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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28290 results found.

  1. EP250302a: Mondy Observations and Optical Light Curve
  2. EP250302a: VLT/MUSE optical redshift z = 1.131
  3. EP250302A: VLT near-infrared observations
  4. EP250302A: VLT/X-shooter tentative redshift
  5. EP250302a: OHP/T193 optical and spectroscopic observations
  6. EP250302a: Swift-XRT observations of a fading X-ray source
  7. EP250302a: Einstein Probe detection of an X-ray transient
  8. EP250302a: SVOM/C-GFT optical observations
  9. GRB 250226A: GRANDMA Optical Observations
  10. EP250302a: Montarrenti Observatory optical detection
  11. EP250302a: Nanshan/HMT optical counterpart detection
  12. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  13. GRB 250225B: VLT near-infrared afterglow confirmation
  14. EP250228a: Optical observations with Kinder and Swift/UVOT
  15. Konus-Wind detection of GRB 250226A
  16. GRB 250225B: EIRSAT-1 GMOD Detection
  17. GRB 250226A: KAO Optical Upper Limit
  18. GRB 250226A: AbAO AS-32 Optical Upper Limit
  19. EP250227a: Global MASTER-Net observations report
  20. EP250223A: Upper limits from Fermi-GBM Observations
  21. EP250227a: TRT optical upper limit
  22. GRB 250225B: VLT/HAWKI near-infrared observations
  23. EP250227a: Optical upper limits with Kinder observations
  24. EP250227a: NOT optical observations
  25. EP250227a: Einstein Probe detected of a fast X-ray transient
  26. EP250228a: updates on the EP observations
  27. GRB 250226A: Fermi GBM Observation
  28. EP250223a: J band upper limit by SYSU 80cm telescope
  29. EP250228a: Swift/XRT localisation
  30. EP250228a: Einstein Probe detection of an X-ray transient
  31. GRB 250226A / EP250226a: LCO detection of the afterglow
  32. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  33. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  34. GRB 250225B: VLT/Xshooter imaging
  35. GRB 250205A / EP250205A: further radio observations with the VLA
  36. EP250225a: NOT optical candidate counterpart
  37. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  38. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  39. EP250225a: TRT optical upper limits
  40. EP250226a/GRB 250226A: 1.6m Mephisto observations
  41. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  42. EP250226a/GRB 250226A: Kinder optical follow-up observations
  43. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  44. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  45. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  46. GRB 250225B: Fermi GBM Observation
  47. GRB 250225B: REM NIR upper limits
  48. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  49. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  50. EP250223a: CrAO ZTSH optical observation
  51. GRB 250225B: VLT optical and near-infrared candidate counterpart
  52. GRB 250225B: SVOM/GRM observation of a long burst
  53. EP250226a/GRB 250226A: GSP detects optical counterpart
  54. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  55. EP250226a / GRB 250226A: TRT optical counterpart observation
  56. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  57. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  58. EP250225a: GSP optical upper limit
  59. EP250223a: GMG Optical Observation
  60. EP250225a: Einstein Probe detected of a fast X-ray transient
  61. GRB 250225B: Swift detection of a burst
  62. EP250223a: GROWTH-India Telescope optical observations
  63. GRB 250221A: Swift-BAT refined analysis
  64. EP250215A: J band upper limit by SYSU 80cm telescope
  65. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  66. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  67. EP250223a: Kinder optical follow-up observations
  68. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  69. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  70. GRB 250119B: VZLUSAT-2 detection
  71. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  72. GRB 250202B: VZLUSAT-2 detection
  73. GRB 250222A: SVOM/GRM observation of a burst
  74. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  75. GRB 250206A: VZLUSAT-2 detection
  76. EP250223a: REM NIR upper limit
  77. EP250223a: TRT optical afterglow observation
  78. EP250223a: refined analysis of the EP-WXT and FXT observations
  79. EP250223a: 1.6m Mephisto and 50cm array observations
  80. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  81. 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
  82. EP250223a: OASDG optical observations
  83. EP250223a: LCO detection of the afterglow
  84. EP250223a: Swift/XRT localization
  85. EP250223a: NOT optical afterglow candidate
  86. EP250223a: Einstein Probe detection of an X-ray transient
  87. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  88. GRB 250221A: Optical counterpart detection by LCO.
  89. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  90. GRB 250221A: GRANDMA/TAROT Detection
  91. GRB 250221A: Swift-XRT refined Analysis
  92. GRB 250221A: NOT optical observations
  93. GRB 250221A: 1.6m Mephisto optical detection
  94. GRB 250221A: AKO Optical Upper Limit
  95. GRB 250221A: Swift/UVOT Detection
  96. EP250220a: Liverpool Telescope upper limits
  97. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  98. GRB 250221A: REM optical/NIR afterglow detection
  99. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  100. GRB 250221A: Enhanced Swift-XRT position

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