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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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. Fermi GRB 250703A: Global MASTER-Net observations report
  2. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  3. GRB 250702F: Swift-XRT refined Analysis
  4. GRB 250702F: Fermi GBM Observation
  5. GRB 250702F: Leavitt Observatory optical observations
  6. GRB 250702F: AKO Optical Afterglow Detection
  7. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  8. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  9. GRB 250702A: GECAM-B detection
  10. GRB 250702F: Skynet Optical Observations
  11. GRB 250424A: VIRT Optical Upper Limit
  12. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  13. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  14. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  15. GRB 250702F: TRT Optical Observation
  16. GRB 250703A: DDOTI Optical Upper Limit
  17. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  18. GRB 250702F: REM optical afterglow detection
  19. EP250702a: Global MASTER-Net observations report
  20. GRB 250702F: DDOTI Optical Observation
  21. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  22. GRB 250703A: Fermi GBM Final Real-time Localization
  23. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  24. GRB 250702F: COLIBRÍ Observations of the Afterglow
  25. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  26. Fermi GRB 250702E: Global MASTER-Net observations report
  27. Fermi GRB 250702B: Global MASTER-Net observations report
  28. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  29. GRB 250702F: Enhanced Swift-XRT position
  30. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  31. GRB 250702F: NOT observations of the optical afterglow
  32. GRB 250702F: MASTER optical afterglow observation
  33. Fermi GRB 250702F: Global MASTER-Net observations report
  34. Fermi GRB 250702C: Global MASTER-Net observations report
  35. GRB 250702F: GOTO optical counterpart detection
  36. GRB 250702F: Ondrejov D50 optical afterglow detection
  37. GRB 250702F: Swift detection of a burst with an optical counterpart
  38. Swift GRB 250702F: Global MASTER-Net observations report
  39. GRB 250702F: Fermi GBM Final Real-time Localization
  40. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  41. GRB 250702E: Fermi GBM Final Real-time Localization
  42. Konus-Wind detection of GRB 250627A
  43. IPN triangulation of GRB 250627A (short)
  44. GRB 250702A: Fermi GBM Detection
  45. GRB 250702D: Fermi GBM Final Localization Correction
  46. GRB 250702C: Fermi GBM Final Real-time Localization
  47. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  48. GRB 250702B: Fermi GBM Final Real-time Localization
  49. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  50. GRB 250702A: Fermi GBM Final Real-time Localization
  51. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  52. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  53. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  54. GRB 250628B: Swift-XRT observations
  55. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  56. GRB 250628B: SVOM/VT optical upper limit
  57. GRB 250628B: EP-FXT counterpart detection
  58. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  59. GRB 250627A: Insight-HXMT detection
  60. GRB 250627A: SVOM/GRM detection of a short burst
  61. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  62. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  63. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  64. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  65. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  66. GRB 250628A: REM optical/NIR upper limits
  67. GRB 250628C: Fermi GBM Final Real-time Localization
  68. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  69. GRB 250628B: SVOM detection of a long burst
  70. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  71. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  72. GRB 250628A: VLT/X-shooter upper limits
  73. GRB 250628A: Swift/UVOT Upper Limits
  74. GRB 250628A: Swift-XRT refined Analysis
  75. Fermi GRB 250626A: Global MASTER-Net observations report
  76. Swift GRB 250628A: Global MASTER-Net observations report
  77. GRB 250628A: Enhanced Swift-XRT position
  78. GRB 250628A: Swift detection of a burst
  79. GRB 250625A: Swift-BAT refined analysis
  80. GRB 250625A: Leavitt Observatory afterglow detection
  81. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  82. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  83. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  84. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  85. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  86. GRB 250626A: Fermi GBM Final Real-time Localization
  87. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  88. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  89. GRB 250625A: SVOM/C-GFT upper limit in early phase
  90. GRB 250625A: GECAM-B detection
  91. GRB 250625A: Swift/UVOT Upper Limits
  92. GRB 250625A: ABObservatory afterglow detection
  93. GRB 250625A: OHP/T193 optical detection
  94. GRB 250625A: COLIBRÍ optical observations
  95. GRB 250625A: Fermi-LAT detection
  96. GRB 250625A: Swift-XRT refined Analysis
  97. GRB 250625A: JinShan optical observations
  98. GRB250625A: Fermi GBM Observation
  99. Swift GRB 250625A: Global MASTER-Net observations report
  100. GRB 250625A: NOT z-band upper limit

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