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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"

19858 results found.

  1. GRB 250314A: Keck/NIRC2 J-band upper limit
  2. EP250226a/GRB 250226A: KAIT optical observations
  3. GRB 250321A: Swift detection of a burst
  4. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  5. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  6. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  7. EP250302a: VLA observations
  8. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  9. GRB 250317C: SVOM/GRM observation of a long burst
  10. GRB 250317B: Leavitt Observatory optical upper limit
  11. GRB 250317B: Mondy AZT-33IK Optical Observations
  12. GRB 250317B: NOT optical observations suggest an optical plateau phase
  13. GRB 250317B: OHP/T193 optical observations
  14. GRB250312A: Swift/UVOT Upper Limits
  15. GRB 250317B: REM optical/NIR observations
  16. GRB 250316A: Swift/UVOT Upper Limits
  17. GRB 250314A: REM optical/NIR upper limits
  18. GRB 250316A: AbAO AS-32 Optical Upper Limit
  19. EP 250317B: Fading optical counterpart detection by LCO
  20. GRB 250316A: Swift-XRT afterglow detection
  21. GRB 250317B: LCO detection of the fading optical afterglow
  22. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  23. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  24. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  25. GRB 250317B: SVOM detection of a burst
  26. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  27. GRB 250314A: Swift/UVOT Upper Limits
  28. GRB 250314A: Swift XRT Detection
  29. EP250315a: optical counterpart candidate detected by Gemini North
  30. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  31. EP250315a: Einstein Probe detection of an X-ray transient
  32. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  33. SVOM/MXT upper limit on GRB 250314A
  34. GRB 250314A: SVOM/VT upper limit
  35. GRB 250314A: NOT near-infrared candidate counterpart
  36. GRB 250313A: Fermi GBM Detection
  37. GRB 250313A: Swift-XRT observations
  38. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  39. Konus-Wind detection of GRB 250313A
  40. GRB 250314A: SVOM detection of a burst
  41. EP250304a: Pan-STARRS r and i-band imaging and photometry
  42. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  43. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  44. GRB 250312A: Enhanced Swift-XRT position
  45. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  46. GRB 250312A: Swift detection of a burst
  47. GRB 241213A: VIRT Optical Upper Limit
  48. GRB 241228A: VIRT Optical Upper Limit
  49. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  50. GRB 250311A: Swift-XRT observations
  51. GRB 250309B: 1.3m DFOT Optical observations
  52. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  54. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  55. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  56. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  57. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  58. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  59. GRB 250309B: PRIME near-infrared detection
  60. GRB 250225B: Swift-BAT refined analysis
  61. GRB 250311A/EP250311a: TRT optical upper limit
  62. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  63. EP250311a/GRB 250311A: EP-WXT detection
  64. GRB 250309B / AT2025dws: further SAO RAS optical observations
  65. EP250308a: 1.6m Mephisto optical upper limits
  66. IPN triangulation of GRB 250308A (short)
  67. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  68. GRB 250309B / AT2025dws: SAO RAS optical observations
  69. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  70. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  71. IceCube-250309A: No candidates from the Zwicky Transient Facility
  72. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  73. EP250308a: Einstein Probe detection of an X-ray transient
  74. EP250308a: NOT optical upper limit
  75. EP250304a: MeerKAT detection of a possible radio counterpart
  76. EP250302a:Xinglong optical observations
  77. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  78. GRB250101A: Radio upper limits from VLA observations
  79. GRB 250305A: SVOM/GRM observation of a burst
  80. EP250302a: Optical Observations at CrAO and SAO RAS
  81. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  82. EP 250304A: Optical counterpart detection by LCO
  83. EP250302A: 1.3m DFOT optical afterglow detection
  84. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  85. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  86. EP250304a: REM NIR upper limits
  87. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  88. EP250302a: Mondy Continued Optical Observations
  89. EP250304a: VLT/X-shooter redshift z = 0.200
  90. EP250304a: TRT optical counterpart detection
  91. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  92. EP250304a: Einstein Probe detection of an X-ray transient
  93. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  94. EP250302a: SAO RAS optical observations
  95. EP250302a : GIT optical follow-up
  96. EP250302a: Kinder optical follow-up observations
  97. EP250302a: Swift/UVOT detection
  98. EP250302a: NUTTelA-TAO Early Measurments
  99. EP250302a: optical observation from the INAF Asiago Observatory
  100. EP250302a: REM NIR upper limits

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