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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"

44433 results found.

  1. GRB 241001A: Swift-XRT observations
  2. EP trigger ID 01709064214: the X-ray transient is most likely a stellar flare event
  3. GRB 241002B: Fermi GBM Final Real-time Localization
  4. GRB241001A: optical afterglow candidate
  5. GRB 241002A: 1.5m OSN optical upper limit
  6. GRB 241002A: Enhanced Swift-XRT position
  7. GRB 241001A: BOOTES-6/DPRT optical upper limit
  8. LIGO/Virgo/KAGRA S241002e: Identification of a GW compact binary merger candidate
  9. GRB 241002A: Swift detection of a burst
  10. LIGO/Virgo/KAGRA S240930du: Updated Sky localization
  11. GRB 240930B: Fermi GBM Observation
  12. GRB 241001A: Swift ToO observations
  13. GRB 240930B: GRBAlpha detection
  14. GRB 240929A: GRBAlpha detection
  15. EP240930a : KAIT optical upper limit
  16. GRB 241001A : Detection of a soft transient by ECLAIRs onboard SVOM
  17. GRB 240930B: Swift/BAT-GUANO localization skymap of a burst
  18. EP240930a: EP-FXT follow-up observation update
  19. Fermi-LAT Gamma-ray Observations of IceCube-240929A
  20. EP240930a: GOTO optical upper limits
  21. GRB 240929A: SVOM/GRM observation
  22. EP EP240930a: Global MASTER-Net observations report
  23. EP240930a: EP-WXT detection of a fast X-ray transient
  24. SVOM/GRM detection of a burst from SGR Swift J1818.0-1607
  25. LIGO/Virgo/KAGRA S240930du: Identification of a GW compact binary merger candidate
  26. IceCube-240929A: Upper limits from a search for additional neutrino events in IceCube
  27. LIGO/Virgo/KAGRA S240930df: 1 counterpart neutrino candidate event from an IceCube neutrino search
  28. AMON NuEM 240926A: Swift XRT Follow-up
  29. GRB 240929A : Leavitt Observatory optical upper limit
  30. Fermi GRB 240930B: Global MASTER-Net observations report
  31. GRB 240930B: Fermi GBM Final Real-time Localization
  32. IPN triangulation of GRB 240926A
  33. GRB 240825A: LBT optical observations
  34. GRB 240928A: SVOM/GRM observation
  35. Fermi GRB 240930A: Global MASTER-Net observations report
  36. Fermi Gamma-ray Burst Monitor trigger 749362078/240930172 (GRB 240930A) is not a GRB
  37. LIGO/Virgo/KAGRA S240930aa: Identification of a GW compact binary merger candidate
  38. GRB 240930A: Fermi GBM Final Real-time Localization
  39. Fermi trigger No 749339671: Global MASTER-Net observations report
  40. Fermi Gamma-ray Burst Monitor trigger 749339671/240929913 is not a GRB
  41. GRB 240929A long GRB detected by INTEGRAL
  42. GRB 240929A: BALROG localization (Fermi Trigger 749332209 / GRB 240929826)
  43. Fermi GRB 240929A: Global MASTER-Net observations report
  44. GRB 240929A: Fermi GBM Final Real-time Localization
  45. Integral GRB240929.83: Global MASTER-Net observations report
  46. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  47. Konus-Wind detection of GRB 240912A
  48. Swift Trigger 1256950 is probably not a GRB
  49. Fermi Gamma-ray Burst Monitor trigger 749191601/240928199 is not a GRB
  50. LIGO/Virgo/KAGRA S240921cw: Upper limits from Swift/BAT-GUANO
  51. LIGO/Virgo/KAGRA S240920dw: Upper limits from Swift/BAT-GUANO
  52. LIGO/Virgo/KAGRA S240919bn: Upper limits from Swift/BAT-GUANO
  53. EP trigger ID 01709059262: Lick/Kast spectroscopy with 3 m Shane telescope
  54. NuEm-240926A / IC240926A: BZQJ0955+4532 ~0.6m optical decay and rebrightening detection by MASTER
  55. GRB 240926A: SVOM/GRM observation
  56. EP trigger ID 01709061302: the X-ray transient is likely a stellar flare event
  57. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-240926A
  58. Konus-Wind detection of GRB 240905B
  59. GRB 240529A: FRAM-ORM early optical afterglow observations reveal plateau and rebrightening
  60. GW S240915b and S240919bn : Swift UVOT follow-up
  61. EP240919a / GRB 240919A: SVOM/VT upper limit
  62. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  63. EP240918b and EP240918c: EP-FXT follow-up observations
  64. LIGO/Virgo/KAGRA S240925n: Updated Sky localization and Source Classification
  65. Insight-HXMT ToO observations of X-ray bursts from SGR 1E 1841-045 / Kes 73
  66. GRB 240716A: Swift/BAT-GUANO localization skymap of a long burst
  67. LIGO/Virgo/KAGRA S240925n: Identification of a GW compact binary merger candidate
  68. Konus-Wind detection of GRB 240918B
  69. IPN triangulation of GRB 240918B
  70. GRB 240905B: VZLUSAT-2 detection
  71. LIGO/Virgo/KAGRA S240922df: Updated Sky localization
  72. LIGO/Virgo/KAGRA S240920dw: Updated Sky localization
  73. LIGO/Virgo/KAGRA S240921cw: Updated Sky localization
  74. LIGO/Virgo/KAGRA S240924a: Updated Sky localization
  75. LIGO/Virgo/KAGRA S240920bz: Updated Sky localization and Source Classification
  76. LIGO/Virgo/KAGRA S240923ct: Updated Sky localization and Source Classification
  77. EP trigger ID 01709059262: the X-ray transient is likely a stellar flare event
  78. LIGO/Virgo/KAGRA S240924a: Identification of a GW compact binary merger candidate
  79. LIGO/Virgo/KAGRA S240923ct: Identification of a GW compact binary merger candidate
  80. LIGO/Virgo S240919bn: GOTO optical upper limits
  81. LIGO/Virgo S240919bn: Swift XRT observations, 10 X-ray sources
  82. GRB 240918B: AstroSat CZTI detection
  83. LIGO/Virgo/KAGRA S240922df: Identification of a GW compact binary merger candidate
  84. LIGO/Virgo/KAGRA S240921cw: Identification of a GW compact binary merger candidate
  85. EP240919a: EP-FXT follow-up observation update
  86. EP240913A/GRB 240913C: AbAO optical upper limit
  87. EP240919a / GRB 240919A: Mondy optical upper limit
  88. EP240913a/GRB 240913C: 1.6m Mephisto observations
  89. EP240918a: SVOM/VT upper limit
  90. Fermi GBM Sub-Threshold Detection of GRB240919A / EP240919a
  91. EP240919a / GRB 240919A: REM optical and NIR upper limits
  92. EP240919a / GRB 240919A: KAIT optical upper limit
  93. EP240918b and EP240918c: Optical upper limits with Kinder observations
  94. GRB 240414A: further radio observations with the VLA
  95. EP240919a: Optical upper limit with Kinder observations
  96. GRB 240919A / EP240919a: SVOM/GRM observation
  97. EP240919a: INTEGRAL SPI-ACS confirmation of reported high-energy counterpart
  98. EP240919a: INTEGRAL SPI-ACS confirmation of reported high-energy counterpart
  99. LIGO/Virgo/KAGRA S240920dw: Identification of a GW compact binary merger candidate
  100. EP EP240919a: Global MASTER-Net observations report

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