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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"

80 results found.

  1. Fermi GRB 260212A: Global MASTER-Net observations report
  2. GRB 250818B: MeerKAT Detection
  3. EP250812a: NOT, NTT, and GS observations
  4. GRB 250520A: Gemini-South optical afterglow detection
  5. GRB 250520A: Gemini-South optical observations
  6. EP250508a: Gemini NIR upper limits
  7. GRB 250322A: Gemini-South optical observations
  8. GRB 250210A: AstroSat CZTI detection
  9. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  10. IceCube Alert 241224.30: Global MASTER-Net observations report
  11. Fermi GRB 241118A: Global MASTER-Net observations report
  12. EP241107a: Gemini-South spectroscopic confirmation (z = 0.456)
  13. GRB241105A: Gemini-South Optical Afterglow Detection
  14. GRB 241030A: Swift/UVOT Detection
  15. EP241021a: Gemini-South detection of optical rebrightening
  16. GRB 230204B: Fermi GBM detection
  17. GRB 230204A: Swift/UVOT Upper Limits
  18. GRB 230102A: Fermi GBM Observation
  19. GRB221009A: Gemini-South Optical Afterglow Detection
  20. GRB 220715B: Swift/UVOT Upper Limits
  21. GRB 220608A: AstroSat CZTI detection
  22. GRB 220308B: Fermi GBM detection
  23. Fermi GRB 211211B: Global MASTER-Net observations report
  24. ZTF21aayokph (AT2021lfa): Redshift from Gemini South
  25. GRB 210104B: Swift/UVOT Upper Limits
  26. GRB 201223A: Swift/UVOT Detection
  27. Fermi GRB 201109A: Global MASTER-Net observations report
  28. GRB 201024A: Swift/UVOT Detection
  29. Fermi trigger No 607537834: Global MASTER-Net observations report
  30. LIGO/Virgo S200114f: Gemini Spectra of AT 2020vu, AT 2020vw, AT 2020vy, and AT 2020vz
  31. Swift GRB191226.25: Global MASTER-Net observations report
  32. GRB 191201A: AstroSat CZTI detection
  33. GRB190604B: Swift/UVOT detection
  34. GRB 181228A: Swift/UVOT Upper Limits
  35. GRB 180602A: Swift/UVOT Upper Limits
  36. GRB 171102B: Nanshan 0.36m and 0.60m optical upper limits
  37. GRB 170311A: Swift/UVOT Upper Limits
  38. GRB 160824A: Swift/UVOT Possible Afterglow Detection
  39. GRB 151031A: Swift/UVOT Detection
  40. GRB 151027A: UVOT Observations
  41. GRB 151023A: Swift/UVOT Upper Limits
  42. GRB 150710A: Swift/UVOT Upper Limits
  43. Swift Trigger 646423 is GS 1354-645
  44. GRB 140614A: Swift/UVOT Upper Limits
  45. GRB 140206A: Swift/UVOT Detection
  46. GRB 131127A: Swift/UVOT Upper Limits
  47. GRB 131002A: Swift/UVOT Detection
  48. GRB 130925A: Swift/UVOT Upper Limits
  49. GRB 130702A: P200 Spectroscopic Confirmation of Associated Supernova
  50. GRB 130515A: Swift/UVOT Upper Limits
  51. GRB 121123A: Swift/UVOT Observations
  52. GRB 120521C: Swift/UVOT Upper Limits
  53. GRB 111215A: Swift/UVOT Upper Limits
  54. GRB 111109A: Swift-BAT refined analysis
  55. GRB 110709B: Preliminary Swift-BAT refined analysis
  56. Swift/UVOT observations of GRB110520A
  57. Swift/UVOT observations of GRB110223b
  58. GRB 100606A: Enhanced Swift-XRT position
  59. INTEGRAL Alert n. 5995: MASTER-Net optical observations
  60. GRB 100302A: Swift/UVOT Upper Limits
  61. GRB090418A Rc-band photometry
  62. GRB 080919: Swift/UVOT Refined Analysis
  63. GRB 080916C: Swift UVOT Refined Analysis
  64. GRB 071117: Gemini Observations
  65. GRB 070419A, deep LBT photometry and possible supernova detection
  66. GRB070420: Swift UVOT continuing observations
  67. GRB061222A Swift/UVOT: Upper Limits
  68. GRB 061201: UVOT Observations of a Fading Optical Afterglow
  69. GRB061002: Swift UVOT followup observations
  70. GRB 060807: UVOT Upper limits
  71. GRB 060510A: Swift/UVOT Detection of an Optical Afterglow
  72. GRB000418, HST/STIS Observations
  73. GRB 000418: Detection of the Host Galaxy
  74. The redshift of GRB 000418
  75. GRB000418, Radio detection
  76. GRB000418, K'-band photometry
  77. GRB 000418, Optical Observation
  78. GRB 000418, optical observation
  79. GRB 000418, Optical Observation
  80. GRB 000418, Optical Observation

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