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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"

32484 results found.

  1. LXT 240402A / GRB 240402B: VLT X-shooter redshift of host
  2. GRB 240502A: GOTO optical upper limit
  3. GRB 240502A: Fermi GBM Observation
  4. GRB 240415A 1.3m DFOT Optical upper limit
  5. GRB 240502C: GOTO possible optical counterpart candidates
  6. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  7. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  8. Fermi GRB 240502B: Global MASTER-Net observations report
  9. Fermi GRB 240502A: Global MASTER-Net observations report
  10. GRB 240501B: GRBAlpha detection
  11. GRB 240430A: GRBAlpha detection
  12. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet Transient Candidates
  13. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  14. Fermi GRB 240501A: Global MASTER-Net observations report
  15. GRB 240426A: VZLUSAT-2 detection
  16. GRB 240425A: VZLUSAT-2 detection
  17. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  18. GRB 240408B: VZLUSAT-2 detection
  19. GRB 240407A: VZLUSAT-2 detection
  20. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  21. X-ray transient EP240414a: Detection of associated supernova
  22. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  23. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  24. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  25. Additional DECam GW-MMADS Candidates from three nights of observations
  26. GRB 240425A: GRBAlpha detection
  27. Fermi-LAT gamma-ray observations of IceCube-240424A
  28. LIGO/Virgo/KAGRA S240426s: Updated Sky localization
  29. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  30. LIGO/Virgo/KAGRA S240426dl: Updated Sky localization
  31. LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
  32. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  33. LIGO/Virgo/KAGRA S240422ed: ENGRAVE VLT/XShooter spectroscopy of the host galaxy of J-GEM24a
  34. LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
  35. Fermi GRB 240428A: Global MASTER-Net observations report
  36. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  37. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  38. EP240426b: AST3-2 optical upper limit
  39. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  40. LIGO/Virgo/KAGRA S240422ed: A transient discovered from Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  41. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  42. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  43. EP240426b: EP-WXT detection of a new fast X-ray transient
  44. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  45. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  46. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  47. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  48. EP240426a: YAHPT optical upper limit
  49. XMM-Newton observation of EP240426a
  50. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  51. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  52. LIGO/Virgo/KAGRA S240422ed: EP-FXT Detection of the Potential Opitcal Electromagnetic Counterpart AT 2024hfq Reported by DECam
  53. GRB 240414A: NOEMA detection
  54. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  55. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  56. EP240426a: GMG optical upper limit
  57. LVK S240422ed: Further Swift-XRT followup of three sources
  58. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  59. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  60. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  61. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
  62. IceCube-240424A: Upper limits from a search for additional neutrino events in IceCube
  63. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search update and AT2024hfx, AT2024hgl observations
  64. S240422ed: BlackGEM/MeerLICHT transient detection AT2024hgl/MLTJ080628.10-250116.4
  65. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  66. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  67. S240422ed: MeerLICHT/BlackGEM photometry on AT2024hfx and archival ZTF detection
  68. LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
  69. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  70. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-FXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  71. LIGO/Virgo/KAGRA S240422ed: Upper limits from GECAM Observations
  72. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  73. LIGO/Virgo/KAGRA S240422ed: Additional DECam GW-MMADS Candidates from the first two nights of observations
  74. LIGO/Virgo/KAGRA S240422ed: ANU 2.3m followup of candidate counterparts
  75. LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
  76. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  77. GRB 240419B: Swift-BAT refined analysis
  78. GRB 240421B: Swift-BAT refined analysis
  79. GRB 240422A: Glowbug gamma-ray detection
  80. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  81. LIGO/Virgo/KAGRA S240413p: DESGW DECam Follow-Up
  82. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  83. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  84. LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure
  85. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  86. IceCube-240424A - IceCube observation of a high-energy neutrino candidate track-like event
  87. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  88. LIGO/Virgo/KAGRA S240422ed: MOSFIRE spectroscopy of the DECam GW-MMADS candidate AT 2024hdn
  89. LIGO/Virgo/KAGRA S240422ed: ATCA follow-up of candidate counterparts
  90. LIGO/Virgo/KAGRA S240422ed: MOSFIRE imaging of the DECam GW-MMADS candidate AT 2024hdm
  91. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  92. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  93. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  94. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  95. LIGO/Virgo/KAGRA S240422ed: DECam GW-MMADS Candidates
  96. LIGO/Virgo/KAGRA S240422ed: Potential Magellan candidates from GCN 36263 are unrelated.
  97. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  98. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  99. GRB 240421B: GRBAlpha detection
  100. LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart

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