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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. LIGO/Virgo/KAGRA S240513cx: Coverage and upper limits from MAXI/GSC observations
  2. Fermi trigger No 737258655: Global MASTER-Net observations report
  3. GRB 240511A: J-band observations with WINTER
  4. Fermi trigger No 737247400: Global MASTER-Net observations report
  5. Fermi trigger No 737244199: Global MASTER-Net observations report
  6. Fermi trigger No 737218721: Global MASTER-Net observations report
  7. Fermi trigger No 737196587: Global MASTER-Net observations report
  8. Fermi trigger No 737168073: Global MASTER-Net observations report
  9. GRB 240511A: Enhanced Swift-XRT position
  10. GRB 240511A : MITSuME Akeno optical upper limits
  11. LIGO/Virgo/KAGRA S240512r: Updated Sky localization and EM Bright Classification
  12. GRB 240511A: Swift-XRT refined Analysis
  13. GRB 240511A: optical afterglow detection from the NOT
  14. Fermi Gamma-ray Burst Monitor trigger 737102480/240511279 is not a GRB
  15. Fermi Gamma-ray Burst Monitor trigger 737111207/240511380 is not a GRB
  16. Fermi GBM trigger 737105243/240511311 is not a GRB
  17. Fermi trigger No 737173236: Global MASTER-Net observations report
  18. LIGO/Virgo/KAGRA S240512r: Identification of a GW compact binary merger candidate
  19. Fermi GRB 240511A: Global MASTER-Net observations report
  20. Swift GRB 240511A: Global MASTER-Net observations report
  21. Fermi trigger No 737105243: Global MASTER-Net observations report
  22. Fermi Gamma-ray Burst Monitor trigger 737133200/240511634 is not a GRB
  23. Fermi trigger No 737152719: Global MASTER-Net observations report
  24. GRB 240511A: Prompt enhanced Swift-XRT position
  25. GRB 240511A: Swift detection of a burst
  26. LIGO/Virgo/KAGRA S240511i: Updated Sky localization
  27. GRB 240511A: Fermi GBM Final Real-time Localization
  28. Fermi trigger No 737102480: Global MASTER-Net observations report
  29. Fermi trigger No 737111207: Global MASTER-Net observations report
  30. LIGO/Virgo/KAGRA S240511i: Identification of a GW compact binary merger candidate
  31. Fermi Gamma-ray Burst Monitor trigger 737076431/240510977 is not a GRB
  32. LIGO/Virgo/KAGRA S240422ed: GMOS-S photometry of J-GEM24a
  33. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
  34. LIGO/Virgo/KAGRA S240422ed: Candidates from the latest GW-MMADS DECam Observations
  35. Fermi trigger No 736967879: Global MASTER-Net observations report
  36. EP240506a: Xinglong optical upper limit
  37. Fermi Gamma-ray Burst Monitor trigger 230925241/717313591 is not a GRB
  38. EP240506a: CrAO ZTSH optical upper limit
  39. GRB 240504A: Fermi GBM Observation
  40. Fermi Gamma-ray Burst Monitor trigger 736837160/240508208 is not a GRB
  41. EP240506a: Archival radio searching
  42. EP240506a: TRT optical upper limit
  43. EP240506a: BOOTES Network optical upper limit
  44. LIGO/Virgo/KAGRA S240507p: Updated Sky localization and EM Bright Classification
  45. LIGO/Virgo/KAGRA S240422ed: Upper limits from a two-week IceCube neutrino search
  46. Fermi trigger No 736733320: Global MASTER-Net observations report
  47. EP240506a: Optical upper limit with Kinder observations
  48. IPN triangulation of GRB 240504A
  49. GRB 240502A: 1.3m DFOT Optical upper limit
  50. EP240506a: EP-WXT detection of a new fast X-ray transient
  51. LIGO/Virgo/KAGRA S240507p: Identification of a GW compact binary merger candidate
  52. LIGO/Virgo/KAGRA S240422ed: Additional WINTER near-infrared J-band observations
  53. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
  54. GRB 240504A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  55. Fermi GBM triggers 736668287/240506253 and 736669277/240506265 are not GRBs
  56. LIGO/Virgo/KAGRA S240505av: Updated Sky localization and EM Bright Classification
  57. Fermi trigger No 736564880: Global MASTER-Net observations report
  58. LIGO/Virgo/KAGRA S240505av: Identification of a GW compact binary merger candidate
  59. IceCube-240424A: GRANDMA Optical Upper Limit of Fermi J2151.3+0220
  60. GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
  61. Fermi trigger No 736461232: Global MASTER-Net observations report
  62. IPN triangulation of GRB 240501B and GRB 240501A - possible episodes of ultra long GRB
  63. Fermi GRB 240504A: Global MASTER-Net observations report
  64. Fermi trigger No 736472503: Global MASTER-Net observations report
  65. GW170817: VLA observations at ~5.5 yrs since merger
  66. GRB 240503A: AstroSat CZTI detection
  67. GRB 240504A: BALROG localization (Fermi Trigger 736492377 / GRB 240504217)
  68. GRB 240504A: Fermi GBM Final Real-time Localization
  69. Fermi trigger No 736387941: Global MASTER-Net observations report
  70. LXT 240402A / GRB 240402B: VLT X-shooter redshift of host
  71. GRB 240502A: GOTO optical upper limit
  72. Fermi trigger No 736379109: Global MASTER-Net observations report
  73. GRB 240502A: Fermi GBM Observation
  74. GRB 240415A 1.3m DFOT Optical upper limit
  75. GRB 240502C: GOTO possible optical counterpart candidates
  76. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  77. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  78. Fermi GRB 240502B: Global MASTER-Net observations report
  79. GRB 240502C: Fermi GBM Final Localization
  80. Fermi GRB 240502A: Global MASTER-Net observations report
  81. GRB 240501B: GRBAlpha detection
  82. GRB 240430A: GRBAlpha detection
  83. GRB 240502B: Fermi GBM Final Real-time Localization
  84. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet Transient Candidates
  85. Integral GRB240502.23: Global MASTER-Net observations report
  86. GRB 240502A long GRB detected by INTEGRAL
  87. GRB 240502A: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  89. Fermi GRB 240501A: Global MASTER-Net observations report
  90. Fermi trigger No 736197684: Global MASTER-Net observations report
  91. GRB 240426A: VZLUSAT-2 detection
  92. GRB 240425A: VZLUSAT-2 detection
  93. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  94. GRB240430A: Fermi GBM Final Localization
  95. GRB 240501B: AstroSat CZTI detection
  96. GRB 240501A: Fermi GBM Final Real-time Localization
  97. GRB 240408B: VZLUSAT-2 detection
  98. GRB 240407A: VZLUSAT-2 detection
  99. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  100. X-ray transient EP240414a: Detection of associated supernova

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