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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. EP trigger ID 01709064214: GOTO confirms detection as a flare star
  2. GRB 241002C : Detection of a long soft transient by SVOM/ECLAIRs
  3. GRB 241001A: correction to GCN 37667
  4. GRB 240929A: Liverpool Telescope prompt followup observations
  5. Fermi GRB 241002B: Global MASTER-Net observations report
  6. GRB 241001A: Swift-XRT observations
  7. EP trigger ID 01709064214: the X-ray transient is most likely a stellar flare event
  8. GRB 241002B: Fermi GBM Final Real-time Localization
  9. GRB241001A: optical afterglow candidate
  10. GRB 241002A: 1.5m OSN optical upper limit
  11. GRB 241002A: Enhanced Swift-XRT position
  12. GRB 241001A: BOOTES-6/DPRT optical upper limit
  13. LIGO/Virgo/KAGRA S241002e: Identification of a GW compact binary merger candidate
  14. GRB 241002A: Swift detection of a burst
  15. LIGO/Virgo/KAGRA S240930du: Updated Sky localization
  16. GRB 240930B: Fermi GBM Observation
  17. GRB 241001A: Swift ToO observations
  18. GRB 240930B: GRBAlpha detection
  19. GRB 240929A: GRBAlpha detection
  20. EP240930a : KAIT optical upper limit
  21. GRB 241001A : Detection of a soft transient by ECLAIRs onboard SVOM
  22. GRB 240930B: Swift/BAT-GUANO localization skymap of a burst
  23. EP240930a: EP-FXT follow-up observation update
  24. Fermi-LAT Gamma-ray Observations of IceCube-240929A
  25. EP240930a: GOTO optical upper limits
  26. GRB 240929A: SVOM/GRM observation
  27. EP EP240930a: Global MASTER-Net observations report
  28. EP240930a: EP-WXT detection of a fast X-ray transient
  29. SVOM/GRM detection of a burst from SGR Swift J1818.0-1607
  30. LIGO/Virgo/KAGRA S240930du: Identification of a GW compact binary merger candidate
  31. IceCube-240929A: Upper limits from a search for additional neutrino events in IceCube
  32. LIGO/Virgo/KAGRA S240930df: 1 counterpart neutrino candidate event from an IceCube neutrino search
  33. AMON NuEM 240926A: Swift XRT Follow-up
  34. GRB 240929A : Leavitt Observatory optical upper limit
  35. Fermi GRB 240930B: Global MASTER-Net observations report
  36. GRB 240930B: Fermi GBM Final Real-time Localization
  37. IPN triangulation of GRB 240926A
  38. GRB 240825A: LBT optical observations
  39. GRB 240928A: SVOM/GRM observation
  40. Fermi GRB 240930A: Global MASTER-Net observations report
  41. Fermi Gamma-ray Burst Monitor trigger 749362078/240930172 (GRB 240930A) is not a GRB
  42. LIGO/Virgo/KAGRA S240930aa: Identification of a GW compact binary merger candidate
  43. GRB 240930A: Fermi GBM Final Real-time Localization
  44. Fermi trigger No 749339671: Global MASTER-Net observations report
  45. Fermi Gamma-ray Burst Monitor trigger 749339671/240929913 is not a GRB
  46. GRB 240929A long GRB detected by INTEGRAL
  47. GRB 240929A: BALROG localization (Fermi Trigger 749332209 / GRB 240929826)
  48. Fermi GRB 240929A: Global MASTER-Net observations report
  49. GRB 240929A: Fermi GBM Final Real-time Localization
  50. Integral GRB240929.83: Global MASTER-Net observations report
  51. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  52. Konus-Wind detection of GRB 240912A
  53. Swift Trigger 1256950 is probably not a GRB
  54. Fermi Gamma-ray Burst Monitor trigger 749191601/240928199 is not a GRB
  55. LIGO/Virgo/KAGRA S240921cw: Upper limits from Swift/BAT-GUANO
  56. LIGO/Virgo/KAGRA S240920dw: Upper limits from Swift/BAT-GUANO
  57. LIGO/Virgo/KAGRA S240919bn: Upper limits from Swift/BAT-GUANO
  58. EP trigger ID 01709059262: Lick/Kast spectroscopy with 3 m Shane telescope
  59. NuEm-240926A / IC240926A: BZQJ0955+4532 ~0.6m optical decay and rebrightening detection by MASTER
  60. GRB 240926A: SVOM/GRM observation
  61. EP trigger ID 01709061302: the X-ray transient is likely a stellar flare event
  62. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-240926A
  63. Konus-Wind detection of GRB 240905B
  64. GRB 240529A: FRAM-ORM early optical afterglow observations reveal plateau and rebrightening
  65. GW S240915b and S240919bn : Swift UVOT follow-up
  66. EP240919a / GRB 240919A: SVOM/VT upper limit
  67. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  68. EP240918b and EP240918c: EP-FXT follow-up observations
  69. LIGO/Virgo/KAGRA S240925n: Updated Sky localization and Source Classification
  70. Insight-HXMT ToO observations of X-ray bursts from SGR 1E 1841-045 / Kes 73
  71. GRB 240716A: Swift/BAT-GUANO localization skymap of a long burst
  72. LIGO/Virgo/KAGRA S240925n: Identification of a GW compact binary merger candidate
  73. Konus-Wind detection of GRB 240918B
  74. IPN triangulation of GRB 240918B
  75. GRB 240905B: VZLUSAT-2 detection
  76. LIGO/Virgo/KAGRA S240922df: Updated Sky localization
  77. LIGO/Virgo/KAGRA S240920dw: Updated Sky localization
  78. LIGO/Virgo/KAGRA S240921cw: Updated Sky localization
  79. LIGO/Virgo/KAGRA S240924a: Updated Sky localization
  80. LIGO/Virgo/KAGRA S240920bz: Updated Sky localization and Source Classification
  81. LIGO/Virgo/KAGRA S240923ct: Updated Sky localization and Source Classification
  82. EP trigger ID 01709059262: correction to the observation start time and source localization
  83. EP trigger ID 01709059262: the X-ray transient is likely a stellar flare event
  84. LIGO/Virgo/KAGRA S240924a: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo/KAGRA S240923ct: Identification of a GW compact binary merger candidate
  86. LIGO/Virgo S240919bn: GOTO optical upper limits
  87. LIGO/Virgo S240919bn: Swift XRT observations, 10 X-ray sources
  88. GRB 240918B: AstroSat CZTI detection
  89. LIGO/Virgo/KAGRA S240922df: Identification of a GW compact binary merger candidate
  90. LIGO/Virgo/KAGRA S240921cw: Identification of a GW compact binary merger candidate
  91. EP240919a: EP-FXT follow-up observation update
  92. EP240913A/GRB 240913C: AbAO optical upper limit
  93. EP240919a / GRB 240919A: Mondy optical upper limit
  94. EP240913a/GRB 240913C: 1.6m Mephisto observations
  95. EP240918a: SVOM/VT upper limit
  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. EP240918b and EP240918c: Optical upper limits with Kinder observations
  100. GRB 240414A: further radio observations with the VLA

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