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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').
  1. GRB 250101A: Terskol Zeiss-2000 optical observations
  2. EP250108a / AT 2025kg: SAO RAS optical observations
  3. EP241021a: SMA radio observation
  4. GRB 250113A: SVOM/GRM observation of a long burst
  5. GRB 250107A: VZLUSAT-2 detection
  6. EP250109b: optical upper limits with the Liverpool Telescope
  7. GRB 250109A / EP250109a: GRBAlpha detection
  8. GRB 250107D: GRBAlpha detection
  9. GRB 250106A: Swift-XRT afterglow detection
  10. Fermi trigger No 758442826: Global MASTER-Net observations report
  11. EP250111a: KAIT optical observations
  12. GRB 250109A / EP250109a: Mephisto optical upper limits
  13. EP250108a: Mephisto detection
  14. EP250111a: Mondy optical observation
  15. EP250108a / AT 2025kg: LCO optical observations
  16. EP250111a: Global MASTER-Net observations report
  17. EP250111a: Swift/XRT detection and fading
  18. EP250108a / AT 2025kg: Swift UVOT detections
  19. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  20. EP250108a: optical follow-up observations with the Liverpool Telescope
  21. EP250111a: NOT likely optical counterpart
  22. EP250111a: a new X-ray transient detected by Einstein Probe
  23. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  24. GRB 250101B: Fermi GBM Observation
  25. EP250108a: further NOT optical observations
  26. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  27. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  28. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  29. GRB 250108A: Swift/XRT afterglow fading
  30. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  31. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  32. Konus-Wind detection of GRB 250107C
  33. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  34. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  35. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  36. EP-WXT trigger EP250108a:Xinglong optical follow-up observations
  37. GRB 250101A: CMO RC-500 optical observations
  38. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  39. EP250108a: EP-FXT follow-up observation
  40. GRB 250109A: Fermi GBM Observation
  41. The EP-WXT trigger 01709130111 is likely a flaring star
  42. EP250108a: NOT optical observations
  43. EP-WXT trigger EP250109a:Xinglong optical follow-up observations
  44. GRB 250109a: GMG Optical Upper Limit
  45. EP250109a: Swift/UVOT non-detection
  46. Konus-Wind detection of GRB 250107D (short/hard)
  47. IPN triangulation of GRB 250107D (short/hard)
  48. IPN triangulation of GRB 250107C
  49. EP250108a: Liverpool Telescope likely optical counterpart
  50. GRB 250108B: Gemini-North likely redshift z = 2.197
  51. GRB 250108B: Swift-BAT refined analysis
  52. GRB 250108B: 1.3m DFOT upper limit
  53. GRB 250108B: REM optical/NIR upper limits
  54. GRB 250109A /EP250109a: Fermi GBM Final Localization
  55. EP250109a: SVOM/VT optical candidate
  56. EP250109a: Global MASTER-Net observations report
  57. GRB 250107C: SVOM/GRM observation
  58. GRB 250101A: Terskol K-800 optical observations
  59. EP250109a: GOTO optical upper limits
  60. EP250109a: Swift/XRT non-detection
  61. GRB 250108A: Swift/UVOT Upper Limits
  62. EP250108a: Global MASTER-Net observations report
  63. EP250109a: EP-WXT detection of an X-ray transient
  64. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  65. GRB 250108A: NOT optical upper limit
  66. EP250108a: EP-WXT detection of an X-ray transient
  67. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  68. GRB 250108B: Swift-XRT refined Analysis
  69. Swift GRB 250108B: Global MASTER-Net observations report
  70. Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
  71. LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
  72. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  73. GRB 250103A: 1.6m Mephisto optical observations
  74. GRB 250108A: Swift-XRT afterglow detection
  75. GRB 250108A:SVOM/VT optical candidate
  76. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  77. GRB 250108B: Swift/UVOT Upper Limits
  78. GRB 250103A: Swift-XRT afterglow detection
  79. GRB 250108B: Enhanced Swift-XRT position
  80. GRB 250108B: Swift detection of a burst
  81. GRB 250108A: Swift ToO observations
  82. GRB 250108A: SVOM detection of a soft long burst
  83. GRB 250107A: Fermi GBM Observation
  84. GRB 241228B: Fermi-LAT detection
  85. Fermi GRB 250107B: Global MASTER-Net observations report
  86. GRB 250107A: Swift ToO observations
  87. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  88. GRB 250107B: Fermi GBM Final Real-time Localization
  89. GRB 250106A: SVOM/VT 2nd optical deep observation
  90. GRB 250101A: J band upper limit by SYSU 80cm telescope
  91. GRB 250107A: Fermi GBM Final Real-time Localization
  92. EPWXT01709129925: Xinglong optical observations
  93. GRB 250106A: NOT optical observations
  94. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  95. GRB 250103B: REM optical/NIR upper limits
  96. GRB 250101A: REM optical/NIR counterpart detection
  97. GRB 250106A: Swift-XRT observations
  98. GRB 250106A: SVOM/VT optical candidate
  99. GRB 250106A: Swift ToO observations
  100. The EP-WXT trigger 01709129925 is likely a flaring star

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