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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. GRB 240414A: AKO Optical Upper Limit
  2. X-ray transient EP 240414a - GTC spectroscopic observations
  3. GRB 240415A: Prompt Swift-XRT observations
  4. GRB 240415A: Swift detection of a burst
  5. GRB 240415A: Fermi GBM Final Real-time Localization
  6. EP240413a: Upper limits from GECAM-B Observation
  7. EP 240414a: NOT optical counterpart confirmation
  8. GRB 240414A: Swift-XRT refined Analysis
  9. GRB240414A : J-band upper limits from WINTER
  10. GRB 240414A: Enhanced Swift-XRT position
  11. GRB 240414A : OHP/T193 second epoch of optical follow-up and afterglow detection
  12. GRB 240414A: MarSEC Observatory, Vicenza, Italy, UPPER LIMIT
  13. LIGO/Virgo/KAGRA S240413p: No Counterparts in DDOTI/OAN Optical Observations
  14. EP240413A: GOTO optical upper limits
  15. GRB 240414A: Skynet Optical Afterglow Observations
  16. Fermi trigger No 734754044: Global MASTER-Net observations report
  17. Swift GRB 240414A: Global MASTER-Net observations report
  18. EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3
  19. IPN triangulation of GRB 240410A
  20. EP240413a: possible detection of the X-ray emission with EP-FXT after 14 hours
  21. EP240414a: EP-WXT detection of a fast X-ray transient
  22. IPN triangulation of GRB 240411A
  23. Fermi-LAT gamma-ray observations of IceCube-240412A
  24. GRB 240414A : MITSuME Akeno optical upper limits
  25. GRB 240414A: Redshift confirmation from GTC/OSIRIS+
  26. EP240413a: EP-WXT detection of a fast X-ray transient
  27. GRB 240414A : OHP/T193 redshift determination
  28. GRB 240414A : OHP/T193 optical counterpart detection
  29. GRB 240414A: Swift detection of a burst
  30. LIGO/Virgo/KAGRA S240413p: Updated Sky localization
  31. LIGO/Virgo/KAGRA S240413p: Global MASTER-Net observations report
  32. LIGO/Virgo/KAGRA S240413p: Zwicky Transient Facility observations
  33. EP240408a: GSP optical upper limit
  34. GRB 240411B: CrAO/ZTSh optical observations
  35. GRB 240411B: Kinder observations with Lulin observatory
  36. LIGO/Virgo/Kagra S240413p: NED Galaxies in the Localization Volume
  37. LIGO/Virgo/KAGRA S240413p: Identification of a GW compact binary merger candidate
  38. GRB 240411B: HiPERCAM/GTC observation
  39. IceCube Alert 240412.23: Global MASTER-Net observations report
  40. GRB 240411B: Swift-BAT refined analysis
  41. GRB 240411B: Swift-XRT refined Analysis
  42. IceCube-240412A - IceCube observation of a high-energy neutrino candidate track-like event
  43. GRB 240411B: 1.3m DFOT Optical observations
  44. GRB 240411A: GRBAlpha detection
  45. GRB 240411B: OHP/T193 optical observations
  46. GRB 240405A: Glowbug gamma-ray detection
  47. GRB 240411B: Enhanced Swift-XRT position
  48. GRB 240411B: LCO optical afterglow detection
  49. GRB 240411B: Swift detection of a burst
  50. GRB 240408B: GRBAlpha detection
  51. GRB 240411A: Fermi GBM Final Real-time Localization
  52. EP240408A: MASTER optical observations
  53. EP240408a: GROND detection of a candidate counterpart
  54. EP240408a: Upper limits from GECAM-B Observation
  55. EP240408a: Swift follow-up observation
  56. EP240408a: BOOTES-6/DPRT optical upper limit
  57. X-ray transient EP240315a: second epoch e-MERLIN radio observations
  58. GRB 240405A: GRBAlpha detection
  59. EP240408a: EP-WXT detection of a fast X-ray transient
  60. Swift Trigger 1220736: detection of 4U 1543-62.
  61. GRB 240408B: AstroSat CZTI detection
  62. IceCube-240327B: GRANDMA/Kilonova-Catcher observations of 4FGL J0555.9+0030 and optical upper limits
  63. Fermi GRB 240408A: Global MASTER-Net observations report
  64. GRB 240408A: Fermi GBM Final Real-time Localization
  65. GRB 240407A: BALROG localization (Fermi Trigger 734144396 / GRB 240407042)
  66. GRB 240402C: CALET Gamma-Ray Burst Monitor detection
  67. Fermi GRB 240407A: Global MASTER-Net observations report
  68. GRB 240407A: Fermi GBM Final Real-time Localization
  69. Fermi-LAT gamma-ray observations of IceCube-240327B
  70. Fermi-LAT gamma-ray observations of IceCube-240327A
  71. LXT 240402A/GRB 240402B: rest-frame energetics from Konus-Wind observation
  72. Fermi GRB 240405B: Global MASTER-Net observations report
  73. GRB 240405B: Fermi GBM Final Real-time Localization
  74. GRB 240402C: Glowbug gamma-ray detection
  75. GRB 240405A: Fermi GBM Final Real-time Localization
  76. GRB 240402C: GRBAlpha detection
  77. GRB 240331A: GRBAlpha detection
  78. LXT 240402A/GRB 240402B: GECAM-C refined analysis
  79. Swift satellite resumes pointed science observations
  80. GRB 240403B: Glowbug gamma-ray detection
  81. GRB 240403A: Glowbug gamma-ray detection
  82. LXT 240402A/GRB 240402B: Glowbug gamma-ray detection
  83. X-ray transient LXT 240402A: WFST optical upper limits​
  84. Konus-Wind detection of LXT 240402A/GRB 240402B
  85. GRB/FXT 240402B: Kinder optical counterpart candidate
  86. IceCube-240327B: GRANDMA observations of 4FGL J0555.9+0030
  87. GRB/FXT 240402B: VLT/FORS2 optical afterglow candidate
  88. GRB 240403A: Fermi GBM Detection
  89. X-ray transient LXT240402A: AST3-3 optical upper limits
  90. LXT 240402A: EP-FXT detection of the X-ray afterglow
  91. Fermi GRB 240404A: Global MASTER-Net observations report
  92. GRB 240404A: Fermi GBM Final Real-time Localization
  93. LXT 240402A: MASTER optical observations with AGN in error-box
  94. GRB 240402B: GWAC-F50A optical upper limit
  95. GRB 240402B: GECAM-C detection
  96. X-ray transient LXT 240402A: LEIA detection
  97. GRB 240403A: BALROG localization (Fermi Trigger 733838255 / GRB 240403498)
  98. Fermi trigger No 733808041: Global MASTER-Net observations report
  99. Fermi GRB 240402A: Global MASTER-Net observations report
  100. GRB 240402A: Fermi GBM Final Real-time Localization

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