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

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