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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. GRB 250702F: SVOM/VT optical observation
  2. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  3. GRB 250704A: SVOM detection of a burst
  4. GRB 250702F: Swift/UVOT Detection
  5. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  6. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  7. Fermi GRB 250703A: Global MASTER-Net observations report
  8. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  9. GRB 250702F: Swift-XRT refined Analysis
  10. GRB 250702F: Fermi GBM Observation
  11. GRB 250702F: Leavitt Observatory optical observations
  12. GRB 250702F: AKO Optical Afterglow Detection
  13. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  14. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  15. GRB 250702A: GECAM-B detection
  16. GRB 250702F: Skynet Optical Observations
  17. GRB 250424A: VIRT Optical Upper Limit
  18. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  19. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  20. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  21. GRB 250702F: TRT Optical Observation
  22. GRB 250703A: DDOTI Optical Upper Limit
  23. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  24. GRB 250702F: REM optical afterglow detection
  25. EP250702a: Global MASTER-Net observations report
  26. GRB 250702F: DDOTI Optical Observation
  27. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  28. GRB 250703A: Fermi GBM Final Real-time Localization
  29. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  30. GRB 250702F: COLIBRÍ Observations of the Afterglow
  31. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  32. Fermi GRB 250702E: Global MASTER-Net observations report
  33. Fermi GRB 250702B: Global MASTER-Net observations report
  34. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  35. GRB 250702F: Enhanced Swift-XRT position
  36. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  37. GRB 250702F: NOT observations of the optical afterglow
  38. GRB 250702F: MASTER optical afterglow observation
  39. Fermi GRB 250702F: Global MASTER-Net observations report
  40. Fermi GRB 250702C: Global MASTER-Net observations report
  41. GRB 250702F: GOTO optical counterpart detection
  42. GRB 250702F: Ondrejov D50 optical afterglow detection
  43. GRB 250702F: Swift detection of a burst with an optical counterpart
  44. Swift GRB 250702F: Global MASTER-Net observations report
  45. GRB 250702F: Fermi GBM Final Real-time Localization
  46. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  47. GRB 250702E: Fermi GBM Final Real-time Localization
  48. Konus-Wind detection of GRB 250627A
  49. IPN triangulation of GRB 250627A (short)
  50. GRB 250702A: Fermi GBM Detection
  51. GRB 250702D: Fermi GBM Final Localization Correction
  52. GRB 250702C: Fermi GBM Final Real-time Localization
  53. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  54. GRB 250702B: Fermi GBM Final Real-time Localization
  55. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  56. GRB 250702A: Fermi GBM Final Real-time Localization
  57. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  58. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  59. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  60. GRB 250628B: Swift-XRT observations
  61. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  62. GRB 250628B: SVOM/VT optical upper limit
  63. GRB 250628B: EP-FXT counterpart detection
  64. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  65. GRB 250627A: Insight-HXMT detection
  66. GRB 250627A: SVOM/GRM detection of a short burst
  67. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  68. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  69. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  70. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  71. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  72. GRB 250628A: REM optical/NIR upper limits
  73. GRB 250628C: Fermi GBM Final Real-time Localization
  74. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  75. GRB 250628B: SVOM detection of a long burst
  76. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  77. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  78. GRB 250628A: VLT/X-shooter upper limits
  79. GRB 250628A: Swift/UVOT Upper Limits
  80. GRB 250628A: Swift-XRT refined Analysis
  81. Fermi GRB 250626A: Global MASTER-Net observations report
  82. Swift GRB 250628A: Global MASTER-Net observations report
  83. GRB 250628A: Enhanced Swift-XRT position
  84. GRB 250628A: Swift detection of a burst
  85. GRB 250625A: Swift-BAT refined analysis
  86. GRB 250625A: Leavitt Observatory afterglow detection
  87. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  88. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  89. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  90. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  91. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  92. GRB 250626A: Fermi GBM Final Real-time Localization
  93. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  94. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  95. GRB 250625A: SVOM/C-GFT upper limit in early phase
  96. GRB 250625A: GECAM-B detection
  97. GRB 250625A: Swift/UVOT Upper Limits
  98. GRB 250625A: ABObservatory afterglow detection
  99. GRB 250625A: OHP/T193 optical detection
  100. GRB 250625A: COLIBRÍ optical observations

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