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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. LAT GRB240513.31: Global MASTER-Net observations report
  2. GRB 240513A: Fermi-LAT detection
  3. LIGO/Virgo/KAGRA S240513ei: Identification of a GW compact binary merger candidate
  4. GRB 240511A: Fermi GBM Observation
  5. GRB 240511A: Swift-BAT refined analysis
  6. Fermi GRB 240513B: Global MASTER-Net observations report
  7. Fermi trigger No 737277727: Global MASTER-Net observations report
  8. GRB 240513B: Fermi GBM Final Real-time Localization
  9. GRB 240513A: AstroSat CZTI detection
  10. LIGO/Virgo/KAGRA S240513cx: Coverage and upper limits from MAXI/GSC observations
  11. Fermi trigger No 737258655: Global MASTER-Net observations report
  12. GRB 240511A: J-band observations with WINTER
  13. Fermi trigger No 737247400: Global MASTER-Net observations report
  14. Fermi trigger No 737244199: Global MASTER-Net observations report
  15. Fermi trigger No 737218721: Global MASTER-Net observations report
  16. Fermi trigger No 737196587: Global MASTER-Net observations report
  17. Fermi trigger No 737168073: Global MASTER-Net observations report
  18. GRB 240511A: Enhanced Swift-XRT position
  19. GRB 240511A : MITSuME Akeno optical upper limits
  20. LIGO/Virgo/KAGRA S240512r: Updated Sky localization and EM Bright Classification
  21. GRB 240511A: Swift-XRT refined Analysis
  22. GRB 240511A: optical afterglow detection from the NOT
  23. Fermi Gamma-ray Burst Monitor trigger 737102480/240511279 is not a GRB
  24. Fermi Gamma-ray Burst Monitor trigger 737111207/240511380 is not a GRB
  25. Fermi GBM trigger 737105243/240511311 is not a GRB
  26. Fermi trigger No 737173236: Global MASTER-Net observations report
  27. LIGO/Virgo/KAGRA S240512r: Identification of a GW compact binary merger candidate
  28. Fermi GRB 240511A: Global MASTER-Net observations report
  29. Swift GRB 240511A: Global MASTER-Net observations report
  30. Fermi trigger No 737105243: Global MASTER-Net observations report
  31. Fermi Gamma-ray Burst Monitor trigger 737133200/240511634 is not a GRB
  32. Fermi trigger No 737152719: Global MASTER-Net observations report
  33. GRB 240511A: Prompt enhanced Swift-XRT position
  34. GRB 240511A: Swift detection of a burst
  35. LIGO/Virgo/KAGRA S240511i: Updated Sky localization
  36. GRB 240511A: Fermi GBM Final Real-time Localization
  37. Fermi trigger No 737102480: Global MASTER-Net observations report
  38. Fermi trigger No 737111207: Global MASTER-Net observations report
  39. LIGO/Virgo/KAGRA S240511i: Identification of a GW compact binary merger candidate
  40. Fermi Gamma-ray Burst Monitor trigger 737076431/240510977 is not a GRB
  41. LIGO/Virgo/KAGRA S240422ed: GMOS-S photometry of J-GEM24a
  42. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
  43. LIGO/Virgo/KAGRA S240422ed: Candidates from the latest GW-MMADS DECam Observations
  44. Fermi trigger No 736967879: Global MASTER-Net observations report
  45. EP240506a: Xinglong optical upper limit
  46. Fermi Gamma-ray Burst Monitor trigger 230925241/717313591 is not a GRB
  47. EP240506a: CrAO ZTSH optical upper limit
  48. GRB 240504A: Fermi GBM Observation
  49. Fermi Gamma-ray Burst Monitor trigger 736837160/240508208 is not a GRB
  50. EP240506a: Archival radio searching
  51. EP240506a: TRT optical upper limit
  52. EP240506a: BOOTES Network optical upper limit
  53. LIGO/Virgo/KAGRA S240507p: Updated Sky localization and EM Bright Classification
  54. LIGO/Virgo/KAGRA S240422ed: Upper limits from a two-week IceCube neutrino search
  55. Fermi trigger No 736733320: Global MASTER-Net observations report
  56. EP240506a: Optical upper limit with Kinder observations
  57. IPN triangulation of GRB 240504A
  58. GRB 240502A: 1.3m DFOT Optical upper limit
  59. EP240506a: EP-WXT detection of a new fast X-ray transient
  60. LIGO/Virgo/KAGRA S240507p: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S240422ed: Additional WINTER near-infrared J-band observations
  62. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
  63. GRB 240504A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  64. Fermi GBM triggers 736668287/240506253 and 736669277/240506265 are not GRBs
  65. LIGO/Virgo/KAGRA S240505av: Updated Sky localization and EM Bright Classification
  66. Fermi trigger No 736564880: Global MASTER-Net observations report
  67. LIGO/Virgo/KAGRA S240505av: Identification of a GW compact binary merger candidate
  68. IceCube-240424A: GRANDMA Optical Upper Limit of Fermi J2151.3+0220
  69. GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
  70. Fermi trigger No 736461232: Global MASTER-Net observations report
  71. IPN triangulation of GRB 240501B and GRB 240501A - possible episodes of ultra long GRB
  72. Fermi GRB 240504A: Global MASTER-Net observations report
  73. Fermi trigger No 736472503: Global MASTER-Net observations report
  74. GW170817: VLA observations at ~5.5 yrs since merger
  75. GRB 240503A: AstroSat CZTI detection
  76. GRB 240504A: BALROG localization (Fermi Trigger 736492377 / GRB 240504217)
  77. GRB 240504A: Fermi GBM Final Real-time Localization
  78. Fermi trigger No 736387941: Global MASTER-Net observations report
  79. LXT 240402A / GRB 240402B: VLT X-shooter redshift of host
  80. GRB 240502A: GOTO optical upper limit
  81. Fermi trigger No 736379109: Global MASTER-Net observations report
  82. GRB 240502A: Fermi GBM Observation
  83. GRB 240415A 1.3m DFOT Optical upper limit
  84. GRB 240502C: GOTO possible optical counterpart candidates
  85. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  86. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  87. Fermi GRB 240502B: Global MASTER-Net observations report
  88. GRB 240502C: Fermi GBM Final Localization
  89. Fermi GRB 240502A: Global MASTER-Net observations report
  90. GRB 240501B: GRBAlpha detection
  91. GRB 240430A: GRBAlpha detection
  92. GRB 240502B: Fermi GBM Final Real-time Localization
  93. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet Transient Candidates
  94. Integral GRB240502.23: Global MASTER-Net observations report
  95. GRB 240502A long GRB detected by INTEGRAL
  96. GRB 240502A: Fermi GBM Final Real-time Localization
  97. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  98. Fermi GRB 240501A: Global MASTER-Net observations report
  99. Fermi trigger No 736197684: Global MASTER-Net observations report
  100. GRB 240426A: VZLUSAT-2 detection

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