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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 241209B: GRANDMA/TRT upper limit
  2. GRB 241207A: TSHAO Zeiss-1000 optical observations
  3. GRB 241212A: SVOM detection of a bright long burst
  4. GRB 241212A: Fermi GBM Final Real-time Localization
  5. GRB 241209B: Mondy AZT-33IK and AbAO AS-32 optical observations
  6. GRB 241209A: Chandra X-ray Detection
  7. Konus-Wind detection of GRB 241209B
  8. GRB 241207A: EIRSAT-1 GMOD Detection
  9. GRB 241209A: Redshift of the likely host galaxy z = 0.784 from OSIRIS+/GTC
  10. GRB 241209B: GRBAlpha detection
  11. GRB 241206C: GRBAlpha detection
  12. LIGO/Virgo/KAGRA S241210cw: Updated Sky localization
  13. LIGO/Virgo/KAGRA S241210d: Updated Sky localization and EM Bright Classification
  14. GRB 241211A: Fermi GBM Final Real-time Localization
  15. GRB 241129A: Fermi GBM Observation
  16. GRB 241209B: Swift/BAT-GUANO localization skymap of a burst
  17. GRB 241209D: REM optical/NIR upper limits
  18. Konus-Wind detection of GRB 241209D
  19. GRB 241209B: Swift-XRT afterglow detection
  20. GRB 241209C: Fermi GBM Observation
  21. GRB 241209A: Swift-XRT refined Analysis
  22. Fermi Gamma-ray Burst Monitor trigger 755485387 / 241210044 is not a GRB
  23. LIGO/Virgo/KAGRA S241210fu: Identification of a GW compact binary merger candidate
  24. EP241208a: Optical upper limit with Kinder observations
  25. GRB 241128A: CrAO ZTSh and Mondy AZT-33IK optical observations
  26. GRB 241209D: AstroSat CZTI detection
  27. GRB 241209A: EP-FXT follow-up observations
  28. GRB 241209B: SVOM/VT afterglow detection
  29. LIGO/Virgo/KAGRA S241210cw: Identification of a GW compact binary merger candidate
  30. EP241208a: Global MASTER-Net observations report
  31. EP241208a: EP-FXT follow-up observations
  32. LIGO/Virgo/KAGRA S241210d: Identification of a GW compact binary merger candidate
  33. Fermi trigger No 755485387: Global MASTER-Net observations report
  34. GRB 241207B: Fermi GBM Observation
  35. GRB 241209A: BOOTES-7 and 2.2m CAHA early optical upper limits
  36. GRB 241209D: Swift-XRT refined Analysis
  37. GRB 241209D: Fermi GBM Observation
  38. GRB 241209A: VLT/HAWK-I near-IR counterpart candidate
  39. GRB 241209D: COLIBRÍ detection of the afterglow
  40. GRB 241209A: COLIBRÍ Optical Upper Limit
  41. Fermi GRB 241209D: Global MASTER-Net observations report
  42. GRB 241209A: Fermi GBM Observation
  43. GRB 241209C: Swift/BAT-GUANO localization skymap of a burst
  44. GRB 241209A: GRANDMA/TAROT upper limit
  45. GRB 241209B: BOOTES-5 optical upper limit
  46. Swift GRB 241209D: Global MASTER-Net observations report
  47. Fermi GRB 241209C: Global MASTER-Net observations report
  48. Fermi GRB 241209E: Global MASTER-Net observations report
  49. GRB 241209E: Fermi GBM Final Real-time Localization
  50. GRB 241209B: Swift ToO observations
  51. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  52. GRB 241209A: REM optical/NIR observations
  53. GRB 241209D: Enhanced Swift-XRT position
  54. GRB 241209C: AstroSat CZTI detection
  55. GRB 241209D: Swift detection of a burst
  56. GRB 241209D: Fermi GBM Final Real-time Localization
  57. GRB 241209A: VLT/X-shooter spectroscopy
  58. GRB 241209A: Enhanced Swift-XRT position
  59. GRB 241114B: cubesat Avion detection
  60. GRB 241209A: VLT optical observations
  61. Fermi GRB 241209A: Global MASTER-Net observations report
  62. GRB 241209C: Fermi GBM Final Real-time Localization
  63. GRB 241209A: GOTO optical upper limits
  64. EP241206a: 1.5m OSN optical limit
  65. GRB 241209A: Prompt enhanced Swift-XRT position
  66. GRB 241209B: SVOM/ECLAIRs and GRM detection of a long burst
  67. EP241208a: EP detection of a fast X-ray transient
  68. GRB 241209A: Swift detection of a short burst
  69. Swift GRB241209.23: Global MASTER-Net observations report
  70. GRB 241209A: Fermi GBM Final Real-time Localization
  71. Fermi GRB 241207B: Global MASTER-Net observations report
  72. GRB 241207B: Swift/BAT-GUANO localization skymap of a short burst
  73. Fermi Gamma-ray Burst Monitor trigger 755277791/241207641 is not a GRB
  74. GRB 241201A: AstroSat CZTI detection
  75. GRB 241206A: DDOTI Upper Limit on the Afterglow
  76. AT2024adec: X-ray Upper Limits from EP-FXT Observation
  77. AT2024adec: X-ray Upper Limits from EP-FXT Observation
  78. EP241206a: BOOTES Global Network optical limits
  79. GRB 241207C: MASTER optical observations
  80. Fermi trigger No 755225799: Global MASTER-Net observations report
  81. GRB 241207C: Tiled Swift observations
  82. GRB 241207C: MAXI/GSC detection
  83. GRB 241207B: Fermi GBM Final Real-time Localization
  84. Fermi trigger No 755277791: Global MASTER-Net observations report
  85. Fermi GRB 241207A: Global MASTER-Net observations report
  86. EP241206a: Global MASTER-Net observations report
  87. EP241206a: EP detection of a fast X-ray transient
  88. GRB 241206A: Fermi GBM observation
  89. GRB 241206C: SVOM/GRM observation of a likely short burst
  90. GRB 241207A: Fermi GBM Final Real-time Localization
  91. GRB 241206A: Swift/BAT-GUANO localization skymap of a burst
  92. GRB 241206B: SVOM/MXT observations: a probable flare from the QSO 1ES 1959+650
  93. GRB 241206B: GWAC-F50A optical upper limit
  94. GRB 241206B: SVOM/ECLAIRs detection of a long soft transient
  95. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift
  96. Fermi GRB 241206A: Global MASTER-Net observations report
  97. GRB 241206A: Fermi GBM Final Real-time Localization
  98. EP241201a: 1.6m Mephisto Optical Upper Limits
  99. GRB 241204A: COLIBRÍ Optical Upper Limit
  100. EP241202b: KAIT optical upper limit

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