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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"

24615 results found.

  1. GRB 241030B: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.82
  2. GRB 241030B : MITSuME Akeno optical upper limits
  3. GRB 241030A: COLIBRI Continuing Detection of the Afterglow
  4. GRB 241030B: SVOM/VT optical afterglow observations
  5. GRB 241030B: COLIBRÍ Upper Limits on the Optical Counterpart
  6. EP241030a: EP detection of GRB 241030A X-ray Afterglow
  7. GRB241030B: Fermi GBM Observation
  8. GRB 241030B: BTA observations
  9. GRB 241029A: SVOM/VT optical afterglow observations
  10. GRB 241030A: detection of the bright optical counterpart in ATLAS forced photometry
  11. GRB 241030B: Enhanced Swift-XRT position
  12. GRB241030B: GRANDMA/TAROT Upper Limit
  13. GRB 241030A: Swift-XRT refined Analysis
  14. GRB 241030B: SAO RAS optical observations
  15. GRB 241030B: AKO Optical Afterglow Detection
  16. GRB 241030B: Nanshan/HMT optical afterglow detection
  17. GRB 241030B: Swift detection of a burst
  18. GRB 240912A: radio detection with the VLA
  19. GRB 241030A: AKO Optical Afterglow Detection
  20. GRB 241030A: Swift/UVOT Detection
  21. EP 241021a: further Swift-XRT observations and X-ray counterpart detection
  22. GRB 241026A: Swift-BAT refined analysis
  23. GRB 241030A: SVOM/C-GFT optical observations
  24. GRB 241026A: LBT optical observations
  25. EP241021a: Optical rebrightening observations with Mephisto
  26. GRB 241030A: Multiband optical detection with Mephisto
  27. GRB 241030A: SVOM/VT optical afterglow observations
  28. GRB 241030A : MITSuME Akeno optical afterglow detection
  29. GRB 241030A: Enhanced Swift-XRT position
  30. GRB 241029A: GROWTH-India Telescope optical follow up
  31. GRB 241030A: ULL-ASTRO-MASTER detection of a bright optical counterpart with the LCOGT 40-cm telescope at McDonald Observatory
  32. GRB 241030A: COLIBRÍ Detection of the Bright Optical Counterpart
  33. GRB 241030A: Swift detection of a burst with a bright optical counterpart
  34. GRB 241029A: SAO RAS optical observations
  35. GRB 241026A: SAO RAS optical observations
  36. EP241021a: SAO RAS observations of rebrightening
  37. GRB 241029A: GTC/OSIRIS+ spectroscopic redshift z=1.072
  38. MISTRAL@OHP photometric and spectroscopic observations of GRB 241029A
  39. GRB 241026A: Swift/UVOT Upper Limits
  40. GRB 241029A: Swift-XRT observations
  41. GRB 241029A: Fermi GBM Observation
  42. GRB 241029A: AKO Optical Afterglow Detection
  43. EP241021a: continued SOAR observations confirm optical rebrightening
  44. GRB 241029A: Xinglong-2.16m optical afterglow confirmation
  45. GRB 241029A: Mephisto observations
  46. EP 241026b: LBT possible optical counterpart (brightening source)
  47. GRB 241029A: TRT optical afterglow candidate detection
  48. GRB 241026A: TNOT optical counterpart detection
  49. GRB 241025A (EP241025a): Optical afterglow observations with the Tsinghua-Nanshan Optical Telescope
  50. GRB 241025A: further SAO RAS optical observations
  51. GRB 241026A: BTA and Zeiss-1000 optical observations
  52. GRB 241026A: SVOM/GRM observation
  53. EP241026B: GROWTH-India Telescope optical upper limit
  54. GRB 241025A: Swift/UVOT Detection
  55. GRB 241026A: GROWTH-India Telescope optical observations
  56. GRB 241026A Fermi GBM Analysis
  57. GRB 241026A: J-band observations with WINTER
  58. GRB 241025A: SAO RAS optical observations
  59. GRB 241026A: Las Cumbres optical detection
  60. GRB 241025A: Mondy optical observations
  61. EP241021a: SOAR observations of the optical counterpart
  62. EP241021a: further SAO RAS optical observations
  63. GRB 241026A: Swift-XRT refined Analysis
  64. EP 241026b: LBT optical observations
  65. GRB 241026A: Enhanced Swift-XRT position
  66. EP241026b: EP detection of a fast X-ray transient
  67. GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
  68. GRB 241026A: SAO RAS observations of possible optical afterglow
  69. GRB 241026A: Swift detection of a burst
  70. GRB241025A: 1.3m DFOT optical afterglow detection
  71. EP241021a: optical follow-up observations with Xinglong Observatory
  72. GRB 241025A: GROWTH-India Telescope optical observations
  73. GRB 241025A: COLIBRÍ Detection of the Afterglow
  74. GRB 241025A: Swift-XRT refined Analysis
  75. GRB 241025C: Fermi GBM Detection
  76. GRB 241025A: Fermi GBM Observation
  77. IPN triangulation of GRB 241022A (short/hard)
  78. LIGO/Virgo/KAGRA S241009l: Upper limits from Swift/BAT-GUANO
  79. EP 241021a: Swift-XRT observations
  80. GRB 241025A : SVOM/VT optical afterglow observations
  81. EP241021a: Liverpool Telescope optical follow-up observations
  82. GRB 241025A: Enhanced Swift-XRT position
  83. GRB 241025A: DDOTI Afterglow detection
  84. GRB 241025A: TRT optical afterglow observation
  85. GRB 241025A: Swift detection of a burst with an optical counterpart
  86. EP241021a: GTC OSIRIS+ spectroscopy of the optical counterpart
  87. GRB 241001A: ATCA radio observations
  88. GRB 241010A: VIRT Optical Upper Limit
  89. EP241021a: SAO RAS optical observations
  90. EP241021a: KAIT optical observations
  91. EP241021a: 1.3m DFOT Optical observations
  92. EP241021a: GSP detects optical candidate counterpart
  93. EP241021a: Optical upper limits with Kinder observations
  94. EP241021a: TRT optical observations
  95. GRB 241018A: SVOM/C-GFT optical observations
  96. EP241021a: NOT likely optical counterpart
  97. EP EP241021a: Global MASTER-Net observations report
  98. GRB241017A: 1.3m DFOT optical upper limit
  99. GRB 241018A: 1.3m DFOT Optical upper limit
  100. EP241021a: GOTO optical upper limits

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