
  28. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  29. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  30. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  31. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  32. GRB 250101A: CMO RC-500 optical observations
  33. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  34. EP250108a: EP-FXT follow-up observation
  35. GRB 250109A: Fermi GBM Observation
  36. The EP-WXT trigger 01709130111 is likely a flaring star
  37. EP250108a: NOT optical observations
  38. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  39. GRB 250109a: GMG Optical Upper Limit
  40. EP250109a: Swift/UVOT non-detection
  41. Konus-Wind detection of GRB 250107D (short/hard)
  42. IPN triangulation of GRB 250107D (short/hard)
  43. IPN triangulation of GRB 250107C
  44. EP250108a: Liverpool Telescope likely optical counterpart
  45. GRB 250108B: Gemini-North likely redshift z = 2.197
  46. GRB 250108B: Swift-BAT refined analysis
  47. GRB 250108B: 1.3m DFOT upper limit
  48. GRB 250108B: REM optical/NIR upper limits
  49. GRB 250109A /EP250109a: Fermi GBM Final Localization
  50. EP250109a: SVOM/VT optical candidate
  51. EP250109a: Global MASTER-Net observations report
  52. GRB 250107C: SVOM/GRM observation
  53. GRB 250101A: Terskol K-800 optical observations
  54. EP250109a: GOTO optical upper limits
  55. EP250109a: Swift/XRT non-detection
  56. GRB 250108A: Swift/UVOT Upper Limits
  57. EP250108a: Global MASTER-Net observations report
  58. EP250109a: EP-WXT detection of an X-ray transient
  59. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  60. GRB 250108A: NOT optical upper limit
  61. EP250108a: EP-WXT detection of an X-ray transient
  62. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  63. GRB 250108B: Swift-XRT refined Analysis
  64. Swift GRB 250108B: Global MASTER-Net observations report
  65. Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
  66. LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
  67. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  68. GRB 250103A: 1.6m Mephisto optical observations
  69. GRB 250108A: Swift-XRT afterglow detection
  70. GRB 250108A:SVOM/VT optical candidate
  71. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  72. GRB 250108B: Swift/UVOT Upper Limits
  73. GRB 250103A: Swift-XRT afterglow detection
  74. GRB 250108B: Enhanced Swift-XRT position
  75. GRB 250108B: Swift detection of a burst
  76. GRB 250108A: Swift ToO observations
  77. GRB 250108A: SVOM detection of a soft long burst
  78. GRB 250107A: Fermi GBM Observation
  79. GRB 241228B: Fermi-LAT detection
  80. Fermi GRB 250107B: Global MASTER-Net observations report
  81. GRB 250107A: Swift ToO observations
  82. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  83. GRB 250107B: Fermi GBM Final Real-time Localization
  84. GRB 250106A: SVOM/VT 2nd optical deep observation
  85. GRB 250101A: J band upper limit by SYSU 80cm telescope
  86. GRB 250107A: Fermi GBM Final Real-time Localization
  87. EPWXT01709129925: Xinglong optical observations
  88. GRB 250106A: NOT optical observations
  89. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  90. GRB 250103B: REM optical/NIR upper limits
  91. GRB 250101A: REM optical/NIR counterpart detection
  92. GRB 250106A: Swift-XRT observations
  93. GRB 250106A: SVOM/VT optical candidate
  94. GRB 250106A: Swift ToO observations
  95. The EP-WXT trigger 01709129925 is likely a flaring star
  96. GRB 250106A: SVOM detection of a long burst
  97. Fermi trigger No 757753930: Global MASTER-Net observations report
  98. GRB 241229A: SVOM/VT optical upperlimit
  99. GRB 250103B: Swift-XRT refined Analysis
  100. GRB 250103B: LCO/1m optical afterglow candidate detection

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