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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"

32505 results found.

  1. GRB 250225B: VLT optical and near-infrared candidate counterpart
  2. GRB 250225B: VLT/FORS2 candidate optical afterglow
  3. GRB 250225B: SVOM/GRM observation of a long burst
  4. GRB 250226A: GECAM-B detection
  5. GRB 250221A: EP-FXT detection of the X-ray afterglow
  6. GRB 250214A: SVOM/GRM observation
  7. EP250226a/GRB 250226A: GSP detects optical counterpart
  8. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  9. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  10. EP250226a / GRB 250226A: TRT optical counterpart observation
  11. EP250226a: Global MASTER-Net observations report
  12. Swift GRB 250225B: Global MASTER-Net observations report
  13. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  14. Fermi GRB 250226A: Global MASTER-Net observations report
  15. EP250225a: Global MASTER-Net observations report
  16. EP250225a: GSP optical upper limit
  17. EP250223a: GMG Optical Observation
  18. Fermi GRB 250225A: Global MASTER-Net observations report
  19. EP250223a: GROWTH-India Telescope optical observations
  20. GRB 250221A: Swift-BAT refined analysis
  21. GRB 250223C: SVOM/GRM observation of a long burst
  22. EP250215A: J band upper limit by SYSU 80cm telescope
  23. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  24. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  25. EP250223a: Kinder optical follow-up observations
  26. GRB 250207a: ATCA Radio Upper Limits
  27. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  28. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  29. GRB 250119B: VZLUSAT-2 detection
  30. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  31. GRB 250202B: VZLUSAT-2 detection
  32. GRB 250219A: EP-FXT afterglow detection
  33. EP250223a: GOTO optical afterglow detections
  34. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  35. GRB 250210A: VZLUSAT-2 detection
  36. GRB 250206A: VZLUSAT-2 detection
  37. EP250223a: REM NIR upper limit
  38. EP250223a: TRT optical afterglow observation
  39. EP250223a: refined analysis of the EP-WXT and FXT observations
  40. EP250223a: 1.6m Mephisto and 50cm array observations
  41. GRB 250221A: TNOT detection of the optical counterpart
  42. EP250223a: SVOM/VT optical observation
  43. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  44. 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
  45. EP250223a: OASDG optical observations
  46. EP250223a: LCO detection of the afterglow
  47. EP250223a: NOT redshift z = 2.756
  48. EP250223a: Swift/XRT localization
  49. EP250223a: NOT optical afterglow candidate
  50. EP250223a: Global MASTER-Net observations report
  51. GRB 250221A: VLA radio detection
  52. Fermi GRB 250223A: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  54. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  55. GRB 250221A: continued Mondy optical observations, brightening afterglow
  56. GRB 250221A: Optical counterpart detection by LCO.
  57. GRB 250221A: Mondy optical observations
  58. Konus-Wind detection of GRB 250221A
  59. GRB 250221A: Assy optical observations
  60. EP250220a: FTW optical and NIR observations and upper limits
  61. EP250220a: EP-FXT follow-up observations
  62. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  63. GRB 250221A: VLT/X-shooter redshift z = 0.768
  64. GRB 250221A: GRANDMA/TAROT Detection
  65. GRB 250221A: NOT optical observations
  66. GRB 250221A: 1.6m Mephisto optical detection
  67. GRB 250221A: AKO Optical Upper Limit
  68. GRB 250221A: Swift/UVOT Detection
  69. EP250220a: Liverpool Telescope upper limits
  70. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  71. GRB 250221A: REM optical/NIR afterglow detection
  72. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  73. EP250220a: 1.6m Mephisto observations
  74. EP250220a: Liverpool Telescope optical upper limits
  75. EP250220a: Optical upper limit with Kinder observations
  76. SVOM trigger sb25022102 is not an astrophysical event
  77. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  78. EP250220a: Xinglong optical upper limit
  79. EP250220a: Global MASTER-Net observations report
  80. Konus-Wind detection of GRB 250217C (short)
  81. GRB 250219A: Swift/UVOT Upper Limits
  82. GRB 250219A: OHP/T193 optical upper limit
  83. GRB 250219A: NOT optical observations
  84. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  85. GRB 250219A: 1.6m Mephisto optical upper limits
  86. GRB 250219A: SVOM/VT optical counterpart
  87. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  88. GRB 250219A: Swift ToO observations
  89. Konus-Wind detection of GRB 250215A / EP250215a
  90. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  91. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  92. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  93. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  94. GRB 250217C: SVOM/GRM observation
  95. GRB 250217C: Tiled Swift observations
  96. GRB 250217C: Fermi GBM Observation
  97. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  98. IPN triangulation of GRB 250217C (short)
  99. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  100. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations

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