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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"

32502 results found.

  1. GRB 250226A: GECAM-B detection
  2. GRB 250221A: EP-FXT detection of the X-ray afterglow
  3. GRB 250214A: SVOM/GRM observation
  4. EP250226a/GRB 250226A: GSP detects optical counterpart
  5. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  6. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  7. EP250226a / GRB 250226A: TRT optical counterpart observation
  8. EP250226a: Global MASTER-Net observations report
  9. Swift GRB 250225B: Global MASTER-Net observations report
  10. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  11. Fermi GRB 250226A: Global MASTER-Net observations report
  12. EP250225a: Global MASTER-Net observations report
  13. EP250225a: GSP optical upper limit
  14. EP250223a: GMG Optical Observation
  15. Fermi GRB 250225A: Global MASTER-Net observations report
  16. EP250223a: GROWTH-India Telescope optical observations
  17. GRB 250221A: Swift-BAT refined analysis
  18. GRB 250223C: SVOM/GRM observation of a long burst
  19. EP250215A: J band upper limit by SYSU 80cm telescope
  20. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  21. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  22. EP250223a: Kinder optical follow-up observations
  23. GRB 250207a: ATCA Radio Upper Limits
  24. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  25. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  26. GRB 250119B: VZLUSAT-2 detection
  27. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  28. GRB 250202B: VZLUSAT-2 detection
  29. GRB 250219A: EP-FXT afterglow detection
  30. EP250223a: GOTO optical afterglow detections
  31. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  32. GRB 250210A: VZLUSAT-2 detection
  33. GRB 250206A: VZLUSAT-2 detection
  34. EP250223a: REM NIR upper limit
  35. EP250223a: TRT optical afterglow observation
  36. EP250223a: refined analysis of the EP-WXT and FXT observations
  37. EP250223a: 1.6m Mephisto and 50cm array observations
  38. GRB 250221A: TNOT detection of the optical counterpart
  39. EP250223a: SVOM/VT optical observation
  40. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  41. 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
  42. EP250223a: OASDG optical observations
  43. EP250223a: LCO detection of the afterglow
  44. EP250223a: NOT redshift z = 2.756
  45. EP250223a: Swift/XRT localization
  46. EP250223a: NOT optical afterglow candidate
  47. EP250223a: Global MASTER-Net observations report
  48. GRB 250221A: VLA radio detection
  49. Fermi GRB 250223A: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  51. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  52. GRB 250221A: continued Mondy optical observations, brightening afterglow
  53. GRB 250221A: Optical counterpart detection by LCO.
  54. GRB 250221A: Mondy optical observations
  55. Konus-Wind detection of GRB 250221A
  56. GRB 250221A: Assy optical observations
  57. EP250220a: FTW optical and NIR observations and upper limits
  58. EP250220a: EP-FXT follow-up observations
  59. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  60. GRB 250221A: VLT/X-shooter redshift z = 0.768
  61. GRB 250221A: GRANDMA/TAROT Detection
  62. GRB 250221A: NOT optical observations
  63. GRB 250221A: 1.6m Mephisto optical detection
  64. GRB 250221A: AKO Optical Upper Limit
  65. GRB 250221A: Swift/UVOT Detection
  66. EP250220a: Liverpool Telescope upper limits
  67. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  68. GRB 250221A: REM optical/NIR afterglow detection
  69. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  70. EP250220a: 1.6m Mephisto observations
  71. EP250220a: Liverpool Telescope optical upper limits
  72. EP250220a: Optical upper limit with Kinder observations
  73. SVOM trigger sb25022102 is not an astrophysical event
  74. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  75. EP250220a: Xinglong optical upper limit
  76. EP250220a: Global MASTER-Net observations report
  77. Konus-Wind detection of GRB 250217C (short)
  78. GRB 250219A: Swift/UVOT Upper Limits
  79. GRB 250219A: OHP/T193 optical upper limit
  80. GRB 250219A: NOT optical observations
  81. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  82. GRB 250219A: 1.6m Mephisto optical upper limits
  83. GRB 250219A: SVOM/VT optical counterpart
  84. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  85. GRB 250219A: Swift ToO observations
  86. Konus-Wind detection of GRB 250215A / EP250215a
  87. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  88. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  89. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  90. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  91. GRB 250217C: SVOM/GRM observation
  92. GRB 250217C: Tiled Swift observations
  93. GRB 250217C: Fermi GBM Observation
  94. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  95. IPN triangulation of GRB 250217C (short)
  96. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  97. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  98. GRB 250216A: AstroSat CZTI detection
  99. GRB 250217C: AstroSat CZTI detection of a short burst
  100. Fermi GRB 250217C: Global MASTER-Net observations report

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