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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"

5544 results found.

  1. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  2. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  3. GRB 250709A: Fermi GBM Final Localization
  4. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  5. GRB 250704B / EP250704a: VLA radio detection
  6. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  7. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  8. GRB 250703A: EIRSAT-1 GMOD Detection
  9. Konus-Wind detection of GRB 250703A
  10. IPN triangulation of GRB 250703A
  11. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  12. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  13. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  14. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  15. Fermi GRB 250703A: Global MASTER-Net observations report
  16. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  17. GRB 250703A: DDOTI Optical Upper Limit
  18. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  19. GRB 250703A: Fermi GBM Final Real-time Localization
  20. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  21. Fermi GRB 250702F: Global MASTER-Net observations report
  22. GRB 250702F: Swift detection of a burst with an optical counterpart
  23. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  24. GRB 250702A: Fermi GBM Detection
  25. GRB 250702D: Fermi GBM Final Localization Correction
  26. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  27. GRB 250702A: Fermi GBM Final Real-time Localization
  28. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  29. Fermi GRB 250626A: Global MASTER-Net observations report
  30. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  31. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  32. GRB 250625A: ABObservatory afterglow detection
  33. GRB 250521A: VZLUSAT-2 detection
  34. Fermi trigger No 772190032: Global MASTER-Net observations report
  35. GRB 250620C: Fermi GBM Final Real-time Localization
  36. Fermi trigger No 772128434: Global MASTER-Net observations report
  37. GRB 250617B: Nickel telescope optical observations
  38. GRB 250617B: COLIBRÍ optical observations
  39. GRB 250617B: NUTTelA-TAO early time optical observations
  40. GRB 250617A: Fermi GBM Final Real-time Localization
  41. EP#01709178975: Swift-XRT counterpart detection
  42. GRB 250615A: DDOTI Optical Upper Limit
  43. Fermi trigger No 771752663: Global MASTER-Net observations report
  44. IceCube alert 141029_8144692 retraction
  45. EP250610a: Global MASTER-Net observations report
  46. EP250610a: REM optical/NIR observations
  47. GRB 250609A: Fermi GBM Observation
  48. Fermi trigger No 771072240: Global MASTER-Net observations report
  49. The EP-WXT trigger 01709178283 is likely a flaring star
  50. Fermi trigger No 770867684: Global MASTER-Net observations report
  51. Fermi GRB 250601A: Global MASTER-Net observations report
  52. EP#01709177494: SVOM/VT optical observations
  53. GRB 250530C: BOOTES-7 optical upper limit
  54. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  55. Fermi trigger No 770047117: Global MASTER-Net observations report
  56. Fermi trigger No 769611916: Global MASTER-Net observations report
  57. Fermi GRB 250522B: Global MASTER-Net observations report
  58. Fermi GRB 250521D: Global MASTER-Net observations report
  59. GRB 250521D: DDOTI Optical Upper Limit
  60. GRB 250520A: 10 GHz VLA radio source
  61. GRB 250516A: COLIBRÍ optical upper limit
  62. Fermi GRB 250516A: Global MASTER-Net observations report
  63. Fermi GRB 250512A: Global MASTER-Net observations report
  64. GRB 250507B: AstroSat CZTI detection
  65. EP250512a: Global MASTER-Net observations report
  66. GRB 250507B: GRBAlpha detection
  67. EP250511a: COLIBRÍ optical counterpart candidate
  68. EP250511a: BOOTES-5 optical upper limit
  69. Fermi GRB 250510C: Global MASTER-Net observations report
  70. GRB 250509A: Fermi GBM Observation
  71. Fermi GRB 250509A: Global MASTER-Net observations report
  72. Swift GRB 250509A: Global MASTER-Net observations report
  73. GRB 250509A: Swift detection of a burst
  74. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  75. IceCube Alert 250506.59: Global MASTER-Net observations report
  76. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  77. GRB 250504A: REM optical/NIR observations
  78. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  79. Fermi trigger No 767623859: Global MASTER-Net observations report
  80. EP250427A: COLIBRÍ Continuing Optical Observations
  81. EP250427A: COLIBRÍ Optical Detection
  82. EP 250427a: BOOTES-7 optical afterglow candidate
  83. EP250427a: Global MASTER-Net observations report
  84. GRB 250424A: SVOM/VT optical observation
  85. Fermi-LAT gamma-ray observations of IceCube-250421A
  86. GRB 250424A: BlackGEM optical afterglow detection
  87. IceCube Alert 250421.71: Global MASTER-Net observations report
  88. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  89. EP250225a: SVOM/VT optical brightening
  90. IceCube 250414.324: DDOTI Optical Observations
  91. Fermi trigger No 766148493: Global MASTER-Net observations report
  92. Fermi trigger No 766173972: Global MASTER-Net observations report
  93. GRB 250411A: Fermi GBM Final Real-time Localization
  94. GRB 250407A: Continued KAIT/Nickel optical observations
  95. GRB 250407A: Mondy and AbAO Optical Observations
  96. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  97. IPN triangulation of GRB 250407A
  98. Fermi GRB 250407A: Global MASTER-Net observations report
  99. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  100. Fermi trigger No 765619921: Global MASTER-Net observations report

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