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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. Swift GRB 241213A: Global MASTER-Net observations report
  2. GRB 241213A: Swift detection of a burst
  3. GRB 241212A : SVOM/C-GFT optical upper limit at early phase
  4. GRB 241212A : SVOM/VT bright optical afterglow
  5. GRB 241212A: AstroSat CZTI detection
  6. GRB 241209B: GRANDMA/TRT upper limit
  7. GRB 241207A: TSHAO Zeiss-1000 optical observations
  8. GRB 241212A: SVOM detection of a bright long burst
  9. GRB 241212A: Fermi GBM Final Real-time Localization
  10. GRB 241209B: Mondy AZT-33IK and AbAO AS-32 optical observations
  11. GRB 241209A: Chandra X-ray Detection
  12. Konus-Wind detection of GRB 241209B
  13. GRB 241207A: EIRSAT-1 GMOD Detection
  14. GRB 241209A: Redshift of the likely host galaxy z = 0.784 from OSIRIS+/GTC
  15. GRB 241209B: GRBAlpha detection
  16. GRB 241206C: GRBAlpha detection
  17. LIGO/Virgo/KAGRA S241210cw: Updated Sky localization
  18. LIGO/Virgo/KAGRA S241210d: Updated Sky localization and EM Bright Classification
  19. GRB 241211A: Fermi GBM Final Real-time Localization
  20. GRB 241129A: Fermi GBM Observation
  21. GRB 241209B: Swift/BAT-GUANO localization skymap of a burst
  22. GRB 241209D: REM optical/NIR upper limits
  23. Konus-Wind detection of GRB 241209D
  24. GRB 241209B: Swift-XRT afterglow detection
  25. GRB 241209C: Fermi GBM Observation
  26. GRB 241209A: Swift-XRT refined Analysis
  27. Fermi Gamma-ray Burst Monitor trigger 755485387 / 241210044 is not a GRB
  28. LIGO/Virgo/KAGRA S241210fu: Identification of a GW compact binary merger candidate
  29. EP241208a: Optical upper limit with Kinder observations
  30. GRB 241128A: CrAO ZTSh and Mondy AZT-33IK optical observations
  31. GRB 241209D: AstroSat CZTI detection
  32. GRB 241209A: EP-FXT follow-up observations
  33. GRB 241209B: SVOM/VT afterglow detection
  34. LIGO/Virgo/KAGRA S241210cw: Identification of a GW compact binary merger candidate
  35. EP241208a: Global MASTER-Net observations report
  36. EP241208a: EP-FXT follow-up observations
  37. LIGO/Virgo/KAGRA S241210d: Identification of a GW compact binary merger candidate
  38. Fermi trigger No 755485387: Global MASTER-Net observations report
  39. GRB 241207B: Fermi GBM Observation
  40. GRB 241209A: BOOTES-7 and 2.2m CAHA early optical upper limits
  41. GRB 241209D: Swift-XRT refined Analysis
  42. GRB 241209D: Fermi GBM Observation
  43. GRB 241209A: VLT/HAWK-I near-IR counterpart candidate
  44. GRB 241209D: COLIBRÍ detection of the afterglow
  45. GRB 241209A: COLIBRÍ Optical Upper Limit
  46. Fermi GRB 241209D: Global MASTER-Net observations report
  47. GRB 241209A: Fermi GBM Observation
  48. GRB 241209C: Swift/BAT-GUANO localization skymap of a burst
  49. GRB 241209A: GRANDMA/TAROT upper limit
  50. GRB 241209B: BOOTES-5 optical upper limit
  51. Swift GRB 241209D: Global MASTER-Net observations report
  52. Fermi GRB 241209C: Global MASTER-Net observations report
  53. Fermi GRB 241209E: Global MASTER-Net observations report
  54. GRB 241209E: Fermi GBM Final Real-time Localization
  55. GRB 241209B: Swift ToO observations
  56. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  57. GRB 241209A: REM optical/NIR observations
  58. GRB 241209D: Enhanced Swift-XRT position
  59. GRB 241209C: AstroSat CZTI detection
  60. GRB 241209D: Swift detection of a burst
  61. GRB 241209D: Fermi GBM Final Real-time Localization
  62. GRB 241209A: VLT/X-shooter spectroscopy
  63. GRB 241209A: Enhanced Swift-XRT position
  64. GRB 241114B: cubesat Avion detection
  65. GRB 241209A: VLT optical observations
  66. Fermi GRB 241209A: Global MASTER-Net observations report
  67. GRB 241209C: Fermi GBM Final Real-time Localization
  68. GRB 241209A: GOTO optical upper limits
  69. EP241206a: 1.5m OSN optical limit
  70. GRB 241209A: Prompt enhanced Swift-XRT position
  71. GRB 241209B: SVOM/ECLAIRs and GRM detection of a long burst
  72. EP241208a: EP detection of a fast X-ray transient
  73. GRB 241209A: Swift detection of a short burst
  74. Swift GRB241209.23: Global MASTER-Net observations report
  75. GRB 241209A: Fermi GBM Final Real-time Localization
  76. Fermi GRB 241207B: Global MASTER-Net observations report
  77. GRB 241207B: Swift/BAT-GUANO localization skymap of a short burst
  78. Fermi Gamma-ray Burst Monitor trigger 755277791/241207641 is not a GRB
  79. GRB 241201A: AstroSat CZTI detection
  80. GRB 241206A: DDOTI Upper Limit on the Afterglow
  81. AT2024adec: X-ray Upper Limits from EP-FXT Observation
  82. AT2024adec: X-ray Upper Limits from EP-FXT Observation
  83. EP241206a: BOOTES Global Network optical limits
  84. GRB 241207C: MASTER optical observations
  85. Fermi trigger No 755225799: Global MASTER-Net observations report
  86. GRB 241207C: Tiled Swift observations
  87. GRB 241207C: MAXI/GSC detection
  88. GRB 241207B: Fermi GBM Final Real-time Localization
  89. Fermi trigger No 755277791: Global MASTER-Net observations report
  90. Fermi GRB 241207A: Global MASTER-Net observations report
  91. EP241206a: Global MASTER-Net observations report
  92. EP241206a: EP detection of a fast X-ray transient
  93. GRB 241206A: Fermi GBM observation
  94. GRB 241206C: SVOM/GRM observation of a likely short burst
  95. GRB 241207A: Fermi GBM Final Real-time Localization
  96. GRB 241206A: Swift/BAT-GUANO localization skymap of a burst
  97. GRB 241206B: SVOM/MXT observations: a probable flare from the QSO 1ES 1959+650
  98. GRB 241206B: GWAC-F50A optical upper limit
  99. GRB 241206B: SVOM/ECLAIRs detection of a long soft transient
  100. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift

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