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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"

44399 results found.

  1. GRB 250114B: a short GRB detected with INTEGRAL
  2. EP250108a: correction to GCN 38908
  3. GRB 250114A: Enhanced Swift-XRT position
  4. GRB 250113A: INTEGRAL/SPI-ACS detection
  5. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  6. GRB 250114A: REM detection of the optical and NIR counterpart
  7. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  8. Swift GRB250114A: Global MASTER-Net OT detection
  9. GRB 250114A: LCO optical observations
  10. GRB 250114A: TRT optical observations
  11. Swift GRB 250114A: Global MASTER-Net observations report
  12. GRB 250114A: Swift detection of a burst with an optical counterpart
  13. GRB 250101A: Terskol Zeiss-2000 optical observations
  14. EP250108a / AT 2025kg: SAO RAS optical observations
  15. EP241021a: SMA radio observation
  16. GRB 250113A: SVOM/GRM observation of a long burst
  17. GRB 250107A: VZLUSAT-2 detection
  18. EP250109b: optical upper limits with the Liverpool Telescope
  19. GRB 250109A / EP250109a: GRBAlpha detection
  20. GRB 250107D: GRBAlpha detection
  21. GRB 250106A: Swift-XRT afterglow detection
  22. Fermi trigger No 758442826: Global MASTER-Net observations report
  23. EP250111a: KAIT optical observations
  24. GRB 250109A / EP250109a: Mephisto optical upper limits
  25. EP250108a: Mephisto detection
  26. EP250111a: Mondy optical observation
  27. EP250108a / AT 2025kg: LCO optical observations
  28. EP250111a: Global MASTER-Net observations report
  29. EP250111a: Swift/XRT detection and fading
  30. EP250108a / AT 2025kg: Swift UVOT detections
  31. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  32. EP250108a: optical follow-up observations with the Liverpool Telescope
  33. EP250111a: NOT likely optical counterpart
  34. EP250111a: a new X-ray transient detected by Einstein Probe
  35. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  36. GRB 250101B: Fermi GBM Observation
  37. EP250108a: further NOT optical observations
  38. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  39. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  40. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  41. GRB 250108A: Swift/XRT afterglow fading
  42. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  43. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  44. Konus-Wind detection of GRB 250107C
  45. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  46. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  47. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  48. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  49. GRB 250101A: CMO RC-500 optical observations
  50. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  51. EP250108a: EP-FXT follow-up observation
  52. GRB 250109A: Fermi GBM Observation
  53. The EP-WXT trigger 01709130111 is likely a flaring star
  54. EP250108a: NOT optical observations
  55. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  56. GRB 250109a: GMG Optical Upper Limit
  57. EP250109a: Swift/UVOT non-detection
  58. Konus-Wind detection of GRB 250107D (short/hard)
  59. IPN triangulation of GRB 250107D (short/hard)
  60. IPN triangulation of GRB 250107C
  61. EP250108a: Liverpool Telescope likely optical counterpart
  62. GRB 250108B: Gemini-North likely redshift z = 2.197
  63. GRB 250108B: Swift-BAT refined analysis
  64. GRB 250108B: 1.3m DFOT upper limit
  65. GRB 250108B: REM optical/NIR upper limits
  66. GRB 250109A /EP250109a: Fermi GBM Final Localization
  67. EP250109a: SVOM/VT optical candidate
  68. EP250109a: Global MASTER-Net observations report
  69. GRB 250107C: SVOM/GRM observation
  70. GRB 250101A: Terskol K-800 optical observations
  71. EP250109a: GOTO optical upper limits
  72. EP250109a: Swift/XRT non-detection
  73. GRB 250108A: Swift/UVOT Upper Limits
  74. EP250108a: Global MASTER-Net observations report
  75. EP250109a: EP-WXT detection of an X-ray transient
  76. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  77. GRB 250108A: NOT optical upper limit
  78. EP250108a: EP-WXT detection of an X-ray transient
  79. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  80. GRB 250108B: Swift-XRT refined Analysis
  81. Swift GRB 250108B: Global MASTER-Net observations report
  82. Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
  83. LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
  84. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  85. GRB 250103A: 1.6m Mephisto optical observations
  86. GRB 250108A: Swift-XRT afterglow detection
  87. GRB 250108A:SVOM/VT optical candidate
  88. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  89. GRB 250108B: Swift/UVOT Upper Limits
  90. GRB 250103A: Swift-XRT afterglow detection
  91. GRB 250108B: Enhanced Swift-XRT position
  92. GRB 250108B: Swift detection of a burst
  93. GRB 250108A: Swift ToO observations
  94. GRB 250108A: SVOM detection of a soft long burst
  95. GRB 250107A: Fermi GBM Observation
  96. GRB 241228B: Fermi-LAT detection
  97. Fermi GRB 250107B: Global MASTER-Net observations report
  98. GRB 250107A: Swift ToO observations
  99. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  100. GRB 250107B: Fermi GBM Final Real-time Localization

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