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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. EP250704a / GRB 250704B - REM observations
  2. GRB 250702F: GROWTH-India Telescope optical observations
  3. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  4. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  5. EP250702a: WFST optical observations
  6. EP250704a: COLIBRÍ optical counterpart candidate
  7. EP250704a: Einstein Probe detection of an X-ray transient
  8. GRB 250704B: SVOM/GRM observation of a short burst
  9. GRB 250702F: optical photometry from Konkoly
  10. GRB 250704A: REM detection of the optical afterglow
  11. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  12. GRB 250702F: SVOM/VT optical observation
  13. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  14. GRB 250704A: SVOM detection of a burst
  15. GRB 250702F: Swift/UVOT Detection
  16. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  17. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  18. Fermi GRB 250703A: Global MASTER-Net observations report
  19. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  20. GRB 250702F: Swift-XRT refined Analysis
  21. GRB 250702F: Fermi GBM Observation
  22. GRB 250702F: Leavitt Observatory optical observations
  23. GRB 250702F: AKO Optical Afterglow Detection
  24. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  25. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  26. GRB 250702A: GECAM-B detection
  27. GRB 250702F: Skynet Optical Observations
  28. GRB 250424A: VIRT Optical Upper Limit
  29. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  30. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  31. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  32. GRB 250702F: TRT Optical Observation
  33. GRB 250703A: DDOTI Optical Upper Limit
  34. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  35. GRB 250702F: REM optical afterglow detection
  36. EP250702a: Global MASTER-Net observations report
  37. GRB 250702F: DDOTI Optical Observation
  38. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  39. GRB 250703A: Fermi GBM Final Real-time Localization
  40. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  41. GRB 250702F: COLIBRÍ Observations of the Afterglow
  42. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  43. Fermi GRB 250702E: Global MASTER-Net observations report
  44. Fermi GRB 250702B: Global MASTER-Net observations report
  45. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  46. GRB 250702F: Enhanced Swift-XRT position
  47. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  48. GRB 250702F: NOT observations of the optical afterglow
  49. GRB 250702F: MASTER optical afterglow observation
  50. Fermi GRB 250702F: Global MASTER-Net observations report
  51. Fermi GRB 250702C: Global MASTER-Net observations report
  52. GRB 250702F: GOTO optical counterpart detection
  53. GRB 250702F: Ondrejov D50 optical afterglow detection
  54. GRB 250702F: Swift detection of a burst with an optical counterpart
  55. Swift GRB 250702F: Global MASTER-Net observations report
  56. GRB 250702F: Fermi GBM Final Real-time Localization
  57. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  58. GRB 250702E: Fermi GBM Final Real-time Localization
  59. Konus-Wind detection of GRB 250627A
  60. IPN triangulation of GRB 250627A (short)
  61. GRB 250702A: Fermi GBM Detection
  62. GRB 250702D: Fermi GBM Final Localization Correction
  63. GRB 250702C: Fermi GBM Final Real-time Localization
  64. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  65. GRB 250702B: Fermi GBM Final Real-time Localization
  66. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  67. GRB 250702A: Fermi GBM Final Real-time Localization
  68. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  69. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  70. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  71. GRB 250628B: Swift-XRT observations
  72. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  73. GRB 250628B: SVOM/VT optical upper limit
  74. GRB 250628B: EP-FXT counterpart detection
  75. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  76. GRB 250627A: Insight-HXMT detection
  77. GRB 250627A: SVOM/GRM detection of a short burst
  78. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  79. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  80. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  81. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  82. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  83. GRB 250628A: REM optical/NIR upper limits
  84. GRB 250628C: Fermi GBM Final Real-time Localization
  85. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  86. GRB 250628B: SVOM detection of a long burst
  87. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  88. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  89. GRB 250628A: VLT/X-shooter upper limits
  90. GRB 250628A: Swift/UVOT Upper Limits
  91. GRB 250628A: Swift-XRT refined Analysis
  92. Fermi GRB 250626A: Global MASTER-Net observations report
  93. Swift GRB 250628A: Global MASTER-Net observations report
  94. GRB 250628A: Enhanced Swift-XRT position
  95. GRB 250628A: Swift detection of a burst
  96. GRB 250625A: Swift-BAT refined analysis
  97. GRB 250625A: Leavitt Observatory afterglow detection
  98. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  99. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  100. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations

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