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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.

Lucene Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

23217 results found.

  1. EP250215A: J band upper limit by SYSU 80cm telescope
  2. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  3. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  4. EP250223a: Kinder optical follow-up observations
  5. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  6. GRB 250119B: VZLUSAT-2 detection
  7. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  8. GRB 250202B: VZLUSAT-2 detection
  9. GRB 250219A: EP-FXT afterglow detection
  10. GRB 250222A: SVOM/GRM observation of a burst
  11. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  12. GRB 250210A: VZLUSAT-2 detection
  13. GRB 250206A: VZLUSAT-2 detection
  14. EP250223a: REM NIR upper limit
  15. EP250223a: TRT optical afterglow observation
  16. EP250223a: refined analysis of the EP-WXT and FXT observations
  17. EP250223a: 1.6m Mephisto and 50cm array observations
  18. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  19. 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
  20. The EP-WXT trigger 01709131882 is likely a flaring star
  21. EP250223a: OASDG optical observations
  22. EP250223a: Swift/XRT localization
  23. EP250223a: NOT optical afterglow candidate
  24. EP250223a: Einstein Probe detection of an X-ray transient
  25. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  26. GRB 250221A: Optical counterpart detection by LCO.
  27. Konus-Wind detection of GRB 250221A
  28. EP250220a: EP-FXT follow-up observations
  29. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  30. GRB 250221A: GRANDMA/TAROT Detection
  31. GRB 250221A: Swift-XRT refined Analysis
  32. GRB 250221A: 1.6m Mephisto optical detection
  33. GRB 250221A: AKO Optical Upper Limit
  34. GRB 250221A: Swift/UVOT Detection
  35. EP250220a: Liverpool Telescope upper limits
  36. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  37. GRB 250221A: REM optical/NIR afterglow detection
  38. GRB 250221A: Enhanced Swift-XRT position
  39. EP250220a: 1.6m Mephisto observations
  40. EP250220a: Liverpool Telescope optical upper limits
  41. EP250220a: Optical upper limit with Kinder observations
  42. SVOM trigger sb25022102 is not an astrophysical event
  43. SVOM/sb25022102: SVOM detection of an X-ray transient
  44. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  45. GRB 250221A: Swift detection of a burst with an optical counterpart
  46. EP250220a: Xinglong optical upper limit
  47. EP250220a: EP-WXT detection of a fast X-ray transient
  48. GRB 250219A: Swift/UVOT Upper Limits
  49. GRB 250219A: OHP/T193 optical upper limit
  50. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  51. GRB 250219A: 1.6m Mephisto optical upper limits
  52. GRB 250219A: Swift-XRT observations
  53. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  54. GRB 250219A: SVOM detection of a burst
  55. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  56. GRB 250217C: Swift-XRT observations
  57. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  58. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  59. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  60. GRB 250217C: SVOM/GRM observation
  61. GRB 250217C: Fermi GBM Observation
  62. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  63. SVOM/sb25021804: SVOM detection of a long X-ray transient
  64. GRB 250213A: Swift-XRT observations
  65. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  66. GRANDMA/OPD observations of GRB250215A
  67. The EP-WXT trigger 01709131775 is likely a flaring star
  68. GRB 250215A / EP250215a: LCO detection of the afterglow
  69. GRB 250215A: Swift/UVOT Upper Limits
  70. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  71. EP250215a / GRB 250215A : GTC redshift z = 4.61
  72. GRB 250215A: Fermi GBM Observation
  73. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  74. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  75. GRB 250215A: Swift-XRT refined Analysis
  76. GRB 250215A: SVOM/GRM observation
  77. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  78. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  79. EP250207b: Xinglong optical upper limit
  80. EP250212a: Xinglong optical upper limit
  81. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  82. GRB 250213A: SVOM detection of a burst
  83. GRB 250205A: VIRT Optical Upper Limit
  84. GRB 250205A: Leavitt Observatory optical upper limit
  85. EP250207B: Chandra localization of the X-ray counterpart
  86. EP250212a: Liverpool Telescope optical upper limits
  87. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  88. GRB250101A: Radio upper limits from GMRT observations
  89. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  90. EP250207B: GTC z-band Observations
  91. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  92. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  93. EP250207b: NOT optical counterpart candidate
  94. GRB 250211B: A long GRB detected by INTEGRAL
  95. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  96. Integral GRB250211.89: Global MASTER-Net observations report
  97. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  98. GRB 250207A: Fermi GBM Observation
  99. GRB 250206A: Fermi GBM Observation
  100. GRB 250205A / EP250205A: radio detection with the VLA

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