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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"

28234 results found.

  1. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  2. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  3. EP250308a: GSP optical upper limit
  4. EP250308a: Einstein Probe detection of an X-ray transient
  5. EP250308a: NOT optical upper limit
  6. GRB 250306A: EIRSAT-1 GMOD detection
  7. GRB 250306A: Swift-BAT refined analysis
  8. GRB 250306A: NuSTAR detection of the prompt emission
  9. EP250304a: MeerKAT detection of a possible radio counterpart
  10. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  11. GRB 250305A: AstroSat CZTI detection
  12. EP250302a:Xinglong optical observations
  13. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  14. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  15. GRB250101A: Radio upper limits from VLA observations
  16. GRB 250305A: SVOM/GRM observation of a burst
  17. The EP-WXT trigger 01709132323 is likely a flaring star
  18. EP250304A: Upper limits from Fermi-GBM Observations
  19. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  20. EP250302a: Optical Observations at CrAO and SAO RAS
  21. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  22. EP 250304A: Optical counterpart detection by LCO
  23. EP250302A: 1.3m DFOT optical afterglow detection
  24. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  25. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  26. EP250304a: REM NIR upper limits
  27. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  28. EP250302a: Mondy Continued Optical Observations
  29. EP250304a: Swift-XRT detection of a fading X-ray source
  30. EP250304a: TRT optical counterpart detection
  31. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  32. EP250304a: Einstein Probe detection of an X-ray transient
  33. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  34. EP250302a: SAO RAS optical observations
  35. EP250302a : GIT optical follow-up
  36. EP250225a: the candidate optical counterpart is an AGN
  37. EP250302a: Kinder optical follow-up observations
  38. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  39. EP250302a: Swift/UVOT detection
  40. EP250302a: optical observation from the INAF Asiago Observatory
  41. EP250302a: REM NIR upper limits
  42. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  43. EP250302a: Mondy Observations and Optical Light Curve
  44. EP250302a: VLT/MUSE optical redshift z = 1.131
  45. EP250302A: VLT near-infrared observations
  46. EP250302A: VLT/X-shooter tentative redshift
  47. EP250302a: OHP/T193 optical and spectroscopic observations
  48. EP250302a: Swift-XRT observations of a fading X-ray source
  49. EP250302a: Einstein Probe detection of an X-ray transient
  50. EP250302a: SVOM/C-GFT optical observations
  51. GRB 250226A: GRANDMA Optical Observations
  52. EP250302a: Montarrenti Observatory optical detection
  53. EP250302a: Nanshan/HMT optical counterpart detection
  54. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  55. GRB 250225B: VLT near-infrared afterglow confirmation
  56. EP250228a: Optical observations with Kinder and Swift/UVOT
  57. Konus-Wind detection of GRB 250226A
  58. GRB 250225B: EIRSAT-1 GMOD Detection
  59. GRB 250226A: KAO Optical Upper Limit
  60. GRB 250226A: AbAO AS-32 Optical Upper Limit
  61. EP250227a: Global MASTER-Net observations report
  62. EP250223A: Upper limits from Fermi-GBM Observations
  63. EP250227a: TRT optical upper limit
  64. GRB 250225B: VLT/HAWKI near-infrared observations
  65. EP250227a: Optical upper limits with Kinder observations
  66. EP250227a: NOT optical observations
  67. EP250227a: Einstein Probe detected of a fast X-ray transient
  68. EP250228a: updates on the EP observations
  69. GRB 250226A: Fermi GBM Observation
  70. EP250223a: J band upper limit by SYSU 80cm telescope
  71. EP250228a: Swift/XRT localisation
  72. EP250228a: Einstein Probe detection of an X-ray transient
  73. GRB 250226A / EP250226a: LCO detection of the afterglow
  74. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  75. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  76. GRB 250225B: VLT/Xshooter imaging
  77. GRB 250205A / EP250205A: further radio observations with the VLA
  78. EP250225a: NOT optical candidate counterpart
  79. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  80. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  81. EP250225a: TRT optical upper limits
  82. EP250226a/GRB 250226A: 1.6m Mephisto observations
  83. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  84. EP250226a/GRB 250226A: Kinder optical follow-up observations
  85. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  86. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  87. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  88. GRB 250225B: Fermi GBM Observation
  89. GRB 250225B: REM NIR upper limits
  90. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  91. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  92. EP250223a: CrAO ZTSH optical observation
  93. GRB 250225B: VLT optical and near-infrared candidate counterpart
  94. GRB 250225B: SVOM/GRM observation of a long burst
  95. EP250226a/GRB 250226A: GSP detects optical counterpart
  96. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  97. EP250226a / GRB 250226A: TRT optical counterpart observation
  98. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  99. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  100. EP250225a: GSP optical upper limit

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