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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"

32509 results found.

  1. GRB 250225B: REM NIR upper limits
  2. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  3. Konus-Wind detection of GRB 250225B
  4. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  5. EP250223a: CrAO ZTSH optical observation
  6. GRB 250225B: VLT optical and near-infrared candidate counterpart
  7. GRB 250225B: VLT/FORS2 candidate optical afterglow
  8. GRB 250225B: SVOM/GRM observation of a long burst
  9. GRB 250226A: GECAM-B detection
  10. GRB 250221A: EP-FXT detection of the X-ray afterglow
  11. GRB 250214A: SVOM/GRM observation
  12. EP250226a/GRB 250226A: GSP detects optical counterpart
  13. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  14. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  15. EP250226a / GRB 250226A: TRT optical counterpart observation
  16. EP250226a: Global MASTER-Net observations report
  17. Swift GRB 250225B: Global MASTER-Net observations report
  18. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  19. Fermi GRB 250226A: Global MASTER-Net observations report
  20. EP250225a: Global MASTER-Net observations report
  21. EP250225a: GSP optical upper limit
  22. EP250223a: GMG Optical Observation
  23. Fermi GRB 250225A: Global MASTER-Net observations report
  24. EP250223a: GROWTH-India Telescope optical observations
  25. GRB 250221A: Swift-BAT refined analysis
  26. GRB 250223C: SVOM/GRM observation of a long burst
  27. EP250215A: J band upper limit by SYSU 80cm telescope
  28. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  29. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  30. EP250223a: Kinder optical follow-up observations
  31. GRB 250207a: ATCA Radio Upper Limits
  32. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  33. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  34. GRB 250119B: VZLUSAT-2 detection
  35. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  36. GRB 250202B: VZLUSAT-2 detection
  37. GRB 250219A: EP-FXT afterglow detection
  38. EP250223a: GOTO optical afterglow detections
  39. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  40. GRB 250210A: VZLUSAT-2 detection
  41. GRB 250206A: VZLUSAT-2 detection
  42. EP250223a: REM NIR upper limit
  43. EP250223a: TRT optical afterglow observation
  44. EP250223a: refined analysis of the EP-WXT and FXT observations
  45. EP250223a: 1.6m Mephisto and 50cm array observations
  46. GRB 250221A: TNOT detection of the optical counterpart
  47. EP250223a: SVOM/VT optical observation
  48. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  49. 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
  50. EP250223a: OASDG optical observations
  51. EP250223a: LCO detection of the afterglow
  52. EP250223a: NOT redshift z = 2.756
  53. EP250223a: Swift/XRT localization
  54. EP250223a: NOT optical afterglow candidate
  55. EP250223a: Global MASTER-Net observations report
  56. GRB 250221A: VLA radio detection
  57. Fermi GRB 250223A: Global MASTER-Net observations report
  58. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  59. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  60. GRB 250221A: continued Mondy optical observations, brightening afterglow
  61. GRB 250221A: Optical counterpart detection by LCO.
  62. GRB 250221A: Mondy optical observations
  63. Konus-Wind detection of GRB 250221A
  64. GRB 250221A: Assy optical observations
  65. EP250220a: FTW optical and NIR observations and upper limits
  66. EP250220a: EP-FXT follow-up observations
  67. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  68. GRB 250221A: VLT/X-shooter redshift z = 0.768
  69. GRB 250221A: GRANDMA/TAROT Detection
  70. GRB 250221A: NOT optical observations
  71. GRB 250221A: 1.6m Mephisto optical detection
  72. GRB 250221A: AKO Optical Upper Limit
  73. GRB 250221A: Swift/UVOT Detection
  74. EP250220a: Liverpool Telescope upper limits
  75. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  76. GRB 250221A: REM optical/NIR afterglow detection
  77. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  78. EP250220a: 1.6m Mephisto observations
  79. EP250220a: Liverpool Telescope optical upper limits
  80. EP250220a: Optical upper limit with Kinder observations
  81. SVOM trigger sb25022102 is not an astrophysical event
  82. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  83. EP250220a: Xinglong optical upper limit
  84. EP250220a: Global MASTER-Net observations report
  85. Konus-Wind detection of GRB 250217C (short)
  86. GRB 250219A: Swift/UVOT Upper Limits
  87. GRB 250219A: OHP/T193 optical upper limit
  88. GRB 250219A: NOT optical observations
  89. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  90. GRB 250219A: 1.6m Mephisto optical upper limits
  91. GRB 250219A: SVOM/VT optical counterpart
  92. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  93. GRB 250219A: Swift ToO observations
  94. Konus-Wind detection of GRB 250215A / EP250215a
  95. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  96. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  97. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  98. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  99. GRB 250217C: SVOM/GRM observation
  100. GRB 250217C: Tiled Swift observations

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