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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"

28053 results found.

  1. EP250226a/GRB 250226A: 1.6m Mephisto observations
  2. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  3. EP250226a/GRB 250226A: Kinder optical follow-up observations
  4. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  5. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  6. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  7. GRB 250225B: Fermi GBM Observation
  8. GRB 250225B: REM NIR upper limits
  9. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  10. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  11. EP250223a: CrAO ZTSH optical observation
  12. GRB 250225B: VLT optical and near-infrared candidate counterpart
  13. GRB 250225B: SVOM/GRM observation of a long burst
  14. EP250226a/GRB 250226A: GSP detects optical counterpart
  15. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  16. EP250226a / GRB 250226A: TRT optical counterpart observation
  17. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  18. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  19. EP250225a: GSP optical upper limit
  20. EP250223a: GMG Optical Observation
  21. EP250225a: Einstein Probe detected of a fast X-ray transient
  22. GRB 250225B: Swift detection of a burst
  23. EP250223a: GROWTH-India Telescope optical observations
  24. GRB 250221A: Swift-BAT refined analysis
  25. EP250215A: J band upper limit by SYSU 80cm telescope
  26. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  27. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  28. EP250223a: Kinder optical follow-up observations
  29. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  30. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  31. GRB 250119B: VZLUSAT-2 detection
  32. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  33. GRB 250202B: VZLUSAT-2 detection
  34. GRB 250222A: SVOM/GRM observation of a burst
  35. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  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. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  42. 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
  43. EP250223a: OASDG optical observations
  44. EP250223a: LCO detection of the afterglow
  45. EP250223a: Swift/XRT localization
  46. EP250223a: NOT optical afterglow candidate
  47. EP250223a: Einstein Probe detection of an X-ray transient
  48. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  49. GRB 250221A: Optical counterpart detection by LCO.
  50. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  51. GRB 250221A: GRANDMA/TAROT Detection
  52. GRB 250221A: Swift-XRT refined Analysis
  53. GRB 250221A: NOT optical observations
  54. GRB 250221A: 1.6m Mephisto optical detection
  55. GRB 250221A: AKO Optical Upper Limit
  56. GRB 250221A: Swift/UVOT Detection
  57. EP250220a: Liverpool Telescope upper limits
  58. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  59. GRB 250221A: REM optical/NIR afterglow detection
  60. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  61. GRB 250221A: Enhanced Swift-XRT position
  62. EP250220a: 1.6m Mephisto observations
  63. EP250220a: Liverpool Telescope optical upper limits
  64. EP250220a: Optical upper limit with Kinder observations
  65. SVOM trigger sb25022102 is not an astrophysical event
  66. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  67. GRB 250221A: Swift detection of a burst with an optical counterpart
  68. Swift GRB250221.15: Global MASTER-Net OT detection
  69. EP250220a: Xinglong optical upper limit
  70. GRB 250219A: Swift/UVOT Upper Limits
  71. GRB 250219A: OHP/T193 optical upper limit
  72. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  73. GRB 250219A: 1.6m Mephisto optical upper limits
  74. GRB 250219A: Swift-XRT observations
  75. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  76. Konus-Wind detection of GRB 250215A / EP250215a
  77. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  78. GRB 250217C: Swift-XRT observations
  79. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  80. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  81. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  82. GRB 250217C: SVOM/GRM observation
  83. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  84. SVOM/sb25021804: SVOM detection of a long X-ray transient
  85. GRB 250213A: Swift-XRT observations
  86. GRB 250216A: AstroSat CZTI detection
  87. GRB 250217C: AstroSat CZTI detection of a short burst
  88. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  89. GRANDMA/OPD observations of GRB250215A
  90. GRB 250215A / EP250215a: LCO detection of the afterglow
  91. GRB 250215A: Swift/UVOT Upper Limits
  92. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  93. GRB 250215A: Fermi GBM Observation
  94. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  95. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  96. GRB 250215A: Swift-XRT refined Analysis
  97. GRB 250215A: SVOM/GRM observation
  98. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  99. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  100. EP250207b: Xinglong optical upper limit

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