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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. EP241208a: NOT optical upper limits
  2. GRB 241212A: Swift ToO observations
  3. GRB 241213A: LCOGT Optical Upper Limits
  4. EP 241208A : Detection of a long soft transient by SVOM/ECLAIRs
  5. EP241213a/GRB241213a: Likely joint detection and INTEGRAL/SPI-ACS counterpart
  6. GRB 241213B: MAXI/GSC detection
  7. EP241213a: EP detection of An X-ray Transient
  8. GRB 241213A: REM optical/NIR upper limits
  9. GRB 241213A: Enhanced Swift-XRT position
  10. GRB241212A: OHP/T193 optical observations
  11. GRB 241213A: SAO RAS optical upper limit
  12. LIGO/Virgo/KAGRA S241210fu: Updated Sky localization
  13. Swift GRB 241213A: Global MASTER-Net observations report
  14. GRB 241213A: Swift detection of a burst
  15. GRB 241212A : SVOM/C-GFT optical upper limit at early phase
  16. GRB 241212A : SVOM/VT bright optical afterglow
  17. GRB 241212A: AstroSat CZTI detection
  18. GRB 241209B: GRANDMA/TRT upper limit
  19. GRB 241207A: TSHAO Zeiss-1000 optical observations
  20. GRB 241212A: SVOM detection of a bright long burst
  21. GRB 241212A: Fermi GBM Final Real-time Localization
  22. GRB 241209B: Mondy AZT-33IK and AbAO AS-32 optical observations
  23. GRB 241209A: Chandra X-ray Detection
  24. Konus-Wind detection of GRB 241209B
  25. GRB 241207A: EIRSAT-1 GMOD Detection
  26. GRB 241209A: Redshift of the likely host galaxy z = 0.784 from OSIRIS+/GTC
  27. GRB 241209B: GRBAlpha detection
  28. GRB 241206C: GRBAlpha detection
  29. LIGO/Virgo/KAGRA S241210cw: Updated Sky localization
  30. LIGO/Virgo/KAGRA S241210d: Updated Sky localization and EM Bright Classification
  31. GRB 241211A: Fermi GBM Final Real-time Localization
  32. GRB 241129A: Fermi GBM Observation
  33. GRB 241209B: Swift/BAT-GUANO localization skymap of a burst
  34. GRB 241209D: REM optical/NIR upper limits
  35. Konus-Wind detection of GRB 241209D
  36. GRB 241209B: Swift-XRT afterglow detection
  37. GRB 241209C: Fermi GBM Observation
  38. GRB 241209A: Swift-XRT refined Analysis
  39. Fermi Gamma-ray Burst Monitor trigger 755485387 / 241210044 is not a GRB
  40. LIGO/Virgo/KAGRA S241210fu: Identification of a GW compact binary merger candidate
  41. EP241208a: Optical upper limit with Kinder observations
  42. GRB 241128A: CrAO ZTSh and Mondy AZT-33IK optical observations
  43. GRB 241209D: AstroSat CZTI detection
  44. GRB 241209A: EP-FXT follow-up observations
  45. GRB 241209B: SVOM/VT afterglow detection
  46. LIGO/Virgo/KAGRA S241210cw: Identification of a GW compact binary merger candidate
  47. EP241208a: Global MASTER-Net observations report
  48. EP241208a: EP-FXT follow-up observations
  49. LIGO/Virgo/KAGRA S241210d: Identification of a GW compact binary merger candidate
  50. Fermi trigger No 755485387: Global MASTER-Net observations report
  51. GRB 241207B: Fermi GBM Observation
  52. GRB 241209A: BOOTES-7 and 2.2m CAHA early optical upper limits
  53. GRB 241209D: Swift-XRT refined Analysis
  54. GRB 241209D: Fermi GBM Observation
  55. GRB 241209A: VLT/HAWK-I near-IR counterpart candidate
  56. GRB 241209D: COLIBRÍ detection of the afterglow
  57. GRB 241209A: COLIBRÍ Optical Upper Limit
  58. Fermi GRB 241209D: Global MASTER-Net observations report
  59. GRB 241209A: Fermi GBM Observation
  60. GRB 241209C: Swift/BAT-GUANO localization skymap of a burst
  61. GRB 241209A: GRANDMA/TAROT upper limit
  62. GRB 241209B: BOOTES-5 optical upper limit
  63. Swift GRB 241209D: Global MASTER-Net observations report
  64. Fermi GRB 241209C: Global MASTER-Net observations report
  65. Fermi GRB 241209E: Global MASTER-Net observations report
  66. GRB 241209E: Fermi GBM Final Real-time Localization
  67. GRB 241209B: Swift ToO observations
  68. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  69. GRB 241209A: REM optical/NIR observations
  70. GRB 241209D: Enhanced Swift-XRT position
  71. GRB 241209C: AstroSat CZTI detection
  72. GRB 241209D: Swift detection of a burst
  73. GRB 241209D: Fermi GBM Final Real-time Localization
  74. GRB 241209A: VLT/X-shooter spectroscopy
  75. GRB 241209A: Enhanced Swift-XRT position
  76. GRB 241114B: cubesat Avion detection
  77. GRB 241209A: VLT optical observations
  78. Fermi GRB 241209A: Global MASTER-Net observations report
  79. GRB 241209C: Fermi GBM Final Real-time Localization
  80. GRB 241209A: GOTO optical upper limits
  81. EP241206a: 1.5m OSN optical limit
  82. GRB 241209A: Prompt enhanced Swift-XRT position
  83. GRB 241209B: SVOM/ECLAIRs and GRM detection of a long burst
  84. EP241208a: EP detection of a fast X-ray transient
  85. GRB 241209A: Swift detection of a short burst
  86. Swift GRB241209.23: Global MASTER-Net observations report
  87. GRB 241209A: Fermi GBM Final Real-time Localization
  88. Fermi GRB 241207B: Global MASTER-Net observations report
  89. GRB 241207B: Swift/BAT-GUANO localization skymap of a short burst
  90. Fermi Gamma-ray Burst Monitor trigger 755277791/241207641 is not a GRB
  91. GRB 241201A: AstroSat CZTI detection
  92. GRB 241206A: DDOTI Upper Limit on the Afterglow
  93. AT2024adec: X-ray Upper Limits from EP-FXT Observation
  94. AT2024adec: X-ray Upper Limits from EP-FXT Observation
  95. EP241206a: BOOTES Global Network optical limits
  96. GRB 241207C: MASTER optical observations
  97. Fermi trigger No 755225799: Global MASTER-Net observations report
  98. GRB 241207C: Tiled Swift observations
  99. GRB 241207C: MAXI/GSC detection
  100. GRB 241207B: Fermi GBM Final Real-time Localization

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