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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. EP trigger ID 01709065118: the X-ray transient is likely a stellar flare event
  2. GRB 240930B / EP 240930a: SVOM/GRM observation
  3. GRB 241001A : ECLAIRs spectral analysis and XRF classification
  4. GRB 241002B: PRIME near-infrared detection in 2nd epoch
  5. GRB 241002B: Fermi GBM Observation
  6. Fermi trigger No 749735279: Global MASTER-Net observations report
  7. Fermi trigger No 749630753: Global MASTER-Net observations report
  8. Fermi trigger No 749693019: Global MASTER-Net observations report
  9. GRB 241002B: Swift-XRT observations
  10. GRB 241002C: SVOM/C-GFT optical upper limit
  11. GRB 241002A: Swift-BAT refined analysis
  12. GRB 241002B: Swift/BAT-GUANO localization skymap of a burst
  13. GRB 241002B: Swift ToO observations
  14. GRB 241002C: Swift-XRT observations confirm the source to be EI Eri
  15. Konus-Wind detection of GRB 240926A
  16. GRB 241002B: PRIME near-infrared detection
  17. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  18. GRB 241002C: Swift ToO observations
  19. Fermi-GBM Sub-Threshold Detection of GRB 241002D
  20. IPN triangulation of GRB 240930B / EP 240930a
  21. GRB 241001A : SVOM/VT optical detection
  22. GRB 241002B: GOTO24gpc/AT 2024xbg follow-up observations update
  23. GRB 241002D: SVOM/GRM observation
  24. GRB 241002B: ULL-ASTRO-MASTER LCOGT 0.4m + QHY600 detection of the GOTO optical counterpart candidate AT 2024xbg / GOTO24gpc
  25. GRB 240930B: CALET Gamma-Ray Burst Monitor detection
  26. GRB 241002C: X-ray afterglow candidate observed by SVOM/MXT
  27. GRB 240929A: SAO RAS, Mondy, and CrAO optical observations
  28. GRB 241002C : MITSuME Akeno optical upper limits
  29. LIGO/Virgo/KAGRA S240925n: Updated Sky localization
  30. NuEm-240926A: Upper limits from a search for coincident neutrino events in IceCube
  31. GRB241001A: REM optical/NIR upper limits
  32. LIGO/Virgo/KAGRA S241002e: Updated Sky localization
  33. GRB 241002A: Swift/UVOT Upper Limits
  34. EP240930a: Liverpool Telescope observations
  35. GRB 241002A: Swift-XRT refined Analysis
  36. GRB 241002A: LCOGT Optical Upper Limits
  37. GRB 241001A: GRANDMA and Kilonova-Catcher optical afterglow detection and upper limits
  38. GRB 241001A: Swift/UVOT Detection
  39. GRB 241001A: VLT/X-shooter redshift
  40. GRB 241002B: GOTO optical counterpart candidate
  41. EP trigger ID 01709064214: GOTO confirms detection as a flare star
  42. GRB 241002C : Detection of a long soft transient by SVOM/ECLAIRs
  43. GRB 241001A: correction to GCN 37667
  44. GRB 240929A: Liverpool Telescope prompt followup observations
  45. Fermi GRB 241002B: Global MASTER-Net observations report
  46. GRB 241001A: Swift-XRT observations
  47. EP trigger ID 01709064214: the X-ray transient is most likely a stellar flare event
  48. GRB 241002B: Fermi GBM Final Real-time Localization
  49. GRB241001A: optical afterglow candidate
  50. GRB 241002A: 1.5m OSN optical upper limit
  51. GRB 241002A: Enhanced Swift-XRT position
  52. GRB 241001A: BOOTES-6/DPRT optical upper limit
  53. LIGO/Virgo/KAGRA S241002e: Identification of a GW compact binary merger candidate
  54. GRB 241002A: Swift detection of a burst
  55. LIGO/Virgo/KAGRA S240930du: Updated Sky localization
  56. GRB 240930B: Fermi GBM Observation
  57. GRB 241001A: Swift ToO observations
  58. GRB 240930B: GRBAlpha detection
  59. GRB 240929A: GRBAlpha detection
  60. EP240930a : KAIT optical upper limit
  61. GRB 241001A : Detection of a soft transient by ECLAIRs onboard SVOM
  62. GRB 240930B: Swift/BAT-GUANO localization skymap of a burst
  63. EP240930a: EP-FXT follow-up observation update
  64. Fermi-LAT Gamma-ray Observations of IceCube-240929A
  65. EP240930a: GOTO optical upper limits
  66. GRB 240929A: SVOM/GRM observation
  67. EP EP240930a: Global MASTER-Net observations report
  68. EP240930a: EP-WXT detection of a fast X-ray transient
  69. SVOM/GRM detection of a burst from SGR Swift J1818.0-1607
  70. LIGO/Virgo/KAGRA S240930du: Identification of a GW compact binary merger candidate
  71. IceCube-240929A: Upper limits from a search for additional neutrino events in IceCube
  72. LIGO/Virgo/KAGRA S240930df: 1 counterpart neutrino candidate event from an IceCube neutrino search
  73. AMON NuEM 240926A: Swift XRT Follow-up
  74. GRB 240929A : Leavitt Observatory optical upper limit
  75. Fermi GRB 240930B: Global MASTER-Net observations report
  76. GRB 240930B: Fermi GBM Final Real-time Localization
  77. IPN triangulation of GRB 240926A
  78. GRB 240825A: LBT optical observations
  79. GRB 240928A: SVOM/GRM observation
  80. Fermi GRB 240930A: Global MASTER-Net observations report
  81. Fermi Gamma-ray Burst Monitor trigger 749362078/240930172 (GRB 240930A) is not a GRB
  82. LIGO/Virgo/KAGRA S240930aa: Identification of a GW compact binary merger candidate
  83. GRB 240930A: Fermi GBM Final Real-time Localization
  84. Fermi trigger No 749339671: Global MASTER-Net observations report
  85. Fermi Gamma-ray Burst Monitor trigger 749339671/240929913 is not a GRB
  86. GRB 240929A long GRB detected by INTEGRAL
  87. GRB 240929A: BALROG localization (Fermi Trigger 749332209 / GRB 240929826)
  88. Fermi GRB 240929A: Global MASTER-Net observations report
  89. GRB 240929A: Fermi GBM Final Real-time Localization
  90. Integral GRB240929.83: Global MASTER-Net observations report
  91. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  92. Konus-Wind detection of GRB 240912A
  93. Swift Trigger 1256950 is probably not a GRB
  94. Fermi Gamma-ray Burst Monitor trigger 749191601/240928199 is not a GRB
  95. LIGO/Virgo/KAGRA S240921cw: Upper limits from Swift/BAT-GUANO
  96. LIGO/Virgo/KAGRA S240920dw: Upper limits from Swift/BAT-GUANO
  97. LIGO/Virgo/KAGRA S240919bn: Upper limits from Swift/BAT-GUANO
  98. EP trigger ID 01709059262: Lick/Kast spectroscopy with 3 m Shane telescope
  99. NuEm-240926A / IC240926A: BZQJ0955+4532 ~0.6m optical decay and rebrightening detection by MASTER
  100. GRB 240926A: SVOM/GRM observation

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