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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. LIGO/Virgo/KAGRA S240511i: Identification of a GW compact binary merger candidate
  2. Fermi Gamma-ray Burst Monitor trigger 737076431/240510977 is not a GRB
  3. LIGO/Virgo/KAGRA S240422ed: GMOS-S photometry of J-GEM24a
  4. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
  5. LIGO/Virgo/KAGRA S240422ed: Candidates from the latest GW-MMADS DECam Observations
  6. Fermi trigger No 736967879: Global MASTER-Net observations report
  7. EP240506a: Xinglong optical upper limit
  8. Fermi Gamma-ray Burst Monitor trigger 230925241/717313591 is not a GRB
  9. EP240506a: CrAO ZTSH optical upper limit
  10. GRB 240504A: Fermi GBM Observation
  11. Fermi Gamma-ray Burst Monitor trigger 736837160/240508208 is not a GRB
  12. EP240506a: Archival radio searching
  13. EP240506a: TRT optical upper limit
  14. EP240506a: BOOTES Network optical upper limit
  15. LIGO/Virgo/KAGRA S240507p: Updated Sky localization and EM Bright Classification
  16. LIGO/Virgo/KAGRA S240422ed: Upper limits from a two-week IceCube neutrino search
  17. Fermi trigger No 736733320: Global MASTER-Net observations report
  18. EP240506a: Optical upper limit with Kinder observations
  19. IPN triangulation of GRB 240504A
  20. GRB 240502A: 1.3m DFOT Optical upper limit
  21. EP240506a: EP-WXT detection of a new fast X-ray transient
  22. LIGO/Virgo/KAGRA S240507p: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo/KAGRA S240422ed: Additional WINTER near-infrared J-band observations
  24. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
  25. GRB 240504A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  26. Fermi GBM triggers 736668287/240506253 and 736669277/240506265 are not GRBs
  27. LIGO/Virgo/KAGRA S240505av: Updated Sky localization and EM Bright Classification
  28. Fermi trigger No 736564880: Global MASTER-Net observations report
  29. LIGO/Virgo/KAGRA S240505av: Identification of a GW compact binary merger candidate
  30. IceCube-240424A: GRANDMA Optical Upper Limit of Fermi J2151.3+0220
  31. GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
  32. Fermi trigger No 736461232: Global MASTER-Net observations report
  33. IPN triangulation of GRB 240501B and GRB 240501A - possible episodes of ultra long GRB
  34. Fermi GRB 240504A: Global MASTER-Net observations report
  35. Fermi trigger No 736472503: Global MASTER-Net observations report
  36. GW170817: VLA observations at ~5.5 yrs since merger
  37. GRB 240503A: AstroSat CZTI detection
  38. GRB 240504A: BALROG localization (Fermi Trigger 736492377 / GRB 240504217)
  39. GRB 240504A: Fermi GBM Final Real-time Localization
  40. Fermi trigger No 736387941: Global MASTER-Net observations report
  41. LXT 240402A / GRB 240402B: VLT X-shooter redshift of host
  42. GRB 240502A: GOTO optical upper limit
  43. Fermi trigger No 736379109: Global MASTER-Net observations report
  44. GRB 240502A: Fermi GBM Observation
  45. GRB 240415A 1.3m DFOT Optical upper limit
  46. GRB 240502C: GOTO possible optical counterpart candidates
  47. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  48. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  49. Fermi GRB 240502B: Global MASTER-Net observations report
  50. GRB 240502C: Fermi GBM Final Localization
  51. Fermi GRB 240502A: Global MASTER-Net observations report
  52. GRB 240501B: GRBAlpha detection
  53. GRB 240430A: GRBAlpha detection
  54. GRB 240502B: Fermi GBM Final Real-time Localization
  55. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet Transient Candidates
  56. Integral GRB240502.23: Global MASTER-Net observations report
  57. GRB 240502A long GRB detected by INTEGRAL
  58. GRB 240502A: Fermi GBM Final Real-time Localization
  59. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  60. Fermi GRB 240501A: Global MASTER-Net observations report
  61. Fermi trigger No 736197684: Global MASTER-Net observations report
  62. GRB 240426A: VZLUSAT-2 detection
  63. GRB 240425A: VZLUSAT-2 detection
  64. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  65. GRB240430A: Fermi GBM Final Localization
  66. GRB 240501B: AstroSat CZTI detection
  67. GRB 240501A: Fermi GBM Final Real-time Localization
  68. GRB 240408B: VZLUSAT-2 detection
  69. GRB 240407A: VZLUSAT-2 detection
  70. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  71. X-ray transient EP240414a: Detection of associated supernova
  72. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  73. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  75. Additional DECam GW-MMADS Candidates from three nights of observations
  76. GRB 240425A: GRBAlpha detection
  77. Fermi-LAT gamma-ray observations of IceCube-240424A
  78. LIGO/Virgo/KAGRA S240426s: Updated Sky localization
  79. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  80. LIGO/Virgo/KAGRA S240426dl: Updated Sky localization
  81. GRB 240429A: Fermi GBM Final Real-time Localization
  82. LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
  83. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  84. LIGO/Virgo/KAGRA S240429an: Retraction of GW compact binary merger candidate
  85. LIGO/Virgo/KAGRA S240422ed: ENGRAVE VLT/XShooter spectroscopy of the host galaxy of J-GEM24a
  86. LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
  87. Fermi GRB 240428A: Global MASTER-Net observations report
  88. GRB 240428A: Fermi GBM Final Real-time Localization
  89. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  90. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  91. EP240426b: AST3-2 optical upper limit
  92. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  93. LIGO/Virgo/KAGRA S240422ed: A transient discovered from Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  94. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  95. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  96. EP240426b: EP-WXT detection of a new fast X-ray transient
  97. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  98. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  99. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  100. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a

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