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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 240929A: SVOM/GRM observation
  2. EP EP240930a: Global MASTER-Net observations report
  3. EP240930a: EP-WXT detection of a fast X-ray transient
  4. SVOM/GRM detection of a burst from SGR Swift J1818.0-1607
  5. LIGO/Virgo/KAGRA S240930du: Identification of a GW compact binary merger candidate
  6. IceCube-240929A: Upper limits from a search for additional neutrino events in IceCube
  7. LIGO/Virgo/KAGRA S240930df: 1 counterpart neutrino candidate event from an IceCube neutrino search
  8. AMON NuEM 240926A: Swift XRT Follow-up
  9. GRB 240929A : Leavitt Observatory optical upper limit
  10. Fermi GRB 240930B: Global MASTER-Net observations report
  11. GRB 240930B: Fermi GBM Final Real-time Localization
  12. IPN triangulation of GRB 240926A
  13. GRB 240825A: LBT optical observations
  14. GRB 240928A: SVOM/GRM observation
  15. Fermi GRB 240930A: Global MASTER-Net observations report
  16. Fermi Gamma-ray Burst Monitor trigger 749362078/240930172 (GRB 240930A) is not a GRB
  17. LIGO/Virgo/KAGRA S240930aa: Identification of a GW compact binary merger candidate
  18. GRB 240930A: Fermi GBM Final Real-time Localization
  19. Fermi trigger No 749339671: Global MASTER-Net observations report
  20. Fermi Gamma-ray Burst Monitor trigger 749339671/240929913 is not a GRB
  21. GRB 240929A long GRB detected by INTEGRAL
  22. GRB 240929A: BALROG localization (Fermi Trigger 749332209 / GRB 240929826)
  23. Fermi GRB 240929A: Global MASTER-Net observations report
  24. GRB 240929A: Fermi GBM Final Real-time Localization
  25. Integral GRB240929.83: Global MASTER-Net observations report
  26. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  27. Konus-Wind detection of GRB 240912A
  28. Swift Trigger 1256950 is probably not a GRB
  29. Fermi Gamma-ray Burst Monitor trigger 749191601/240928199 is not a GRB
  30. LIGO/Virgo/KAGRA S240921cw: Upper limits from Swift/BAT-GUANO
  31. LIGO/Virgo/KAGRA S240920dw: Upper limits from Swift/BAT-GUANO
  32. LIGO/Virgo/KAGRA S240919bn: Upper limits from Swift/BAT-GUANO
  33. EP trigger ID 01709059262: Lick/Kast spectroscopy with 3 m Shane telescope
  34. NuEm-240926A / IC240926A: BZQJ0955+4532 ~0.6m optical decay and rebrightening detection by MASTER
  35. GRB 240926A: SVOM/GRM observation
  36. EP trigger ID 01709061302: the X-ray transient is likely a stellar flare event
  37. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-240926A
  38. Konus-Wind detection of GRB 240905B
  39. GRB 240529A: FRAM-ORM early optical afterglow observations reveal plateau and rebrightening
  40. GW S240915b and S240919bn : Swift UVOT follow-up
  41. EP240919a / GRB 240919A: SVOM/VT upper limit
  42. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  43. EP240918b and EP240918c: EP-FXT follow-up observations
  44. LIGO/Virgo/KAGRA S240925n: Updated Sky localization and Source Classification
  45. Insight-HXMT ToO observations of X-ray bursts from SGR 1E 1841-045 / Kes 73
  46. GRB 240716A: Swift/BAT-GUANO localization skymap of a long burst
  47. LIGO/Virgo/KAGRA S240925n: Identification of a GW compact binary merger candidate
  48. Konus-Wind detection of GRB 240918B
  49. IPN triangulation of GRB 240918B
  50. GRB 240905B: VZLUSAT-2 detection
  51. LIGO/Virgo/KAGRA S240922df: Updated Sky localization
  52. LIGO/Virgo/KAGRA S240920dw: Updated Sky localization
  53. LIGO/Virgo/KAGRA S240921cw: Updated Sky localization
  54. LIGO/Virgo/KAGRA S240924a: Updated Sky localization
  55. LIGO/Virgo/KAGRA S240920bz: Updated Sky localization and Source Classification
  56. LIGO/Virgo/KAGRA S240923ct: Updated Sky localization and Source Classification
  57. EP trigger ID 01709059262: correction to the observation start time and source localization
  58. EP trigger ID 01709059262: the X-ray transient is likely a stellar flare event
  59. LIGO/Virgo/KAGRA S240924a: Identification of a GW compact binary merger candidate
  60. LIGO/Virgo/KAGRA S240923ct: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo S240919bn: GOTO optical upper limits
  62. LIGO/Virgo S240919bn: Swift XRT observations, 10 X-ray sources
  63. GRB 240918B: AstroSat CZTI detection
  64. LIGO/Virgo/KAGRA S240922df: Identification of a GW compact binary merger candidate
  65. LIGO/Virgo/KAGRA S240921cw: Identification of a GW compact binary merger candidate
  66. EP240919a: EP-FXT follow-up observation update
  67. EP240913A/GRB 240913C: AbAO optical upper limit
  68. EP240919a / GRB 240919A: Mondy optical upper limit
  69. EP240913a/GRB 240913C: 1.6m Mephisto observations
  70. EP240918a: SVOM/VT upper limit
  71. Fermi GBM Sub-Threshold Detection of GRB240919A / EP240919a
  72. EP240919a / GRB 240919A: REM optical and NIR upper limits
  73. EP240919a / GRB 240919A: KAIT optical upper limit
  74. EP240918b and EP240918c: Optical upper limits with Kinder observations
  75. GRB 240414A: further radio observations with the VLA
  76. EP240919a: Optical upper limit with Kinder observations
  77. GRB 240919A / EP240919a: SVOM/GRM observation
  78. EP240919a: INTEGRAL SPI-ACS confirmation of reported high-energy counterpart
  79. EP240919a: INTEGRAL SPI-ACS confirmation of reported high-energy counterpart
  80. LIGO/Virgo/KAGRA S240920dw: Identification of a GW compact binary merger candidate
  81. EP EP240919a: Global MASTER-Net observations report
  82. GRB 240910A: radio detection with the VLA
  83. EP240918a: 1.6m Mephisto multi-band Optical Upper Limit
  84. EP240919a: NOT and Gemini optical observations
  85. EP240919a: GOTO optical upper limits
  86. EP240919a: JinShan optical upper limits
  87. EP240919a is likely a GRB event (duplicate submission of 37563)
  88. EP240919a is likely a GRB event
  89. LIGO/Virgo/KAGRA S240920bz: Identification of a GW compact binary merger candidate
  90. EP240919a: EP-WXT detection of a fast X-ray transient
  91. GRB 240918A and GRB 240918B : INTEGRAL SPI ACS LIGHT CURVE
  92. LIGO/Virgo/KAGRA S240919bn: Updated Sky localization
  93. GRB 240918B: Fermi GBM Detection
  94. LIGO/Virgo/KAGRA S240917cb: Updated Sky localization and EM Bright Classification
  95. LIGO/Virgo/KAGRA S240916ar: Updated Sky localization and EM Bright Classification
  96. EP240918b and EP240918c: EP-WXT detection of two fast X-ray transients
  97. EP240918a: EP observation update
  98. GRB 240910A: further Swift observations and confirmation of afterglow
  99. LIGO/Virgo/KAGRA S240919bn: Identification of a GW compact binary merger candidate
  100. EP240918a: Swift-XRT observation

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