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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. EP240804a: VLT/X-shooter spectroscopic redshift
  2. EP240804a: LCOGT optical counterpart detection
  3. GRB 240805A: A long GRB detected by INTEGRAL
  4. EP-WXT trigger 00109017646 is not a real source
  5. EP240804a: NOT optical counterpart detection
  6. EP240804a: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  7. EP240802a: correction of EP-WXT trigger time in GCN 37019
  8. GRB 240805A: Swift detection of a burst
  9. GRB 240805A: Fermi GBM Final Real-time Localization
  10. Fermi GRB 240804A: Global MASTER-Net observations report
  11. EP240802a: Montarrenti Observatory optical upper limit
  12. GRB 240804A: Fermi GBM Final Real-time Localization
  13. Fermi trigger No 744459130: Global MASTER-Net observations report
  14. IPN triangulation of GRB 240802A / EP 240802a
  15. Fermi Gamma-ray Burst Monitor trigger 744459130/240804425 is not a GRB
  16. EP240801a: Osservatorio Astronomico Nastro Verde upper limit
  17. EP240802A: Bassano Bresciano Observatory upper limit
  18. GRB 240802A: SVOM/GRM observation
  19. EP240802a: Time coincidence with GRB 240802A and optical upper limits with Kinder observations
  20. Fermi trigger No 744278264: Global MASTER-Net observations report
  21. EP240802a: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  22. GRB 240802A: AstroSat CZTI detection of a long burst
  23. EP240801a: further SAO RAS optical observations
  24. EP240801a: optical observations at CrAO and AbAO
  25. EP240801a: GRANDMA and Kilonova-Catcher optical observations
  26. EP240801a: Leavitt Observatory optical observations
  27. EP240801a: GTC spectroscopy and absorption redshift
  28. EP240801a: SAO RAS optical observations
  29. GRB 240801B: AstroSat CZTI Updated classification - likely a solar flare
  30. EP240801a: JinShan optical observations
  31. GRB 240727C: SVOM/GRM observation
  32. EP240801a: NOT optical observations
  33. EP240801a: follow-up observation with LCOGT
  34. Fermi GBM trigger 744179961 / 240801194 can not be confirmed as a GRB
  35. GRB 240730A: Swift-BAT refined analysis
  36. EP240801a: GSP follow-up observations of the candidate counterpart
  37. Fermi trigger No 744204856: Global MASTER-Net observations report
  38. EP240801a: Kinder follow-up observations of the candidate counterpart
  39. EP240708a: Kinder follow-up observations of the candidate counterpart (duplicate submission of GCN 37002)
  40. EP240801a: KAIT optical counterpart observations
  41. EP240801a: GMG observation
  42. EP240801a: TRT optical counterpart detection
  43. EP240801a: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  44. GRB 240801B: AstroSat CZTI detection of a bright long burst
  45. Fermi GRB 240801A: Global MASTER-Net observations report
  46. GRB 240801A: Fermi GBM Final Real-time Localization
  47. GRB 240730C: AstroSat CZTI detection of a long burst
  48. GRB 240731A: Fermi GBM Final Localization
  49. Fermi trigger No 744128417: Global MASTER-Net observations report
  50. Fermi trigger No 744083370: Global MASTER-Net observations report
  51. GRB 240731A: AstroSat CZTI detection
  52. GRB 240730A: Osservatorio Astronomico Nastro Verde upper limit
  53. GRB240730A: BOOTES-5/JGT early optical upper limit
  54. Fermi Gamma-ray Burst Monitor trigger 744061103/240730818 is not a GRB
  55. Fermi GRB 240730B: Global MASTER-Net observations report
  56. GRB 240730B: Fermi GBM Final Real-time Localization
  57. Swift GRB 240730A: Global MASTER-Net observations report
  58. GRB 240730A: Swift-XRT refined Analysis
  59. GRB 240715A: Swift-XRT afterglow detection
  60. GRB 240730A: KAIT Optical Upper Limit
  61. GRB 240727C: GRBAlpha detection
  62. GRB 240730A: Swift/UVOT Upper Limits
  63. GRB 240730A: Enhanced Swift-XRT position
  64. GRB 240730A: Swift detection of a burst
  65. Fermi trigger No 743953682: Global MASTER-Net observations report
  66. GRB 240727A: Swift-BAT refined analysis
  67. Fermi Gamma-ray Burst Monitor trigger 743953682/240729575 is not a GRB
  68. LIGO/Virgo/KAGRA S240615dg: GRAWITA wide-field optical observations
  69. GRB 240727A: observations of optical counterpart.
  70. GRB 240727B: Swift-XRT observations
  71. Fermi GRB 240727A: Global MASTER-Net observations report
  72. GRB 240727A: Swift/UVOT detection
  73. Fermi trigger No 743868421: Global MASTER-Net observations report
  74. Fermi Gamma-ray Burst Monitor trigger 743868421/240728588 is not a GRB
  75. GRB 240727A: Correction to time in GCN36960
  76. GRB 240727A: Osservatorio Astronomico Nastro Verde upper limit
  77. EP-WXT trigger 01709002661 is not a real source
  78. GRB 240727A: NOT optical observation
  79. GRB 240727A: JinShan optical upper limits
  80. GRB 240727A Bassano Bresciano Observatory upper limit
  81. GRB 240727D: Correction to the GRB name in GCN 36958
  82. GRB 240727A: Fermi GBM Final Real-time Localization
  83. GRB 240727C: AstroSat CZTI detection of a long burst
  84. GRB 240727A: Swift-XRT refined Analysis
  85. GRB 240720B: GRBAlpha detection
  86. GRB 240718A: GRBAlpha detection
  87. GRB 240710B: GRBAlpha detection
  88. GRB 240627A: GRBAlpha detection
  89. Fermi GRB 240726A: Global MASTER-Net observations report
  90. GRB 240727A: Enhanced Swift-XRT position
  91. GRB 240727B: Fermi GBM Observation
  92. Swift GRB240727.16: Global MASTER-Net observations report
  93. GRB240529A: VIRT optical transient detection
  94. GRB 240727B: Swift ToO observations
  95. GRB 240727B: Swift/BAT-GUANO arcminute localization of a long burst
  96. GRB 240726A: SVOM/GRM observation
  97. GRB 240727B: AstroSat CZTI detection
  98. GRB 240726B: AstroSat CZTI detection of a short burst
  99. GRB240727A: Skynet Optical Afterglow Observations
  100. GRB 240727A: TRT optical afterglow detection

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