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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 240910A: SVOM/VT optical observations
  2. GRB 240914A: Swift ToO observations
  3. EP240913a: NOT optical upper limits
  4. EP240913a: JinShan optical upper limits
  5. EP240913a: ESO-NTT optical observations
  6. GRB 240914A: ESO-NTT optical observations
  7. EP240913a: Swift/XRT detection of an X-ray source within the EP/WXT error circle
  8. GRB 240914B: BALROG localization (Fermi Trigger 747990592 / GRB 240914298)
  9. GRB 240914A : An intermediate duration GRB located on-board by SVOM/ECLAIRs.
  10. GRB 240905E: further NOT optical observations
  11. EP240913a: A GRB Event
  12. EP240913a: EP-WXT detection of a fast X-ray transient
  13. GRB 240913B: Fermi GBM Final Real-time Localization
  14. GRB 240911A: LCO optical observations
  15. GRB 240911A: JinShan optical upper limits on two Swift/XRT candidates
  16. Fermi Gamma-ray Burst Monitor trigger 747837485/240912526 is not a GRB
  17. GRB 240912A: Swift/UVOT Detection
  18. GRB 240911A: GOTO optical limits on Swift/XRT candidates
  19. Fermi trigger No 747920561: Global MASTER-Net observations report
  20. GRB 240912A: SVOM/GRM observation
  21. GRB 240911A: Swift-XRT observations
  22. Fermi GRB 240913A: Global MASTER-Net observations report
  23. GRB 240913A: Fermi GBM Final Real-time Localization
  24. GRB 240912A: J-band observations with WINTER
  25. GRB 240912A: Swift-XRT refined Analysis
  26. GRB 240912A: Fermi GBM Observation
  27. Swift GRB 240912A: Global MASTER-Net observations report
  28. GRB 240912A: LCOGT detection and Legacy Surveys likely host galaxy
  29. GRB 240911A: Tiled Swift observations
  30. Fermi Gamma-ray Burst Monitor trigger 747839931/240912555 is not a GRB
  31. GRB 240912A : INTEGRAL SPI ACS LIGHT CURVE
  32. GRB 240912B: Fermi GBM Final Real-time Localization
  33. GRB 240912A: NOT optical spectroscopy
  34. GRB 240912A: Enhanced Swift-XRT position
  35. GRB 240912A: Redshift from OSIRIS+/GTC
  36. Fast X-ray Transient EP240801a: GMRT radio observations
  37. GRB 240910A: Redshift from OSIRIS+/GTC
  38. GRB 240912A: Swift detection of a burst with an optical counterpart
  39. GRB 240912A: Fermi GBM Final Real-time Localization
  40. GRB 240910A: Fermi GBM Observation
  41. GRB 240910A: NOT optical observations
  42. GRB 240911A : a likely weak GRB detected by SVOM/ECLAIRs
  43. GRB 240910A: Swift-XRT detection of GOTO24fvl/AT2024vfp
  44. GRB 240910A: JinShan optical observations
  45. GRB 240910A: GOTO candidate optical counterpart
  46. EP240908a: Optical afterglow confirmation
  47. GRB 240710A: SVOM/GRM observation
  48. GRB 240910A: Swift ToO observations
  49. IPN triangulation of GRB 240905B (short)
  50. GRB 240825A: 7DT Optical Upper Limit
  51. GRB 240905E: SVOM/VT optical observations
  52. GRB 240905E: SVOM/VT optical observations (duplicate submission of GCN 37453)
  53. LIGO/Virgo/KAGRA S240910ci: NED Galaxies in the Localization Volume
  54. GRB 240910A: GRBAlpha detection
  55. GRB 240910B: Fermi GBM Final Real-time Localization
  56. LIGO/Virgo/KAGRA S240910ci: Coverage and upper limits from MAXI/GSC observations
  57. LIGO/Virgo/KAGRA S240910ci: Updated Sky localization and EM Bright Classification
  58. LIGO/Virgo/KAGRA S240910ci: Identification of a GW compact binary merger candidate
  59. GRB 240910A: SVOM/GRM observation
  60. EP240908a: Mondy and AbAO follow-up observations
  61. EP240908a: Updates on the WXT detection result around the trigger time
  62. Fermi GRB 240910A: Global MASTER-Net observations report
  63. GRB 240910A: Fermi GBM Final Real-time Localization
  64. LIGO/Virgo/KAGRA S240908bs: Upper limits from Swift/BAT-GUANO
  65. LIGO/Virgo/KAGRA S240907cg: Upper limits from Swift/BAT-GUANO
  66. EP240908a: optical afterglow candidate
  67. EP EP240908a: Global MASTER-Net observations report
  68. GRB 240905B: Fermi GBM Observation
  69. Fermi trigger No 747553301: Global MASTER-Net observations report
  70. EP240908a: TRT optical upper limit
  71. GRB 240905B: GOTO optical upper limits
  72. EP240908a: EP detection of a fast X-ray transient
  73. Fermi GRB 240908A: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S240908dg: Updated Sky localization
  75. LIGO/Virgo/KAGRA S240908bs: Updated Sky localization
  76. GRB 240908A: Fermi GBM Final Real-time Localization
  77. LIGO/Virgo/KAGRA S240908dg: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S240908bs: Identification of a GW compact binary merger candidate
  79. LIGO/Virgo/KAGRA S240907cg: Updated Sky localization
  80. GRB 240801A: SVOM/GRM observation
  81. LIGO/Virgo/KAGRA S240907cg: Identification of a GW compact binary merger candidate
  82. GRB 240905E: GIT optical upper limit
  83. GRB 240905B: Swift-XRT observations
  84. GRB 240905E: Gaoyazi/GOT optical upper limits
  85. GRB 240905E: NUTTelA-TAO / BSTI Optical Limits
  86. GRB 240905B: Fermi-LAT detection
  87. GRB 240905B: Swift ToO observations
  88. GRB 240905E: J-band observations with WINTER
  89. GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
  90. GRB 240905E: AKO Optical Upper Limit
  91. GRB 240905E: SVOM/C-GFT optical upper limit
  92. GRB 240905E: OHP/MISTRAL T193 optical upper limit
  93. Fermi GRB 240905D: Global MASTER-Net observations report
  94. Fermi GRB 240905A: Global MASTER-Net observations report
  95. GRB 240905E: NOT optical upper limits
  96. GRB 240905E: REM optical/NIR upper limits
  97. GRB 240902B: AstroSat CZTI detection of a long burst
  98. GRB 240905E: Swift-XRT refined Analysis
  99. GRB 240902A: AstroSat CZTI detection of a long burst
  100. GRB 240905E: SVOM/GRM observation

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