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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"

23577 results found.

  1. GRB 250221A: Swift-BAT refined analysis
  2. EP250223a: Kinder optical follow-up observations
  3. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  4. GRB 250119B: VZLUSAT-2 detection
  5. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  6. GRB 250202B: VZLUSAT-2 detection
  7. GRB 250219A: EP-FXT afterglow detection
  8. EP250223a: GOTO optical afterglow detections
  9. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  10. GRB 250210A: VZLUSAT-2 detection
  11. GRB 250206A: VZLUSAT-2 detection
  12. EP250223a: REM NIR upper limit
  13. EP250223a: TRT optical afterglow observation
  14. EP250223a: 1.6m Mephisto and 50cm array observations
  15. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  16. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  17. EP250223a: OASDG optical observations
  18. EP250223a: LCO detection of the afterglow
  19. EP250223a: early optical detection by BOOTES-4
  20. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  21. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  22. GRB 250221A: Optical counterpart detection by LCO.
  23. Konus-Wind detection of GRB 250221A
  24. GRB 250221A: Assy optical observations
  25. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  26. GRB 250221A: GRANDMA/TAROT Detection
  27. GRB 250221A: Swift-XRT refined Analysis
  28. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  29. GRB 250221A: REM optical/NIR afterglow detection
  30. EP250220a: 1.6m Mephisto observations
  31. EP250220a: Optical upper limit with Kinder observations
  32. SVOM trigger sb25022102 is not an astrophysical event
  33. SVOM/sb25022102: SVOM detection of an X-ray transient
  34. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  35. GRB 250221A: Swift detection of a burst with an optical counterpart
  36. EP250220a: Xinglong optical upper limit
  37. Konus-Wind detection of GRB 250217C (short)
  38. GRB 250219A: OHP/T193 optical upper limit
  39. GRB 250219A: NOT optical observations
  40. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  41. GRB 250219A: 1.6m Mephisto optical upper limits
  42. GRB 250219A: SVOM/VT optical counterpart
  43. GRB 250219A: Swift-XRT observations
  44. GRB 250219A: SVOM detection of a burst
  45. Konus-Wind detection of GRB 250215A / EP250215a
  46. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  47. GRB 250217C: Swift-XRT observations
  48. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  49. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  50. GRB 250217C: SVOM/GRM observation
  51. GRB 250217C: Fermi GBM Observation
  52. IPN triangulation of GRB 250217C (short)
  53. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  54. SVOM/sb25021804: SVOM detection of a long X-ray transient
  55. GRB 250213A: Swift-XRT observations
  56. GRB 250216A: AstroSat CZTI detection
  57. GRB 250217C: AstroSat CZTI detection of a short burst
  58. GRANDMA/OPD observations of GRB250215A
  59. GRB 250215A / EP250215a: LCO detection of the afterglow
  60. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  61. EP250215a / GRB 250215A : GTC redshift z = 4.61
  62. EP250215a / GRB 250215A : NOT optical observations
  63. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  64. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  65. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  66. GRB 250215A: Swift-XRT refined Analysis
  67. GRB 250215A: SVOM/GRM observation
  68. EP250215a / GRB 250215A: AstroSat CZTI detection
  69. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  70. EP250207b: Xinglong optical upper limit
  71. EP250212a: Xinglong optical upper limit
  72. GRB 250210A: GRBAlpha detection
  73. EP250207b: VLA radio upper limits
  74. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  75. EP250207B: GTC z-band Observations
  76. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  77. EP250207b: NOT optical counterpart candidate
  78. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  79. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  80. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  81. GRB 250205A / EP250205A: radio detection with the VLA
  82. IceCube-250207A: One candidate from the Zwicky Transient Facility
  83. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  84. Konus-Wind detection of GRB 250207A
  85. Konus-Wind detection of GRB 250206A
  86. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  87. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  88. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  89. GRB 250207A: Skynet optical afterglow observations
  90. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  91. EP250207b: Gemini GMOS-N z-band observations
  92. EP250207A: Upper limits from Fermi-GBM Observations
  93. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  94. Fermi GRB 250210A: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  97. LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
  98. GRB 250204B: GRBAlpha detection
  99. GRB 250204A: GRBAlpha detection
  100. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder

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