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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"

23582 results found.

  1. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  2. Swift GRB 250225B: Global MASTER-Net observations report
  3. EP250225a: GSP optical upper limit
  4. EP250223a: GMG Optical Observation
  5. GRB 250225B: Swift detection of a burst
  6. GRB 250221A: Swift-BAT refined analysis
  7. EP250223a: Kinder optical follow-up observations
  8. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  9. GRB 250119B: VZLUSAT-2 detection
  10. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  11. GRB 250202B: VZLUSAT-2 detection
  12. GRB 250219A: EP-FXT afterglow detection
  13. EP250223a: GOTO optical afterglow detections
  14. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  15. GRB 250210A: VZLUSAT-2 detection
  16. GRB 250206A: VZLUSAT-2 detection
  17. EP250223a: REM NIR upper limit
  18. EP250223a: TRT optical afterglow observation
  19. EP250223a: 1.6m Mephisto and 50cm array observations
  20. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  21. 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
  22. EP250223a: OASDG optical observations
  23. EP250223a: LCO detection of the afterglow
  24. EP250223a: early optical detection by BOOTES-4
  25. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  26. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  27. GRB 250221A: Optical counterpart detection by LCO.
  28. Konus-Wind detection of GRB 250221A
  29. GRB 250221A: Assy optical observations
  30. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  31. GRB 250221A: GRANDMA/TAROT Detection
  32. GRB 250221A: Swift-XRT refined Analysis
  33. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  34. GRB 250221A: REM optical/NIR afterglow detection
  35. EP250220a: 1.6m Mephisto observations
  36. EP250220a: Optical upper limit with Kinder observations
  37. SVOM trigger sb25022102 is not an astrophysical event
  38. SVOM/sb25022102: SVOM detection of an X-ray transient
  39. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  40. GRB 250221A: Swift detection of a burst with an optical counterpart
  41. EP250220a: Xinglong optical upper limit
  42. Konus-Wind detection of GRB 250217C (short)
  43. GRB 250219A: OHP/T193 optical upper limit
  44. GRB 250219A: NOT optical observations
  45. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  46. GRB 250219A: 1.6m Mephisto optical upper limits
  47. GRB 250219A: SVOM/VT optical counterpart
  48. GRB 250219A: Swift-XRT observations
  49. GRB 250219A: SVOM detection of a burst
  50. Konus-Wind detection of GRB 250215A / EP250215a
  51. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  52. GRB 250217C: Swift-XRT observations
  53. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  54. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  55. GRB 250217C: SVOM/GRM observation
  56. GRB 250217C: Fermi GBM Observation
  57. IPN triangulation of GRB 250217C (short)
  58. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  59. SVOM/sb25021804: SVOM detection of a long X-ray transient
  60. GRB 250213A: Swift-XRT observations
  61. GRB 250216A: AstroSat CZTI detection
  62. GRB 250217C: AstroSat CZTI detection of a short burst
  63. GRANDMA/OPD observations of GRB250215A
  64. GRB 250215A / EP250215a: LCO detection of the afterglow
  65. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  66. EP250215a / GRB 250215A : GTC redshift z = 4.61
  67. EP250215a / GRB 250215A : NOT optical observations
  68. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  69. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  70. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  71. GRB 250215A: Swift-XRT refined Analysis
  72. GRB 250215A: SVOM/GRM observation
  73. EP250215a / GRB 250215A: AstroSat CZTI detection
  74. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  75. EP250207b: Xinglong optical upper limit
  76. EP250212a: Xinglong optical upper limit
  77. GRB 250210A: GRBAlpha detection
  78. EP250207b: VLA radio upper limits
  79. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  80. EP250207B: GTC z-band Observations
  81. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  82. EP250207b: NOT optical counterpart candidate
  83. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  84. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  85. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  86. GRB 250205A / EP250205A: radio detection with the VLA
  87. IceCube-250207A: One candidate from the Zwicky Transient Facility
  88. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  89. Konus-Wind detection of GRB 250207A
  90. Konus-Wind detection of GRB 250206A
  91. Fermi Gamma-ray Burst Monitor trigger 760945500/250211240 is not a GRB
  92. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate
  93. LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
  94. GRB 250207A: Skynet optical afterglow observations
  95. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  96. EP250207b: Gemini GMOS-N z-band observations
  97. EP250207A: Upper limits from Fermi-GBM Observations
  98. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  99. Fermi GRB 250210A: Global MASTER-Net observations report
  100. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report

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