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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').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

36784 results found.

  1. GRB 241004A: SVOM/GRM observation
  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. GRB 241002C: Swift ToO observations
  18. Fermi-GBM Sub-Threshold Detection of GRB 241002D
  19. IPN triangulation of GRB 240930B / EP 240930a
  20. GRB 241001A : SVOM/VT optical detection
  21. GRB 241002B: GOTO24gpc/AT 2024xbg follow-up observations update
  22. GRB 241002D: SVOM/GRM observation
  23. GRB 241002B: ULL-ASTRO-MASTER LCOGT 0.4m + QHY600 detection of the GOTO optical counterpart candidate AT 2024xbg / GOTO24gpc
  24. GRB 240930B: CALET Gamma-Ray Burst Monitor detection
  25. GRB 241002C: X-ray afterglow candidate observed by SVOM/MXT
  26. GRB 240929A: SAO RAS, Mondy, and CrAO optical observations
  27. GRB 241002C : MITSuME Akeno optical upper limits
  28. GRB241001A: REM optical/NIR upper limits
  29. GRB 241002A: Swift/UVOT Upper Limits
  30. EP240930a: Liverpool Telescope observations
  31. GRB 241002A: Swift-XRT refined Analysis
  32. GRB 241002A: LCOGT Optical Upper Limits
  33. GRB 241001A: GRANDMA and Kilonova-Catcher optical afterglow detection and upper limits
  34. GRB 241001A: Swift/UVOT Detection
  35. GRB 241001A: VLT/X-shooter redshift
  36. GRB 241002B: GOTO optical counterpart candidate
  37. GRB 241002C : Detection of a long soft transient by SVOM/ECLAIRs
  38. GRB 241001A: correction to GCN 37667
  39. GRB 240929A: Liverpool Telescope prompt followup observations
  40. Fermi GRB 241002B: Global MASTER-Net observations report
  41. GRB 241001A: Swift-XRT observations
  42. GRB 241002B: Fermi GBM Final Real-time Localization
  43. GRB241001A: optical afterglow candidate
  44. GRB 241002A: 1.5m OSN optical upper limit
  45. GRB 241002A: Enhanced Swift-XRT position
  46. GRB 241001A: BOOTES-6/DPRT optical upper limit
  47. GRB 241002A: Swift detection of a burst
  48. GRB 240930B: Fermi GBM Observation
  49. GRB 241001A: Swift ToO observations
  50. GRB 240930B: GRBAlpha detection
  51. GRB 240929A: GRBAlpha detection
  52. EP240930a : KAIT optical upper limit
  53. GRB 241001A : Detection of a soft transient by ECLAIRs onboard SVOM
  54. GRB 240930B: Swift/BAT-GUANO localization skymap of a burst
  55. EP240930a: EP-FXT follow-up observation update
  56. Fermi-LAT Gamma-ray Observations of IceCube-240929A
  57. EP240930a: GOTO optical upper limits
  58. GRB 240929A: SVOM/GRM observation
  59. EP240930a: EP-WXT detection of a fast X-ray transient
  60. GRB 240929A : Leavitt Observatory optical upper limit
  61. Fermi GRB 240930B: Global MASTER-Net observations report
  62. GRB 240930B: Fermi GBM Final Real-time Localization
  63. IPN triangulation of GRB 240926A
  64. GRB 240825A: LBT optical observations
  65. GRB 240928A: SVOM/GRM observation
  66. Fermi GRB 240930A: Global MASTER-Net observations report
  67. Fermi Gamma-ray Burst Monitor trigger 749362078/240930172 (GRB 240930A) is not a GRB
  68. GRB 240930A: Fermi GBM Final Real-time Localization
  69. Fermi trigger No 749339671: Global MASTER-Net observations report
  70. Fermi Gamma-ray Burst Monitor trigger 749339671/240929913 is not a GRB
  71. GRB 240929A long GRB detected by INTEGRAL
  72. GRB 240929A: BALROG localization (Fermi Trigger 749332209 / GRB 240929826)
  73. Fermi GRB 240929A: Global MASTER-Net observations report
  74. GRB 240929A: Fermi GBM Final Real-time Localization
  75. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  76. Konus-Wind detection of GRB 240912A
  77. Swift Trigger 1256950 is probably not a GRB
  78. Fermi Gamma-ray Burst Monitor trigger 749191601/240928199 is not a GRB
  79. LIGO/Virgo/KAGRA S240921cw: Upper limits from Swift/BAT-GUANO
  80. LIGO/Virgo/KAGRA S240920dw: Upper limits from Swift/BAT-GUANO
  81. LIGO/Virgo/KAGRA S240919bn: Upper limits from Swift/BAT-GUANO
  82. EP trigger ID 01709059262: Lick/Kast spectroscopy with 3 m Shane telescope
  83. GRB 240926A: SVOM/GRM observation
  84. Konus-Wind detection of GRB 240905B
  85. GRB 240529A: FRAM-ORM early optical afterglow observations reveal plateau and rebrightening
  86. EP240919a / GRB 240919A: SVOM/VT upper limit
  87. Insight-HXMT ToO observations of X-ray bursts from SGR 1E 1841-045 / Kes 73
  88. GRB 240716A: Swift/BAT-GUANO localization skymap of a long burst
  89. Konus-Wind detection of GRB 240918B
  90. IPN triangulation of GRB 240918B
  91. GRB 240905B: VZLUSAT-2 detection
  92. GRB 240918B: AstroSat CZTI detection
  93. EP240913A/GRB 240913C: AbAO optical upper limit
  94. EP240919a / GRB 240919A: Mondy optical upper limit
  95. EP240913a/GRB 240913C: 1.6m Mephisto observations
  96. Fermi GBM Sub-Threshold Detection of GRB240919A / EP240919a
  97. EP240919a / GRB 240919A: REM optical and NIR upper limits
  98. EP240919a / GRB 240919A: KAIT optical upper limit
  99. GRB 240414A: further radio observations with the VLA
  100. GRB 240919A / EP240919a: SVOM/GRM observation

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