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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"

32489 results found.

  1. EP250225a: GSP optical upper limit
  2. EP250223a: GMG Optical Observation
  3. Fermi GRB 250225A: Global MASTER-Net observations report
  4. EP250223a: GROWTH-India Telescope optical observations
  5. GRB 250221A: Swift-BAT refined analysis
  6. GRB 250223C: SVOM/GRM observation of a long burst
  7. EP250215A: J band upper limit by SYSU 80cm telescope
  8. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  9. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  10. EP250223a: Kinder optical follow-up observations
  11. GRB 250207a: ATCA Radio Upper Limits
  12. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  13. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  14. GRB 250119B: VZLUSAT-2 detection
  15. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  16. GRB 250202B: VZLUSAT-2 detection
  17. GRB 250219A: EP-FXT afterglow detection
  18. EP250223a: GOTO optical afterglow detections
  19. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  20. GRB 250210A: VZLUSAT-2 detection
  21. GRB 250206A: VZLUSAT-2 detection
  22. EP250223a: REM NIR upper limit
  23. EP250223a: TRT optical afterglow observation
  24. EP250223a: refined analysis of the EP-WXT and FXT observations
  25. EP250223a: 1.6m Mephisto and 50cm array observations
  26. GRB 250221A: TNOT detection of the optical counterpart
  27. EP250223a: SVOM/VT optical observation
  28. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  29. 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
  30. EP250223a: OASDG optical observations
  31. EP250223a: LCO detection of the afterglow
  32. EP250223a: NOT redshift z = 2.756
  33. EP250223a: Swift/XRT localization
  34. EP250223a: NOT optical afterglow candidate
  35. EP250223a: Global MASTER-Net observations report
  36. GRB 250221A: VLA radio detection
  37. Fermi GRB 250223A: Global MASTER-Net observations report
  38. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  39. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  40. GRB 250221A: continued Mondy optical observations, brightening afterglow
  41. GRB 250221A: Optical counterpart detection by LCO.
  42. GRB 250221A: Mondy optical observations
  43. Konus-Wind detection of GRB 250221A
  44. GRB 250221A: Assy optical observations
  45. EP250220a: FTW optical and NIR observations and upper limits
  46. EP250220a: EP-FXT follow-up observations
  47. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  48. GRB 250221A: VLT/X-shooter redshift z = 0.768
  49. GRB 250221A: GRANDMA/TAROT Detection
  50. GRB 250221A: NOT optical observations
  51. GRB 250221A: 1.6m Mephisto optical detection
  52. GRB 250221A: AKO Optical Upper Limit
  53. GRB 250221A: Swift/UVOT Detection
  54. EP250220a: Liverpool Telescope upper limits
  55. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  56. GRB 250221A: REM optical/NIR afterglow detection
  57. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  58. EP250220a: 1.6m Mephisto observations
  59. EP250220a: Liverpool Telescope optical upper limits
  60. EP250220a: Optical upper limit with Kinder observations
  61. SVOM trigger sb25022102 is not an astrophysical event
  62. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  63. EP250220a: Xinglong optical upper limit
  64. EP250220a: Global MASTER-Net observations report
  65. Konus-Wind detection of GRB 250217C (short)
  66. GRB 250219A: Swift/UVOT Upper Limits
  67. GRB 250219A: OHP/T193 optical upper limit
  68. GRB 250219A: NOT optical observations
  69. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  70. GRB 250219A: 1.6m Mephisto optical upper limits
  71. GRB 250219A: SVOM/VT optical counterpart
  72. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  73. GRB 250219A: Swift ToO observations
  74. Konus-Wind detection of GRB 250215A / EP250215a
  75. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  76. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  77. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  78. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  79. GRB 250217C: SVOM/GRM observation
  80. GRB 250217C: Tiled Swift observations
  81. GRB 250217C: Fermi GBM Observation
  82. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  83. IPN triangulation of GRB 250217C (short)
  84. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  85. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  86. GRB 250216A: AstroSat CZTI detection
  87. GRB 250217C: AstroSat CZTI detection of a short burst
  88. Fermi GRB 250217C: Global MASTER-Net observations report
  89. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  90. Fermi GRB 250217A: Global MASTER-Net observations report
  91. GRANDMA/OPD observations of GRB250215A
  92. Fermi GRB 250216A: Global MASTER-Net observations report
  93. GRB 250215A / EP250215a: LCO detection of the afterglow
  94. EP250212a: FTW optical and NIR upper limits
  95. GRB 250215A: Swift/UVOT Upper Limits
  96. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  97. EP250215a / GRB 250215A : GTC redshift z = 4.61
  98. GRB 250215A: Fermi GBM Observation
  99. EP250215a / GRB 250215A : NOT optical observations
  100. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report

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