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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. EP240506a: EP-WXT detection of a new fast X-ray transient
  2. LIGO/Virgo/KAGRA S240507p: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S240422ed: Additional WINTER near-infrared J-band observations
  4. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
  5. GRB 240504A: Swift/BAT-GUANO detection of a burst outside the coded FOV
  6. Fermi GBM triggers 736668287/240506253 and 736669277/240506265 are not GRBs
  7. LIGO/Virgo/KAGRA S240505av: Updated Sky localization and EM Bright Classification
  8. Fermi trigger No 736564880: Global MASTER-Net observations report
  9. LIGO/Virgo/KAGRA S240505av: Identification of a GW compact binary merger candidate
  10. IceCube-240424A: GRANDMA Optical Upper Limit of Fermi J2151.3+0220
  11. GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
  12. Fermi trigger No 736461232: Global MASTER-Net observations report
  13. IPN triangulation of GRB 240501B and GRB 240501A - possible episodes of ultra long GRB
  14. Fermi GRB 240504A: Global MASTER-Net observations report
  15. Fermi trigger No 736472503: Global MASTER-Net observations report
  16. GW170817: VLA observations at ~5.5 yrs since merger
  17. GRB 240503A: AstroSat CZTI detection
  18. GRB 240504A: BALROG localization (Fermi Trigger 736492377 / GRB 240504217)
  19. GRB 240504A: Fermi GBM Final Real-time Localization
  20. Fermi trigger No 736387941: Global MASTER-Net observations report
  21. LXT 240402A / GRB 240402B: VLT X-shooter redshift of host
  22. GRB 240502A: GOTO optical upper limit
  23. Fermi trigger No 736379109: Global MASTER-Net observations report
  24. GRB 240502A: Fermi GBM Observation
  25. GRB 240415A 1.3m DFOT Optical upper limit
  26. GRB 240502C: GOTO possible optical counterpart candidates
  27. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  28. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  29. Fermi GRB 240502B: Global MASTER-Net observations report
  30. GRB 240502C: Fermi GBM Final Localization
  31. Fermi GRB 240502A: Global MASTER-Net observations report
  32. GRB 240501B: GRBAlpha detection
  33. GRB 240430A: GRBAlpha detection
  34. GRB 240502B: Fermi GBM Final Real-time Localization
  35. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet Transient Candidates
  36. Integral GRB240502.23: Global MASTER-Net observations report
  37. GRB 240502A long GRB detected by INTEGRAL
  38. GRB 240502A: Fermi GBM Final Real-time Localization
  39. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  40. Fermi GRB 240501A: Global MASTER-Net observations report
  41. Fermi trigger No 736197684: Global MASTER-Net observations report
  42. GRB 240426A: VZLUSAT-2 detection
  43. GRB 240425A: VZLUSAT-2 detection
  44. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  45. GRB240430A: Fermi GBM Final Localization
  46. GRB 240501B: AstroSat CZTI detection
  47. GRB 240501A: Fermi GBM Final Real-time Localization
  48. GRB 240408B: VZLUSAT-2 detection
  49. GRB 240407A: VZLUSAT-2 detection
  50. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  51. X-ray transient EP240414a: Detection of associated supernova
  52. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  53. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  54. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  55. Additional DECam GW-MMADS Candidates from three nights of observations
  56. GRB 240425A: GRBAlpha detection
  57. Fermi-LAT gamma-ray observations of IceCube-240424A
  58. LIGO/Virgo/KAGRA S240426s: Updated Sky localization
  59. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  60. LIGO/Virgo/KAGRA S240426dl: Updated Sky localization
  61. GRB 240429A: Fermi GBM Final Real-time Localization
  62. LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
  63. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  64. LIGO/Virgo/KAGRA S240429an: Retraction of GW compact binary merger candidate
  65. LIGO/Virgo/KAGRA S240422ed: ENGRAVE VLT/XShooter spectroscopy of the host galaxy of J-GEM24a
  66. LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
  67. Fermi GRB 240428A: Global MASTER-Net observations report
  68. GRB 240428A: Fermi GBM Final Real-time Localization
  69. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  70. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  71. EP240426b: AST3-2 optical upper limit
  72. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  73. LIGO/Virgo/KAGRA S240422ed: A transient discovered from Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  74. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  75. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  76. EP240426b: EP-WXT detection of a new fast X-ray transient
  77. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  78. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  79. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  80. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  81. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  82. GRB 240426A: AstroSat CZTI detection
  83. EP240426a: YAHPT optical upper limit
  84. XMM-Newton observation of EP240426a
  85. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  87. LIGO/Virgo/KAGRA S240422ed: EP-FXT Detection of the Potential Opitcal Electromagnetic Counterpart AT 2024hfq Reported by DECam
  88. GRB 240414A: NOEMA detection
  89. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  90. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  91. EP240426a: GMG optical upper limit
  92. LVK S240422ed: Further Swift-XRT followup of three sources
  93. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  94. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  96. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
  97. IceCube-240424A: Upper limits from a search for additional neutrino events in IceCube
  98. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search update and AT2024hfx, AT2024hgl observations
  99. S240422ed: BlackGEM/MeerLICHT transient detection AT2024hgl/MLTJ080628.10-250116.4
  100. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations

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