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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 240727A Bassano Bresciano Observatory upper limit
  2. GRB 240727D: Correction to the GRB name in GCN 36958
  3. GRB 240727A: Fermi GBM Final Real-time Localization
  4. GRB 240727C: AstroSat CZTI detection of a long burst
  5. GRB 240727A: Swift-XRT refined Analysis
  6. GRB 240720B: GRBAlpha detection
  7. GRB 240718A: GRBAlpha detection
  8. GRB 240710B: GRBAlpha detection
  9. GRB 240627A: GRBAlpha detection
  10. Fermi GRB 240726A: Global MASTER-Net observations report
  11. GRB 240727A: Enhanced Swift-XRT position
  12. GRB 240727B: Fermi GBM Observation
  13. Swift GRB240727.16: Global MASTER-Net observations report
  14. GRB240529A: VIRT optical transient detection
  15. GRB 240727B: Swift ToO observations
  16. GRB 240727B: Swift/BAT-GUANO arcminute localization of a long burst
  17. GRB 240726A: SVOM/GRM observation
  18. GRB 240727B: AstroSat CZTI detection
  19. GRB 240726B: AstroSat CZTI detection of a short burst
  20. GRB240727A: Skynet Optical Afterglow Observations
  21. GRB 240727A: TRT optical afterglow detection
  22. GRB 240727A: KAIT Optical Afterglow Candidate
  23. GRB 240727A: Swift detection of a burst
  24. GRB 240726A: AstroSat CZTI detection of a short burst
  25. IceCube-240725A: Upper limits from a search for additional neutrino events in IceCube
  26. GRB 240726A: Fermi GBM Final Real-time Localization
  27. Fermi-LAT gamma-ray observations of IceCube-240725A
  28. IceCube Alert 240725.22: Global MASTER-Net observations report
  29. IceCube-240725A - IceCube observation of a high-energy neutrino candidate track-like event
  30. Swift Trigger 1244778 is not a GRB
  31. Swift GRB240725.11: Global MASTER-Net observations report
  32. IceCube-240721A: Two candidates from the Zwicky Transient Facility
  33. GRB 240720A: Swift-BAT refined analysis
  34. IceCube-240721A: Upper limits from a search for additional neutrino events in IceCube
  35. Fermi trigger No 743418632: Global MASTER-Net observations report
  36. Fermi trigger No 743315411: Global MASTER-Net observations report
  37. LIGO/Virgo/KAGRA S240716b: Upper limits from Swift/BAT-GUANO
  38. LIGO/Virgo/KAGRA S240703ad: Upper limits from Swift/BAT-GUANO
  39. Fermi trigger No 743345551: Global MASTER-Net observations report
  40. Fermi-LAT gamma-ray observations of IceCube-240721A
  41. Fermi Gamma-ray Burst Monitor trigger 743271526/240721680 is not a GRB
  42. Fermi trigger No 743219692: Global MASTER-Net observations report
  43. IceCube-240721A - IceCube observation of a high-energy neutrino candidate track-like event
  44. IceCube Alert 240721.68: Global MASTER-Net observations report
  45. Fermi Gamma-ray Burst Monitor trigger 743243582/240721356 (GRB 240721A) is not a GRB
  46. GRB 240720B: SVOM/GRM observation
  47. GRB 240721A: Fermi GBM Final Real-time Localization
  48. GRB 240720B: AstroSat CZTI detection of a short burst
  49. Fermi GRB 240720A: Global MASTER-Net observations report
  50. GRB 240720A: AstroSat CZTI detection
  51. GRB 240720A: Fermi GBM observation
  52. GRB 240720A: Swift detection of a burst
  53. Swift GRB240720.02: Global MASTER-Net observations report
  54. Konus-Wind detection of GRB 240718A
  55. GRB 240713A: SVOM/GRM observation
  56. Fermi GRB 240718A: Global MASTER-Net observations report
  57. LAT GRB240718.27: Global MASTER-Net observations report
  58. GRB 240718A: Fermi GBM Observation
  59. IceCube-Cascade 240714A: TRT optical observations on the EP/FXT positions
  60. GRB 240718A: Fermi-LAT Detection
  61. GRB 240718A: SVOM/GRM observation
  62. GRB 240718A: BALROG localization (Fermi Trigger 742976945 / GRB 240718270)
  63. GRB 240718A: Fermi GBM Final Real-time Localization
  64. GRB 240712A: Swift-BAT refined analysis
  65. GRB 240716A: GECAM-B detection of a long burst
  66. SVOM/GRM In-Flight Trigger of GRB 240716A
  67. IceCube-Cascade 240714A: X-ray follow-up observation with EP-FXT
  68. GRB 240713A: 2.2m CAHA optical limit
  69. Fermi-LAT gamma-ray observations of IceCube-cascade-240714A
  70. GRB 240715A: Swift/UVOT observations of the XRT sources.
  71. GRB 240715A: Swift-XRT observations
  72. GRB240713A: Swift/UVOT Upper LImits
  73. EP240708a: X-ray follow-up observations with Swift/XRT
  74. GRB 240715A: GECAM-C detection of a short burst
  75. Konus-Wind detection of GRB 240715A
  76. LIGO/Virgo/KAGRA S240716b: Updated Sky localization
  77. GRB 240713A: Swift-XRT observations
  78. GRB 240715A: TRT optical upper limit on one Swift/XRT candidate
  79. GRB 240712A: Swift-XRT refined Analysis
  80. SVOM/GRM In-Flight Trigger of GRB 240715A
  81. GRB 240713A: LAST optical upper limit
  82. LIGO/Virgo/KAGRA S240716b: Identification of a GW compact binary merger candidate
  83. GRB 240715A: Swift ToO observations
  84. Fermi GRB 240715A: Global MASTER-Net observations report
  85. GRB 240713A: optical upper limits from the INAF Asiago Observatory
  86. GRB 240715A: Fermi GBM Observation
  87. GRB 240712A ATCA radio observations
  88. GRB240715A: GRANDMA Optical Upper Limits
  89. IPN triangulation of GRB 240715A (short)
  90. GW s240422ed: Swift UVOT follow-up
  91. GRB 240712A: Swift/UVOT Upper Limits
  92. EP-WXT flaring star and the optical flaring activity during its decay phase
  93. JinShan confirmation of the EP-WXT source triggered on July 14th due to a flaring star
  94. The EP-WXT source triggered on July 14th is likely a flaring star
  95. GRB 240715A: Fermi GBM Final Real-time Localization
  96. GRB 240713A: Tiled Swift observations
  97. GRB 240713A: J-band upper limit from WINTER
  98. GRB 240713A: NOT optical upper limits on three EP/FXT candidates
  99. GRB 240713A: JinShan optical upper limits
  100. GRB 240713A: OHP/T120 optical upper limit

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