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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. Fermi Gamma-ray Burst Monitor trigger 737102480/240511279 is not a GRB
  2. Fermi Gamma-ray Burst Monitor trigger 737111207/240511380 is not a GRB
  3. Fermi GBM trigger 737105243/240511311 is not a GRB
  4. Fermi trigger No 737173236: Global MASTER-Net observations report
  5. LIGO/Virgo/KAGRA S240512r: Identification of a GW compact binary merger candidate
  6. Fermi GRB 240511A: Global MASTER-Net observations report
  7. Swift GRB 240511A: Global MASTER-Net observations report
  8. Fermi trigger No 737105243: Global MASTER-Net observations report
  9. Fermi Gamma-ray Burst Monitor trigger 737133200/240511634 is not a GRB
  10. Fermi trigger No 737152719: Global MASTER-Net observations report
  11. GRB 240511A: Prompt enhanced Swift-XRT position
  12. GRB 240511A: Swift detection of a burst
  13. LIGO/Virgo/KAGRA S240511i: Updated Sky localization
  14. GRB 240511A: Fermi GBM Final Real-time Localization
  15. Fermi trigger No 737102480: Global MASTER-Net observations report
  16. Fermi trigger No 737111207: Global MASTER-Net observations report
  17. LIGO/Virgo/KAGRA S240511i: Identification of a GW compact binary merger candidate
  18. Fermi Gamma-ray Burst Monitor trigger 737076431/240510977 is not a GRB
  19. LIGO/Virgo/KAGRA S240422ed: GMOS-S photometry of J-GEM24a
  20. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
  21. LIGO/Virgo/KAGRA S240422ed: Candidates from the latest GW-MMADS DECam Observations
  22. Fermi trigger No 736967879: Global MASTER-Net observations report
  23. EP240506a: Xinglong optical upper limit
  24. Fermi Gamma-ray Burst Monitor trigger 230925241/717313591 is not a GRB
  25. EP240506a: CrAO ZTSH optical upper limit
  26. GRB 240504A: Fermi GBM Observation
  27. Fermi Gamma-ray Burst Monitor trigger 736837160/240508208 is not a GRB
  28. EP240506a: Archival radio searching
  29. EP240506a: TRT optical upper limit
  30. EP240506a: BOOTES Network optical upper limit
  31. LIGO/Virgo/KAGRA S240507p: Updated Sky localization and EM Bright Classification
  32. LIGO/Virgo/KAGRA S240422ed: Upper limits from a two-week IceCube neutrino search
  33. Fermi trigger No 736733320: Global MASTER-Net observations report
  34. EP240506a: Optical upper limit with Kinder observations
  35. IPN triangulation of GRB 240504A
  36. GRB 240502A: 1.3m DFOT Optical upper limit
  37. EP240506a: EP-WXT detection of a new fast X-ray transient
  38. LIGO/Virgo/KAGRA S240507p: Identification of a GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S240422ed: Additional WINTER near-infrared J-band observations
  40. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
  41. GRB 240504A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  42. Fermi GBM triggers 736668287/240506253 and 736669277/240506265 are not GRBs
  43. LIGO/Virgo/KAGRA S240505av: Updated Sky localization and EM Bright Classification
  44. Fermi trigger No 736564880: Global MASTER-Net observations report
  45. LIGO/Virgo/KAGRA S240505av: Identification of a GW compact binary merger candidate
  46. IceCube-240424A: GRANDMA Optical Upper Limit of Fermi J2151.3+0220
  47. GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
  48. Fermi trigger No 736461232: Global MASTER-Net observations report
  49. IPN triangulation of GRB 240501B and GRB 240501A - possible episodes of ultra long GRB
  50. Fermi GRB 240504A: Global MASTER-Net observations report
  51. Fermi trigger No 736472503: Global MASTER-Net observations report
  52. GW170817: VLA observations at ~5.5 yrs since merger
  53. GRB 240503A: AstroSat CZTI detection
  54. GRB 240504A: BALROG localization (Fermi Trigger 736492377 / GRB 240504217)
  55. GRB 240504A: Fermi GBM Final Real-time Localization
  56. Fermi trigger No 736387941: Global MASTER-Net observations report
  57. LXT 240402A / GRB 240402B: VLT X-shooter redshift of host
  58. GRB 240502A: GOTO optical upper limit
  59. Fermi trigger No 736379109: Global MASTER-Net observations report
  60. GRB 240502A: Fermi GBM Observation
  61. GRB 240415A 1.3m DFOT Optical upper limit
  62. GRB 240502C: GOTO possible optical counterpart candidates
  63. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  64. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  65. Fermi GRB 240502B: Global MASTER-Net observations report
  66. GRB 240502C: Fermi GBM Final Localization
  67. Fermi GRB 240502A: Global MASTER-Net observations report
  68. GRB 240501B: GRBAlpha detection
  69. GRB 240430A: GRBAlpha detection
  70. GRB 240502B: Fermi GBM Final Real-time Localization
  71. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet Transient Candidates
  72. Integral GRB240502.23: Global MASTER-Net observations report
  73. GRB 240502A long GRB detected by INTEGRAL
  74. GRB 240502A: Fermi GBM Final Real-time Localization
  75. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  76. Fermi GRB 240501A: Global MASTER-Net observations report
  77. Fermi trigger No 736197684: Global MASTER-Net observations report
  78. GRB 240426A: VZLUSAT-2 detection
  79. GRB 240425A: VZLUSAT-2 detection
  80. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  81. GRB240430A: Fermi GBM Final Localization
  82. GRB 240501B: AstroSat CZTI detection
  83. GRB 240501A: Fermi GBM Final Real-time Localization
  84. GRB 240408B: VZLUSAT-2 detection
  85. GRB 240407A: VZLUSAT-2 detection
  86. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  87. X-ray transient EP240414a: Detection of associated supernova
  88. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  89. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  90. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  91. Additional DECam GW-MMADS Candidates from three nights of observations
  92. GRB 240425A: GRBAlpha detection
  93. Fermi-LAT gamma-ray observations of IceCube-240424A
  94. LIGO/Virgo/KAGRA S240426s: Updated Sky localization
  95. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  96. LIGO/Virgo/KAGRA S240426dl: Updated Sky localization
  97. GRB 240429A: Fermi GBM Final Real-time Localization
  98. LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
  99. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  100. LIGO/Virgo/KAGRA S240429an: Retraction of GW compact binary merger candidate

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