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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 240913C: Fermi GBM detection
  2. GRB 240914A: Swift-XRT observations
  3. GRB 240913C: Joint location by ETJASMIN
  4. GRB 240914B: AstroSat CZTI detection
  5. EP240913A / GRB 240913C: AstroSat CZTI detection
  6. GRB 240914A: SVOM/GRM observation
  7. GRB 240910A: SVOM/VT optical observations
  8. GRB 240914A: Swift ToO observations
  9. EP240913a: NOT optical upper limits
  10. EP240913a: JinShan optical upper limits
  11. EP240913a: ESO-NTT optical observations
  12. GRB 240914A: ESO-NTT optical observations
  13. EP240913a: Swift/XRT detection of an X-ray source within the EP/WXT error circle
  14. GRB 240914B: BALROG localization (Fermi Trigger 747990592 / GRB 240914298)
  15. GRB 240914A : An intermediate duration GRB located on-board by SVOM/ECLAIRs.
  16. GRB 240905E: further NOT optical observations
  17. EP240913a: A GRB Event
  18. EP240913a: EP-WXT detection of a fast X-ray transient
  19. GRB 240913B: Fermi GBM Final Real-time Localization
  20. GRB 240911A: LCO optical observations
  21. GRB 240911A: JinShan optical upper limits on two Swift/XRT candidates
  22. Fermi Gamma-ray Burst Monitor trigger 747837485/240912526 is not a GRB
  23. GRB 240912A: Swift/UVOT Detection
  24. GRB 240911A: GOTO optical limits on Swift/XRT candidates
  25. Fermi trigger No 747920561: Global MASTER-Net observations report
  26. GRB 240912A: SVOM/GRM observation
  27. GRB 240911A: Swift-XRT observations
  28. Fermi GRB 240913A: Global MASTER-Net observations report
  29. GRB 240913A: Fermi GBM Final Real-time Localization
  30. GRB 240912A: J-band observations with WINTER
  31. GRB 240912A: Swift-XRT refined Analysis
  32. GRB 240912A: Fermi GBM Observation
  33. Swift GRB 240912A: Global MASTER-Net observations report
  34. GRB 240912A: LCOGT detection and Legacy Surveys likely host galaxy
  35. GRB 240911A: Tiled Swift observations
  36. Fermi Gamma-ray Burst Monitor trigger 747839931/240912555 is not a GRB
  37. GRB 240912A : INTEGRAL SPI ACS LIGHT CURVE
  38. GRB 240912B: Fermi GBM Final Real-time Localization
  39. GRB 240912A: NOT optical spectroscopy
  40. GRB 240912A: Enhanced Swift-XRT position
  41. GRB 240912A: Redshift from OSIRIS+/GTC
  42. Fast X-ray Transient EP240801a: GMRT radio observations
  43. GRB 240910A: Redshift from OSIRIS+/GTC
  44. GRB 240912A: Swift detection of a burst with an optical counterpart
  45. GRB 240912A: Fermi GBM Final Real-time Localization
  46. GRB 240910A: Fermi GBM Observation
  47. GRB 240910A: NOT optical observations
  48. GRB 240911A : a likely weak GRB detected by SVOM/ECLAIRs
  49. GRB 240910A: Swift-XRT detection of GOTO24fvl/AT2024vfp
  50. GRB 240910A: JinShan optical observations
  51. GRB 240910A: GOTO candidate optical counterpart
  52. EP240908a: Optical afterglow confirmation
  53. GRB 240710A: SVOM/GRM observation
  54. GRB 240910A: Swift ToO observations
  55. IPN triangulation of GRB 240905B (short)
  56. GRB 240825A: 7DT Optical Upper Limit
  57. GRB 240905E: SVOM/VT optical observations
  58. GRB 240905E: SVOM/VT optical observations (duplicate submission of GCN 37453)
  59. LIGO/Virgo/KAGRA S240910ci: NED Galaxies in the Localization Volume
  60. GRB 240910A: GRBAlpha detection
  61. GRB 240910B: Fermi GBM Final Real-time Localization
  62. LIGO/Virgo/KAGRA S240910ci: Coverage and upper limits from MAXI/GSC observations
  63. LIGO/Virgo/KAGRA S240910ci: Updated Sky localization and EM Bright Classification
  64. LIGO/Virgo/KAGRA S240910ci: Identification of a GW compact binary merger candidate
  65. GRB 240910A: SVOM/GRM observation
  66. EP240908a: Mondy and AbAO follow-up observations
  67. EP240908a: Updates on the WXT detection result around the trigger time
  68. Fermi GRB 240910A: Global MASTER-Net observations report
  69. GRB 240910A: Fermi GBM Final Real-time Localization
  70. LIGO/Virgo/KAGRA S240908bs: Upper limits from Swift/BAT-GUANO
  71. LIGO/Virgo/KAGRA S240907cg: Upper limits from Swift/BAT-GUANO
  72. EP240908a: optical afterglow candidate
  73. EP EP240908a: Global MASTER-Net observations report
  74. GRB 240905B: Fermi GBM Observation
  75. Fermi trigger No 747553301: Global MASTER-Net observations report
  76. EP240908a: TRT optical upper limit
  77. GRB 240905B: GOTO optical upper limits
  78. EP240908a: EP detection of a fast X-ray transient
  79. Fermi GRB 240908A: Global MASTER-Net observations report
  80. LIGO/Virgo/KAGRA S240908dg: Updated Sky localization
  81. LIGO/Virgo/KAGRA S240908bs: Updated Sky localization
  82. GRB 240908A: Fermi GBM Final Real-time Localization
  83. LIGO/Virgo/KAGRA S240908dg: Identification of a GW compact binary merger candidate
  84. LIGO/Virgo/KAGRA S240908bs: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo/KAGRA S240907cg: Updated Sky localization
  86. GRB 240801A: SVOM/GRM observation
  87. LIGO/Virgo/KAGRA S240907cg: Identification of a GW compact binary merger candidate
  88. GRB 240905E: GIT optical upper limit
  89. GRB 240905B: Swift-XRT observations
  90. GRB 240905E: Gaoyazi/GOT optical upper limits
  91. GRB 240905E: NUTTelA-TAO / BSTI Optical Limits
  92. GRB 240905B: Fermi-LAT detection
  93. GRB 240905B: Swift ToO observations
  94. GRB 240905E: J-band observations with WINTER
  95. GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
  96. GRB 240905E: AKO Optical Upper Limit
  97. GRB 240905E: SVOM/C-GFT optical upper limit
  98. GRB 240905E: OHP/MISTRAL T193 optical upper limit
  99. Fermi GRB 240905D: Global MASTER-Net observations report
  100. Fermi GRB 240905A: Global MASTER-Net observations report

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