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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"
  1. GRB 241002B: Fermi GBM Observation
  2. Fermi trigger No 749735279: Global MASTER-Net observations report
  3. Fermi trigger No 749630753: Global MASTER-Net observations report
  4. Fermi trigger No 749693019: Global MASTER-Net observations report
  5. GRB 241002B: Swift-XRT observations
  6. GRB 241002C: SVOM/C-GFT optical upper limit
  7. GRB 241002A: Swift-BAT refined analysis
  8. GRB 241002B: Swift/BAT-GUANO localization skymap of a burst
  9. GRB 241002B: Swift ToO observations
  10. GRB 241002C: Swift-XRT observations confirm the source to be EI Eri
  11. Konus-Wind detection of GRB 240926A
  12. GRB 241002B: PRIME near-infrared detection
  13. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  14. GRB 241002C: Swift ToO observations
  15. Fermi-GBM Sub-Threshold Detection of GRB 241002D
  16. IPN triangulation of GRB 240930B / EP 240930a
  17. GRB 241001A : SVOM/VT optical detection
  18. GRB 241002B: GOTO24gpc/AT 2024xbg follow-up observations update
  19. GRB 241002D: SVOM/GRM observation
  20. GRB 241002B: ULL-ASTRO-MASTER LCOGT 0.4m + QHY600 detection of the GOTO optical counterpart candidate AT 2024xbg / GOTO24gpc
  21. GRB 240930B: CALET Gamma-Ray Burst Monitor detection
  22. GRB 241002C: X-ray afterglow candidate observed by SVOM/MXT
  23. GRB 240929A: SAO RAS, Mondy, and CrAO optical observations
  24. GRB 241002C : MITSuME Akeno optical upper limits
  25. LIGO/Virgo/KAGRA S240925n: Updated Sky localization
  26. NuEm-240926A: Upper limits from a search for coincident neutrino events in IceCube
  27. GRB241001A: REM optical/NIR upper limits
  28. LIGO/Virgo/KAGRA S241002e: Updated Sky localization
  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. EP trigger ID 01709064214: GOTO confirms detection as a flare star
  38. GRB 241002C : Detection of a long soft transient by SVOM/ECLAIRs
  39. GRB 241001A: correction to GCN 37667
  40. GRB 240929A: Liverpool Telescope prompt followup observations
  41. Fermi GRB 241002B: Global MASTER-Net observations report
  42. GRB 241001A: Swift-XRT observations
  43. EP trigger ID 01709064214: the X-ray transient is most likely a stellar flare event
  44. GRB 241002B: Fermi GBM Final Real-time Localization
  45. GRB241001A: optical afterglow candidate
  46. GRB 241002A: 1.5m OSN optical upper limit
  47. GRB 241002A: Enhanced Swift-XRT position
  48. GRB 241001A: BOOTES-6/DPRT optical upper limit
  49. LIGO/Virgo/KAGRA S241002e: Identification of a GW compact binary merger candidate
  50. GRB 241002A: Swift detection of a burst
  51. LIGO/Virgo/KAGRA S240930du: Updated Sky localization
  52. GRB 240930B: Fermi GBM Observation
  53. GRB 241001A: Swift ToO observations
  54. GRB 240930B: GRBAlpha detection
  55. GRB 240929A: GRBAlpha detection
  56. EP240930a : KAIT optical upper limit
  57. GRB 241001A : Detection of a soft transient by ECLAIRs onboard SVOM
  58. GRB 240930B: Swift/BAT-GUANO localization skymap of a burst
  59. EP240930a: EP-FXT follow-up observation update
  60. Fermi-LAT Gamma-ray Observations of IceCube-240929A
  61. EP240930a: GOTO optical upper limits
  62. GRB 240929A: SVOM/GRM observation
  63. EP EP240930a: Global MASTER-Net observations report
  64. EP240930a: EP-WXT detection of a fast X-ray transient
  65. SVOM/GRM detection of a burst from SGR Swift J1818.0-1607
  66. LIGO/Virgo/KAGRA S240930du: Identification of a GW compact binary merger candidate
  67. IceCube-240929A: Upper limits from a search for additional neutrino events in IceCube
  68. LIGO/Virgo/KAGRA S240930df: 1 counterpart neutrino candidate event from an IceCube neutrino search
  69. AMON NuEM 240926A: Swift XRT Follow-up
  70. GRB 240929A : Leavitt Observatory optical upper limit
  71. Fermi GRB 240930B: Global MASTER-Net observations report
  72. GRB 240930B: Fermi GBM Final Real-time Localization
  73. IPN triangulation of GRB 240926A
  74. GRB 240825A: LBT optical observations
  75. GRB 240928A: SVOM/GRM observation
  76. Fermi GRB 240930A: Global MASTER-Net observations report
  77. Fermi Gamma-ray Burst Monitor trigger 749362078/240930172 (GRB 240930A) is not a GRB
  78. LIGO/Virgo/KAGRA S240930aa: Identification of a GW compact binary merger candidate
  79. GRB 240930A: Fermi GBM Final Real-time Localization
  80. Fermi trigger No 749339671: Global MASTER-Net observations report
  81. Fermi Gamma-ray Burst Monitor trigger 749339671/240929913 is not a GRB
  82. GRB 240929A long GRB detected by INTEGRAL
  83. GRB 240929A: BALROG localization (Fermi Trigger 749332209 / GRB 240929826)
  84. Fermi GRB 240929A: Global MASTER-Net observations report
  85. GRB 240929A: Fermi GBM Final Real-time Localization
  86. Integral GRB240929.83: Global MASTER-Net observations report
  87. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  88. Konus-Wind detection of GRB 240912A
  89. Swift Trigger 1256950 is probably not a GRB
  90. Fermi Gamma-ray Burst Monitor trigger 749191601/240928199 is not a GRB
  91. LIGO/Virgo/KAGRA S240921cw: Upper limits from Swift/BAT-GUANO
  92. LIGO/Virgo/KAGRA S240920dw: Upper limits from Swift/BAT-GUANO
  93. LIGO/Virgo/KAGRA S240919bn: Upper limits from Swift/BAT-GUANO
  94. EP trigger ID 01709059262: Lick/Kast spectroscopy with 3 m Shane telescope
  95. NuEm-240926A / IC240926A: BZQJ0955+4532 ~0.6m optical decay and rebrightening detection by MASTER
  96. GRB 240926A: SVOM/GRM observation
  97. EP trigger ID 01709061302: the X-ray transient is likely a stellar flare event
  98. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-240926A
  99. Konus-Wind detection of GRB 240905B
  100. GRB 240529A: FRAM-ORM early optical afterglow observations reveal plateau and rebrightening

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